zig/src/link/Elf.zig
Andrew Kelley 507aae4a1a make self-hosted the default compiler
stage1 is available behind the -fstage1 flag.

closes #89
2022-08-19 16:45:15 -07:00

3250 lines
128 KiB
Zig

const Elf = @This();
const std = @import("std");
const builtin = @import("builtin");
const math = std.math;
const mem = std.mem;
const assert = std.debug.assert;
const Allocator = std.mem.Allocator;
const fs = std.fs;
const elf = std.elf;
const log = std.log.scoped(.link);
const Module = @import("../Module.zig");
const Compilation = @import("../Compilation.zig");
const Dwarf = @import("Dwarf.zig");
const codegen = @import("../codegen.zig");
const lldMain = @import("../main.zig").lldMain;
const trace = @import("../tracy.zig").trace;
const Package = @import("../Package.zig");
const Value = @import("../value.zig").Value;
const Type = @import("../type.zig").Type;
const TypedValue = @import("../TypedValue.zig");
const link = @import("../link.zig");
const File = link.File;
const build_options = @import("build_options");
const target_util = @import("../target.zig");
const glibc = @import("../glibc.zig");
const musl = @import("../musl.zig");
const Cache = @import("../Cache.zig");
const Air = @import("../Air.zig");
const Liveness = @import("../Liveness.zig");
const LlvmObject = @import("../codegen/llvm.zig").Object;
const default_entry_addr = 0x8000000;
pub const base_tag: File.Tag = .elf;
base: File,
dwarf: ?Dwarf = null,
ptr_width: PtrWidth,
/// If this is not null, an object file is created by LLVM and linked with LLD afterwards.
llvm_object: ?*LlvmObject = null,
/// Stored in native-endian format, depending on target endianness needs to be bswapped on read/write.
/// Same order as in the file.
sections: std.ArrayListUnmanaged(elf.Elf64_Shdr) = std.ArrayListUnmanaged(elf.Elf64_Shdr){},
shdr_table_offset: ?u64 = null,
/// Stored in native-endian format, depending on target endianness needs to be bswapped on read/write.
/// Same order as in the file.
program_headers: std.ArrayListUnmanaged(elf.Elf64_Phdr) = std.ArrayListUnmanaged(elf.Elf64_Phdr){},
phdr_table_offset: ?u64 = null,
/// The index into the program headers of a PT_LOAD program header with Read and Execute flags
phdr_load_re_index: ?u16 = null,
/// The index into the program headers of the global offset table.
/// It needs PT_LOAD and Read flags.
phdr_got_index: ?u16 = null,
/// The index into the program headers of a PT_LOAD program header with Read flag
phdr_load_ro_index: ?u16 = null,
/// The index into the program headers of a PT_LOAD program header with Write flag
phdr_load_rw_index: ?u16 = null,
phdr_shdr_table: std.AutoHashMapUnmanaged(u16, u16) = .{},
entry_addr: ?u64 = null,
page_size: u32,
shstrtab: std.ArrayListUnmanaged(u8) = std.ArrayListUnmanaged(u8){},
shstrtab_index: ?u16 = null,
symtab_section_index: ?u16 = null,
text_section_index: ?u16 = null,
rodata_section_index: ?u16 = null,
got_section_index: ?u16 = null,
data_section_index: ?u16 = null,
debug_info_section_index: ?u16 = null,
debug_abbrev_section_index: ?u16 = null,
debug_str_section_index: ?u16 = null,
debug_aranges_section_index: ?u16 = null,
debug_line_section_index: ?u16 = null,
/// The same order as in the file. ELF requires global symbols to all be after the
/// local symbols, they cannot be mixed. So we must buffer all the global symbols and
/// write them at the end. These are only the local symbols. The length of this array
/// is the value used for sh_info in the .symtab section.
local_symbols: std.ArrayListUnmanaged(elf.Elf64_Sym) = .{},
global_symbols: std.ArrayListUnmanaged(elf.Elf64_Sym) = .{},
local_symbol_free_list: std.ArrayListUnmanaged(u32) = .{},
global_symbol_free_list: std.ArrayListUnmanaged(u32) = .{},
offset_table_free_list: std.ArrayListUnmanaged(u32) = .{},
/// Same order as in the file. The value is the absolute vaddr value.
/// If the vaddr of the executable program header changes, the entire
/// offset table needs to be rewritten.
offset_table: std.ArrayListUnmanaged(u64) = .{},
phdr_table_dirty: bool = false,
shdr_table_dirty: bool = false,
shstrtab_dirty: bool = false,
offset_table_count_dirty: bool = false,
debug_strtab_dirty: bool = false,
debug_abbrev_section_dirty: bool = false,
debug_aranges_section_dirty: bool = false,
debug_info_header_dirty: bool = false,
debug_line_header_dirty: bool = false,
error_flags: File.ErrorFlags = File.ErrorFlags{},
/// Pointer to the last allocated atom
atoms: std.AutoHashMapUnmanaged(u16, *TextBlock) = .{},
/// A list of text blocks that have surplus capacity. This list can have false
/// positives, as functions grow and shrink over time, only sometimes being added
/// or removed from the freelist.
///
/// A text block has surplus capacity when its overcapacity value is greater than
/// padToIdeal(minimum_text_block_size). That is, when it has so
/// much extra capacity, that we could fit a small new symbol in it, itself with
/// ideal_capacity or more.
///
/// Ideal capacity is defined by size + (size / ideal_factor)
///
/// Overcapacity is measured by actual_capacity - ideal_capacity. Note that
/// overcapacity can be negative. A simple way to have negative overcapacity is to
/// allocate a fresh text block, which will have ideal capacity, and then grow it
/// by 1 byte. It will then have -1 overcapacity.
atom_free_lists: std.AutoHashMapUnmanaged(u16, std.ArrayListUnmanaged(*TextBlock)) = .{},
/// Table of Decls that are currently alive.
/// We store them here so that we can properly dispose of any allocated
/// memory within the atom in the incremental linker.
/// TODO consolidate this.
decls: std.AutoHashMapUnmanaged(Module.Decl.Index, ?u16) = .{},
/// List of atoms that are owned directly by the linker.
/// Currently these are only atoms that are the result of linking
/// object files. Atoms which take part in incremental linking are
/// at present owned by Module.Decl.
/// TODO consolidate this.
managed_atoms: std.ArrayListUnmanaged(*TextBlock) = .{},
atom_by_index_table: std.AutoHashMapUnmanaged(u32, *TextBlock) = .{},
/// Table of unnamed constants associated with a parent `Decl`.
/// We store them here so that we can free the constants whenever the `Decl`
/// needs updating or is freed.
///
/// For example,
///
/// ```zig
/// const Foo = struct{
/// a: u8,
/// };
///
/// pub fn main() void {
/// var foo = Foo{ .a = 1 };
/// _ = foo;
/// }
/// ```
///
/// value assigned to label `foo` is an unnamed constant belonging/associated
/// with `Decl` `main`, and lives as long as that `Decl`.
unnamed_const_atoms: UnnamedConstTable = .{},
/// A table of relocations indexed by the owning them `TextBlock`.
/// Note that once we refactor `TextBlock`'s lifetime and ownership rules,
/// this will be a table indexed by index into the list of Atoms.
relocs: RelocTable = .{},
const Reloc = struct {
target: u32,
offset: u64,
addend: u32,
prev_vaddr: u64,
};
const RelocTable = std.AutoHashMapUnmanaged(*TextBlock, std.ArrayListUnmanaged(Reloc));
const UnnamedConstTable = std.AutoHashMapUnmanaged(Module.Decl.Index, std.ArrayListUnmanaged(*TextBlock));
/// When allocating, the ideal_capacity is calculated by
/// actual_capacity + (actual_capacity / ideal_factor)
const ideal_factor = 3;
/// In order for a slice of bytes to be considered eligible to keep metadata pointing at
/// it as a possible place to put new symbols, it must have enough room for this many bytes
/// (plus extra for reserved capacity).
const minimum_text_block_size = 64;
const min_text_capacity = padToIdeal(minimum_text_block_size);
pub const PtrWidth = enum { p32, p64 };
pub const TextBlock = struct {
/// Each decl always gets a local symbol with the fully qualified name.
/// The vaddr and size are found here directly.
/// The file offset is found by computing the vaddr offset from the section vaddr
/// the symbol references, and adding that to the file offset of the section.
/// If this field is 0, it means the codegen size = 0 and there is no symbol or
/// offset table entry.
local_sym_index: u32,
/// This field is undefined for symbols with size = 0.
offset_table_index: u32,
/// Points to the previous and next neighbors, based on the `text_offset`.
/// This can be used to find, for example, the capacity of this `TextBlock`.
prev: ?*TextBlock,
next: ?*TextBlock,
dbg_info_atom: Dwarf.Atom,
pub const empty = TextBlock{
.local_sym_index = 0,
.offset_table_index = undefined,
.prev = null,
.next = null,
.dbg_info_atom = undefined,
};
/// Returns how much room there is to grow in virtual address space.
/// File offset relocation happens transparently, so it is not included in
/// this calculation.
fn capacity(self: TextBlock, elf_file: Elf) u64 {
const self_sym = elf_file.local_symbols.items[self.local_sym_index];
if (self.next) |next| {
const next_sym = elf_file.local_symbols.items[next.local_sym_index];
return next_sym.st_value - self_sym.st_value;
} else {
// We are the last block. The capacity is limited only by virtual address space.
return std.math.maxInt(u32) - self_sym.st_value;
}
}
fn freeListEligible(self: TextBlock, elf_file: Elf) bool {
// No need to keep a free list node for the last block.
const next = self.next orelse return false;
const self_sym = elf_file.local_symbols.items[self.local_sym_index];
const next_sym = elf_file.local_symbols.items[next.local_sym_index];
const cap = next_sym.st_value - self_sym.st_value;
const ideal_cap = padToIdeal(self_sym.st_size);
if (cap <= ideal_cap) return false;
const surplus = cap - ideal_cap;
return surplus >= min_text_capacity;
}
};
pub const Export = struct {
sym_index: ?u32 = null,
};
pub fn openPath(allocator: Allocator, sub_path: []const u8, options: link.Options) !*Elf {
assert(options.target.ofmt == .elf);
if (build_options.have_llvm and options.use_llvm) {
return createEmpty(allocator, options);
}
const self = try createEmpty(allocator, options);
errdefer self.base.destroy();
const file = try options.emit.?.directory.handle.createFile(sub_path, .{
.truncate = false,
.read = true,
.mode = link.determineMode(options),
});
self.base.file = file;
self.shdr_table_dirty = true;
// Index 0 is always a null symbol.
try self.local_symbols.append(allocator, .{
.st_name = 0,
.st_info = 0,
.st_other = 0,
.st_shndx = 0,
.st_value = 0,
.st_size = 0,
});
// There must always be a null section in index 0
try self.sections.append(allocator, .{
.sh_name = 0,
.sh_type = elf.SHT_NULL,
.sh_flags = 0,
.sh_addr = 0,
.sh_offset = 0,
.sh_size = 0,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = 0,
.sh_entsize = 0,
});
try self.populateMissingMetadata();
return self;
}
pub fn createEmpty(gpa: Allocator, options: link.Options) !*Elf {
const ptr_width: PtrWidth = switch (options.target.cpu.arch.ptrBitWidth()) {
0...32 => .p32,
33...64 => .p64,
else => return error.UnsupportedELFArchitecture,
};
const self = try gpa.create(Elf);
errdefer gpa.destroy(self);
const page_size: u32 = switch (options.target.cpu.arch) {
.powerpc64le => 0x10000,
.sparc64 => 0x2000,
else => 0x1000,
};
var dwarf: ?Dwarf = if (!options.strip and options.module != null)
Dwarf.init(gpa, .elf, options.target)
else
null;
self.* = .{
.base = .{
.tag = .elf,
.options = options,
.allocator = gpa,
.file = null,
},
.dwarf = dwarf,
.ptr_width = ptr_width,
.page_size = page_size,
};
const use_llvm = build_options.have_llvm and options.use_llvm;
const use_stage1 = build_options.have_stage1 and options.use_stage1;
if (use_llvm and !use_stage1) {
self.llvm_object = try LlvmObject.create(gpa, options);
}
return self;
}
pub fn deinit(self: *Elf) void {
if (build_options.have_llvm) {
if (self.llvm_object) |llvm_object| llvm_object.destroy(self.base.allocator);
}
self.sections.deinit(self.base.allocator);
self.program_headers.deinit(self.base.allocator);
self.shstrtab.deinit(self.base.allocator);
self.local_symbols.deinit(self.base.allocator);
self.global_symbols.deinit(self.base.allocator);
self.global_symbol_free_list.deinit(self.base.allocator);
self.local_symbol_free_list.deinit(self.base.allocator);
self.offset_table_free_list.deinit(self.base.allocator);
self.offset_table.deinit(self.base.allocator);
self.phdr_shdr_table.deinit(self.base.allocator);
self.decls.deinit(self.base.allocator);
self.atoms.deinit(self.base.allocator);
{
var it = self.atom_free_lists.valueIterator();
while (it.next()) |free_list| {
free_list.deinit(self.base.allocator);
}
self.atom_free_lists.deinit(self.base.allocator);
}
for (self.managed_atoms.items) |atom| {
self.base.allocator.destroy(atom);
}
self.managed_atoms.deinit(self.base.allocator);
{
var it = self.unnamed_const_atoms.valueIterator();
while (it.next()) |atoms| {
atoms.deinit(self.base.allocator);
}
self.unnamed_const_atoms.deinit(self.base.allocator);
}
{
var it = self.relocs.valueIterator();
while (it.next()) |relocs| {
relocs.deinit(self.base.allocator);
}
self.relocs.deinit(self.base.allocator);
}
self.atom_by_index_table.deinit(self.base.allocator);
if (self.dwarf) |*dw| {
dw.deinit();
}
}
pub fn getDeclVAddr(self: *Elf, decl_index: Module.Decl.Index, reloc_info: File.RelocInfo) !u64 {
const mod = self.base.options.module.?;
const decl = mod.declPtr(decl_index);
assert(self.llvm_object == null);
assert(decl.link.elf.local_sym_index != 0);
const target = decl.link.elf.local_sym_index;
const vaddr = self.local_symbols.items[target].st_value;
const atom = self.atom_by_index_table.get(reloc_info.parent_atom_index).?;
const gop = try self.relocs.getOrPut(self.base.allocator, atom);
if (!gop.found_existing) {
gop.value_ptr.* = .{};
}
try gop.value_ptr.append(self.base.allocator, .{
.target = target,
.offset = reloc_info.offset,
.addend = reloc_info.addend,
.prev_vaddr = vaddr,
});
return vaddr;
}
/// Returns end pos of collision, if any.
fn detectAllocCollision(self: *Elf, start: u64, size: u64) ?u64 {
const small_ptr = self.ptr_width == .p32;
const ehdr_size: u64 = if (small_ptr) @sizeOf(elf.Elf32_Ehdr) else @sizeOf(elf.Elf64_Ehdr);
if (start < ehdr_size)
return ehdr_size;
const end = start + padToIdeal(size);
if (self.shdr_table_offset) |off| {
const shdr_size: u64 = if (small_ptr) @sizeOf(elf.Elf32_Shdr) else @sizeOf(elf.Elf64_Shdr);
const tight_size = self.sections.items.len * shdr_size;
const increased_size = padToIdeal(tight_size);
const test_end = off + increased_size;
if (end > off and start < test_end) {
return test_end;
}
}
if (self.phdr_table_offset) |off| {
const phdr_size: u64 = if (small_ptr) @sizeOf(elf.Elf32_Phdr) else @sizeOf(elf.Elf64_Phdr);
const tight_size = self.sections.items.len * phdr_size;
const increased_size = padToIdeal(tight_size);
const test_end = off + increased_size;
if (end > off and start < test_end) {
return test_end;
}
}
for (self.sections.items) |section| {
const increased_size = padToIdeal(section.sh_size);
const test_end = section.sh_offset + increased_size;
if (end > section.sh_offset and start < test_end) {
return test_end;
}
}
for (self.program_headers.items) |program_header| {
const increased_size = padToIdeal(program_header.p_filesz);
const test_end = program_header.p_offset + increased_size;
if (end > program_header.p_offset and start < test_end) {
return test_end;
}
}
return null;
}
pub fn allocatedSize(self: *Elf, start: u64) u64 {
if (start == 0)
return 0;
var min_pos: u64 = std.math.maxInt(u64);
if (self.shdr_table_offset) |off| {
if (off > start and off < min_pos) min_pos = off;
}
if (self.phdr_table_offset) |off| {
if (off > start and off < min_pos) min_pos = off;
}
for (self.sections.items) |section| {
if (section.sh_offset <= start) continue;
if (section.sh_offset < min_pos) min_pos = section.sh_offset;
}
for (self.program_headers.items) |program_header| {
if (program_header.p_offset <= start) continue;
if (program_header.p_offset < min_pos) min_pos = program_header.p_offset;
}
return min_pos - start;
}
pub fn findFreeSpace(self: *Elf, object_size: u64, min_alignment: u32) u64 {
var start: u64 = 0;
while (self.detectAllocCollision(start, object_size)) |item_end| {
start = mem.alignForwardGeneric(u64, item_end, min_alignment);
}
return start;
}
/// TODO Improve this to use a table.
fn makeString(self: *Elf, bytes: []const u8) !u32 {
try self.shstrtab.ensureUnusedCapacity(self.base.allocator, bytes.len + 1);
const result = self.shstrtab.items.len;
self.shstrtab.appendSliceAssumeCapacity(bytes);
self.shstrtab.appendAssumeCapacity(0);
return @intCast(u32, result);
}
fn getString(self: Elf, str_off: u32) []const u8 {
assert(str_off < self.shstrtab.items.len);
return mem.sliceTo(@ptrCast([*:0]const u8, self.shstrtab.items.ptr + str_off), 0);
}
fn updateString(self: *Elf, old_str_off: u32, new_name: []const u8) !u32 {
const existing_name = self.getString(old_str_off);
if (mem.eql(u8, existing_name, new_name)) {
return old_str_off;
}
return self.makeString(new_name);
}
pub fn populateMissingMetadata(self: *Elf) !void {
assert(self.llvm_object == null);
const small_ptr = switch (self.ptr_width) {
.p32 => true,
.p64 => false,
};
const ptr_size: u8 = self.ptrWidthBytes();
if (self.phdr_load_re_index == null) {
self.phdr_load_re_index = @intCast(u16, self.program_headers.items.len);
const file_size = self.base.options.program_code_size_hint;
const p_align = self.page_size;
const off = self.findFreeSpace(file_size, p_align);
log.debug("found PT_LOAD RE free space 0x{x} to 0x{x}", .{ off, off + file_size });
const entry_addr: u64 = self.entry_addr orelse if (self.base.options.target.cpu.arch == .spu_2) @as(u64, 0) else default_entry_addr;
try self.program_headers.append(self.base.allocator, .{
.p_type = elf.PT_LOAD,
.p_offset = off,
.p_filesz = file_size,
.p_vaddr = entry_addr,
.p_paddr = entry_addr,
.p_memsz = file_size,
.p_align = p_align,
.p_flags = elf.PF_X | elf.PF_R,
});
try self.atom_free_lists.putNoClobber(self.base.allocator, self.phdr_load_re_index.?, .{});
self.entry_addr = null;
self.phdr_table_dirty = true;
}
if (self.phdr_got_index == null) {
self.phdr_got_index = @intCast(u16, self.program_headers.items.len);
const file_size = @as(u64, ptr_size) * self.base.options.symbol_count_hint;
// We really only need ptr alignment but since we are using PROGBITS, linux requires
// page align.
const p_align = if (self.base.options.target.os.tag == .linux) self.page_size else @as(u16, ptr_size);
const off = self.findFreeSpace(file_size, p_align);
log.debug("found PT_LOAD GOT free space 0x{x} to 0x{x}", .{ off, off + file_size });
// TODO instead of hard coding the vaddr, make a function to find a vaddr to put things at.
// we'll need to re-use that function anyway, in case the GOT grows and overlaps something
// else in virtual memory.
const got_addr: u32 = if (self.base.options.target.cpu.arch.ptrBitWidth() >= 32) 0x4000000 else 0x8000;
try self.program_headers.append(self.base.allocator, .{
.p_type = elf.PT_LOAD,
.p_offset = off,
.p_filesz = file_size,
.p_vaddr = got_addr,
.p_paddr = got_addr,
.p_memsz = file_size,
.p_align = p_align,
.p_flags = elf.PF_R,
});
self.phdr_table_dirty = true;
}
if (self.phdr_load_ro_index == null) {
self.phdr_load_ro_index = @intCast(u16, self.program_headers.items.len);
// TODO Find a hint about how much data need to be in rodata ?
const file_size = 1024;
// Same reason as for GOT
const p_align = if (self.base.options.target.os.tag == .linux) self.page_size else @as(u16, ptr_size);
const off = self.findFreeSpace(file_size, p_align);
log.debug("found PT_LOAD RO free space 0x{x} to 0x{x}", .{ off, off + file_size });
// TODO Same as for GOT
const rodata_addr: u32 = if (self.base.options.target.cpu.arch.ptrBitWidth() >= 32) 0xc000000 else 0xa000;
try self.program_headers.append(self.base.allocator, .{
.p_type = elf.PT_LOAD,
.p_offset = off,
.p_filesz = file_size,
.p_vaddr = rodata_addr,
.p_paddr = rodata_addr,
.p_memsz = file_size,
.p_align = p_align,
.p_flags = elf.PF_R,
});
try self.atom_free_lists.putNoClobber(self.base.allocator, self.phdr_load_ro_index.?, .{});
self.phdr_table_dirty = true;
}
if (self.phdr_load_rw_index == null) {
self.phdr_load_rw_index = @intCast(u16, self.program_headers.items.len);
// TODO Find a hint about how much data need to be in data ?
const file_size = 1024;
// Same reason as for GOT
const p_align = if (self.base.options.target.os.tag == .linux) self.page_size else @as(u16, ptr_size);
const off = self.findFreeSpace(file_size, p_align);
log.debug("found PT_LOAD RW free space 0x{x} to 0x{x}", .{ off, off + file_size });
// TODO Same as for GOT
const rwdata_addr: u32 = if (self.base.options.target.cpu.arch.ptrBitWidth() >= 32) 0x10000000 else 0xc000;
try self.program_headers.append(self.base.allocator, .{
.p_type = elf.PT_LOAD,
.p_offset = off,
.p_filesz = file_size,
.p_vaddr = rwdata_addr,
.p_paddr = rwdata_addr,
.p_memsz = file_size,
.p_align = p_align,
.p_flags = elf.PF_R | elf.PF_W,
});
try self.atom_free_lists.putNoClobber(self.base.allocator, self.phdr_load_rw_index.?, .{});
self.phdr_table_dirty = true;
}
if (self.shstrtab_index == null) {
self.shstrtab_index = @intCast(u16, self.sections.items.len);
assert(self.shstrtab.items.len == 0);
try self.shstrtab.append(self.base.allocator, 0); // need a 0 at position 0
const off = self.findFreeSpace(self.shstrtab.items.len, 1);
log.debug("found shstrtab free space 0x{x} to 0x{x}", .{ off, off + self.shstrtab.items.len });
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".shstrtab"),
.sh_type = elf.SHT_STRTAB,
.sh_flags = 0,
.sh_addr = 0,
.sh_offset = off,
.sh_size = self.shstrtab.items.len,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = 1,
.sh_entsize = 0,
});
self.shstrtab_dirty = true;
self.shdr_table_dirty = true;
}
if (self.text_section_index == null) {
self.text_section_index = @intCast(u16, self.sections.items.len);
const phdr = &self.program_headers.items[self.phdr_load_re_index.?];
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".text"),
.sh_type = elf.SHT_PROGBITS,
.sh_flags = elf.SHF_ALLOC | elf.SHF_EXECINSTR,
.sh_addr = phdr.p_vaddr,
.sh_offset = phdr.p_offset,
.sh_size = phdr.p_filesz,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = 1,
.sh_entsize = 0,
});
try self.phdr_shdr_table.putNoClobber(
self.base.allocator,
self.phdr_load_re_index.?,
self.text_section_index.?,
);
self.shdr_table_dirty = true;
}
if (self.got_section_index == null) {
self.got_section_index = @intCast(u16, self.sections.items.len);
const phdr = &self.program_headers.items[self.phdr_got_index.?];
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".got"),
.sh_type = elf.SHT_PROGBITS,
.sh_flags = elf.SHF_ALLOC,
.sh_addr = phdr.p_vaddr,
.sh_offset = phdr.p_offset,
.sh_size = phdr.p_filesz,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = @as(u16, ptr_size),
.sh_entsize = 0,
});
try self.phdr_shdr_table.putNoClobber(
self.base.allocator,
self.phdr_got_index.?,
self.got_section_index.?,
);
self.shdr_table_dirty = true;
}
if (self.rodata_section_index == null) {
self.rodata_section_index = @intCast(u16, self.sections.items.len);
const phdr = &self.program_headers.items[self.phdr_load_ro_index.?];
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".rodata"),
.sh_type = elf.SHT_PROGBITS,
.sh_flags = elf.SHF_ALLOC,
.sh_addr = phdr.p_vaddr,
.sh_offset = phdr.p_offset,
.sh_size = phdr.p_filesz,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = 1,
.sh_entsize = 0,
});
try self.phdr_shdr_table.putNoClobber(
self.base.allocator,
self.phdr_load_ro_index.?,
self.rodata_section_index.?,
);
self.shdr_table_dirty = true;
}
if (self.data_section_index == null) {
self.data_section_index = @intCast(u16, self.sections.items.len);
const phdr = &self.program_headers.items[self.phdr_load_rw_index.?];
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".data"),
.sh_type = elf.SHT_PROGBITS,
.sh_flags = elf.SHF_WRITE | elf.SHF_ALLOC,
.sh_addr = phdr.p_vaddr,
.sh_offset = phdr.p_offset,
.sh_size = phdr.p_filesz,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = @as(u16, ptr_size),
.sh_entsize = 0,
});
try self.phdr_shdr_table.putNoClobber(
self.base.allocator,
self.phdr_load_rw_index.?,
self.data_section_index.?,
);
self.shdr_table_dirty = true;
}
if (self.symtab_section_index == null) {
self.symtab_section_index = @intCast(u16, self.sections.items.len);
const min_align: u16 = if (small_ptr) @alignOf(elf.Elf32_Sym) else @alignOf(elf.Elf64_Sym);
const each_size: u64 = if (small_ptr) @sizeOf(elf.Elf32_Sym) else @sizeOf(elf.Elf64_Sym);
const file_size = self.base.options.symbol_count_hint * each_size;
const off = self.findFreeSpace(file_size, min_align);
log.debug("found symtab free space 0x{x} to 0x{x}", .{ off, off + file_size });
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".symtab"),
.sh_type = elf.SHT_SYMTAB,
.sh_flags = 0,
.sh_addr = 0,
.sh_offset = off,
.sh_size = file_size,
// The section header index of the associated string table.
.sh_link = self.shstrtab_index.?,
.sh_info = @intCast(u32, self.local_symbols.items.len),
.sh_addralign = min_align,
.sh_entsize = each_size,
});
self.shdr_table_dirty = true;
try self.writeSymbol(0);
}
if (self.dwarf) |dw| {
if (self.debug_str_section_index == null) {
self.debug_str_section_index = @intCast(u16, self.sections.items.len);
assert(dw.strtab.items.len == 0);
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".debug_str"),
.sh_type = elf.SHT_PROGBITS,
.sh_flags = elf.SHF_MERGE | elf.SHF_STRINGS,
.sh_addr = 0,
.sh_offset = 0,
.sh_size = 0,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = 1,
.sh_entsize = 1,
});
self.debug_strtab_dirty = true;
self.shdr_table_dirty = true;
}
if (self.debug_info_section_index == null) {
self.debug_info_section_index = @intCast(u16, self.sections.items.len);
const file_size_hint = 200;
const p_align = 1;
const off = self.findFreeSpace(file_size_hint, p_align);
log.debug("found .debug_info free space 0x{x} to 0x{x}", .{
off,
off + file_size_hint,
});
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".debug_info"),
.sh_type = elf.SHT_PROGBITS,
.sh_flags = 0,
.sh_addr = 0,
.sh_offset = off,
.sh_size = file_size_hint,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = p_align,
.sh_entsize = 0,
});
self.shdr_table_dirty = true;
self.debug_info_header_dirty = true;
}
if (self.debug_abbrev_section_index == null) {
self.debug_abbrev_section_index = @intCast(u16, self.sections.items.len);
const file_size_hint = 128;
const p_align = 1;
const off = self.findFreeSpace(file_size_hint, p_align);
log.debug("found .debug_abbrev free space 0x{x} to 0x{x}", .{
off,
off + file_size_hint,
});
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".debug_abbrev"),
.sh_type = elf.SHT_PROGBITS,
.sh_flags = 0,
.sh_addr = 0,
.sh_offset = off,
.sh_size = file_size_hint,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = p_align,
.sh_entsize = 0,
});
self.shdr_table_dirty = true;
self.debug_abbrev_section_dirty = true;
}
if (self.debug_aranges_section_index == null) {
self.debug_aranges_section_index = @intCast(u16, self.sections.items.len);
const file_size_hint = 160;
const p_align = 16;
const off = self.findFreeSpace(file_size_hint, p_align);
log.debug("found .debug_aranges free space 0x{x} to 0x{x}", .{
off,
off + file_size_hint,
});
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".debug_aranges"),
.sh_type = elf.SHT_PROGBITS,
.sh_flags = 0,
.sh_addr = 0,
.sh_offset = off,
.sh_size = file_size_hint,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = p_align,
.sh_entsize = 0,
});
self.shdr_table_dirty = true;
self.debug_aranges_section_dirty = true;
}
if (self.debug_line_section_index == null) {
self.debug_line_section_index = @intCast(u16, self.sections.items.len);
const file_size_hint = 250;
const p_align = 1;
const off = self.findFreeSpace(file_size_hint, p_align);
log.debug("found .debug_line free space 0x{x} to 0x{x}", .{
off,
off + file_size_hint,
});
try self.sections.append(self.base.allocator, .{
.sh_name = try self.makeString(".debug_line"),
.sh_type = elf.SHT_PROGBITS,
.sh_flags = 0,
.sh_addr = 0,
.sh_offset = off,
.sh_size = file_size_hint,
.sh_link = 0,
.sh_info = 0,
.sh_addralign = p_align,
.sh_entsize = 0,
});
self.shdr_table_dirty = true;
self.debug_line_header_dirty = true;
}
}
const shsize: u64 = switch (self.ptr_width) {
.p32 => @sizeOf(elf.Elf32_Shdr),
.p64 => @sizeOf(elf.Elf64_Shdr),
};
const shalign: u16 = switch (self.ptr_width) {
.p32 => @alignOf(elf.Elf32_Shdr),
.p64 => @alignOf(elf.Elf64_Shdr),
};
if (self.shdr_table_offset == null) {
self.shdr_table_offset = self.findFreeSpace(self.sections.items.len * shsize, shalign);
self.shdr_table_dirty = true;
}
const phsize: u64 = switch (self.ptr_width) {
.p32 => @sizeOf(elf.Elf32_Phdr),
.p64 => @sizeOf(elf.Elf64_Phdr),
};
const phalign: u16 = switch (self.ptr_width) {
.p32 => @alignOf(elf.Elf32_Phdr),
.p64 => @alignOf(elf.Elf64_Phdr),
};
if (self.phdr_table_offset == null) {
self.phdr_table_offset = self.findFreeSpace(self.program_headers.items.len * phsize, phalign);
self.phdr_table_dirty = true;
}
{
// Iterate over symbols, populating free_list and last_text_block.
if (self.local_symbols.items.len != 1) {
@panic("TODO implement setting up free_list and last_text_block from existing ELF file");
}
// We are starting with an empty file. The default values are correct, null and empty list.
}
if (self.shdr_table_dirty) {
// We need to find out what the max file offset is according to section headers.
// Otherwise, we may end up with an ELF binary with file size not matching the final section's
// offset + it's filesize.
var max_file_offset: u64 = 0;
for (self.sections.items) |shdr| {
if (shdr.sh_offset + shdr.sh_size > max_file_offset) {
max_file_offset = shdr.sh_offset + shdr.sh_size;
}
}
try self.base.file.?.pwriteAll(&[_]u8{0}, max_file_offset);
}
}
pub fn flush(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node) !void {
if (self.base.options.emit == null) {
if (build_options.have_llvm) {
if (self.llvm_object) |llvm_object| {
return try llvm_object.flushModule(comp, prog_node);
}
}
return;
}
const use_lld = build_options.have_llvm and self.base.options.use_lld;
if (use_lld) {
return self.linkWithLLD(comp, prog_node);
}
switch (self.base.options.output_mode) {
.Exe, .Obj => return self.flushModule(comp, prog_node),
.Lib => return error.TODOImplementWritingLibFiles,
}
}
pub fn flushModule(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node) !void {
const tracy = trace(@src());
defer tracy.end();
if (build_options.have_llvm) {
if (self.llvm_object) |llvm_object| {
return try llvm_object.flushModule(comp, prog_node);
}
}
var sub_prog_node = prog_node.start("ELF Flush", 0);
sub_prog_node.activate();
defer sub_prog_node.end();
// TODO This linker code currently assumes there is only 1 compilation unit and it
// corresponds to the Zig source code.
const module = self.base.options.module orelse return error.LinkingWithoutZigSourceUnimplemented;
const target_endian = self.base.options.target.cpu.arch.endian();
const foreign_endian = target_endian != builtin.cpu.arch.endian();
if (self.dwarf) |*dw| {
try dw.flushModule(&self.base, module);
}
{
var it = self.relocs.iterator();
while (it.next()) |entry| {
const atom = entry.key_ptr.*;
const relocs = entry.value_ptr.*;
const source_sym = self.local_symbols.items[atom.local_sym_index];
const source_shdr = self.sections.items[source_sym.st_shndx];
log.debug("relocating '{s}'", .{self.getString(source_sym.st_name)});
for (relocs.items) |*reloc| {
const target_sym = self.local_symbols.items[reloc.target];
const target_vaddr = target_sym.st_value + reloc.addend;
if (target_vaddr == reloc.prev_vaddr) continue;
const section_offset = (source_sym.st_value + reloc.offset) - source_shdr.sh_addr;
const file_offset = source_shdr.sh_offset + section_offset;
log.debug(" ({x}: [() => 0x{x}] ({s}))", .{
reloc.offset,
target_vaddr,
self.getString(target_sym.st_name),
});
switch (self.ptr_width) {
.p32 => try self.base.file.?.pwriteAll(mem.asBytes(&@intCast(u32, target_vaddr)), file_offset),
.p64 => try self.base.file.?.pwriteAll(mem.asBytes(&target_vaddr), file_offset),
}
reloc.prev_vaddr = target_vaddr;
}
}
}
// Unfortunately these have to be buffered and done at the end because ELF does not allow
// mixing local and global symbols within a symbol table.
try self.writeAllGlobalSymbols();
if (build_options.enable_logging) {
self.logSymtab();
}
if (self.dwarf) |*dw| {
if (self.debug_abbrev_section_dirty) {
try dw.writeDbgAbbrev(&self.base);
if (!self.shdr_table_dirty) {
// Then it won't get written with the others and we need to do it.
try self.writeSectHeader(self.debug_abbrev_section_index.?);
}
self.debug_abbrev_section_dirty = false;
}
if (self.debug_info_header_dirty) {
// Currently only one compilation unit is supported, so the address range is simply
// identical to the main program header virtual address and memory size.
const text_phdr = &self.program_headers.items[self.phdr_load_re_index.?];
const low_pc = text_phdr.p_vaddr;
const high_pc = text_phdr.p_vaddr + text_phdr.p_memsz;
try dw.writeDbgInfoHeader(&self.base, module, low_pc, high_pc);
self.debug_info_header_dirty = false;
}
if (self.debug_aranges_section_dirty) {
// Currently only one compilation unit is supported, so the address range is simply
// identical to the main program header virtual address and memory size.
const text_phdr = &self.program_headers.items[self.phdr_load_re_index.?];
try dw.writeDbgAranges(&self.base, text_phdr.p_vaddr, text_phdr.p_memsz);
if (!self.shdr_table_dirty) {
// Then it won't get written with the others and we need to do it.
try self.writeSectHeader(self.debug_aranges_section_index.?);
}
self.debug_aranges_section_dirty = false;
}
if (self.debug_line_header_dirty) {
try dw.writeDbgLineHeader(&self.base, module);
self.debug_line_header_dirty = false;
}
}
if (self.phdr_table_dirty) {
const phsize: u64 = switch (self.ptr_width) {
.p32 => @sizeOf(elf.Elf32_Phdr),
.p64 => @sizeOf(elf.Elf64_Phdr),
};
const phalign: u16 = switch (self.ptr_width) {
.p32 => @alignOf(elf.Elf32_Phdr),
.p64 => @alignOf(elf.Elf64_Phdr),
};
const allocated_size = self.allocatedSize(self.phdr_table_offset.?);
const needed_size = self.program_headers.items.len * phsize;
if (needed_size > allocated_size) {
self.phdr_table_offset = null; // free the space
self.phdr_table_offset = self.findFreeSpace(needed_size, phalign);
}
switch (self.ptr_width) {
.p32 => {
const buf = try self.base.allocator.alloc(elf.Elf32_Phdr, self.program_headers.items.len);
defer self.base.allocator.free(buf);
for (buf) |*phdr, i| {
phdr.* = progHeaderTo32(self.program_headers.items[i]);
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf32_Phdr, phdr);
}
}
try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), self.phdr_table_offset.?);
},
.p64 => {
const buf = try self.base.allocator.alloc(elf.Elf64_Phdr, self.program_headers.items.len);
defer self.base.allocator.free(buf);
for (buf) |*phdr, i| {
phdr.* = self.program_headers.items[i];
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf64_Phdr, phdr);
}
}
try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), self.phdr_table_offset.?);
},
}
self.phdr_table_dirty = false;
}
{
const shstrtab_sect = &self.sections.items[self.shstrtab_index.?];
if (self.shstrtab_dirty or self.shstrtab.items.len != shstrtab_sect.sh_size) {
const allocated_size = self.allocatedSize(shstrtab_sect.sh_offset);
const needed_size = self.shstrtab.items.len;
if (needed_size > allocated_size) {
shstrtab_sect.sh_size = 0; // free the space
shstrtab_sect.sh_offset = self.findFreeSpace(needed_size, 1);
}
shstrtab_sect.sh_size = needed_size;
log.debug("writing shstrtab start=0x{x} end=0x{x}", .{ shstrtab_sect.sh_offset, shstrtab_sect.sh_offset + needed_size });
try self.base.file.?.pwriteAll(self.shstrtab.items, shstrtab_sect.sh_offset);
if (!self.shdr_table_dirty) {
// Then it won't get written with the others and we need to do it.
try self.writeSectHeader(self.shstrtab_index.?);
}
self.shstrtab_dirty = false;
}
}
if (self.dwarf) |dwarf| {
const debug_strtab_sect = &self.sections.items[self.debug_str_section_index.?];
if (self.debug_strtab_dirty or dwarf.strtab.items.len != debug_strtab_sect.sh_size) {
const allocated_size = self.allocatedSize(debug_strtab_sect.sh_offset);
const needed_size = dwarf.strtab.items.len;
if (needed_size > allocated_size) {
debug_strtab_sect.sh_size = 0; // free the space
debug_strtab_sect.sh_offset = self.findFreeSpace(needed_size, 1);
}
debug_strtab_sect.sh_size = needed_size;
log.debug("debug_strtab start=0x{x} end=0x{x}", .{ debug_strtab_sect.sh_offset, debug_strtab_sect.sh_offset + needed_size });
try self.base.file.?.pwriteAll(dwarf.strtab.items, debug_strtab_sect.sh_offset);
if (!self.shdr_table_dirty) {
// Then it won't get written with the others and we need to do it.
try self.writeSectHeader(self.debug_str_section_index.?);
}
self.debug_strtab_dirty = false;
}
}
if (self.shdr_table_dirty) {
const shsize: u64 = switch (self.ptr_width) {
.p32 => @sizeOf(elf.Elf32_Shdr),
.p64 => @sizeOf(elf.Elf64_Shdr),
};
const shalign: u16 = switch (self.ptr_width) {
.p32 => @alignOf(elf.Elf32_Shdr),
.p64 => @alignOf(elf.Elf64_Shdr),
};
const allocated_size = self.allocatedSize(self.shdr_table_offset.?);
const needed_size = self.sections.items.len * shsize;
if (needed_size > allocated_size) {
self.shdr_table_offset = null; // free the space
self.shdr_table_offset = self.findFreeSpace(needed_size, shalign);
}
switch (self.ptr_width) {
.p32 => {
const buf = try self.base.allocator.alloc(elf.Elf32_Shdr, self.sections.items.len);
defer self.base.allocator.free(buf);
for (buf) |*shdr, i| {
shdr.* = sectHeaderTo32(self.sections.items[i]);
log.debug("writing section {s}: {}", .{ self.getString(shdr.sh_name), shdr.* });
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf32_Shdr, shdr);
}
}
try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), self.shdr_table_offset.?);
},
.p64 => {
const buf = try self.base.allocator.alloc(elf.Elf64_Shdr, self.sections.items.len);
defer self.base.allocator.free(buf);
for (buf) |*shdr, i| {
shdr.* = self.sections.items[i];
log.debug("writing section {s}: {}", .{ self.getString(shdr.sh_name), shdr.* });
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf64_Shdr, shdr);
}
}
try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), self.shdr_table_offset.?);
},
}
self.shdr_table_dirty = false;
}
if (self.entry_addr == null and self.base.options.effectiveOutputMode() == .Exe) {
log.debug("flushing. no_entry_point_found = true", .{});
self.error_flags.no_entry_point_found = true;
} else {
log.debug("flushing. no_entry_point_found = false", .{});
self.error_flags.no_entry_point_found = false;
try self.writeElfHeader();
}
// The point of flush() is to commit changes, so in theory, nothing should
// be dirty after this. However, it is possible for some things to remain
// dirty because they fail to be written in the event of compile errors,
// such as debug_line_header_dirty and debug_info_header_dirty.
assert(!self.debug_abbrev_section_dirty);
assert(!self.debug_aranges_section_dirty);
assert(!self.phdr_table_dirty);
assert(!self.shdr_table_dirty);
assert(!self.shstrtab_dirty);
assert(!self.debug_strtab_dirty);
}
fn linkWithLLD(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node) !void {
const tracy = trace(@src());
defer tracy.end();
var arena_allocator = std.heap.ArenaAllocator.init(self.base.allocator);
defer arena_allocator.deinit();
const arena = arena_allocator.allocator();
const directory = self.base.options.emit.?.directory; // Just an alias to make it shorter to type.
const full_out_path = try directory.join(arena, &[_][]const u8{self.base.options.emit.?.sub_path});
// If there is no Zig code to compile, then we should skip flushing the output file because it
// will not be part of the linker line anyway.
const module_obj_path: ?[]const u8 = if (self.base.options.module) |module| blk: {
// stage1 puts the object file in the cache directory.
if (self.base.options.use_stage1) {
const obj_basename = try std.zig.binNameAlloc(arena, .{
.root_name = self.base.options.root_name,
.target = self.base.options.target,
.output_mode = .Obj,
});
switch (self.base.options.cache_mode) {
.incremental => break :blk try module.zig_cache_artifact_directory.join(
arena,
&[_][]const u8{obj_basename},
),
.whole => break :blk try fs.path.join(arena, &.{
fs.path.dirname(full_out_path).?, obj_basename,
}),
}
}
try self.flushModule(comp, prog_node);
if (fs.path.dirname(full_out_path)) |dirname| {
break :blk try fs.path.join(arena, &.{ dirname, self.base.intermediary_basename.? });
} else {
break :blk self.base.intermediary_basename.?;
}
} else null;
var sub_prog_node = prog_node.start("LLD Link", 0);
sub_prog_node.activate();
sub_prog_node.context.refresh();
defer sub_prog_node.end();
const is_obj = self.base.options.output_mode == .Obj;
const is_lib = self.base.options.output_mode == .Lib;
const is_dyn_lib = self.base.options.link_mode == .Dynamic and is_lib;
const is_exe_or_dyn_lib = is_dyn_lib or self.base.options.output_mode == .Exe;
const have_dynamic_linker = self.base.options.link_libc and
self.base.options.link_mode == .Dynamic and is_exe_or_dyn_lib;
const target = self.base.options.target;
const gc_sections = self.base.options.gc_sections orelse !is_obj;
const stack_size = self.base.options.stack_size_override orelse 16777216;
const allow_shlib_undefined = self.base.options.allow_shlib_undefined orelse !self.base.options.is_native_os;
const compiler_rt_path: ?[]const u8 = blk: {
if (comp.compiler_rt_lib) |x| break :blk x.full_object_path;
if (comp.compiler_rt_obj) |x| break :blk x.full_object_path;
break :blk null;
};
// Here we want to determine whether we can save time by not invoking LLD when the
// output is unchanged. None of the linker options or the object files that are being
// linked are in the hash that namespaces the directory we are outputting to. Therefore,
// we must hash those now, and the resulting digest will form the "id" of the linking
// job we are about to perform.
// After a successful link, we store the id in the metadata of a symlink named "id.txt" in
// the artifact directory. So, now, we check if this symlink exists, and if it matches
// our digest. If so, we can skip linking. Otherwise, we proceed with invoking LLD.
const id_symlink_basename = "lld.id";
var man: Cache.Manifest = undefined;
defer if (!self.base.options.disable_lld_caching) man.deinit();
var digest: [Cache.hex_digest_len]u8 = undefined;
if (!self.base.options.disable_lld_caching) {
man = comp.cache_parent.obtain();
// We are about to obtain this lock, so here we give other processes a chance first.
self.base.releaseLock();
comptime assert(Compilation.link_hash_implementation_version == 7);
try man.addOptionalFile(self.base.options.linker_script);
try man.addOptionalFile(self.base.options.version_script);
for (self.base.options.objects) |obj| {
_ = try man.addFile(obj.path, null);
man.hash.add(obj.must_link);
}
for (comp.c_object_table.keys()) |key| {
_ = try man.addFile(key.status.success.object_path, null);
}
try man.addOptionalFile(module_obj_path);
try man.addOptionalFile(compiler_rt_path);
// We can skip hashing libc and libc++ components that we are in charge of building from Zig
// installation sources because they are always a product of the compiler version + target information.
man.hash.addOptionalBytes(self.base.options.entry);
man.hash.addOptional(self.base.options.image_base_override);
man.hash.add(gc_sections);
man.hash.add(self.base.options.eh_frame_hdr);
man.hash.add(self.base.options.emit_relocs);
man.hash.add(self.base.options.rdynamic);
man.hash.addListOfBytes(self.base.options.lib_dirs);
man.hash.addListOfBytes(self.base.options.rpath_list);
man.hash.add(self.base.options.each_lib_rpath);
if (self.base.options.output_mode == .Exe) {
man.hash.add(stack_size);
man.hash.add(self.base.options.build_id);
}
man.hash.add(self.base.options.skip_linker_dependencies);
man.hash.add(self.base.options.z_nodelete);
man.hash.add(self.base.options.z_notext);
man.hash.add(self.base.options.z_defs);
man.hash.add(self.base.options.z_origin);
man.hash.add(self.base.options.z_nocopyreloc);
man.hash.add(self.base.options.z_now);
man.hash.add(self.base.options.z_relro);
man.hash.add(self.base.options.hash_style);
// strip does not need to go into the linker hash because it is part of the hash namespace
if (self.base.options.link_libc) {
man.hash.add(self.base.options.libc_installation != null);
if (self.base.options.libc_installation) |libc_installation| {
man.hash.addBytes(libc_installation.crt_dir.?);
}
if (have_dynamic_linker) {
man.hash.addOptionalBytes(self.base.options.dynamic_linker);
}
}
man.hash.addOptionalBytes(self.base.options.soname);
man.hash.addOptional(self.base.options.version);
link.hashAddSystemLibs(&man.hash, self.base.options.system_libs);
man.hash.add(allow_shlib_undefined);
man.hash.add(self.base.options.bind_global_refs_locally);
man.hash.add(self.base.options.compress_debug_sections);
man.hash.add(self.base.options.tsan);
man.hash.addOptionalBytes(self.base.options.sysroot);
man.hash.add(self.base.options.linker_optimization);
// We don't actually care whether it's a cache hit or miss; we just need the digest and the lock.
_ = try man.hit();
digest = man.final();
var prev_digest_buf: [digest.len]u8 = undefined;
const prev_digest: []u8 = Cache.readSmallFile(
directory.handle,
id_symlink_basename,
&prev_digest_buf,
) catch |err| blk: {
log.debug("ELF LLD new_digest={s} error: {s}", .{ std.fmt.fmtSliceHexLower(&digest), @errorName(err) });
// Handle this as a cache miss.
break :blk prev_digest_buf[0..0];
};
if (mem.eql(u8, prev_digest, &digest)) {
log.debug("ELF LLD digest={s} match - skipping invocation", .{std.fmt.fmtSliceHexLower(&digest)});
// Hot diggity dog! The output binary is already there.
self.base.lock = man.toOwnedLock();
return;
}
log.debug("ELF LLD prev_digest={s} new_digest={s}", .{ std.fmt.fmtSliceHexLower(prev_digest), std.fmt.fmtSliceHexLower(&digest) });
// We are about to change the output file to be different, so we invalidate the build hash now.
directory.handle.deleteFile(id_symlink_basename) catch |err| switch (err) {
error.FileNotFound => {},
else => |e| return e,
};
}
// Due to a deficiency in LLD, we need to special-case BPF to a simple file
// copy when generating relocatables. Normally, we would expect `lld -r` to work.
// However, because LLD wants to resolve BPF relocations which it shouldn't, it fails
// before even generating the relocatable.
if (self.base.options.output_mode == .Obj and
(self.base.options.lto or target.isBpfFreestanding()))
{
// In this case we must do a simple file copy
// here. TODO: think carefully about how we can avoid this redundant operation when doing
// build-obj. See also the corresponding TODO in linkAsArchive.
const the_object_path = blk: {
if (self.base.options.objects.len != 0)
break :blk self.base.options.objects[0].path;
if (comp.c_object_table.count() != 0)
break :blk comp.c_object_table.keys()[0].status.success.object_path;
if (module_obj_path) |p|
break :blk p;
// TODO I think this is unreachable. Audit this situation when solving the above TODO
// regarding eliding redundant object -> object transformations.
return error.NoObjectsToLink;
};
// This can happen when using --enable-cache and using the stage1 backend. In this case
// we can skip the file copy.
if (!mem.eql(u8, the_object_path, full_out_path)) {
try fs.cwd().copyFile(the_object_path, fs.cwd(), full_out_path, .{});
}
} else {
// Create an LLD command line and invoke it.
var argv = std.ArrayList([]const u8).init(self.base.allocator);
defer argv.deinit();
// We will invoke ourselves as a child process to gain access to LLD.
// This is necessary because LLD does not behave properly as a library -
// it calls exit() and does not reset all global data between invocations.
try argv.appendSlice(&[_][]const u8{ comp.self_exe_path.?, "ld.lld" });
if (is_obj) {
try argv.append("-r");
}
try argv.append("-error-limit=0");
if (self.base.options.sysroot) |sysroot| {
try argv.append(try std.fmt.allocPrint(arena, "--sysroot={s}", .{sysroot}));
}
if (self.base.options.lto) {
switch (self.base.options.optimize_mode) {
.Debug => {},
.ReleaseSmall => try argv.append("--lto-O2"),
.ReleaseFast, .ReleaseSafe => try argv.append("--lto-O3"),
}
}
try argv.append(try std.fmt.allocPrint(arena, "-O{d}", .{
self.base.options.linker_optimization,
}));
if (self.base.options.entry) |entry| {
try argv.append("--entry");
try argv.append(entry);
}
switch (self.base.options.hash_style) {
.gnu => try argv.append("--hash-style=gnu"),
.sysv => try argv.append("--hash-style=sysv"),
.both => {}, // this is the default
}
if (self.base.options.output_mode == .Exe) {
try argv.append("-z");
try argv.append(try std.fmt.allocPrint(arena, "stack-size={d}", .{stack_size}));
if (self.base.options.build_id) {
try argv.append("--build-id");
}
}
if (self.base.options.image_base_override) |image_base| {
try argv.append(try std.fmt.allocPrint(arena, "--image-base={d}", .{image_base}));
}
if (self.base.options.linker_script) |linker_script| {
try argv.append("-T");
try argv.append(linker_script);
}
if (gc_sections) {
try argv.append("--gc-sections");
}
if (self.base.options.eh_frame_hdr) {
try argv.append("--eh-frame-hdr");
}
if (self.base.options.emit_relocs) {
try argv.append("--emit-relocs");
}
if (self.base.options.rdynamic) {
try argv.append("--export-dynamic");
}
if (self.base.options.strip) {
try argv.append("-s");
}
if (self.base.options.z_nodelete) {
try argv.append("-z");
try argv.append("nodelete");
}
if (self.base.options.z_notext) {
try argv.append("-z");
try argv.append("notext");
}
if (self.base.options.z_defs) {
try argv.append("-z");
try argv.append("defs");
}
if (self.base.options.z_origin) {
try argv.append("-z");
try argv.append("origin");
}
if (self.base.options.z_nocopyreloc) {
try argv.append("-z");
try argv.append("nocopyreloc");
}
if (self.base.options.z_now) {
// LLD defaults to -zlazy
try argv.append("-znow");
}
if (!self.base.options.z_relro) {
// LLD defaults to -zrelro
try argv.append("-znorelro");
}
if (getLDMOption(target)) |ldm| {
// Any target ELF will use the freebsd osabi if suffixed with "_fbsd".
const arg = if (target.os.tag == .freebsd)
try std.fmt.allocPrint(arena, "{s}_fbsd", .{ldm})
else
ldm;
try argv.append("-m");
try argv.append(arg);
}
if (self.base.options.link_mode == .Static) {
if (target.cpu.arch.isARM() or target.cpu.arch.isThumb()) {
try argv.append("-Bstatic");
} else {
try argv.append("-static");
}
} else if (is_dyn_lib) {
try argv.append("-shared");
}
if (self.base.options.pie and self.base.options.output_mode == .Exe) {
try argv.append("-pie");
}
if (self.base.options.link_mode == .Dynamic and target.os.tag == .netbsd) {
// Add options to produce shared objects with only 2 PT_LOAD segments.
// NetBSD expects 2 PT_LOAD segments in a shared object, otherwise
// ld.elf_so fails to load, emitting a general "not found" error.
// See https://github.com/ziglang/zig/issues/9109 .
try argv.append("--no-rosegment");
try argv.append("-znorelro");
}
try argv.append("-o");
try argv.append(full_out_path);
// csu prelude
var csu = try CsuObjects.init(arena, self.base.options, comp);
if (csu.crt0) |v| try argv.append(v);
if (csu.crti) |v| try argv.append(v);
if (csu.crtbegin) |v| try argv.append(v);
// rpaths
var rpath_table = std.StringHashMap(void).init(self.base.allocator);
defer rpath_table.deinit();
for (self.base.options.rpath_list) |rpath| {
if ((try rpath_table.fetchPut(rpath, {})) == null) {
try argv.append("-rpath");
try argv.append(rpath);
}
}
if (self.base.options.each_lib_rpath) {
var test_path = std.ArrayList(u8).init(self.base.allocator);
defer test_path.deinit();
for (self.base.options.lib_dirs) |lib_dir_path| {
for (self.base.options.system_libs.keys()) |link_lib| {
test_path.clearRetainingCapacity();
const sep = fs.path.sep_str;
try test_path.writer().print("{s}" ++ sep ++ "lib{s}.so", .{
lib_dir_path, link_lib,
});
fs.cwd().access(test_path.items, .{}) catch |err| switch (err) {
error.FileNotFound => continue,
else => |e| return e,
};
if ((try rpath_table.fetchPut(lib_dir_path, {})) == null) {
try argv.append("-rpath");
try argv.append(lib_dir_path);
}
}
}
for (self.base.options.objects) |obj| {
if (Compilation.classifyFileExt(obj.path) == .shared_library) {
const lib_dir_path = std.fs.path.dirname(obj.path).?;
if ((try rpath_table.fetchPut(lib_dir_path, {})) == null) {
try argv.append("-rpath");
try argv.append(lib_dir_path);
}
}
}
}
for (self.base.options.lib_dirs) |lib_dir| {
try argv.append("-L");
try argv.append(lib_dir);
}
if (self.base.options.link_libc) {
if (self.base.options.libc_installation) |libc_installation| {
try argv.append("-L");
try argv.append(libc_installation.crt_dir.?);
}
if (have_dynamic_linker) {
if (self.base.options.dynamic_linker) |dynamic_linker| {
try argv.append("-dynamic-linker");
try argv.append(dynamic_linker);
}
}
}
if (is_dyn_lib) {
if (self.base.options.soname) |soname| {
try argv.append("-soname");
try argv.append(soname);
}
if (self.base.options.version_script) |version_script| {
try argv.append("-version-script");
try argv.append(version_script);
}
}
// Positional arguments to the linker such as object files.
var whole_archive = false;
for (self.base.options.objects) |obj| {
if (obj.must_link and !whole_archive) {
try argv.append("-whole-archive");
whole_archive = true;
} else if (!obj.must_link and whole_archive) {
try argv.append("-no-whole-archive");
whole_archive = false;
}
try argv.append(obj.path);
}
if (whole_archive) {
try argv.append("-no-whole-archive");
whole_archive = false;
}
for (comp.c_object_table.keys()) |key| {
try argv.append(key.status.success.object_path);
}
if (module_obj_path) |p| {
try argv.append(p);
}
// TSAN
if (self.base.options.tsan) {
try argv.append(comp.tsan_static_lib.?.full_object_path);
}
// libc
if (is_exe_or_dyn_lib and
!self.base.options.skip_linker_dependencies and
!self.base.options.link_libc)
{
if (comp.libc_static_lib) |lib| {
try argv.append(lib.full_object_path);
}
}
// stack-protector.
// Related: https://github.com/ziglang/zig/issues/7265
if (comp.libssp_static_lib) |ssp| {
try argv.append(ssp.full_object_path);
}
// compiler-rt
if (compiler_rt_path) |p| {
try argv.append(p);
}
// Shared libraries.
if (is_exe_or_dyn_lib) {
const system_libs = self.base.options.system_libs.keys();
const system_libs_values = self.base.options.system_libs.values();
// Worst-case, we need an --as-needed argument for every lib, as well
// as one before and one after.
try argv.ensureUnusedCapacity(system_libs.len * 2 + 2);
argv.appendAssumeCapacity("--as-needed");
var as_needed = true;
for (system_libs) |link_lib, i| {
const lib_as_needed = !system_libs_values[i].needed;
switch ((@as(u2, @boolToInt(lib_as_needed)) << 1) | @boolToInt(as_needed)) {
0b00, 0b11 => {},
0b01 => {
argv.appendAssumeCapacity("--no-as-needed");
as_needed = false;
},
0b10 => {
argv.appendAssumeCapacity("--as-needed");
as_needed = true;
},
}
// By this time, we depend on these libs being dynamically linked
// libraries and not static libraries (the check for that needs to be earlier),
// but they could be full paths to .so files, in which case we
// want to avoid prepending "-l".
const ext = Compilation.classifyFileExt(link_lib);
const arg = if (ext == .shared_library) link_lib else try std.fmt.allocPrint(arena, "-l{s}", .{link_lib});
argv.appendAssumeCapacity(arg);
}
if (!as_needed) {
argv.appendAssumeCapacity("--as-needed");
as_needed = true;
}
// libc++ dep
if (self.base.options.link_libcpp) {
try argv.append(comp.libcxxabi_static_lib.?.full_object_path);
try argv.append(comp.libcxx_static_lib.?.full_object_path);
}
// libunwind dep
if (self.base.options.link_libunwind) {
try argv.append(comp.libunwind_static_lib.?.full_object_path);
}
// libc dep
self.error_flags.missing_libc = false;
if (self.base.options.link_libc) {
if (self.base.options.libc_installation != null) {
const needs_grouping = self.base.options.link_mode == .Static;
if (needs_grouping) try argv.append("--start-group");
try argv.appendSlice(target_util.libcFullLinkFlags(target));
if (needs_grouping) try argv.append("--end-group");
} else if (target.isGnuLibC()) {
for (glibc.libs) |lib| {
const lib_path = try std.fmt.allocPrint(arena, "{s}{c}lib{s}.so.{d}", .{
comp.glibc_so_files.?.dir_path, fs.path.sep, lib.name, lib.sover,
});
try argv.append(lib_path);
}
try argv.append(try comp.get_libc_crt_file(arena, "libc_nonshared.a"));
} else if (target.isMusl()) {
try argv.append(try comp.get_libc_crt_file(arena, switch (self.base.options.link_mode) {
.Static => "libc.a",
.Dynamic => "libc.so",
}));
} else {
self.error_flags.missing_libc = true;
return error.FlushFailure;
}
}
}
// crt postlude
if (csu.crtend) |v| try argv.append(v);
if (csu.crtn) |v| try argv.append(v);
if (allow_shlib_undefined) {
try argv.append("--allow-shlib-undefined");
}
switch (self.base.options.compress_debug_sections) {
.none => {},
.zlib => try argv.append("--compress-debug-sections=zlib"),
}
if (self.base.options.bind_global_refs_locally) {
try argv.append("-Bsymbolic");
}
if (self.base.options.verbose_link) {
// Skip over our own name so that the LLD linker name is the first argv item.
Compilation.dump_argv(argv.items[1..]);
}
if (std.process.can_spawn) {
// If possible, we run LLD as a child process because it does not always
// behave properly as a library, unfortunately.
// https://github.com/ziglang/zig/issues/3825
var child = std.ChildProcess.init(argv.items, arena);
if (comp.clang_passthrough_mode) {
child.stdin_behavior = .Inherit;
child.stdout_behavior = .Inherit;
child.stderr_behavior = .Inherit;
const term = child.spawnAndWait() catch |err| {
log.err("unable to spawn {s}: {s}", .{ argv.items[0], @errorName(err) });
return error.UnableToSpawnSelf;
};
switch (term) {
.Exited => |code| {
if (code != 0) {
std.process.exit(code);
}
},
else => std.process.abort(),
}
} else {
child.stdin_behavior = .Ignore;
child.stdout_behavior = .Ignore;
child.stderr_behavior = .Pipe;
try child.spawn();
const stderr = try child.stderr.?.reader().readAllAlloc(arena, 10 * 1024 * 1024);
const term = child.wait() catch |err| {
log.err("unable to spawn {s}: {s}", .{ argv.items[0], @errorName(err) });
return error.UnableToSpawnSelf;
};
switch (term) {
.Exited => |code| {
if (code != 0) {
// TODO parse this output and surface with the Compilation API rather than
// directly outputting to stderr here.
std.debug.print("{s}", .{stderr});
return error.LLDReportedFailure;
}
},
else => {
log.err("{s} terminated with stderr:\n{s}", .{ argv.items[0], stderr });
return error.LLDCrashed;
},
}
if (stderr.len != 0) {
log.warn("unexpected LLD stderr:\n{s}", .{stderr});
}
}
} else {
const exit_code = try lldMain(arena, argv.items, false);
if (exit_code != 0) {
if (comp.clang_passthrough_mode) {
std.process.exit(exit_code);
} else {
return error.LLDReportedFailure;
}
}
}
}
if (!self.base.options.disable_lld_caching) {
// Update the file with the digest. If it fails we can continue; it only
// means that the next invocation will have an unnecessary cache miss.
Cache.writeSmallFile(directory.handle, id_symlink_basename, &digest) catch |err| {
log.warn("failed to save linking hash digest file: {s}", .{@errorName(err)});
};
// Again failure here only means an unnecessary cache miss.
man.writeManifest() catch |err| {
log.warn("failed to write cache manifest when linking: {s}", .{@errorName(err)});
};
// We hang on to this lock so that the output file path can be used without
// other processes clobbering it.
self.base.lock = man.toOwnedLock();
}
}
fn writeDwarfAddrAssumeCapacity(self: *Elf, buf: *std.ArrayList(u8), addr: u64) void {
const target_endian = self.base.options.target.cpu.arch.endian();
switch (self.ptr_width) {
.p32 => mem.writeInt(u32, buf.addManyAsArrayAssumeCapacity(4), @intCast(u32, addr), target_endian),
.p64 => mem.writeInt(u64, buf.addManyAsArrayAssumeCapacity(8), addr, target_endian),
}
}
fn writeElfHeader(self: *Elf) !void {
var hdr_buf: [@sizeOf(elf.Elf64_Ehdr)]u8 = undefined;
var index: usize = 0;
hdr_buf[0..4].* = elf.MAGIC.*;
index += 4;
hdr_buf[index] = switch (self.ptr_width) {
.p32 => elf.ELFCLASS32,
.p64 => elf.ELFCLASS64,
};
index += 1;
const endian = self.base.options.target.cpu.arch.endian();
hdr_buf[index] = switch (endian) {
.Little => elf.ELFDATA2LSB,
.Big => elf.ELFDATA2MSB,
};
index += 1;
hdr_buf[index] = 1; // ELF version
index += 1;
// OS ABI, often set to 0 regardless of target platform
// ABI Version, possibly used by glibc but not by static executables
// padding
mem.set(u8, hdr_buf[index..][0..9], 0);
index += 9;
assert(index == 16);
const elf_type = switch (self.base.options.effectiveOutputMode()) {
.Exe => elf.ET.EXEC,
.Obj => elf.ET.REL,
.Lib => switch (self.base.options.link_mode) {
.Static => elf.ET.REL,
.Dynamic => elf.ET.DYN,
},
};
mem.writeInt(u16, hdr_buf[index..][0..2], @enumToInt(elf_type), endian);
index += 2;
const machine = self.base.options.target.cpu.arch.toElfMachine();
mem.writeInt(u16, hdr_buf[index..][0..2], @enumToInt(machine), endian);
index += 2;
// ELF Version, again
mem.writeInt(u32, hdr_buf[index..][0..4], 1, endian);
index += 4;
const e_entry = if (elf_type == .REL) 0 else self.entry_addr.?;
switch (self.ptr_width) {
.p32 => {
mem.writeInt(u32, hdr_buf[index..][0..4], @intCast(u32, e_entry), endian);
index += 4;
// e_phoff
mem.writeInt(u32, hdr_buf[index..][0..4], @intCast(u32, self.phdr_table_offset.?), endian);
index += 4;
// e_shoff
mem.writeInt(u32, hdr_buf[index..][0..4], @intCast(u32, self.shdr_table_offset.?), endian);
index += 4;
},
.p64 => {
// e_entry
mem.writeInt(u64, hdr_buf[index..][0..8], e_entry, endian);
index += 8;
// e_phoff
mem.writeInt(u64, hdr_buf[index..][0..8], self.phdr_table_offset.?, endian);
index += 8;
// e_shoff
mem.writeInt(u64, hdr_buf[index..][0..8], self.shdr_table_offset.?, endian);
index += 8;
},
}
const e_flags = 0;
mem.writeInt(u32, hdr_buf[index..][0..4], e_flags, endian);
index += 4;
const e_ehsize: u16 = switch (self.ptr_width) {
.p32 => @sizeOf(elf.Elf32_Ehdr),
.p64 => @sizeOf(elf.Elf64_Ehdr),
};
mem.writeInt(u16, hdr_buf[index..][0..2], e_ehsize, endian);
index += 2;
const e_phentsize: u16 = switch (self.ptr_width) {
.p32 => @sizeOf(elf.Elf32_Phdr),
.p64 => @sizeOf(elf.Elf64_Phdr),
};
mem.writeInt(u16, hdr_buf[index..][0..2], e_phentsize, endian);
index += 2;
const e_phnum = @intCast(u16, self.program_headers.items.len);
mem.writeInt(u16, hdr_buf[index..][0..2], e_phnum, endian);
index += 2;
const e_shentsize: u16 = switch (self.ptr_width) {
.p32 => @sizeOf(elf.Elf32_Shdr),
.p64 => @sizeOf(elf.Elf64_Shdr),
};
mem.writeInt(u16, hdr_buf[index..][0..2], e_shentsize, endian);
index += 2;
const e_shnum = @intCast(u16, self.sections.items.len);
mem.writeInt(u16, hdr_buf[index..][0..2], e_shnum, endian);
index += 2;
mem.writeInt(u16, hdr_buf[index..][0..2], self.shstrtab_index.?, endian);
index += 2;
assert(index == e_ehsize);
try self.base.file.?.pwriteAll(hdr_buf[0..index], 0);
}
fn freeTextBlock(self: *Elf, text_block: *TextBlock, phdr_index: u16) void {
const local_sym = self.local_symbols.items[text_block.local_sym_index];
const name_str_index = local_sym.st_name;
const name = self.getString(name_str_index);
log.debug("freeTextBlock {*} ({s})", .{ text_block, name });
const free_list = self.atom_free_lists.getPtr(phdr_index).?;
var already_have_free_list_node = false;
{
var i: usize = 0;
// TODO turn free_list into a hash map
while (i < free_list.items.len) {
if (free_list.items[i] == text_block) {
_ = free_list.swapRemove(i);
continue;
}
if (free_list.items[i] == text_block.prev) {
already_have_free_list_node = true;
}
i += 1;
}
}
if (self.atoms.getPtr(phdr_index)) |last_block| {
if (last_block.* == text_block) {
if (text_block.prev) |prev| {
// TODO shrink the section size here
last_block.* = prev;
} else {
_ = self.atoms.fetchRemove(phdr_index);
}
}
}
if (text_block.prev) |prev| {
prev.next = text_block.next;
if (!already_have_free_list_node and prev.freeListEligible(self.*)) {
// The free list is heuristics, it doesn't have to be perfect, so we can
// ignore the OOM here.
free_list.append(self.base.allocator, prev) catch {};
}
} else {
text_block.prev = null;
}
if (text_block.next) |next| {
next.prev = text_block.prev;
} else {
text_block.next = null;
}
if (self.dwarf) |*dw| {
dw.freeAtom(&text_block.dbg_info_atom);
}
}
fn shrinkTextBlock(self: *Elf, text_block: *TextBlock, new_block_size: u64, phdr_index: u16) void {
_ = self;
_ = text_block;
_ = new_block_size;
_ = phdr_index;
}
fn growTextBlock(self: *Elf, text_block: *TextBlock, new_block_size: u64, alignment: u64, phdr_index: u16) !u64 {
const sym = self.local_symbols.items[text_block.local_sym_index];
const align_ok = mem.alignBackwardGeneric(u64, sym.st_value, alignment) == sym.st_value;
const need_realloc = !align_ok or new_block_size > text_block.capacity(self.*);
if (!need_realloc) return sym.st_value;
return self.allocateTextBlock(text_block, new_block_size, alignment, phdr_index);
}
fn allocateTextBlock(self: *Elf, text_block: *TextBlock, new_block_size: u64, alignment: u64, phdr_index: u16) !u64 {
const shdr_index = self.phdr_shdr_table.get(phdr_index).?;
const phdr = &self.program_headers.items[phdr_index];
const shdr = &self.sections.items[shdr_index];
const new_block_ideal_capacity = padToIdeal(new_block_size);
// We use these to indicate our intention to update metadata, placing the new block,
// and possibly removing a free list node.
// It would be simpler to do it inside the for loop below, but that would cause a
// problem if an error was returned later in the function. So this action
// is actually carried out at the end of the function, when errors are no longer possible.
var block_placement: ?*TextBlock = null;
var free_list_removal: ?usize = null;
var free_list = self.atom_free_lists.get(phdr_index).?;
// First we look for an appropriately sized free list node.
// The list is unordered. We'll just take the first thing that works.
const vaddr = blk: {
var i: usize = 0;
while (i < free_list.items.len) {
const big_block = free_list.items[i];
// We now have a pointer to a live text block that has too much capacity.
// Is it enough that we could fit this new text block?
const sym = self.local_symbols.items[big_block.local_sym_index];
const capacity = big_block.capacity(self.*);
const ideal_capacity = padToIdeal(capacity);
const ideal_capacity_end_vaddr = std.math.add(u64, sym.st_value, ideal_capacity) catch ideal_capacity;
const capacity_end_vaddr = sym.st_value + capacity;
const new_start_vaddr_unaligned = capacity_end_vaddr - new_block_ideal_capacity;
const new_start_vaddr = mem.alignBackwardGeneric(u64, new_start_vaddr_unaligned, alignment);
if (new_start_vaddr < ideal_capacity_end_vaddr) {
// Additional bookkeeping here to notice if this free list node
// should be deleted because the block that it points to has grown to take up
// more of the extra capacity.
if (!big_block.freeListEligible(self.*)) {
_ = free_list.swapRemove(i);
} else {
i += 1;
}
continue;
}
// At this point we know that we will place the new block here. But the
// remaining question is whether there is still yet enough capacity left
// over for there to still be a free list node.
const remaining_capacity = new_start_vaddr - ideal_capacity_end_vaddr;
const keep_free_list_node = remaining_capacity >= min_text_capacity;
// Set up the metadata to be updated, after errors are no longer possible.
block_placement = big_block;
if (!keep_free_list_node) {
free_list_removal = i;
}
break :blk new_start_vaddr;
} else if (self.atoms.get(phdr_index)) |last| {
const sym = self.local_symbols.items[last.local_sym_index];
const ideal_capacity = padToIdeal(sym.st_size);
const ideal_capacity_end_vaddr = sym.st_value + ideal_capacity;
const new_start_vaddr = mem.alignForwardGeneric(u64, ideal_capacity_end_vaddr, alignment);
// Set up the metadata to be updated, after errors are no longer possible.
block_placement = last;
break :blk new_start_vaddr;
} else {
break :blk phdr.p_vaddr;
}
};
const expand_text_section = block_placement == null or block_placement.?.next == null;
if (expand_text_section) {
const text_capacity = self.allocatedSize(shdr.sh_offset);
const needed_size = (vaddr + new_block_size) - phdr.p_vaddr;
if (needed_size > text_capacity) {
// Must move the entire section.
const new_offset = self.findFreeSpace(needed_size, self.page_size);
const text_size = if (self.atoms.get(phdr_index)) |last| blk: {
const sym = self.local_symbols.items[last.local_sym_index];
break :blk (sym.st_value + sym.st_size) - phdr.p_vaddr;
} else 0;
log.debug("new PT_LOAD file offset 0x{x} to 0x{x}", .{ new_offset, new_offset + text_size });
const amt = try self.base.file.?.copyRangeAll(shdr.sh_offset, self.base.file.?, new_offset, text_size);
if (amt != text_size) return error.InputOutput;
shdr.sh_offset = new_offset;
phdr.p_offset = new_offset;
}
_ = try self.atoms.put(self.base.allocator, phdr_index, text_block);
shdr.sh_size = needed_size;
phdr.p_memsz = needed_size;
phdr.p_filesz = needed_size;
if (self.dwarf) |_| {
// The .debug_info section has `low_pc` and `high_pc` values which is the virtual address
// range of the compilation unit. When we expand the text section, this range changes,
// so the DW_TAG.compile_unit tag of the .debug_info section becomes dirty.
self.debug_info_header_dirty = true;
// This becomes dirty for the same reason. We could potentially make this more
// fine-grained with the addition of support for more compilation units. It is planned to
// model each package as a different compilation unit.
self.debug_aranges_section_dirty = true;
}
self.phdr_table_dirty = true; // TODO look into making only the one program header dirty
self.shdr_table_dirty = true; // TODO look into making only the one section dirty
}
shdr.sh_addralign = math.max(shdr.sh_addralign, alignment);
// This function can also reallocate a text block.
// In this case we need to "unplug" it from its previous location before
// plugging it in to its new location.
if (text_block.prev) |prev| {
prev.next = text_block.next;
}
if (text_block.next) |next| {
next.prev = text_block.prev;
}
if (block_placement) |big_block| {
text_block.prev = big_block;
text_block.next = big_block.next;
big_block.next = text_block;
} else {
text_block.prev = null;
text_block.next = null;
}
if (free_list_removal) |i| {
_ = free_list.swapRemove(i);
}
return vaddr;
}
fn allocateLocalSymbol(self: *Elf) !u32 {
try self.local_symbols.ensureUnusedCapacity(self.base.allocator, 1);
const index = blk: {
if (self.local_symbol_free_list.popOrNull()) |index| {
log.debug(" (reusing symbol index {d})", .{index});
break :blk index;
} else {
log.debug(" (allocating symbol index {d})", .{self.local_symbols.items.len});
const index = @intCast(u32, self.local_symbols.items.len);
_ = self.local_symbols.addOneAssumeCapacity();
break :blk index;
}
};
self.local_symbols.items[index] = .{
.st_name = 0,
.st_info = 0,
.st_other = 0,
.st_shndx = 0,
.st_value = 0,
.st_size = 0,
};
return index;
}
pub fn allocateDeclIndexes(self: *Elf, decl_index: Module.Decl.Index) !void {
if (self.llvm_object) |_| return;
const mod = self.base.options.module.?;
const decl = mod.declPtr(decl_index);
if (decl.link.elf.local_sym_index != 0) return;
try self.offset_table.ensureUnusedCapacity(self.base.allocator, 1);
try self.decls.putNoClobber(self.base.allocator, decl_index, null);
const decl_name = try decl.getFullyQualifiedName(mod);
defer self.base.allocator.free(decl_name);
log.debug("allocating symbol indexes for {s}", .{decl_name});
decl.link.elf.local_sym_index = try self.allocateLocalSymbol();
try self.atom_by_index_table.putNoClobber(self.base.allocator, decl.link.elf.local_sym_index, &decl.link.elf);
if (self.offset_table_free_list.popOrNull()) |i| {
decl.link.elf.offset_table_index = i;
} else {
decl.link.elf.offset_table_index = @intCast(u32, self.offset_table.items.len);
_ = self.offset_table.addOneAssumeCapacity();
self.offset_table_count_dirty = true;
}
self.offset_table.items[decl.link.elf.offset_table_index] = 0;
}
fn freeUnnamedConsts(self: *Elf, decl_index: Module.Decl.Index) void {
const unnamed_consts = self.unnamed_const_atoms.getPtr(decl_index) orelse return;
for (unnamed_consts.items) |atom| {
self.freeTextBlock(atom, self.phdr_load_ro_index.?);
self.local_symbol_free_list.append(self.base.allocator, atom.local_sym_index) catch {};
self.local_symbols.items[atom.local_sym_index].st_info = 0;
_ = self.atom_by_index_table.remove(atom.local_sym_index);
}
unnamed_consts.clearAndFree(self.base.allocator);
}
pub fn freeDecl(self: *Elf, decl_index: Module.Decl.Index) void {
if (build_options.have_llvm) {
if (self.llvm_object) |llvm_object| return llvm_object.freeDecl(decl_index);
}
const mod = self.base.options.module.?;
const decl = mod.declPtr(decl_index);
const kv = self.decls.fetchRemove(decl_index);
if (kv.?.value) |index| {
self.freeTextBlock(&decl.link.elf, index);
self.freeUnnamedConsts(decl_index);
}
// Appending to free lists is allowed to fail because the free lists are heuristics based anyway.
if (decl.link.elf.local_sym_index != 0) {
self.local_symbol_free_list.append(self.base.allocator, decl.link.elf.local_sym_index) catch {};
self.local_symbols.items[decl.link.elf.local_sym_index].st_info = 0;
_ = self.atom_by_index_table.remove(decl.link.elf.local_sym_index);
decl.link.elf.local_sym_index = 0;
self.offset_table_free_list.append(self.base.allocator, decl.link.elf.offset_table_index) catch {};
}
if (self.dwarf) |*dw| {
dw.freeDecl(decl);
}
}
fn getDeclPhdrIndex(self: *Elf, decl: *Module.Decl) !u16 {
const ty = decl.ty;
const zig_ty = ty.zigTypeTag();
const val = decl.val;
const phdr_index: u16 = blk: {
if (val.isUndefDeep()) {
// TODO in release-fast and release-small, we should put undef in .bss
break :blk self.phdr_load_rw_index.?;
}
switch (zig_ty) {
.Fn => break :blk self.phdr_load_re_index.?,
else => {
if (val.castTag(.variable)) |_| {
break :blk self.phdr_load_rw_index.?;
}
break :blk self.phdr_load_ro_index.?;
},
}
};
return phdr_index;
}
fn updateDeclCode(self: *Elf, decl_index: Module.Decl.Index, code: []const u8, stt_bits: u8) !*elf.Elf64_Sym {
const mod = self.base.options.module.?;
const decl = mod.declPtr(decl_index);
const decl_name = try decl.getFullyQualifiedName(mod);
defer self.base.allocator.free(decl_name);
log.debug("updateDeclCode {s}{*}", .{ decl_name, decl });
const required_alignment = decl.getAlignment(self.base.options.target);
const decl_ptr = self.decls.getPtr(decl_index).?;
if (decl_ptr.* == null) {
decl_ptr.* = try self.getDeclPhdrIndex(decl);
}
const phdr_index = decl_ptr.*.?;
const shdr_index = self.phdr_shdr_table.get(phdr_index).?;
assert(decl.link.elf.local_sym_index != 0); // Caller forgot to allocateDeclIndexes()
const local_sym = &self.local_symbols.items[decl.link.elf.local_sym_index];
if (local_sym.st_size != 0) {
const capacity = decl.link.elf.capacity(self.*);
const need_realloc = code.len > capacity or
!mem.isAlignedGeneric(u64, local_sym.st_value, required_alignment);
if (need_realloc) {
const vaddr = try self.growTextBlock(&decl.link.elf, code.len, required_alignment, phdr_index);
log.debug("growing {s} from 0x{x} to 0x{x}", .{ decl_name, local_sym.st_value, vaddr });
if (vaddr != local_sym.st_value) {
local_sym.st_value = vaddr;
log.debug(" (writing new offset table entry)", .{});
self.offset_table.items[decl.link.elf.offset_table_index] = vaddr;
try self.writeOffsetTableEntry(decl.link.elf.offset_table_index);
}
} else if (code.len < local_sym.st_size) {
self.shrinkTextBlock(&decl.link.elf, code.len, phdr_index);
}
local_sym.st_size = code.len;
local_sym.st_name = try self.updateString(local_sym.st_name, decl_name);
local_sym.st_info = (elf.STB_LOCAL << 4) | stt_bits;
local_sym.st_other = 0;
local_sym.st_shndx = shdr_index;
// TODO this write could be avoided if no fields of the symbol were changed.
try self.writeSymbol(decl.link.elf.local_sym_index);
} else {
const name_str_index = try self.makeString(decl_name);
const vaddr = try self.allocateTextBlock(&decl.link.elf, code.len, required_alignment, phdr_index);
errdefer self.freeTextBlock(&decl.link.elf, phdr_index);
log.debug("allocated text block for {s} at 0x{x}", .{ decl_name, vaddr });
local_sym.* = .{
.st_name = name_str_index,
.st_info = (elf.STB_LOCAL << 4) | stt_bits,
.st_other = 0,
.st_shndx = shdr_index,
.st_value = vaddr,
.st_size = code.len,
};
self.offset_table.items[decl.link.elf.offset_table_index] = vaddr;
try self.writeSymbol(decl.link.elf.local_sym_index);
try self.writeOffsetTableEntry(decl.link.elf.offset_table_index);
}
const section_offset = local_sym.st_value - self.program_headers.items[phdr_index].p_vaddr;
const file_offset = self.sections.items[shdr_index].sh_offset + section_offset;
try self.base.file.?.pwriteAll(code, file_offset);
return local_sym;
}
pub fn updateFunc(self: *Elf, module: *Module, func: *Module.Fn, air: Air, liveness: Liveness) !void {
if (build_options.skip_non_native and builtin.object_format != .elf) {
@panic("Attempted to compile for object format that was disabled by build configuration");
}
if (build_options.have_llvm) {
if (self.llvm_object) |llvm_object| return llvm_object.updateFunc(module, func, air, liveness);
}
const tracy = trace(@src());
defer tracy.end();
var code_buffer = std.ArrayList(u8).init(self.base.allocator);
defer code_buffer.deinit();
const decl_index = func.owner_decl;
const decl = module.declPtr(decl_index);
self.freeUnnamedConsts(decl_index);
var decl_state: ?Dwarf.DeclState = if (self.dwarf) |*dw| try dw.initDeclState(module, decl) else null;
defer if (decl_state) |*ds| ds.deinit();
const res = if (decl_state) |*ds|
try codegen.generateFunction(&self.base, decl.srcLoc(), func, air, liveness, &code_buffer, .{
.dwarf = ds,
})
else
try codegen.generateFunction(&self.base, decl.srcLoc(), func, air, liveness, &code_buffer, .none);
const code = switch (res) {
.appended => code_buffer.items,
.fail => |em| {
decl.analysis = .codegen_failure;
try module.failed_decls.put(module.gpa, decl_index, em);
return;
},
};
const local_sym = try self.updateDeclCode(decl_index, code, elf.STT_FUNC);
if (decl_state) |*ds| {
try self.dwarf.?.commitDeclState(
&self.base,
module,
decl,
local_sym.st_value,
local_sym.st_size,
ds,
);
}
// Since we updated the vaddr and the size, each corresponding export symbol also needs to be updated.
const decl_exports = module.decl_exports.get(decl_index) orelse &[0]*Module.Export{};
return self.updateDeclExports(module, decl_index, decl_exports);
}
pub fn updateDecl(self: *Elf, module: *Module, decl_index: Module.Decl.Index) !void {
if (build_options.skip_non_native and builtin.object_format != .elf) {
@panic("Attempted to compile for object format that was disabled by build configuration");
}
if (build_options.have_llvm) {
if (self.llvm_object) |llvm_object| return llvm_object.updateDecl(module, decl_index);
}
const tracy = trace(@src());
defer tracy.end();
const decl = module.declPtr(decl_index);
if (decl.val.tag() == .extern_fn) {
return; // TODO Should we do more when front-end analyzed extern decl?
}
if (decl.val.castTag(.variable)) |payload| {
const variable = payload.data;
if (variable.is_extern) {
return; // TODO Should we do more when front-end analyzed extern decl?
}
}
assert(!self.unnamed_const_atoms.contains(decl_index));
var code_buffer = std.ArrayList(u8).init(self.base.allocator);
defer code_buffer.deinit();
var decl_state: ?Dwarf.DeclState = if (self.dwarf) |*dw| try dw.initDeclState(module, decl) else null;
defer if (decl_state) |*ds| ds.deinit();
// TODO implement .debug_info for global variables
const decl_val = if (decl.val.castTag(.variable)) |payload| payload.data.init else decl.val;
const res = if (decl_state) |*ds|
try codegen.generateSymbol(&self.base, decl.srcLoc(), .{
.ty = decl.ty,
.val = decl_val,
}, &code_buffer, .{
.dwarf = ds,
}, .{
.parent_atom_index = decl.link.elf.local_sym_index,
})
else
try codegen.generateSymbol(&self.base, decl.srcLoc(), .{
.ty = decl.ty,
.val = decl_val,
}, &code_buffer, .none, .{
.parent_atom_index = decl.link.elf.local_sym_index,
});
const code = switch (res) {
.externally_managed => |x| x,
.appended => code_buffer.items,
.fail => |em| {
decl.analysis = .codegen_failure;
try module.failed_decls.put(module.gpa, decl_index, em);
return;
},
};
const local_sym = try self.updateDeclCode(decl_index, code, elf.STT_OBJECT);
if (decl_state) |*ds| {
try self.dwarf.?.commitDeclState(
&self.base,
module,
decl,
local_sym.st_value,
local_sym.st_size,
ds,
);
}
// Since we updated the vaddr and the size, each corresponding export symbol also needs to be updated.
const decl_exports = module.decl_exports.get(decl_index) orelse &[0]*Module.Export{};
return self.updateDeclExports(module, decl_index, decl_exports);
}
pub fn lowerUnnamedConst(self: *Elf, typed_value: TypedValue, decl_index: Module.Decl.Index) !u32 {
var code_buffer = std.ArrayList(u8).init(self.base.allocator);
defer code_buffer.deinit();
const mod = self.base.options.module.?;
const decl = mod.declPtr(decl_index);
const gop = try self.unnamed_const_atoms.getOrPut(self.base.allocator, decl_index);
if (!gop.found_existing) {
gop.value_ptr.* = .{};
}
const unnamed_consts = gop.value_ptr;
const atom = try self.base.allocator.create(TextBlock);
errdefer self.base.allocator.destroy(atom);
atom.* = TextBlock.empty;
try self.managed_atoms.append(self.base.allocator, atom);
const name_str_index = blk: {
const decl_name = try decl.getFullyQualifiedName(mod);
defer self.base.allocator.free(decl_name);
const index = unnamed_consts.items.len;
const name = try std.fmt.allocPrint(self.base.allocator, "__unnamed_{s}_{d}", .{ decl_name, index });
defer self.base.allocator.free(name);
break :blk try self.makeString(name);
};
const name = self.getString(name_str_index);
log.debug("allocating symbol indexes for {s}", .{name});
atom.local_sym_index = try self.allocateLocalSymbol();
try self.atom_by_index_table.putNoClobber(self.base.allocator, atom.local_sym_index, atom);
const res = try codegen.generateSymbol(&self.base, decl.srcLoc(), typed_value, &code_buffer, .{
.none = {},
}, .{
.parent_atom_index = atom.local_sym_index,
});
const code = switch (res) {
.externally_managed => |x| x,
.appended => code_buffer.items,
.fail => |em| {
decl.analysis = .codegen_failure;
try mod.failed_decls.put(mod.gpa, decl_index, em);
log.err("{s}", .{em.msg});
return error.AnalysisFail;
},
};
const required_alignment = typed_value.ty.abiAlignment(self.base.options.target);
const phdr_index = self.phdr_load_ro_index.?;
const shdr_index = self.phdr_shdr_table.get(phdr_index).?;
const vaddr = try self.allocateTextBlock(atom, code.len, required_alignment, phdr_index);
errdefer self.freeTextBlock(atom, phdr_index);
log.debug("allocated text block for {s} at 0x{x}", .{ name, vaddr });
const local_sym = &self.local_symbols.items[atom.local_sym_index];
local_sym.* = .{
.st_name = name_str_index,
.st_info = (elf.STB_LOCAL << 4) | elf.STT_OBJECT,
.st_other = 0,
.st_shndx = shdr_index,
.st_value = vaddr,
.st_size = code.len,
};
try self.writeSymbol(atom.local_sym_index);
try unnamed_consts.append(self.base.allocator, atom);
const section_offset = local_sym.st_value - self.program_headers.items[phdr_index].p_vaddr;
const file_offset = self.sections.items[shdr_index].sh_offset + section_offset;
try self.base.file.?.pwriteAll(code, file_offset);
return atom.local_sym_index;
}
pub fn updateDeclExports(
self: *Elf,
module: *Module,
decl_index: Module.Decl.Index,
exports: []const *Module.Export,
) !void {
if (build_options.skip_non_native and builtin.object_format != .elf) {
@panic("Attempted to compile for object format that was disabled by build configuration");
}
if (build_options.have_llvm) {
if (self.llvm_object) |llvm_object| return llvm_object.updateDeclExports(module, decl_index, exports);
}
const tracy = trace(@src());
defer tracy.end();
try self.global_symbols.ensureUnusedCapacity(self.base.allocator, exports.len);
const decl = module.declPtr(decl_index);
if (decl.link.elf.local_sym_index == 0) return;
const decl_sym = self.local_symbols.items[decl.link.elf.local_sym_index];
const decl_ptr = self.decls.getPtr(decl_index).?;
if (decl_ptr.* == null) {
decl_ptr.* = try self.getDeclPhdrIndex(decl);
}
const phdr_index = decl_ptr.*.?;
const shdr_index = self.phdr_shdr_table.get(phdr_index).?;
for (exports) |exp| {
if (exp.options.section) |section_name| {
if (!mem.eql(u8, section_name, ".text")) {
try module.failed_exports.ensureUnusedCapacity(module.gpa, 1);
module.failed_exports.putAssumeCapacityNoClobber(
exp,
try Module.ErrorMsg.create(self.base.allocator, decl.srcLoc(), "Unimplemented: ExportOptions.section", .{}),
);
continue;
}
}
const stb_bits: u8 = switch (exp.options.linkage) {
.Internal => elf.STB_LOCAL,
.Strong => blk: {
const entry_name = self.base.options.entry orelse "_start";
if (mem.eql(u8, exp.options.name, entry_name)) {
self.entry_addr = decl_sym.st_value;
}
break :blk elf.STB_GLOBAL;
},
.Weak => elf.STB_WEAK,
.LinkOnce => {
try module.failed_exports.ensureUnusedCapacity(module.gpa, 1);
module.failed_exports.putAssumeCapacityNoClobber(
exp,
try Module.ErrorMsg.create(self.base.allocator, decl.srcLoc(), "Unimplemented: GlobalLinkage.LinkOnce", .{}),
);
continue;
},
};
const stt_bits: u8 = @truncate(u4, decl_sym.st_info);
if (exp.link.elf.sym_index) |i| {
const sym = &self.global_symbols.items[i];
sym.* = .{
.st_name = try self.updateString(sym.st_name, exp.options.name),
.st_info = (stb_bits << 4) | stt_bits,
.st_other = 0,
.st_shndx = shdr_index,
.st_value = decl_sym.st_value,
.st_size = decl_sym.st_size,
};
} else {
const name = try self.makeString(exp.options.name);
const i = if (self.global_symbol_free_list.popOrNull()) |i| i else blk: {
_ = self.global_symbols.addOneAssumeCapacity();
break :blk self.global_symbols.items.len - 1;
};
self.global_symbols.items[i] = .{
.st_name = name,
.st_info = (stb_bits << 4) | stt_bits,
.st_other = 0,
.st_shndx = shdr_index,
.st_value = decl_sym.st_value,
.st_size = decl_sym.st_size,
};
exp.link.elf.sym_index = @intCast(u32, i);
}
}
}
/// Must be called only after a successful call to `updateDecl`.
pub fn updateDeclLineNumber(self: *Elf, mod: *Module, decl: *const Module.Decl) !void {
const tracy = trace(@src());
defer tracy.end();
const decl_name = try decl.getFullyQualifiedName(mod);
defer self.base.allocator.free(decl_name);
log.debug("updateDeclLineNumber {s}{*}", .{ decl_name, decl });
if (self.llvm_object) |_| return;
if (self.dwarf) |*dw| {
try dw.updateDeclLineNumber(&self.base, decl);
}
}
pub fn deleteExport(self: *Elf, exp: Export) void {
if (self.llvm_object) |_| return;
const sym_index = exp.sym_index orelse return;
self.global_symbol_free_list.append(self.base.allocator, sym_index) catch {};
self.global_symbols.items[sym_index].st_info = 0;
}
fn writeProgHeader(self: *Elf, index: usize) !void {
const foreign_endian = self.base.options.target.cpu.arch.endian() != builtin.cpu.arch.endian();
const offset = self.program_headers.items[index].p_offset;
switch (self.ptr_width) {
.p32 => {
var phdr = [1]elf.Elf32_Phdr{progHeaderTo32(self.program_headers.items[index])};
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf32_Phdr, &phdr[0]);
}
return self.base.file.?.pwriteAll(mem.sliceAsBytes(&phdr), offset);
},
.p64 => {
var phdr = [1]elf.Elf64_Phdr{self.program_headers.items[index]};
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf64_Phdr, &phdr[0]);
}
return self.base.file.?.pwriteAll(mem.sliceAsBytes(&phdr), offset);
},
}
}
fn writeSectHeader(self: *Elf, index: usize) !void {
const foreign_endian = self.base.options.target.cpu.arch.endian() != builtin.cpu.arch.endian();
switch (self.ptr_width) {
.p32 => {
var shdr: [1]elf.Elf32_Shdr = undefined;
shdr[0] = sectHeaderTo32(self.sections.items[index]);
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf32_Shdr, &shdr[0]);
}
const offset = self.shdr_table_offset.? + index * @sizeOf(elf.Elf32_Shdr);
return self.base.file.?.pwriteAll(mem.sliceAsBytes(&shdr), offset);
},
.p64 => {
var shdr = [1]elf.Elf64_Shdr{self.sections.items[index]};
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf64_Shdr, &shdr[0]);
}
const offset = self.shdr_table_offset.? + index * @sizeOf(elf.Elf64_Shdr);
return self.base.file.?.pwriteAll(mem.sliceAsBytes(&shdr), offset);
},
}
}
fn writeOffsetTableEntry(self: *Elf, index: usize) !void {
const shdr = &self.sections.items[self.got_section_index.?];
const phdr = &self.program_headers.items[self.phdr_got_index.?];
const entry_size: u16 = self.archPtrWidthBytes();
if (self.offset_table_count_dirty) {
// TODO Also detect virtual address collisions.
const allocated_size = self.allocatedSize(shdr.sh_offset);
const needed_size = self.offset_table.items.len * entry_size;
if (needed_size > allocated_size) {
// Must move the entire got section.
const new_offset = self.findFreeSpace(needed_size, self.page_size);
const amt = try self.base.file.?.copyRangeAll(shdr.sh_offset, self.base.file.?, new_offset, shdr.sh_size);
if (amt != shdr.sh_size) return error.InputOutput;
shdr.sh_offset = new_offset;
phdr.p_offset = new_offset;
}
shdr.sh_size = needed_size;
phdr.p_memsz = needed_size;
phdr.p_filesz = needed_size;
self.shdr_table_dirty = true; // TODO look into making only the one section dirty
self.phdr_table_dirty = true; // TODO look into making only the one program header dirty
self.offset_table_count_dirty = false;
}
const endian = self.base.options.target.cpu.arch.endian();
const off = shdr.sh_offset + @as(u64, entry_size) * index;
switch (entry_size) {
2 => {
var buf: [2]u8 = undefined;
mem.writeInt(u16, &buf, @intCast(u16, self.offset_table.items[index]), endian);
try self.base.file.?.pwriteAll(&buf, off);
},
4 => {
var buf: [4]u8 = undefined;
mem.writeInt(u32, &buf, @intCast(u32, self.offset_table.items[index]), endian);
try self.base.file.?.pwriteAll(&buf, off);
},
8 => {
var buf: [8]u8 = undefined;
mem.writeInt(u64, &buf, self.offset_table.items[index], endian);
try self.base.file.?.pwriteAll(&buf, off);
},
else => unreachable,
}
}
fn writeSymbol(self: *Elf, index: usize) !void {
const tracy = trace(@src());
defer tracy.end();
const syms_sect = &self.sections.items[self.symtab_section_index.?];
// Make sure we are not pointlessly writing symbol data that will have to get relocated
// due to running out of space.
if (self.local_symbols.items.len != syms_sect.sh_info) {
const sym_size: u64 = switch (self.ptr_width) {
.p32 => @sizeOf(elf.Elf32_Sym),
.p64 => @sizeOf(elf.Elf64_Sym),
};
const sym_align: u16 = switch (self.ptr_width) {
.p32 => @alignOf(elf.Elf32_Sym),
.p64 => @alignOf(elf.Elf64_Sym),
};
const needed_size = (self.local_symbols.items.len + self.global_symbols.items.len) * sym_size;
if (needed_size > self.allocatedSize(syms_sect.sh_offset)) {
// Move all the symbols to a new file location.
const new_offset = self.findFreeSpace(needed_size, sym_align);
log.debug("moving '.symtab' from 0x{x} to 0x{x}", .{ syms_sect.sh_offset, new_offset });
const existing_size = @as(u64, syms_sect.sh_info) * sym_size;
const amt = try self.base.file.?.copyRangeAll(
syms_sect.sh_offset,
self.base.file.?,
new_offset,
existing_size,
);
if (amt != existing_size) return error.InputOutput;
syms_sect.sh_offset = new_offset;
}
syms_sect.sh_info = @intCast(u32, self.local_symbols.items.len);
syms_sect.sh_size = needed_size; // anticipating adding the global symbols later
self.shdr_table_dirty = true; // TODO look into only writing one section
}
const foreign_endian = self.base.options.target.cpu.arch.endian() != builtin.cpu.arch.endian();
const off = switch (self.ptr_width) {
.p32 => syms_sect.sh_offset + @sizeOf(elf.Elf32_Sym) * index,
.p64 => syms_sect.sh_offset + @sizeOf(elf.Elf64_Sym) * index,
};
const local = self.local_symbols.items[index];
log.debug("writing symbol {d}, '{s}' at 0x{x}", .{ index, self.getString(local.st_name), off });
log.debug(" ({})", .{local});
switch (self.ptr_width) {
.p32 => {
var sym = [1]elf.Elf32_Sym{
.{
.st_name = local.st_name,
.st_value = @intCast(u32, local.st_value),
.st_size = @intCast(u32, local.st_size),
.st_info = local.st_info,
.st_other = local.st_other,
.st_shndx = local.st_shndx,
},
};
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf32_Sym, &sym[0]);
}
try self.base.file.?.pwriteAll(mem.sliceAsBytes(sym[0..1]), off);
},
.p64 => {
var sym = [1]elf.Elf64_Sym{local};
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf64_Sym, &sym[0]);
}
try self.base.file.?.pwriteAll(mem.sliceAsBytes(sym[0..1]), off);
},
}
}
fn writeAllGlobalSymbols(self: *Elf) !void {
const syms_sect = &self.sections.items[self.symtab_section_index.?];
const sym_size: u64 = switch (self.ptr_width) {
.p32 => @sizeOf(elf.Elf32_Sym),
.p64 => @sizeOf(elf.Elf64_Sym),
};
const sym_align: u16 = switch (self.ptr_width) {
.p32 => @alignOf(elf.Elf32_Sym),
.p64 => @alignOf(elf.Elf64_Sym),
};
const needed_size = (self.local_symbols.items.len + self.global_symbols.items.len) * sym_size;
if (needed_size > self.allocatedSize(syms_sect.sh_offset)) {
// Move all the symbols to a new file location.
const new_offset = self.findFreeSpace(needed_size, sym_align);
log.debug("moving '.symtab' from 0x{x} to 0x{x}", .{ syms_sect.sh_offset, new_offset });
const existing_size = @as(u64, syms_sect.sh_info) * sym_size;
const amt = try self.base.file.?.copyRangeAll(
syms_sect.sh_offset,
self.base.file.?,
new_offset,
existing_size,
);
if (amt != existing_size) return error.InputOutput;
syms_sect.sh_offset = new_offset;
}
syms_sect.sh_size = needed_size; // anticipating adding the global symbols later
self.shdr_table_dirty = true; // TODO look into only writing one section
const foreign_endian = self.base.options.target.cpu.arch.endian() != builtin.cpu.arch.endian();
const global_syms_off = syms_sect.sh_offset + self.local_symbols.items.len * sym_size;
log.debug("writing {d} global symbols at 0x{x}", .{ self.global_symbols.items.len, global_syms_off });
switch (self.ptr_width) {
.p32 => {
const buf = try self.base.allocator.alloc(elf.Elf32_Sym, self.global_symbols.items.len);
defer self.base.allocator.free(buf);
for (buf) |*sym, i| {
const global = self.global_symbols.items[i];
sym.* = .{
.st_name = global.st_name,
.st_value = @intCast(u32, global.st_value),
.st_size = @intCast(u32, global.st_size),
.st_info = global.st_info,
.st_other = global.st_other,
.st_shndx = global.st_shndx,
};
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf32_Sym, sym);
}
}
try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), global_syms_off);
},
.p64 => {
const buf = try self.base.allocator.alloc(elf.Elf64_Sym, self.global_symbols.items.len);
defer self.base.allocator.free(buf);
for (buf) |*sym, i| {
const global = self.global_symbols.items[i];
sym.* = .{
.st_name = global.st_name,
.st_value = global.st_value,
.st_size = global.st_size,
.st_info = global.st_info,
.st_other = global.st_other,
.st_shndx = global.st_shndx,
};
if (foreign_endian) {
mem.byteSwapAllFields(elf.Elf64_Sym, sym);
}
}
try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), global_syms_off);
},
}
}
/// Always 4 or 8 depending on whether this is 32-bit ELF or 64-bit ELF.
fn ptrWidthBytes(self: Elf) u8 {
return switch (self.ptr_width) {
.p32 => 4,
.p64 => 8,
};
}
/// Does not necessarily match `ptrWidthBytes` for example can be 2 bytes
/// in a 32-bit ELF file.
fn archPtrWidthBytes(self: Elf) u8 {
return @intCast(u8, self.base.options.target.cpu.arch.ptrBitWidth() / 8);
}
fn progHeaderTo32(phdr: elf.Elf64_Phdr) elf.Elf32_Phdr {
return .{
.p_type = phdr.p_type,
.p_flags = phdr.p_flags,
.p_offset = @intCast(u32, phdr.p_offset),
.p_vaddr = @intCast(u32, phdr.p_vaddr),
.p_paddr = @intCast(u32, phdr.p_paddr),
.p_filesz = @intCast(u32, phdr.p_filesz),
.p_memsz = @intCast(u32, phdr.p_memsz),
.p_align = @intCast(u32, phdr.p_align),
};
}
fn sectHeaderTo32(shdr: elf.Elf64_Shdr) elf.Elf32_Shdr {
return .{
.sh_name = shdr.sh_name,
.sh_type = shdr.sh_type,
.sh_flags = @intCast(u32, shdr.sh_flags),
.sh_addr = @intCast(u32, shdr.sh_addr),
.sh_offset = @intCast(u32, shdr.sh_offset),
.sh_size = @intCast(u32, shdr.sh_size),
.sh_link = shdr.sh_link,
.sh_info = shdr.sh_info,
.sh_addralign = @intCast(u32, shdr.sh_addralign),
.sh_entsize = @intCast(u32, shdr.sh_entsize),
};
}
fn getLDMOption(target: std.Target) ?[]const u8 {
switch (target.cpu.arch) {
.i386 => return "elf_i386",
.aarch64 => return "aarch64linux",
.aarch64_be => return "aarch64_be_linux",
.arm, .thumb => return "armelf_linux_eabi",
.armeb, .thumbeb => return "armebelf_linux_eabi",
.powerpc => return "elf32ppclinux",
.powerpc64 => return "elf64ppc",
.powerpc64le => return "elf64lppc",
.sparc, .sparcel => return "elf32_sparc",
.sparc64 => return "elf64_sparc",
.mips => return "elf32btsmip",
.mipsel => return "elf32ltsmip",
.mips64 => {
if (target.abi == .gnuabin32) {
return "elf32btsmipn32";
} else {
return "elf64btsmip";
}
},
.mips64el => {
if (target.abi == .gnuabin32) {
return "elf32ltsmipn32";
} else {
return "elf64ltsmip";
}
},
.s390x => return "elf64_s390",
.x86_64 => {
if (target.abi == .gnux32) {
return "elf32_x86_64";
} else {
return "elf_x86_64";
}
},
.riscv32 => return "elf32lriscv",
.riscv64 => return "elf64lriscv",
else => return null,
}
}
fn padToIdeal(actual_size: anytype) @TypeOf(actual_size) {
// TODO https://github.com/ziglang/zig/issues/1284
return std.math.add(@TypeOf(actual_size), actual_size, actual_size / ideal_factor) catch
std.math.maxInt(@TypeOf(actual_size));
}
// Provide a blueprint of csu (c-runtime startup) objects for supported
// link modes.
//
// This is for cross-mode targets only. For host-mode targets the system
// compiler can be probed to produce a robust blueprint.
//
// Targets requiring a libc for which zig does not bundle a libc are
// host-mode targets. Unfortunately, host-mode probes are not yet
// implemented. For now the data is hard-coded here. Such targets are
// { freebsd, netbsd, openbsd, dragonfly }.
const CsuObjects = struct {
crt0: ?[]const u8 = null,
crti: ?[]const u8 = null,
crtbegin: ?[]const u8 = null,
crtend: ?[]const u8 = null,
crtn: ?[]const u8 = null,
fn init(arena: mem.Allocator, link_options: link.Options, comp: *const Compilation) !CsuObjects {
// crt objects are only required for libc.
if (!link_options.link_libc) return CsuObjects{};
var result: CsuObjects = .{};
// TODO: https://github.com/ziglang/zig/issues/4629
// - use inline enum type
// - reduce to enum-literals for values
const Mode = enum {
dynamic_lib,
dynamic_exe,
dynamic_pie,
static_exe,
static_pie,
};
// Flatten crt case types.
const mode: Mode = switch (link_options.output_mode) {
.Obj => return CsuObjects{},
.Lib => switch (link_options.link_mode) {
.Dynamic => Mode.dynamic_lib,
.Static => return CsuObjects{},
},
.Exe => switch (link_options.link_mode) {
.Dynamic => if (link_options.pie) Mode.dynamic_pie else Mode.dynamic_exe,
.Static => if (link_options.pie) Mode.static_pie else Mode.static_exe,
},
};
if (link_options.target.isAndroid()) {
switch (mode) {
// zig fmt: off
.dynamic_lib => result.set( null, null, "crtbegin_so.o", "crtend_so.o", null ),
.dynamic_exe,
.dynamic_pie => result.set( null, null, "crtbegin_dynamic.o", "crtend_android.o", null ),
.static_exe,
.static_pie => result.set( null, null, "crtbegin_static.o", "crtend_android.o", null ),
// zig fmt: on
}
} else {
switch (link_options.target.os.tag) {
.linux => {
switch (mode) {
// zig fmt: off
.dynamic_lib => result.set( null, "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
.dynamic_exe => result.set( "crt1.o", "crti.o", "crtbegin.o", "crtend.o", "crtn.o" ),
.dynamic_pie => result.set( "Scrt1.o", "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
.static_exe => result.set( "crt1.o", "crti.o", "crtbeginT.o", "crtend.o", "crtn.o" ),
.static_pie => result.set( "rcrt1.o", "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
// zig fmt: on
}
if (link_options.libc_installation) |_| {
// hosted-glibc provides crtbegin/end objects in platform/compiler-specific dirs
// and they are not known at comptime. For now null-out crtbegin/end objects;
// there is no feature loss, zig has never linked those objects in before.
// TODO: probe for paths, ie. `cc -print-file-name`
result.crtbegin = null;
result.crtend = null;
} else {
// Bundled glibc only has Scrt1.o .
if (result.crt0 != null and link_options.target.isGnuLibC()) result.crt0 = "Scrt1.o";
}
},
.dragonfly => switch (mode) {
// zig fmt: off
.dynamic_lib => result.set( null, "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
.dynamic_exe => result.set( "crt1.o", "crti.o", "crtbegin.o", "crtend.o", "crtn.o" ),
.dynamic_pie => result.set( "Scrt1.o", "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
.static_exe => result.set( "crt1.o", "crti.o", "crtbegin.o", "crtend.o", "crtn.o" ),
.static_pie => result.set( "Scrt1.o", "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
// zig fmt: on
},
.freebsd => switch (mode) {
// zig fmt: off
.dynamic_lib => result.set( null, "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
.dynamic_exe => result.set( "crt1.o", "crti.o", "crtbegin.o", "crtend.o", "crtn.o" ),
.dynamic_pie => result.set( "Scrt1.o", "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
.static_exe => result.set( "crt1.o", "crti.o", "crtbeginT.o", "crtend.o", "crtn.o" ),
.static_pie => result.set( "Scrt1.o", "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
// zig fmt: on
},
.netbsd => switch (mode) {
// zig fmt: off
.dynamic_lib => result.set( null, "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
.dynamic_exe => result.set( "crt0.o", "crti.o", "crtbegin.o", "crtend.o", "crtn.o" ),
.dynamic_pie => result.set( "crt0.o", "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
.static_exe => result.set( "crt0.o", "crti.o", "crtbeginT.o", "crtend.o", "crtn.o" ),
.static_pie => result.set( "crt0.o", "crti.o", "crtbeginT.o", "crtendS.o", "crtn.o" ),
// zig fmt: on
},
.openbsd => switch (mode) {
// zig fmt: off
.dynamic_lib => result.set( null, null, "crtbeginS.o", "crtendS.o", null ),
.dynamic_exe,
.dynamic_pie => result.set( "crt0.o", null, "crtbegin.o", "crtend.o", null ),
.static_exe,
.static_pie => result.set( "rcrt0.o", null, "crtbegin.o", "crtend.o", null ),
// zig fmt: on
},
.haiku => switch (mode) {
// zig fmt: off
.dynamic_lib => result.set( null, "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
.dynamic_exe => result.set( "start_dyn.o", "crti.o", "crtbegin.o", "crtend.o", "crtn.o" ),
.dynamic_pie => result.set( "start_dyn.o", "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
.static_exe => result.set( "start_dyn.o", "crti.o", "crtbegin.o", "crtend.o", "crtn.o" ),
.static_pie => result.set( "start_dyn.o", "crti.o", "crtbeginS.o", "crtendS.o", "crtn.o" ),
// zig fmt: on
},
.solaris => switch (mode) {
// zig fmt: off
.dynamic_lib => result.set( null, "crti.o", null, null, "crtn.o" ),
.dynamic_exe,
.dynamic_pie => result.set( "crt1.o", "crti.o", null, null, "crtn.o" ),
.static_exe,
.static_pie => result.set( null, null, null, null, null ),
// zig fmt: on
},
else => {},
}
}
// Convert each object to a full pathname.
if (link_options.libc_installation) |lci| {
const crt_dir_path = lci.crt_dir orelse return error.LibCInstallationMissingCRTDir;
switch (link_options.target.os.tag) {
.dragonfly => {
if (result.crt0) |*obj| obj.* = try fs.path.join(arena, &[_][]const u8{ crt_dir_path, obj.* });
if (result.crti) |*obj| obj.* = try fs.path.join(arena, &[_][]const u8{ crt_dir_path, obj.* });
if (result.crtn) |*obj| obj.* = try fs.path.join(arena, &[_][]const u8{ crt_dir_path, obj.* });
var gccv: []const u8 = undefined;
if (link_options.target.os.version_range.semver.isAtLeast(.{ .major = 5, .minor = 4 }) orelse true) {
gccv = "gcc80";
} else {
gccv = "gcc54";
}
if (result.crtbegin) |*obj| obj.* = try fs.path.join(arena, &[_][]const u8{ crt_dir_path, gccv, obj.* });
if (result.crtend) |*obj| obj.* = try fs.path.join(arena, &[_][]const u8{ crt_dir_path, gccv, obj.* });
},
.haiku => {
const gcc_dir_path = lci.gcc_dir orelse return error.LibCInstallationMissingCRTDir;
if (result.crt0) |*obj| obj.* = try fs.path.join(arena, &[_][]const u8{ crt_dir_path, obj.* });
if (result.crti) |*obj| obj.* = try fs.path.join(arena, &[_][]const u8{ crt_dir_path, obj.* });
if (result.crtn) |*obj| obj.* = try fs.path.join(arena, &[_][]const u8{ crt_dir_path, obj.* });
if (result.crtbegin) |*obj| obj.* = try fs.path.join(arena, &[_][]const u8{ gcc_dir_path, obj.* });
if (result.crtend) |*obj| obj.* = try fs.path.join(arena, &[_][]const u8{ gcc_dir_path, obj.* });
},
else => {
inline for (std.meta.fields(@TypeOf(result))) |f| {
if (@field(result, f.name)) |*obj| {
obj.* = try fs.path.join(arena, &[_][]const u8{ crt_dir_path, obj.* });
}
}
},
}
} else {
inline for (std.meta.fields(@TypeOf(result))) |f| {
if (@field(result, f.name)) |*obj| {
if (comp.crt_files.get(obj.*)) |crtf| {
obj.* = crtf.full_object_path;
} else {
@field(result, f.name) = null;
}
}
}
}
return result;
}
fn set(
self: *CsuObjects,
crt0: ?[]const u8,
crti: ?[]const u8,
crtbegin: ?[]const u8,
crtend: ?[]const u8,
crtn: ?[]const u8,
) void {
self.crt0 = crt0;
self.crti = crti;
self.crtbegin = crtbegin;
self.crtend = crtend;
self.crtn = crtn;
}
};
fn logSymtab(self: Elf) void {
log.debug("locals:", .{});
for (self.local_symbols.items) |sym, id| {
log.debug(" {d}: {s}: @{x} in {d}", .{ id, self.getString(sym.st_name), sym.st_value, sym.st_shndx });
}
log.debug("globals:", .{});
for (self.global_symbols.items) |sym, id| {
log.debug(" {d}: {s}: @{x} in {d}", .{ id, self.getString(sym.st_name), sym.st_value, sym.st_shndx });
}
}