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Redo local symbols and offsets tracking to match Elf's approach

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This commit is contained in:
Jakub Konka 2020-10-01 20:20:01 +02:00
parent 2ba23abd9d
commit 737a8bf204
2 changed files with 48 additions and 30 deletions
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4
src/codegen.zig
View File

@ -1532,7 +1532,7 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
if (func_inst.val.cast(Value.Payload.Function)) |func_val| {
const func = func_val.func;
const got = &macho_file.sections.items[macho_file.got_section_index.?];
const got_addr = got.addr + func.owner_decl.link.macho.offset_table_index.? * @sizeOf(u64);
const got_addr = got.addr + func.owner_decl.link.macho.offset_table_index * @sizeOf(u64);
// Here, we store the got address in %rax, and then call %rax
// movabsq [addr], %rax
try self.genSetReg(inst.base.src, .rax, .{ .memory = got_addr });
@ -2591,7 +2591,7 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
} else if (self.bin_file.cast(link.File.MachO)) |macho_file| {
const decl = payload.decl;
const got = &macho_file.sections.items[macho_file.got_section_index.?];
const got_addr = got.addr + decl.link.macho.offset_table_index.? * ptr_bytes;
const got_addr = got.addr + decl.link.macho.offset_table_index * ptr_bytes;
return MCValue{ .memory = got_addr };
} else if (self.bin_file.cast(link.File.Coff)) |coff_file| {
const decl = payload.decl;

74
src/link/MachO.zig
View File

@ -149,19 +149,27 @@ const LIB_SYSTEM_NAME: [*:0]const u8 = "System";
const LIB_SYSTEM_PATH: [*:0]const u8 = DEFAULT_LIB_SEARCH_PATH ++ "/libSystem.B.dylib";
pub const TextBlock = struct {
/// Index into the symbol table
symbol_table_index: ?u32,
/// 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,
/// Index into offset table
offset_table_index: ?u32,
/// This field is undefined for symbols with size = 0.
offset_table_index: u32,
/// Size of this text block
/// Unlike in Elf, we need to store the size of this symbol as part of
/// the TextBlock since macho.nlist_64 lacks this information.
size: u64,
/// Points to the previous and next neighbours
prev: ?*TextBlock,
next: ?*TextBlock,
pub const empty = TextBlock{
.symbol_table_index = null,
.offset_table_index = null,
.local_sym_index = 0,
.offset_table_index = undefined,
.size = 0,
.prev = null,
.next = null,
@ -190,6 +198,15 @@ pub fn openPath(allocator: *Allocator, sub_path: []const u8, options: link.Optio
self.base.file = file;
// Index 0 is always a null symbol.
try self.local_symbols.append(allocator, .{
.n_strx = 0,
.n_type = 0,
.n_sect = 0,
.n_desc = 0,
.n_value = 0,
});
switch (options.output_mode) {
.Exe => {},
.Obj => {},
@ -717,26 +734,26 @@ pub fn deinit(self: *MachO) void {
}
pub fn allocateDeclIndexes(self: *MachO, decl: *Module.Decl) !void {
if (decl.link.macho.symbol_table_index) |_| return;
if (decl.link.macho.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);
log.debug("allocating symbol index {} for {}\n", .{ self.local_symbols.items.len, decl.name });
decl.link.macho.symbol_table_index = @intCast(u32, self.local_symbols.items.len);
decl.link.macho.local_sym_index = @intCast(u32, self.local_symbols.items.len);
_ = self.local_symbols.addOneAssumeCapacity();
decl.link.macho.offset_table_index = @intCast(u32, self.offset_table.items.len);
_ = self.offset_table.addOneAssumeCapacity();
self.local_symbols.items[decl.link.macho.symbol_table_index.?] = .{
self.local_symbols.items[decl.link.macho.local_sym_index] = .{
.n_strx = 0,
.n_type = 0,
.n_sect = 0,
.n_desc = 0,
.n_value = 0,
};
self.offset_table.items[decl.link.macho.offset_table_index.?] = 0;
self.offset_table.items[decl.link.macho.offset_table_index] = 0;
}
pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
@ -761,7 +778,7 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
log.debug("generated code {}\n", .{code});
const required_alignment = typed_value.ty.abiAlignment(self.base.options.target);
const symbol = &self.local_symbols.items[decl.link.macho.symbol_table_index.?];
const symbol = &self.local_symbols.items[decl.link.macho.local_sym_index];
const decl_name = mem.spanZ(decl.name);
const name_str_index = try self.makeString(decl_name);
@ -776,10 +793,10 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
.n_desc = 0,
.n_value = addr,
};
self.offset_table.items[decl.link.macho.offset_table_index.?] = addr;
self.offset_table.items[decl.link.macho.offset_table_index] = addr;
try self.writeSymbol(decl.link.macho.symbol_table_index.?);
try self.writeOffsetTableEntry(decl.link.macho.offset_table_index.?);
try self.writeSymbol(decl.link.macho.local_sym_index);
try self.writeOffsetTableEntry(decl.link.macho.offset_table_index);
const text_section = self.sections.items[self.text_section_index.?];
const section_offset = symbol.n_value - text_section.addr;
@ -805,8 +822,8 @@ pub fn updateDeclExports(
defer tracy.end();
try self.global_symbols.ensureCapacity(self.base.allocator, self.global_symbols.items.len + exports.len);
if (decl.link.macho.symbol_table_index == null) return;
const decl_sym = &self.local_symbols.items[decl.link.macho.symbol_table_index.?];
if (decl.link.macho.local_sym_index == 0) return;
const decl_sym = &self.local_symbols.items[decl.link.macho.local_sym_index];
for (exports) |exp| {
if (exp.options.section) |section_name| {
@ -867,7 +884,8 @@ pub fn updateDeclExports(
pub fn freeDecl(self: *MachO, decl: *Module.Decl) void {}
pub fn getDeclVAddr(self: *MachO, decl: *const Module.Decl) u64 {
return self.local_symbols.items[decl.link.macho.symbol_table_index.?].n_value;
assert(decl.link.macho.local_sym_index != 0);
return self.local_symbols.items[decl.link.macho.local_sym_index].n_value;
}
pub fn populateMissingMetadata(self: *MachO) !void {
@ -1126,17 +1144,6 @@ pub fn populateMissingMetadata(self: *MachO) !void {
});
self.cmd_table_dirty = true;
}
if (self.dyld_stub_binder_index == null) {
self.dyld_stub_binder_index = @intCast(u16, self.undef_symbols.items.len);
const name = try self.makeString("dyld_stub_binder");
try self.undef_symbols.append(self.base.allocator, .{
.n_strx = name,
.n_type = macho.N_UNDF | macho.N_EXT,
.n_sect = 0,
.n_desc = macho.REFERENCE_FLAG_UNDEFINED_NON_LAZY | macho.N_SYMBOL_RESOLVER,
.n_value = 0,
});
}
{
const linkedit = &self.load_commands.items[self.linkedit_segment_cmd_index.?].Segment;
const dyld_info = &self.load_commands.items[self.dyld_info_cmd_index.?].DyldInfo;
@ -1175,6 +1182,17 @@ pub fn populateMissingMetadata(self: *MachO) !void {
symtab.strsize = file_size;
}
}
if (self.dyld_stub_binder_index == null) {
self.dyld_stub_binder_index = @intCast(u16, self.undef_symbols.items.len);
const name = try self.makeString("dyld_stub_binder");
try self.undef_symbols.append(self.base.allocator, .{
.n_strx = name,
.n_type = macho.N_UNDF | macho.N_EXT,
.n_sect = 0,
.n_desc = macho.REFERENCE_FLAG_UNDEFINED_NON_LAZY | macho.N_SYMBOL_RESOLVER,
.n_value = 0,
});
}
}
fn allocateTextBlock(self: *MachO, text_block: *TextBlock, new_block_size: u64, alignment: u64) !u64 {
@ -1184,7 +1202,7 @@ fn allocateTextBlock(self: *MachO, text_block: *TextBlock, new_block_size: u64,
var block_placement: ?*TextBlock = null;
const addr = blk: {
if (self.last_text_block) |last| {
const last_symbol = self.local_symbols.items[last.symbol_table_index.?];
const last_symbol = self.local_symbols.items[last.local_sym_index];
// TODO pad out with NOPs and reenable
// const ideal_capacity = last.size * alloc_num / alloc_den;
// const ideal_capacity_end_addr = last_symbol.n_value + ideal_capacity;