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zig/src-self-hosted/link.zig
Isaac Freund 3370b5f109
stage2/wasm: implement basic container generation 
Thus far, we only generate the type, function, export, and code
sections. These are sufficient to generate and export simple functions.

Codegen is currently hardcoded to `i32.const 42`, the main goal of this
commit is to create infrastructure for the container format which will
work with incremental compilation.
2020-08-18 00:32:58 +02:00

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const std = @import("std");
const mem = std.mem;
const assert = std.debug.assert;
const Allocator = std.mem.Allocator;
const ir = @import("ir.zig");
const Module = @import("Module.zig");
const fs = std.fs;
const elf = std.elf;
const codegen = @import("codegen.zig");
const c_codegen = @import("codegen/c.zig");
const log = std.log.scoped(.link);
const DW = std.dwarf;
const trace = @import("tracy.zig").trace;
const leb128 = std.debug.leb;
const Package = @import("Package.zig");
const Value = @import("value.zig").Value;
const Type = @import("type.zig").Type;
const build_options = @import("build_options");
const producer_string = if (std.builtin.is_test) "zig test" else "zig " ++ build_options.version;
// TODO Turn back on zig fmt when https://github.com/ziglang/zig/issues/5948 is implemented.
// zig fmt: off
const default_entry_addr = 0x8000000;
pub const Options = struct {
target: std.Target,
output_mode: std.builtin.OutputMode,
link_mode: std.builtin.LinkMode,
object_format: std.builtin.ObjectFormat,
optimize_mode: std.builtin.Mode,
root_name: []const u8,
root_pkg: *const Package,
/// Used for calculating how much space to reserve for symbols in case the binary file
/// does not already have a symbol table.
symbol_count_hint: u64 = 32,
/// Used for calculating how much space to reserve for executable program code in case
/// the binary file deos not already have such a section.
program_code_size_hint: u64 = 256 * 1024,
};
pub const File = struct {
pub const LinkBlock = union {
elf: Elf.TextBlock,
macho: MachO.TextBlock,
c: void,
wasm: void,
};
pub const LinkFn = union {
elf: Elf.SrcFn,
macho: MachO.SrcFn,
c: void,
wasm: ?Wasm.FnData,
};
tag: Tag,
options: Options,
file: ?fs.File,
allocator: *Allocator,
/// Attempts incremental linking, if the file already exists. If
/// incremental linking fails, falls back to truncating the file and
/// rewriting it. A malicious file is detected as incremental link failure
/// and does not cause Illegal Behavior. This operation is not atomic.
pub fn openPath(allocator: *Allocator, dir: fs.Dir, sub_path: []const u8, options: Options) !*File {
switch (options.object_format) {
.unknown => unreachable,
.coff => return error.TODOImplementCoff,
.elf => return Elf.openPath(allocator, dir, sub_path, options),
.macho => return MachO.openPath(allocator, dir, sub_path, options),
.wasm => return Wasm.openPath(allocator, dir, sub_path, options),
.c => return C.openPath(allocator, dir, sub_path, options),
.hex => return error.TODOImplementHex,
.raw => return error.TODOImplementRaw,
}
}
pub fn cast(base: *File, comptime T: type) ?*T {
if (base.tag != T.base_tag)
return null;
return @fieldParentPtr(T, "base", base);
}
pub fn makeWritable(base: *File, dir: fs.Dir, sub_path: []const u8) !void {
switch (base.tag) {
.elf, .macho => {
if (base.file != null) return;
base.file = try dir.createFile(sub_path, .{
.truncate = false,
.read = true,
.mode = determineMode(base.options),
});
},
.c, .wasm => {},
}
}
pub fn makeExecutable(base: *File) !void {
std.debug.assert(base.tag != .c);
if (base.file) |f| {
f.close();
base.file = null;
}
}
pub fn updateDecl(base: *File, module: *Module, decl: *Module.Decl) !void {
switch (base.tag) {
.elf => return @fieldParentPtr(Elf, "base", base).updateDecl(module, decl),
.macho => return @fieldParentPtr(MachO, "base", base).updateDecl(module, decl),
.c => return @fieldParentPtr(C, "base", base).updateDecl(module, decl),
.wasm => return @fieldParentPtr(Wasm, "base", base).updateDecl(module, decl),
}
}
pub fn updateDeclLineNumber(base: *File, module: *Module, decl: *Module.Decl) !void {
switch (base.tag) {
.elf => return @fieldParentPtr(Elf, "base", base).updateDeclLineNumber(module, decl),
.macho => return @fieldParentPtr(MachO, "base", base).updateDeclLineNumber(module, decl),
.c, .wasm => {},
}
}
pub fn allocateDeclIndexes(base: *File, decl: *Module.Decl) !void {
switch (base.tag) {
.elf => return @fieldParentPtr(Elf, "base", base).allocateDeclIndexes(decl),
.macho => return @fieldParentPtr(MachO, "base", base).allocateDeclIndexes(decl),
.c, .wasm => {},
}
}
pub fn deinit(base: *File) void {
if (base.file) |f| f.close();
switch (base.tag) {
.elf => @fieldParentPtr(Elf, "base", base).deinit(),
.macho => @fieldParentPtr(MachO, "base", base).deinit(),
.c => @fieldParentPtr(C, "base", base).deinit(),
.wasm => @fieldParentPtr(Wasm, "base", base).deinit(),
}
}
pub fn destroy(base: *File) void {
switch (base.tag) {
.elf => {
const parent = @fieldParentPtr(Elf, "base", base);
parent.deinit();
base.allocator.destroy(parent);
},
.macho => {
const parent = @fieldParentPtr(MachO, "base", base);
parent.deinit();
base.allocator.destroy(parent);
},
.c => {
const parent = @fieldParentPtr(C, "base", base);
parent.deinit();
base.allocator.destroy(parent);
},
.wasm => {
const parent = @fieldParentPtr(Wasm, "base", base);
parent.deinit();
base.allocator.destroy(parent);
},
}
}
/// Commit pending changes and write headers.
pub fn flush(base: *File) !void {
const tracy = trace(@src());
defer tracy.end();
try switch (base.tag) {
.elf => @fieldParentPtr(Elf, "base", base).flush(),
.macho => @fieldParentPtr(MachO, "base", base).flush(),
.c => @fieldParentPtr(C, "base", base).flush(),
.wasm => @fieldParentPtr(Wasm, "base", base).flush(),
};
}
pub fn freeDecl(base: *File, decl: *Module.Decl) void {
switch (base.tag) {
.elf => @fieldParentPtr(Elf, "base", base).freeDecl(decl),
.macho => @fieldParentPtr(MachO, "base", base).freeDecl(decl),
.c => unreachable,
.wasm => @fieldParentPtr(Wasm, "base", base).freeDecl(decl),
}
}
pub fn errorFlags(base: *File) ErrorFlags {
return switch (base.tag) {
.elf => @fieldParentPtr(Elf, "base", base).error_flags,
.macho => @fieldParentPtr(MachO, "base", base).error_flags,
.c => return .{ .no_entry_point_found = false },
.wasm => return ErrorFlags{},
};
}
/// Must be called only after a successful call to `updateDecl`.
pub fn updateDeclExports(
base: *File,
module: *Module,
decl: *const Module.Decl,
exports: []const *Module.Export,
) !void {
switch (base.tag) {
.elf => return @fieldParentPtr(Elf, "base", base).updateDeclExports(module, decl, exports),
.macho => return @fieldParentPtr(MachO, "base", base).updateDeclExports(module, decl, exports),
.c => return {},
.wasm => return @fieldParentPtr(Wasm, "base", base).updateDeclExports(module, decl, exports),
}
}
pub const Tag = enum {
elf,
macho,
c,
wasm,
};
pub const ErrorFlags = struct {
no_entry_point_found: bool = false,
};
pub const C = struct {
pub const base_tag: Tag = .c;
base: File,
header: std.ArrayList(u8),
constants: std.ArrayList(u8),
main: std.ArrayList(u8),
called: std.StringHashMap(void),
need_stddef: bool = false,
need_stdint: bool = false,
error_msg: *Module.ErrorMsg = undefined,
pub fn openPath(allocator: *Allocator, dir: fs.Dir, sub_path: []const u8, options: Options) !*File {
assert(options.object_format == .c);
const file = try dir.createFile(sub_path, .{ .truncate = true, .read = true, .mode = determineMode(options) });
errdefer file.close();
var c_file = try allocator.create(C);
errdefer allocator.destroy(c_file);
c_file.* = File.C{
.base = .{
.tag = .c,
.options = options,
.file = file,
.allocator = allocator,
},
.main = std.ArrayList(u8).init(allocator),
.header = std.ArrayList(u8).init(allocator),
.constants = std.ArrayList(u8).init(allocator),
.called = std.StringHashMap(void).init(allocator),
};
return &c_file.base;
}
pub fn fail(self: *C, src: usize, comptime format: []const u8, args: anytype) error{AnalysisFail, OutOfMemory} {
self.error_msg = try Module.ErrorMsg.create(self.base.allocator, src, format, args);
return error.AnalysisFail;
}
pub fn deinit(self: *File.C) void {
self.main.deinit();
self.header.deinit();
self.constants.deinit();
self.called.deinit();
}
pub fn updateDecl(self: *File.C, module: *Module, decl: *Module.Decl) !void {
c_codegen.generate(self, decl) catch |err| {
if (err == error.AnalysisFail) {
try module.failed_decls.put(module.gpa, decl, self.error_msg);
}
return err;
};
}
pub fn flush(self: *File.C) !void {
const writer = self.base.file.?.writer();
try writer.writeAll(@embedFile("cbe.h"));
var includes = false;
if (self.need_stddef) {
try writer.writeAll("#include <stddef.h>\n");
includes = true;
}
if (self.need_stdint) {
try writer.writeAll("#include <stdint.h>\n");
includes = true;
}
if (includes) {
try writer.writeByte('\n');
}
if (self.header.items.len > 0) {
try writer.print("{}\n", .{self.header.items});
}
if (self.constants.items.len > 0) {
try writer.print("{}\n", .{self.constants.items});
}
if (self.main.items.len > 1) {
const last_two = self.main.items[self.main.items.len - 2 ..];
if (std.mem.eql(u8, last_two, "\n\n")) {
self.main.items.len -= 1;
}
}
try writer.writeAll(self.main.items);
self.base.file.?.close();
self.base.file = null;
}
};
pub const Elf = struct {
pub const base_tag: Tag = .elf;
base: File,
ptr_width: enum { p32, p64 },
/// 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,
entry_addr: ?u64 = null,
debug_strtab: std.ArrayListUnmanaged(u8) = std.ArrayListUnmanaged(u8){},
shstrtab: std.ArrayListUnmanaged(u8) = std.ArrayListUnmanaged(u8){},
shstrtab_index: ?u16 = null,
text_section_index: ?u16 = null,
symtab_section_index: ?u16 = null,
got_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,
debug_abbrev_table_offset: ?u64 = 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,
debug_strtab_dirty: bool = false,
offset_table_count_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: ErrorFlags = ErrorFlags{},
/// 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
/// minimum_text_block_size * alloc_num / alloc_den. 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 * alloc_num / alloc_den.
///
/// 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.
text_block_free_list: std.ArrayListUnmanaged(*TextBlock) = .{},
last_text_block: ?*TextBlock = null,
/// A list of `SrcFn` whose Line Number Programs have surplus capacity.
/// This is the same concept as `text_block_free_list`; see those doc comments.
dbg_line_fn_free_list: std.AutoHashMapUnmanaged(*SrcFn, void) = .{},
dbg_line_fn_first: ?*SrcFn = null,
dbg_line_fn_last: ?*SrcFn = null,
/// A list of `TextBlock` whose corresponding .debug_info tags have surplus capacity.
/// This is the same concept as `text_block_free_list`; see those doc comments.
dbg_info_decl_free_list: std.AutoHashMapUnmanaged(*TextBlock, void) = .{},
dbg_info_decl_first: ?*TextBlock = null,
dbg_info_decl_last: ?*TextBlock = null,
/// `alloc_num / alloc_den` is the factor of padding when allocating.
const alloc_num = 4;
const alloc_den = 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 = minimum_text_block_size * alloc_num / alloc_den;
pub const DbgInfoTypeRelocsTable = std.HashMapUnmanaged(Type, DbgInfoTypeReloc, Type.hash, Type.eql, true);
const DbgInfoTypeReloc = struct {
/// Offset from `TextBlock.dbg_info_off` (the buffer that is local to a Decl).
/// This is where the .debug_info tag for the type is.
off: u32,
/// Offset from `TextBlock.dbg_info_off` (the buffer that is local to a Decl).
/// List of DW.AT_type / DW.FORM_ref4 that points to the type.
relocs: std.ArrayListUnmanaged(u32),
};
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,
/// Previous/next linked list pointers. This value is `next ^ prev`.
/// This is the linked list node for this Decl's corresponding .debug_info tag.
dbg_info_prev: ?*TextBlock,
dbg_info_next: ?*TextBlock,
/// Offset into .debug_info pointing to the tag for this Decl.
dbg_info_off: u32,
/// Size of the .debug_info tag for this Decl, not including padding.
dbg_info_len: u32,
pub const empty = TextBlock{
.local_sym_index = 0,
.offset_table_index = undefined,
.prev = null,
.next = null,
.dbg_info_prev = null,
.dbg_info_next = null,
.dbg_info_off = undefined,
.dbg_info_len = 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 = self_sym.st_size * alloc_num / alloc_den;
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 const SrcFn = struct {
/// Offset from the beginning of the Debug Line Program header that contains this function.
off: u32,
/// Size of the line number program component belonging to this function, not
/// including padding.
len: u32,
/// Points to the previous and next neighbors, based on the offset from .debug_line.
/// This can be used to find, for example, the capacity of this `SrcFn`.
prev: ?*SrcFn,
next: ?*SrcFn,
pub const empty: SrcFn = .{
.off = 0,
.len = 0,
.prev = null,
.next = null,
};
};
pub fn openPath(allocator: *Allocator, dir: fs.Dir, sub_path: []const u8, options: Options) !*File {
assert(options.object_format == .elf);
const file = try dir.createFile(sub_path, .{ .truncate = false, .read = true, .mode = determineMode(options) });
errdefer file.close();
var elf_file = try allocator.create(Elf);
errdefer allocator.destroy(elf_file);
elf_file.* = openFile(allocator, file, options) catch |err| switch (err) {
error.IncrFailed => try createFile(allocator, file, options),
else => |e| return e,
};
return &elf_file.base;
}
/// Returns error.IncrFailed if incremental update could not be performed.
fn openFile(allocator: *Allocator, file: fs.File, options: Options) !Elf {
switch (options.output_mode) {
.Exe => {},
.Obj => {},
.Lib => return error.IncrFailed,
}
var self: Elf = .{
.base = .{
.file = file,
.tag = .elf,
.options = options,
.allocator = allocator,
},
.ptr_width = switch (options.target.cpu.arch.ptrBitWidth()) {
32 => .p32,
64 => .p64,
else => return error.UnsupportedELFArchitecture,
},
};
errdefer self.deinit();
// TODO implement reading the elf file
return error.IncrFailed;
//try self.populateMissingMetadata();
//return self;
}
/// Truncates the existing file contents and overwrites the contents.
/// Returns an error if `file` is not already open with +read +write +seek abilities.
fn createFile(allocator: *Allocator, file: fs.File, options: Options) !Elf {
switch (options.output_mode) {
.Exe => {},
.Obj => {},
.Lib => return error.TODOImplementWritingLibFiles,
}
var self: Elf = .{
.base = .{
.tag = .elf,
.options = options,
.allocator = allocator,
.file = file,
},
.ptr_width = switch (options.target.cpu.arch.ptrBitWidth()) {
32 => .p32,
64 => .p64,
else => return error.UnsupportedELFArchitecture,
},
.shdr_table_dirty = true,
};
errdefer self.deinit();
// 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 deinit(self: *Elf) void {
self.sections.deinit(self.base.allocator);
self.program_headers.deinit(self.base.allocator);
self.shstrtab.deinit(self.base.allocator);
self.debug_strtab.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.text_block_free_list.deinit(self.base.allocator);
self.dbg_line_fn_free_list.deinit(self.base.allocator);
self.dbg_info_decl_free_list.deinit(self.base.allocator);
self.offset_table.deinit(self.base.allocator);
}
fn getDebugLineProgramOff(self: Elf) u32 {
return self.dbg_line_fn_first.?.off;
}
fn getDebugLineProgramEnd(self: Elf) u32 {
return self.dbg_line_fn_last.?.off + self.dbg_line_fn_last.?.len;
}
/// Returns end pos of collision, if any.
fn detectAllocCollision(self: *Elf, start: u64, size: u64) ?u64 {
const small_ptr = self.base.options.target.cpu.arch.ptrBitWidth() == 32;
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 + satMul(size, alloc_num) / alloc_den;
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 = satMul(tight_size, alloc_num) / alloc_den;
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 = satMul(tight_size, alloc_num) / alloc_den;
const test_end = off + increased_size;
if (end > off and start < test_end) {
return test_end;
}
}
for (self.sections.items) |section| {
const increased_size = satMul(section.sh_size, alloc_num) / alloc_den;
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 = satMul(program_header.p_filesz, alloc_num) / alloc_den;
const test_end = program_header.p_offset + increased_size;
if (end > program_header.p_offset and start < test_end) {
return test_end;
}
}
return null;
}
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;
}
fn findFreeSpace(self: *Elf, object_size: u64, min_alignment: u16) 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.ensureCapacity(self.base.allocator, self.shstrtab.items.len + bytes.len + 1);
const result = self.shstrtab.items.len;
self.shstrtab.appendSliceAssumeCapacity(bytes);
self.shstrtab.appendAssumeCapacity(0);
return @intCast(u32, result);
}
/// TODO Improve this to use a table.
fn makeDebugString(self: *Elf, bytes: []const u8) !u32 {
try self.debug_strtab.ensureCapacity(self.base.allocator, self.debug_strtab.items.len + bytes.len + 1);
const result = self.debug_strtab.items.len;
self.debug_strtab.appendSliceAssumeCapacity(bytes);
self.debug_strtab.appendAssumeCapacity(0);
return @intCast(u32, result);
}
fn getString(self: *Elf, str_off: u32) []const u8 {
assert(str_off < self.shstrtab.items.len);
return mem.spanZ(@ptrCast([*:0]const u8, self.shstrtab.items.ptr + str_off));
}
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 {
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 = 0x1000;
const off = self.findFreeSpace(file_size, p_align);
log.debug("found PT_LOAD free space 0x{x} to 0x{x}\n", .{ off, off + file_size });
try self.program_headers.append(self.base.allocator, .{
.p_type = elf.PT_LOAD,
.p_offset = off,
.p_filesz = file_size,
.p_vaddr = default_entry_addr,
.p_paddr = default_entry_addr,
.p_memsz = file_size,
.p_align = p_align,
.p_flags = elf.PF_X | elf.PF_R,
});
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) 0x1000 else @as(u16, ptr_size);
const off = self.findFreeSpace(file_size, p_align);
log.debug("found PT_LOAD free space 0x{x} to 0x{x}\n", .{ 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 default_got_addr = if (ptr_size == 2) @as(u32, 0x8000) else 0x4000000;
try self.program_headers.append(self.base.allocator, .{
.p_type = elf.PT_LOAD,
.p_offset = off,
.p_filesz = file_size,
.p_vaddr = default_got_addr,
.p_paddr = default_got_addr,
.p_memsz = file_size,
.p_align = p_align,
.p_flags = elf.PF_R,
});
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}\n", .{ 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 = phdr.p_align,
.sh_entsize = 0,
});
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 = phdr.p_align,
.sh_entsize = 0,
});
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}\n", .{ 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.debug_str_section_index == null) {
self.debug_str_section_index = @intCast(u16, self.sections.items.len);
assert(self.debug_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 = self.debug_strtab.items.len,
.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}\n", .{
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}\n", .{
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}\n", .{
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}\n", .{
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.
}
}
pub const abbrev_compile_unit = 1;
pub const abbrev_subprogram = 2;
pub const abbrev_subprogram_retvoid = 3;
pub const abbrev_base_type = 4;
pub const abbrev_pad1 = 5;
pub const abbrev_parameter = 6;
pub fn flush(self: *Elf) !void {
const target_endian = self.base.options.target.cpu.arch.endian();
const foreign_endian = target_endian != std.Target.current.cpu.arch.endian();
const ptr_width_bytes: u8 = self.ptrWidthBytes();
const init_len_size: usize = switch (self.ptr_width) {
.p32 => 4,
.p64 => 12,
};
// 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 (self.debug_abbrev_section_dirty) {
const debug_abbrev_sect = &self.sections.items[self.debug_abbrev_section_index.?];
// These are LEB encoded but since the values are all less than 127
// we can simply append these bytes.
const abbrev_buf = [_]u8{
abbrev_compile_unit, DW.TAG_compile_unit, DW.CHILDREN_yes, // header
DW.AT_stmt_list, DW.FORM_sec_offset,
DW.AT_low_pc , DW.FORM_addr,
DW.AT_high_pc , DW.FORM_addr,
DW.AT_name , DW.FORM_strp,
DW.AT_comp_dir , DW.FORM_strp,
DW.AT_producer , DW.FORM_strp,
DW.AT_language , DW.FORM_data2,
0, 0, // table sentinel
abbrev_subprogram, DW.TAG_subprogram, DW.CHILDREN_yes, // header
DW.AT_low_pc , DW.FORM_addr,
DW.AT_high_pc , DW.FORM_data4,
DW.AT_type , DW.FORM_ref4,
DW.AT_name , DW.FORM_string,
0, 0, // table sentinel
abbrev_subprogram_retvoid, DW.TAG_subprogram, DW.CHILDREN_yes, // header
DW.AT_low_pc , DW.FORM_addr,
DW.AT_high_pc , DW.FORM_data4,
DW.AT_name , DW.FORM_string,
0, 0, // table sentinel
abbrev_base_type, DW.TAG_base_type, DW.CHILDREN_no, // header
DW.AT_encoding , DW.FORM_data1,
DW.AT_byte_size, DW.FORM_data1,
DW.AT_name , DW.FORM_string,
0, 0, // table sentinel
abbrev_pad1, DW.TAG_unspecified_type, DW.CHILDREN_no, // header
0, 0, // table sentinel
abbrev_parameter, DW.TAG_formal_parameter, DW.CHILDREN_no, // header
DW.AT_location , DW.FORM_exprloc,
DW.AT_type , DW.FORM_ref4,
DW.AT_name , DW.FORM_string,
0, 0, // table sentinel
0, 0, 0, // section sentinel
};
const needed_size = abbrev_buf.len;
const allocated_size = self.allocatedSize(debug_abbrev_sect.sh_offset);
if (needed_size > allocated_size) {
debug_abbrev_sect.sh_size = 0; // free the space
debug_abbrev_sect.sh_offset = self.findFreeSpace(needed_size, 1);
}
debug_abbrev_sect.sh_size = needed_size;
log.debug(".debug_abbrev start=0x{x} end=0x{x}\n", .{
debug_abbrev_sect.sh_offset,
debug_abbrev_sect.sh_offset + needed_size,
});
const abbrev_offset = 0;
self.debug_abbrev_table_offset = abbrev_offset;
try self.base.file.?.pwriteAll(&abbrev_buf, debug_abbrev_sect.sh_offset + abbrev_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_abbrev_section_index.?);
}
self.debug_abbrev_section_dirty = false;
}
if (self.debug_info_header_dirty) debug_info: {
// If this value is null it means there is an error in the module;
// leave debug_info_header_dirty=true.
const first_dbg_info_decl = self.dbg_info_decl_first orelse break :debug_info;
const last_dbg_info_decl = self.dbg_info_decl_last.?;
const debug_info_sect = &self.sections.items[self.debug_info_section_index.?];
var di_buf = std.ArrayList(u8).init(self.base.allocator);
defer di_buf.deinit();
// We have a function to compute the upper bound size, because it's needed
// for determining where to put the offset of the first `LinkBlock`.
try di_buf.ensureCapacity(self.dbgInfoNeededHeaderBytes());
// initial length - length of the .debug_info contribution for this compilation unit,
// not including the initial length itself.
// We have to come back and write it later after we know the size.
const after_init_len = di_buf.items.len + init_len_size;
// +1 for the final 0 that ends the compilation unit children.
const dbg_info_end = last_dbg_info_decl.dbg_info_off + last_dbg_info_decl.dbg_info_len + 1;
const init_len = dbg_info_end - after_init_len;
switch (self.ptr_width) {
.p32 => {
mem.writeInt(u32, di_buf.addManyAsArrayAssumeCapacity(4), @intCast(u32, init_len), target_endian);
},
.p64 => {
di_buf.appendNTimesAssumeCapacity(0xff, 4);
mem.writeInt(u64, di_buf.addManyAsArrayAssumeCapacity(8), init_len, target_endian);
},
}
mem.writeInt(u16, di_buf.addManyAsArrayAssumeCapacity(2), 4, target_endian); // DWARF version
const abbrev_offset = self.debug_abbrev_table_offset.?;
switch (self.ptr_width) {
.p32 => {
mem.writeInt(u32, di_buf.addManyAsArrayAssumeCapacity(4), @intCast(u32, abbrev_offset), target_endian);
di_buf.appendAssumeCapacity(4); // address size
},
.p64 => {
mem.writeInt(u64, di_buf.addManyAsArrayAssumeCapacity(8), abbrev_offset, target_endian);
di_buf.appendAssumeCapacity(8); // address size
},
}
// Write the form for the compile unit, which must match the abbrev table above.
const name_strp = try self.makeDebugString(self.base.options.root_pkg.root_src_path);
const comp_dir_strp = try self.makeDebugString(self.base.options.root_pkg.root_src_dir_path);
const producer_strp = try self.makeDebugString(producer_string);
// 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;
di_buf.appendAssumeCapacity(abbrev_compile_unit);
self.writeDwarfAddrAssumeCapacity(&di_buf, 0); // DW.AT_stmt_list, DW.FORM_sec_offset
self.writeDwarfAddrAssumeCapacity(&di_buf, low_pc);
self.writeDwarfAddrAssumeCapacity(&di_buf, high_pc);
self.writeDwarfAddrAssumeCapacity(&di_buf, name_strp);
self.writeDwarfAddrAssumeCapacity(&di_buf, comp_dir_strp);
self.writeDwarfAddrAssumeCapacity(&di_buf, producer_strp);
// We are still waiting on dwarf-std.org to assign DW_LANG_Zig a number:
// http://dwarfstd.org/ShowIssue.php?issue=171115.1
// Until then we say it is C99.
mem.writeInt(u16, di_buf.addManyAsArrayAssumeCapacity(2), DW.LANG_C99, target_endian);
if (di_buf.items.len > first_dbg_info_decl.dbg_info_off) {
// Move the first N decls to the end to make more padding for the header.
@panic("TODO: handle .debug_info header exceeding its padding");
}
const jmp_amt = first_dbg_info_decl.dbg_info_off - di_buf.items.len;
try self.pwriteDbgInfoNops(0, di_buf.items, jmp_amt, false, debug_info_sect.sh_offset);
self.debug_info_header_dirty = false;
}
if (self.debug_aranges_section_dirty) {
const debug_aranges_sect = &self.sections.items[self.debug_aranges_section_index.?];
var di_buf = std.ArrayList(u8).init(self.base.allocator);
defer di_buf.deinit();
// Enough for all the data without resizing. When support for more compilation units
// is added, the size of this section will become more variable.
try di_buf.ensureCapacity(100);
// initial length - length of the .debug_aranges contribution for this compilation unit,
// not including the initial length itself.
// We have to come back and write it later after we know the size.
const init_len_index = di_buf.items.len;
di_buf.items.len += init_len_size;
const after_init_len = di_buf.items.len;
mem.writeInt(u16, di_buf.addManyAsArrayAssumeCapacity(2), 2, target_endian); // version
// When more than one compilation unit is supported, this will be the offset to it.
// For now it is always at offset 0 in .debug_info.
self.writeDwarfAddrAssumeCapacity(&di_buf, 0); // .debug_info offset
di_buf.appendAssumeCapacity(ptr_width_bytes); // address_size
di_buf.appendAssumeCapacity(0); // segment_selector_size
const end_header_offset = di_buf.items.len;
const begin_entries_offset = mem.alignForward(end_header_offset, ptr_width_bytes * 2);
di_buf.appendNTimesAssumeCapacity(0, begin_entries_offset - end_header_offset);
// 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.?];
self.writeDwarfAddrAssumeCapacity(&di_buf, text_phdr.p_vaddr);
self.writeDwarfAddrAssumeCapacity(&di_buf, text_phdr.p_memsz);
// Sentinel.
self.writeDwarfAddrAssumeCapacity(&di_buf, 0);
self.writeDwarfAddrAssumeCapacity(&di_buf, 0);
// Go back and populate the initial length.
const init_len = di_buf.items.len - after_init_len;
switch (self.ptr_width) {
.p32 => {
mem.writeInt(u32, di_buf.items[init_len_index..][0..4], @intCast(u32, init_len), target_endian);
},
.p64 => {
// initial length - length of the .debug_aranges contribution for this compilation unit,
// not including the initial length itself.
di_buf.items[init_len_index..][0..4].* = [_]u8{ 0xff, 0xff, 0xff, 0xff };
mem.writeInt(u64, di_buf.items[init_len_index + 4..][0..8], init_len, target_endian);
},
}
const needed_size = di_buf.items.len;
const allocated_size = self.allocatedSize(debug_aranges_sect.sh_offset);
if (needed_size > allocated_size) {
debug_aranges_sect.sh_size = 0; // free the space
debug_aranges_sect.sh_offset = self.findFreeSpace(needed_size, 16);
}
debug_aranges_sect.sh_size = needed_size;
log.debug(".debug_aranges start=0x{x} end=0x{x}\n", .{
debug_aranges_sect.sh_offset,
debug_aranges_sect.sh_offset + needed_size,
});
try self.base.file.?.pwriteAll(di_buf.items, debug_aranges_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_aranges_section_index.?);
}
self.debug_aranges_section_dirty = false;
}
if (self.debug_line_header_dirty) debug_line: {
if (self.dbg_line_fn_first == null) {
break :debug_line; // Error in module; leave debug_line_header_dirty=true.
}
const dbg_line_prg_off = self.getDebugLineProgramOff();
const dbg_line_prg_end = self.getDebugLineProgramEnd();
assert(dbg_line_prg_end != 0);
const debug_line_sect = &self.sections.items[self.debug_line_section_index.?];
var di_buf = std.ArrayList(u8).init(self.base.allocator);
defer di_buf.deinit();
// The size of this header is variable, depending on the number of directories,
// files, and padding. We have a function to compute the upper bound size, however,
// because it's needed for determining where to put the offset of the first `SrcFn`.
try di_buf.ensureCapacity(self.dbgLineNeededHeaderBytes());
// initial length - length of the .debug_line contribution for this compilation unit,
// not including the initial length itself.
const after_init_len = di_buf.items.len + init_len_size;
const init_len = dbg_line_prg_end - after_init_len;
switch (self.ptr_width) {
.p32 => {
mem.writeInt(u32, di_buf.addManyAsArrayAssumeCapacity(4), @intCast(u32, init_len), target_endian);
},
.p64 => {
di_buf.appendNTimesAssumeCapacity(0xff, 4);
mem.writeInt(u64, di_buf.addManyAsArrayAssumeCapacity(8), init_len, target_endian);
},
}
mem.writeInt(u16, di_buf.addManyAsArrayAssumeCapacity(2), 4, target_endian); // version
// Empirically, debug info consumers do not respect this field, or otherwise
// consider it to be an error when it does not point exactly to the end of the header.
// Therefore we rely on the NOP jump at the beginning of the Line Number Program for
// padding rather than this field.
const before_header_len = di_buf.items.len;
di_buf.items.len += ptr_width_bytes; // We will come back and write this.
const after_header_len = di_buf.items.len;
const opcode_base = DW.LNS_set_isa + 1;
di_buf.appendSliceAssumeCapacity(&[_]u8{
1, // minimum_instruction_length
1, // maximum_operations_per_instruction
1, // default_is_stmt
1, // line_base (signed)
1, // line_range
opcode_base,
// Standard opcode lengths. The number of items here is based on `opcode_base`.
// The value is the number of LEB128 operands the instruction takes.
0, // `DW.LNS_copy`
1, // `DW.LNS_advance_pc`
1, // `DW.LNS_advance_line`
1, // `DW.LNS_set_file`
1, // `DW.LNS_set_column`
0, // `DW.LNS_negate_stmt`
0, // `DW.LNS_set_basic_block`
0, // `DW.LNS_const_add_pc`
1, // `DW.LNS_fixed_advance_pc`
0, // `DW.LNS_set_prologue_end`
0, // `DW.LNS_set_epilogue_begin`
1, // `DW.LNS_set_isa`
0, // include_directories (none except the compilation unit cwd)
});
// file_names[0]
di_buf.appendSliceAssumeCapacity(self.base.options.root_pkg.root_src_path); // relative path name
di_buf.appendSliceAssumeCapacity(&[_]u8{
0, // null byte for the relative path name
0, // directory_index
0, // mtime (TODO supply this)
0, // file size bytes (TODO supply this)
0, // file_names sentinel
});
const header_len = di_buf.items.len - after_header_len;
switch (self.ptr_width) {
.p32 => {
mem.writeInt(u32, di_buf.items[before_header_len..][0..4], @intCast(u32, header_len), target_endian);
},
.p64 => {
mem.writeInt(u64, di_buf.items[before_header_len..][0..8], header_len, target_endian);
},
}
// We use NOPs because consumers empirically do not respect the header length field.
if (di_buf.items.len > dbg_line_prg_off) {
// Move the first N files to the end to make more padding for the header.
@panic("TODO: handle .debug_line header exceeding its padding");
}
const jmp_amt = dbg_line_prg_off - di_buf.items.len;
try self.pwriteDbgLineNops(0, di_buf.items, jmp_amt, debug_line_sect.sh_offset);
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) {
bswapAllFields(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) {
bswapAllFields(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}\n", .{ 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;
}
}
{
const debug_strtab_sect = &self.sections.items[self.debug_str_section_index.?];
if (self.debug_strtab_dirty or self.debug_strtab.items.len != debug_strtab_sect.sh_size) {
const allocated_size = self.allocatedSize(debug_strtab_sect.sh_offset);
const needed_size = self.debug_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}\n", .{ debug_strtab_sect.sh_offset, debug_strtab_sect.sh_offset + needed_size });
try self.base.file.?.pwriteAll(self.debug_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 {}\n", .{shdr.*});
if (foreign_endian) {
bswapAllFields(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 {}\n", .{shdr.*});
if (foreign_endian) {
bswapAllFields(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.output_mode == .Exe) {
log.debug("flushing. no_entry_point_found = true\n", .{});
self.error_flags.no_entry_point_found = true;
} else {
log.debug("flushing. no_entry_point_found = false\n", .{});
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 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].* = "\x7fELF".*;
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.output_mode) {
.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) void {
var already_have_free_list_node = false;
{
var i: usize = 0;
while (i < self.text_block_free_list.items.len) {
if (self.text_block_free_list.items[i] == text_block) {
_ = self.text_block_free_list.swapRemove(i);
continue;
}
if (self.text_block_free_list.items[i] == text_block.prev) {
already_have_free_list_node = true;
}
i += 1;
}
}
if (self.last_text_block == text_block) {
// TODO shrink the .text section size here
self.last_text_block = text_block.prev;
}
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.
self.text_block_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;
}
}
fn shrinkTextBlock(self: *Elf, text_block: *TextBlock, new_block_size: u64) void {
// TODO check the new capacity, and if it crosses the size threshold into a big enough
// capacity, insert a free list node for it.
}
fn growTextBlock(self: *Elf, text_block: *TextBlock, new_block_size: u64, alignment: u64) !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);
}
fn allocateTextBlock(self: *Elf, text_block: *TextBlock, new_block_size: u64, alignment: u64) !u64 {
const phdr = &self.program_headers.items[self.phdr_load_re_index.?];
const shdr = &self.sections.items[self.text_section_index.?];
const new_block_ideal_capacity = new_block_size * alloc_num / alloc_den;
// 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;
// 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 < self.text_block_free_list.items.len) {
const big_block = self.text_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 = capacity * alloc_num / alloc_den;
const ideal_capacity_end_vaddr = sym.st_value + 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.*)) {
_ = self.text_block_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.last_text_block) |last| {
const sym = self.local_symbols.items[last.local_sym_index];
const ideal_capacity = sym.st_size * alloc_num / alloc_den;
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 text section.
const new_offset = self.findFreeSpace(needed_size, 0x1000);
const text_size = if (self.last_text_block) |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;
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;
}
self.last_text_block = text_block;
shdr.sh_size = needed_size;
phdr.p_memsz = needed_size;
phdr.p_filesz = needed_size;
// 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
}
// 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| {
_ = self.text_block_free_list.swapRemove(i);
}
return vaddr;
}
pub fn allocateDeclIndexes(self: *Elf, decl: *Module.Decl) !void {
if (decl.link.elf.local_sym_index != 0) return;
try self.local_symbols.ensureCapacity(self.base.allocator, self.local_symbols.items.len + 1);
try self.offset_table.ensureCapacity(self.base.allocator, self.offset_table.items.len + 1);
if (self.local_symbol_free_list.popOrNull()) |i| {
log.debug("reusing symbol index {} for {}\n", .{ i, decl.name });
decl.link.elf.local_sym_index = i;
} else {
log.debug("allocating symbol index {} for {}\n", .{ self.local_symbols.items.len, decl.name });
decl.link.elf.local_sym_index = @intCast(u32, self.local_symbols.items.len);
_ = self.local_symbols.addOneAssumeCapacity();
}
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;
}
const phdr = &self.program_headers.items[self.phdr_load_re_index.?];
self.local_symbols.items[decl.link.elf.local_sym_index] = .{
.st_name = 0,
.st_info = 0,
.st_other = 0,
.st_shndx = 0,
.st_value = phdr.p_vaddr,
.st_size = 0,
};
self.offset_table.items[decl.link.elf.offset_table_index] = 0;
}
pub fn freeDecl(self: *Elf, decl: *Module.Decl) void {
// Appending to free lists is allowed to fail because the free lists are heuristics based anyway.
self.freeTextBlock(&decl.link.elf);
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.offset_table_free_list.append(self.base.allocator, decl.link.elf.offset_table_index) catch {};
self.local_symbols.items[decl.link.elf.local_sym_index].st_info = 0;
decl.link.elf.local_sym_index = 0;
}
// TODO make this logic match freeTextBlock. Maybe abstract the logic out since the same thing
// is desired for both.
_ = self.dbg_line_fn_free_list.remove(&decl.fn_link.elf);
if (decl.fn_link.elf.prev) |prev| {
_ = self.dbg_line_fn_free_list.put(self.base.allocator, prev, {}) catch {};
prev.next = decl.fn_link.elf.next;
if (decl.fn_link.elf.next) |next| {
next.prev = prev;
} else {
self.dbg_line_fn_last = prev;
}
} else if (decl.fn_link.elf.next) |next| {
self.dbg_line_fn_first = next;
next.prev = null;
}
if (self.dbg_line_fn_first == &decl.fn_link.elf) {
self.dbg_line_fn_first = null;
}
if (self.dbg_line_fn_last == &decl.fn_link.elf) {
self.dbg_line_fn_last = null;
}
}
pub fn updateDecl(self: *Elf, module: *Module, decl: *Module.Decl) !void {
const tracy = trace(@src());
defer tracy.end();
var code_buffer = std.ArrayList(u8).init(self.base.allocator);
defer code_buffer.deinit();
var dbg_line_buffer = std.ArrayList(u8).init(self.base.allocator);
defer dbg_line_buffer.deinit();
var dbg_info_buffer = std.ArrayList(u8).init(self.base.allocator);
defer dbg_info_buffer.deinit();
var dbg_info_type_relocs: DbgInfoTypeRelocsTable = .{};
defer {
for (dbg_info_type_relocs.items()) |*entry| {
entry.value.relocs.deinit(self.base.allocator);
}
dbg_info_type_relocs.deinit(self.base.allocator);
}
const typed_value = decl.typed_value.most_recent.typed_value;
const is_fn: bool = switch (typed_value.ty.zigTypeTag()) {
.Fn => true,
else => false,
};
if (is_fn) {
//if (mem.eql(u8, mem.spanZ(decl.name), "add")) {
// typed_value.val.cast(Value.Payload.Function).?.func.dump(module.*);
//}
// For functions we need to add a prologue to the debug line program.
try dbg_line_buffer.ensureCapacity(26);
const line_off: u28 = blk: {
if (decl.scope.cast(Module.Scope.File)) |scope_file| {
const tree = scope_file.contents.tree;
const file_ast_decls = tree.root_node.decls();
// TODO Look into improving the performance here by adding a token-index-to-line
// lookup table. Currently this involves scanning over the source code for newlines.
const fn_proto = file_ast_decls[decl.src_index].castTag(.FnProto).?;
const block = fn_proto.body().?.castTag(.Block).?;
const line_delta = std.zig.lineDelta(tree.source, 0, tree.token_locs[block.lbrace].start);
break :blk @intCast(u28, line_delta);
} else if (decl.scope.cast(Module.Scope.ZIRModule)) |zir_module| {
const byte_off = zir_module.contents.module.decls[decl.src_index].inst.src;
const line_delta = std.zig.lineDelta(zir_module.source.bytes, 0, byte_off);
break :blk @intCast(u28, line_delta);
} else {
unreachable;
}
};
const ptr_width_bytes = self.ptrWidthBytes();
dbg_line_buffer.appendSliceAssumeCapacity(&[_]u8{
DW.LNS_extended_op,
ptr_width_bytes + 1,
DW.LNE_set_address,
});
// This is the "relocatable" vaddr, corresponding to `code_buffer` index `0`.
assert(dbg_line_vaddr_reloc_index == dbg_line_buffer.items.len);
dbg_line_buffer.items.len += ptr_width_bytes;
dbg_line_buffer.appendAssumeCapacity(DW.LNS_advance_line);
// This is the "relocatable" relative line offset from the previous function's end curly
// to this function's begin curly.
assert(self.getRelocDbgLineOff() == dbg_line_buffer.items.len);
// Here we use a ULEB128-fixed-4 to make sure this field can be overwritten later.
leb128.writeUnsignedFixed(4, dbg_line_buffer.addManyAsArrayAssumeCapacity(4), line_off);
dbg_line_buffer.appendAssumeCapacity(DW.LNS_set_file);
assert(self.getRelocDbgFileIndex() == dbg_line_buffer.items.len);
// Once we support more than one source file, this will have the ability to be more
// than one possible value.
const file_index = 1;
leb128.writeUnsignedFixed(4, dbg_line_buffer.addManyAsArrayAssumeCapacity(4), file_index);
// Emit a line for the begin curly with prologue_end=false. The codegen will
// do the work of setting prologue_end=true and epilogue_begin=true.
dbg_line_buffer.appendAssumeCapacity(DW.LNS_copy);
// .debug_info subprogram
const decl_name_with_null = decl.name[0..mem.lenZ(decl.name) + 1];
try dbg_info_buffer.ensureCapacity(dbg_info_buffer.items.len + 25 + decl_name_with_null.len);
const fn_ret_type = typed_value.ty.fnReturnType();
const fn_ret_has_bits = fn_ret_type.hasCodeGenBits();
if (fn_ret_has_bits) {
dbg_info_buffer.appendAssumeCapacity(abbrev_subprogram);
} else {
dbg_info_buffer.appendAssumeCapacity(abbrev_subprogram_retvoid);
}
// These get overwritten after generating the machine code. These values are
// "relocations" and have to be in this fixed place so that functions can be
// moved in virtual address space.
assert(dbg_info_low_pc_reloc_index == dbg_info_buffer.items.len);
dbg_info_buffer.items.len += ptr_width_bytes; // DW.AT_low_pc, DW.FORM_addr
assert(self.getRelocDbgInfoSubprogramHighPC() == dbg_info_buffer.items.len);
dbg_info_buffer.items.len += 4; // DW.AT_high_pc, DW.FORM_data4
if (fn_ret_has_bits) {
const gop = try dbg_info_type_relocs.getOrPut(self.base.allocator, fn_ret_type);
if (!gop.found_existing) {
gop.entry.value = .{
.off = undefined,
.relocs = .{},
};
}
try gop.entry.value.relocs.append(self.base.allocator, @intCast(u32, dbg_info_buffer.items.len));
dbg_info_buffer.items.len += 4; // DW.AT_type, DW.FORM_ref4
}
dbg_info_buffer.appendSliceAssumeCapacity(decl_name_with_null); // DW.AT_name, DW.FORM_string
} else {
// TODO implement .debug_info for global variables
}
const res = try codegen.generateSymbol(self, decl.src(), typed_value, &code_buffer, &dbg_line_buffer, &dbg_info_buffer, &dbg_info_type_relocs);
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, em);
return;
},
};
const required_alignment = typed_value.ty.abiAlignment(self.base.options.target);
const stt_bits: u8 = if (is_fn) elf.STT_FUNC else elf.STT_OBJECT;
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);
log.debug("growing {} from 0x{x} to 0x{x}\n", .{ 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)\n", .{});
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);
}
local_sym.st_size = code.len;
local_sym.st_name = try self.updateString(local_sym.st_name, mem.spanZ(decl.name));
local_sym.st_info = (elf.STB_LOCAL << 4) | stt_bits;
local_sym.st_other = 0;
local_sym.st_shndx = self.text_section_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 decl_name = mem.spanZ(decl.name);
const name_str_index = try self.makeString(decl_name);
const vaddr = try self.allocateTextBlock(&decl.link.elf, code.len, required_alignment);
log.debug("allocated text block for {} at 0x{x}\n", .{ decl_name, vaddr });
errdefer self.freeTextBlock(&decl.link.elf);
local_sym.* = .{
.st_name = name_str_index,
.st_info = (elf.STB_LOCAL << 4) | stt_bits,
.st_other = 0,
.st_shndx = self.text_section_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[self.phdr_load_re_index.?].p_vaddr;
const file_offset = self.sections.items[self.text_section_index.?].sh_offset + section_offset;
try self.base.file.?.pwriteAll(code, file_offset);
const target_endian = self.base.options.target.cpu.arch.endian();
const text_block = &decl.link.elf;
// If the Decl is a function, we need to update the .debug_line program.
if (is_fn) {
// Perform the relocations based on vaddr.
switch (self.ptr_width) {
.p32 => {
{
const ptr = dbg_line_buffer.items[dbg_line_vaddr_reloc_index..][0..4];
mem.writeInt(u32, ptr, @intCast(u32, local_sym.st_value), target_endian);
}
{
const ptr = dbg_info_buffer.items[dbg_info_low_pc_reloc_index..][0..4];
mem.writeInt(u32, ptr, @intCast(u32, local_sym.st_value), target_endian);
}
},
.p64 => {
{
const ptr = dbg_line_buffer.items[dbg_line_vaddr_reloc_index..][0..8];
mem.writeInt(u64, ptr, local_sym.st_value, target_endian);
}
{
const ptr = dbg_info_buffer.items[dbg_info_low_pc_reloc_index..][0..8];
mem.writeInt(u64, ptr, local_sym.st_value, target_endian);
}
},
}
{
const ptr = dbg_info_buffer.items[self.getRelocDbgInfoSubprogramHighPC()..][0..4];
mem.writeInt(u32, ptr, @intCast(u32, local_sym.st_size), target_endian);
}
try dbg_line_buffer.appendSlice(&[_]u8{ DW.LNS_extended_op, 1, DW.LNE_end_sequence });
// Now we have the full contents and may allocate a region to store it.
// This logic is nearly identical to the logic below in `updateDeclDebugInfo` for
// `TextBlock` and the .debug_info. If you are editing this logic, you
// probably need to edit that logic too.
const debug_line_sect = &self.sections.items[self.debug_line_section_index.?];
const src_fn = &decl.fn_link.elf;
src_fn.len = @intCast(u32, dbg_line_buffer.items.len);
if (self.dbg_line_fn_last) |last| {
if (src_fn.next) |next| {
// Update existing function - non-last item.
if (src_fn.off + src_fn.len + min_nop_size > next.off) {
// It grew too big, so we move it to a new location.
if (src_fn.prev) |prev| {
_ = self.dbg_line_fn_free_list.put(self.base.allocator, prev, {}) catch {};
prev.next = src_fn.next;
}
next.prev = src_fn.prev;
src_fn.next = null;
// Populate where it used to be with NOPs.
const file_pos = debug_line_sect.sh_offset + src_fn.off;
try self.pwriteDbgLineNops(0, &[0]u8{}, src_fn.len, file_pos);
// TODO Look at the free list before appending at the end.
src_fn.prev = last;
last.next = src_fn;
self.dbg_line_fn_last = src_fn;
src_fn.off = last.off + (last.len * alloc_num / alloc_den);
}
} else if (src_fn.prev == null) {
// Append new function.
// TODO Look at the free list before appending at the end.
src_fn.prev = last;
last.next = src_fn;
self.dbg_line_fn_last = src_fn;
src_fn.off = last.off + (last.len * alloc_num / alloc_den);
}
} else {
// This is the first function of the Line Number Program.
self.dbg_line_fn_first = src_fn;
self.dbg_line_fn_last = src_fn;
src_fn.off = self.dbgLineNeededHeaderBytes() * alloc_num / alloc_den;
}
const last_src_fn = self.dbg_line_fn_last.?;
const needed_size = last_src_fn.off + last_src_fn.len;
if (needed_size != debug_line_sect.sh_size) {
if (needed_size > self.allocatedSize(debug_line_sect.sh_offset)) {
const new_offset = self.findFreeSpace(needed_size, 1);
const existing_size = last_src_fn.off;
log.debug("moving .debug_line section: {} bytes from 0x{x} to 0x{x}\n", .{
existing_size,
debug_line_sect.sh_offset,
new_offset,
});
const amt = try self.base.file.?.copyRangeAll(debug_line_sect.sh_offset, self.base.file.?, new_offset, existing_size);
if (amt != existing_size) return error.InputOutput;
debug_line_sect.sh_offset = new_offset;
}
debug_line_sect.sh_size = needed_size;
self.shdr_table_dirty = true; // TODO look into making only the one section dirty
self.debug_line_header_dirty = true;
}
const prev_padding_size: u32 = if (src_fn.prev) |prev| src_fn.off - (prev.off + prev.len) else 0;
const next_padding_size: u32 = if (src_fn.next) |next| next.off - (src_fn.off + src_fn.len) else 0;
// We only have support for one compilation unit so far, so the offsets are directly
// from the .debug_line section.
const file_pos = debug_line_sect.sh_offset + src_fn.off;
try self.pwriteDbgLineNops(prev_padding_size, dbg_line_buffer.items, next_padding_size, file_pos);
// .debug_info - End the TAG_subprogram children.
try dbg_info_buffer.append(0);
}
// Now we emit the .debug_info types of the Decl. These will count towards the size of
// the buffer, so we have to do it before computing the offset, and we can't perform the actual
// relocations yet.
for (dbg_info_type_relocs.items()) |*entry| {
entry.value.off = @intCast(u32, dbg_info_buffer.items.len);
try self.addDbgInfoType(entry.key, &dbg_info_buffer);
}
try self.updateDeclDebugInfoAllocation(text_block, @intCast(u32, dbg_info_buffer.items.len));
// Now that we have the offset assigned we can finally perform type relocations.
for (dbg_info_type_relocs.items()) |entry| {
for (entry.value.relocs.items) |off| {
mem.writeInt(
u32,
dbg_info_buffer.items[off..][0..4],
text_block.dbg_info_off + entry.value.off,
target_endian,
);
}
}
try self.writeDeclDebugInfo(text_block, dbg_info_buffer.items);
// 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) orelse &[0]*Module.Export{};
return self.updateDeclExports(module, decl, decl_exports);
}
/// Asserts the type has codegen bits.
fn addDbgInfoType(self: *Elf, ty: Type, dbg_info_buffer: *std.ArrayList(u8)) !void {
switch (ty.zigTypeTag()) {
.Void => unreachable,
.NoReturn => unreachable,
.Bool => {
try dbg_info_buffer.appendSlice(&[_]u8{
abbrev_base_type,
DW.ATE_boolean, // DW.AT_encoding , DW.FORM_data1
1, // DW.AT_byte_size, DW.FORM_data1
'b', 'o', 'o', 'l', 0, // DW.AT_name, DW.FORM_string
});
},
.Int => {
const info = ty.intInfo(self.base.options.target);
try dbg_info_buffer.ensureCapacity(dbg_info_buffer.items.len + 12);
dbg_info_buffer.appendAssumeCapacity(abbrev_base_type);
// DW.AT_encoding, DW.FORM_data1
dbg_info_buffer.appendAssumeCapacity(if (info.signed) DW.ATE_signed else DW.ATE_unsigned);
// DW.AT_byte_size, DW.FORM_data1
dbg_info_buffer.appendAssumeCapacity(@intCast(u8, ty.abiSize(self.base.options.target)));
// DW.AT_name, DW.FORM_string
try dbg_info_buffer.writer().print("{}\x00", .{ty});
},
else => {
std.log.scoped(.compiler).err("TODO implement .debug_info for type '{}'", .{ty});
try dbg_info_buffer.append(abbrev_pad1);
},
}
}
fn updateDeclDebugInfoAllocation(self: *Elf, text_block: *TextBlock, len: u32) !void {
const tracy = trace(@src());
defer tracy.end();
// This logic is nearly identical to the logic above in `updateDecl` for
// `SrcFn` and the line number programs. If you are editing this logic, you
// probably need to edit that logic too.
const debug_info_sect = &self.sections.items[self.debug_info_section_index.?];
text_block.dbg_info_len = len;
if (self.dbg_info_decl_last) |last| {
if (text_block.dbg_info_next) |next| {
// Update existing Decl - non-last item.
if (text_block.dbg_info_off + text_block.dbg_info_len + min_nop_size > next.dbg_info_off) {
// It grew too big, so we move it to a new location.
if (text_block.dbg_info_prev) |prev| {
_ = self.dbg_info_decl_free_list.put(self.base.allocator, prev, {}) catch {};
prev.dbg_info_next = text_block.dbg_info_next;
}
next.dbg_info_prev = text_block.dbg_info_prev;
text_block.dbg_info_next = null;
// Populate where it used to be with NOPs.
const file_pos = debug_info_sect.sh_offset + text_block.dbg_info_off;
try self.pwriteDbgInfoNops(0, &[0]u8{}, text_block.dbg_info_len, false, file_pos);
// TODO Look at the free list before appending at the end.
text_block.dbg_info_prev = last;
last.dbg_info_next = text_block;
self.dbg_info_decl_last = text_block;
text_block.dbg_info_off = last.dbg_info_off + (last.dbg_info_len * alloc_num / alloc_den);
}
} else if (text_block.dbg_info_prev == null) {
// Append new Decl.
// TODO Look at the free list before appending at the end.
text_block.dbg_info_prev = last;
last.dbg_info_next = text_block;
self.dbg_info_decl_last = text_block;
text_block.dbg_info_off = last.dbg_info_off + (last.dbg_info_len * alloc_num / alloc_den);
}
} else {
// This is the first Decl of the .debug_info
self.dbg_info_decl_first = text_block;
self.dbg_info_decl_last = text_block;
text_block.dbg_info_off = self.dbgInfoNeededHeaderBytes() * alloc_num / alloc_den;
}
}
fn writeDeclDebugInfo(self: *Elf, text_block: *TextBlock, dbg_info_buf: []const u8) !void {
const tracy = trace(@src());
defer tracy.end();
// This logic is nearly identical to the logic above in `updateDecl` for
// `SrcFn` and the line number programs. If you are editing this logic, you
// probably need to edit that logic too.
const debug_info_sect = &self.sections.items[self.debug_info_section_index.?];
const last_decl = self.dbg_info_decl_last.?;
// +1 for a trailing zero to end the children of the decl tag.
const needed_size = last_decl.dbg_info_off + last_decl.dbg_info_len + 1;
if (needed_size != debug_info_sect.sh_size) {
if (needed_size > self.allocatedSize(debug_info_sect.sh_offset)) {
const new_offset = self.findFreeSpace(needed_size, 1);
const existing_size = last_decl.dbg_info_off;
log.debug("moving .debug_info section: {} bytes from 0x{x} to 0x{x}\n", .{
existing_size,
debug_info_sect.sh_offset,
new_offset,
});
const amt = try self.base.file.?.copyRangeAll(debug_info_sect.sh_offset, self.base.file.?, new_offset, existing_size);
if (amt != existing_size) return error.InputOutput;
debug_info_sect.sh_offset = new_offset;
}
debug_info_sect.sh_size = needed_size;
self.shdr_table_dirty = true; // TODO look into making only the one section dirty
self.debug_info_header_dirty = true;
}
const prev_padding_size: u32 = if (text_block.dbg_info_prev) |prev|
text_block.dbg_info_off - (prev.dbg_info_off + prev.dbg_info_len)
else
0;
const next_padding_size: u32 = if (text_block.dbg_info_next) |next|
next.dbg_info_off - (text_block.dbg_info_off + text_block.dbg_info_len)
else
0;
// To end the children of the decl tag.
const trailing_zero = text_block.dbg_info_next == null;
// We only have support for one compilation unit so far, so the offsets are directly
// from the .debug_info section.
const file_pos = debug_info_sect.sh_offset + text_block.dbg_info_off;
try self.pwriteDbgInfoNops(prev_padding_size, dbg_info_buf, next_padding_size, trailing_zero, file_pos);
}
pub fn updateDeclExports(
self: *Elf,
module: *Module,
decl: *const Module.Decl,
exports: []const *Module.Export,
) !void {
const tracy = trace(@src());
defer tracy.end();
try self.global_symbols.ensureCapacity(self.base.allocator, self.global_symbols.items.len + exports.len);
const typed_value = decl.typed_value.most_recent.typed_value;
if (decl.link.elf.local_sym_index == 0) return;
const decl_sym = self.local_symbols.items[decl.link.elf.local_sym_index];
for (exports) |exp| {
if (exp.options.section) |section_name| {
if (!mem.eql(u8, section_name, ".text")) {
try module.failed_exports.ensureCapacity(module.gpa, module.failed_exports.items().len + 1);
module.failed_exports.putAssumeCapacityNoClobber(
exp,
try Module.ErrorMsg.create(self.base.allocator, 0, "Unimplemented: ExportOptions.section", .{}),
);
continue;
}
}
const stb_bits: u8 = switch (exp.options.linkage) {
.Internal => elf.STB_LOCAL,
.Strong => blk: {
if (mem.eql(u8, exp.options.name, "_start")) {
self.entry_addr = decl_sym.st_value;
}
break :blk elf.STB_GLOBAL;
},
.Weak => elf.STB_WEAK,
.LinkOnce => {
try module.failed_exports.ensureCapacity(module.gpa, module.failed_exports.items().len + 1);
module.failed_exports.putAssumeCapacityNoClobber(
exp,
try Module.ErrorMsg.create(self.base.allocator, 0, "Unimplemented: GlobalLinkage.LinkOnce", .{}),
);
continue;
},
};
const stt_bits: u8 = @truncate(u4, decl_sym.st_info);
if (exp.link.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 = self.text_section_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 = self.text_section_index.?,
.st_value = decl_sym.st_value,
.st_size = decl_sym.st_size,
};
exp.link.sym_index = @intCast(u32, i);
}
}
}
/// Must be called only after a successful call to `updateDecl`.
pub fn updateDeclLineNumber(self: *Elf, module: *Module, decl: *const Module.Decl) !void {
const tracy = trace(@src());
defer tracy.end();
const scope_file = decl.scope.cast(Module.Scope.File).?;
const tree = scope_file.contents.tree;
const file_ast_decls = tree.root_node.decls();
// TODO Look into improving the performance here by adding a token-index-to-line
// lookup table. Currently this involves scanning over the source code for newlines.
const fn_proto = file_ast_decls[decl.src_index].castTag(.FnProto).?;
const block = fn_proto.body().?.castTag(.Block).?;
const line_delta = std.zig.lineDelta(tree.source, 0, tree.token_locs[block.lbrace].start);
const casted_line_off = @intCast(u28, line_delta);
const shdr = &self.sections.items[self.debug_line_section_index.?];
const file_pos = shdr.sh_offset + decl.fn_link.elf.off + self.getRelocDbgLineOff();
var data: [4]u8 = undefined;
leb128.writeUnsignedFixed(4, &data, casted_line_off);
try self.base.file.?.pwriteAll(&data, file_pos);
}
pub fn deleteExport(self: *Elf, exp: Export) void {
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() != std.Target.current.cpu.arch.endian();
const offset = self.program_headers.items[index].p_offset;
switch (self.base.options.target.cpu.arch.ptrBitWidth()) {
32 => {
var phdr = [1]elf.Elf32_Phdr{progHeaderTo32(self.program_headers.items[index])};
if (foreign_endian) {
bswapAllFields(elf.Elf32_Phdr, &phdr[0]);
}
return self.base.file.?.pwriteAll(mem.sliceAsBytes(&phdr), offset);
},
64 => {
var phdr = [1]elf.Elf64_Phdr{self.program_headers.items[index]};
if (foreign_endian) {
bswapAllFields(elf.Elf64_Phdr, &phdr[0]);
}
return self.base.file.?.pwriteAll(mem.sliceAsBytes(&phdr), offset);
},
else => return error.UnsupportedArchitecture,
}
}
fn writeSectHeader(self: *Elf, index: usize) !void {
const foreign_endian = self.base.options.target.cpu.arch.endian() != std.Target.current.cpu.arch.endian();
switch (self.base.options.target.cpu.arch.ptrBitWidth()) {
32 => {
var shdr: [1]elf.Elf32_Shdr = undefined;
shdr[0] = sectHeaderTo32(self.sections.items[index]);
if (foreign_endian) {
bswapAllFields(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);
},
64 => {
var shdr = [1]elf.Elf64_Shdr{self.sections.items[index]};
if (foreign_endian) {
bswapAllFields(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);
},
else => return error.UnsupportedArchitecture,
}
}
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.ptrWidthBytes();
if (self.offset_table_count_dirty) {
// TODO Also detect virtual address collisions.
const allocated_size = self.allocatedSize(shdr.sh_offset);
const needed_size = self.local_symbols.items.len * entry_size;
if (needed_size > allocated_size) {
// Must move the entire got section.
const new_offset = self.findFreeSpace(needed_size, entry_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 (self.ptr_width) {
.p32 => {
var buf: [4]u8 = undefined;
mem.writeInt(u32, &buf, @intCast(u32, self.offset_table.items[index]), endian);
try self.base.file.?.pwriteAll(&buf, off);
},
.p64 => {
var buf: [8]u8 = undefined;
mem.writeInt(u64, &buf, self.offset_table.items[index], endian);
try self.base.file.?.pwriteAll(&buf, off);
},
}
}
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);
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() != std.Target.current.cpu.arch.endian();
switch (self.ptr_width) {
.p32 => {
var sym = [1]elf.Elf32_Sym{
.{
.st_name = self.local_symbols.items[index].st_name,
.st_value = @intCast(u32, self.local_symbols.items[index].st_value),
.st_size = @intCast(u32, self.local_symbols.items[index].st_size),
.st_info = self.local_symbols.items[index].st_info,
.st_other = self.local_symbols.items[index].st_other,
.st_shndx = self.local_symbols.items[index].st_shndx,
},
};
if (foreign_endian) {
bswapAllFields(elf.Elf32_Sym, &sym[0]);
}
const off = syms_sect.sh_offset + @sizeOf(elf.Elf32_Sym) * index;
try self.base.file.?.pwriteAll(mem.sliceAsBytes(sym[0..1]), off);
},
.p64 => {
var sym = [1]elf.Elf64_Sym{self.local_symbols.items[index]};
if (foreign_endian) {
bswapAllFields(elf.Elf64_Sym, &sym[0]);
}
const off = syms_sect.sh_offset + @sizeOf(elf.Elf64_Sym) * index;
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 foreign_endian = self.base.options.target.cpu.arch.endian() != std.Target.current.cpu.arch.endian();
const global_syms_off = syms_sect.sh_offset + self.local_symbols.items.len * sym_size;
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| {
sym.* = .{
.st_name = self.global_symbols.items[i].st_name,
.st_value = @intCast(u32, self.global_symbols.items[i].st_value),
.st_size = @intCast(u32, self.global_symbols.items[i].st_size),
.st_info = self.global_symbols.items[i].st_info,
.st_other = self.global_symbols.items[i].st_other,
.st_shndx = self.global_symbols.items[i].st_shndx,
};
if (foreign_endian) {
bswapAllFields(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| {
sym.* = .{
.st_name = self.global_symbols.items[i].st_name,
.st_value = self.global_symbols.items[i].st_value,
.st_size = self.global_symbols.items[i].st_size,
.st_info = self.global_symbols.items[i].st_info,
.st_other = self.global_symbols.items[i].st_other,
.st_shndx = self.global_symbols.items[i].st_shndx,
};
if (foreign_endian) {
bswapAllFields(elf.Elf64_Sym, sym);
}
}
try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), global_syms_off);
},
}
}
fn ptrWidthBytes(self: Elf) u8 {
return switch (self.ptr_width) {
.p32 => 4,
.p64 => 8,
};
}
/// The reloc offset for the virtual address of a function in its Line Number Program.
/// Size is a virtual address integer.
const dbg_line_vaddr_reloc_index = 3;
/// The reloc offset for the virtual address of a function in its .debug_info TAG_subprogram.
/// Size is a virtual address integer.
const dbg_info_low_pc_reloc_index = 1;
/// The reloc offset for the line offset of a function from the previous function's line.
/// It's a fixed-size 4-byte ULEB128.
fn getRelocDbgLineOff(self: Elf) usize {
return dbg_line_vaddr_reloc_index + self.ptrWidthBytes() + 1;
}
fn getRelocDbgFileIndex(self: Elf) usize {
return self.getRelocDbgLineOff() + 5;
}
fn getRelocDbgInfoSubprogramHighPC(self: Elf) u32 {
return dbg_info_low_pc_reloc_index + self.ptrWidthBytes();
}
fn dbgLineNeededHeaderBytes(self: Elf) u32 {
const directory_entry_format_count = 1;
const file_name_entry_format_count = 1;
const directory_count = 1;
const file_name_count = 1;
return @intCast(u32, 53 + directory_entry_format_count * 2 + file_name_entry_format_count * 2 +
directory_count * 8 + file_name_count * 8 +
// These are encoded as DW.FORM_string rather than DW.FORM_strp as we would like
// because of a workaround for readelf and gdb failing to understand DWARFv5 correctly.
self.base.options.root_pkg.root_src_dir_path.len +
self.base.options.root_pkg.root_src_path.len);
}
fn dbgInfoNeededHeaderBytes(self: Elf) u32 {
return 120;
}
const min_nop_size = 2;
/// Writes to the file a buffer, prefixed and suffixed by the specified number of
/// bytes of NOPs. Asserts each padding size is at least `min_nop_size` and total padding bytes
/// are less than 126,976 bytes (if this limit is ever reached, this function can be
/// improved to make more than one pwritev call, or the limit can be raised by a fixed
/// amount by increasing the length of `vecs`).
fn pwriteDbgLineNops(
self: *Elf,
prev_padding_size: usize,
buf: []const u8,
next_padding_size: usize,
offset: usize,
) !void {
const tracy = trace(@src());
defer tracy.end();
const page_of_nops = [1]u8{DW.LNS_negate_stmt} ** 4096;
const three_byte_nop = [3]u8{DW.LNS_advance_pc, 0b1000_0000, 0};
var vecs: [32]std.os.iovec_const = undefined;
var vec_index: usize = 0;
{
var padding_left = prev_padding_size;
if (padding_left % 2 != 0) {
vecs[vec_index] = .{
.iov_base = &three_byte_nop,
.iov_len = three_byte_nop.len,
};
vec_index += 1;
padding_left -= three_byte_nop.len;
}
while (padding_left > page_of_nops.len) {
vecs[vec_index] = .{
.iov_base = &page_of_nops,
.iov_len = page_of_nops.len,
};
vec_index += 1;
padding_left -= page_of_nops.len;
}
if (padding_left > 0) {
vecs[vec_index] = .{
.iov_base = &page_of_nops,
.iov_len = padding_left,
};
vec_index += 1;
}
}
vecs[vec_index] = .{
.iov_base = buf.ptr,
.iov_len = buf.len,
};
vec_index += 1;
{
var padding_left = next_padding_size;
if (padding_left % 2 != 0) {
vecs[vec_index] = .{
.iov_base = &three_byte_nop,
.iov_len = three_byte_nop.len,
};
vec_index += 1;
padding_left -= three_byte_nop.len;
}
while (padding_left > page_of_nops.len) {
vecs[vec_index] = .{
.iov_base = &page_of_nops,
.iov_len = page_of_nops.len,
};
vec_index += 1;
padding_left -= page_of_nops.len;
}
if (padding_left > 0) {
vecs[vec_index] = .{
.iov_base = &page_of_nops,
.iov_len = padding_left,
};
vec_index += 1;
}
}
try self.base.file.?.pwritevAll(vecs[0..vec_index], offset - prev_padding_size);
}
/// Writes to the file a buffer, prefixed and suffixed by the specified number of
/// bytes of padding.
fn pwriteDbgInfoNops(
self: *Elf,
prev_padding_size: usize,
buf: []const u8,
next_padding_size: usize,
trailing_zero: bool,
offset: usize,
) !void {
const tracy = trace(@src());
defer tracy.end();
const page_of_nops = [1]u8{abbrev_pad1} ** 4096;
var vecs: [32]std.os.iovec_const = undefined;
var vec_index: usize = 0;
{
var padding_left = prev_padding_size;
while (padding_left > page_of_nops.len) {
vecs[vec_index] = .{
.iov_base = &page_of_nops,
.iov_len = page_of_nops.len,
};
vec_index += 1;
padding_left -= page_of_nops.len;
}
if (padding_left > 0) {
vecs[vec_index] = .{
.iov_base = &page_of_nops,
.iov_len = padding_left,
};
vec_index += 1;
}
}
vecs[vec_index] = .{
.iov_base = buf.ptr,
.iov_len = buf.len,
};
vec_index += 1;
{
var padding_left = next_padding_size;
while (padding_left > page_of_nops.len) {
vecs[vec_index] = .{
.iov_base = &page_of_nops,
.iov_len = page_of_nops.len,
};
vec_index += 1;
padding_left -= page_of_nops.len;
}
if (padding_left > 0) {
vecs[vec_index] = .{
.iov_base = &page_of_nops,
.iov_len = padding_left,
};
vec_index += 1;
}
}
if (trailing_zero) {
var zbuf = [1]u8{0};
vecs[vec_index] = .{
.iov_base = &zbuf,
.iov_len = zbuf.len,
};
vec_index += 1;
}
try self.base.file.?.pwritevAll(vecs[0..vec_index], offset - prev_padding_size);
}
};
pub const MachO = @import("link/MachO.zig");
const Wasm = @import("link/Wasm.zig");
};
/// Saturating multiplication
fn satMul(a: anytype, b: anytype) @TypeOf(a, b) {
const T = @TypeOf(a, b);
return std.math.mul(T, a, b) catch std.math.maxInt(T);
}
fn bswapAllFields(comptime S: type, ptr: *S) void {
@panic("TODO implement bswapAllFields");
}
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),
};
}
pub fn determineMode(options: Options) fs.File.Mode {
// On common systems with a 0o022 umask, 0o777 will still result in a file created
// with 0o755 permissions, but it works appropriately if the system is configured
// more leniently. As another data point, C's fopen seems to open files with the
// 666 mode.
const executable_mode = if (std.Target.current.os.tag == .windows) 0 else 0o777;
switch (options.output_mode) {
.Lib => return switch (options.link_mode) {
.Dynamic => executable_mode,
.Static => fs.File.default_mode,
},
.Exe => return executable_mode,
.Obj => return fs.File.default_mode,
}
}
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