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Write local symbols when flushing

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This commit is contained in:
Jakub Konka 2020-11-16 12:04:55 +01:00
parent b3fdfe5ca0
commit 6ac7e99dad
1 changed files with 81 additions and 90 deletions
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171
src/link/MachO.zig
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@ -322,33 +322,15 @@ pub fn flushModule(self: *MachO, comp: *Compilation) !void {
const tracy = trace(@src()); const tracy = trace(@src());
defer tracy.end(); defer tracy.end();
// Unfortunately these have to be buffered and done at the end because MachO does not allow
// mixing local, global and undefined symbols within a symbol table.
try self.writeAllGlobalSymbols();
try self.writeAllUndefSymbols();
switch (self.base.options.output_mode) { switch (self.base.options.output_mode) {
.Exe => { .Exe => {
// Write export trie.
try self.writeExportTrie();
if (self.entry_addr) |addr| { if (self.entry_addr) |addr| {
// Update LC_MAIN with entry offset. // Update LC_MAIN with entry offset.
const text_segment = self.load_commands.items[self.text_segment_cmd_index.?].Segment; const text_segment = self.load_commands.items[self.text_segment_cmd_index.?].Segment;
const main_cmd = &self.load_commands.items[self.main_cmd_index.?].EntryPoint; const main_cmd = &self.load_commands.items[self.main_cmd_index.?].EntryPoint;
main_cmd.entryoff = addr - text_segment.vmaddr; main_cmd.entryoff = addr - text_segment.vmaddr;
} }
{
// Update dynamic symbol table.
const nlocals = @intCast(u32, self.local_symbols.items.len);
const nglobals = @intCast(u32, self.global_symbols.items.len);
const nundefs = @intCast(u32, self.undef_symbols.items.len);
const dysymtab = &self.load_commands.items[self.dysymtab_cmd_index.?].Dysymtab;
dysymtab.nlocalsym = nlocals;
dysymtab.iextdefsym = nlocals;
dysymtab.nextdefsym = nglobals;
dysymtab.iundefsym = nlocals + nglobals;
dysymtab.nundefsym = nundefs;
}
if (self.dylinker_cmd_dirty) { if (self.dylinker_cmd_dirty) {
// Write path to dyld loader. // Write path to dyld loader.
var off: usize = @sizeOf(macho.mach_header_64); var off: usize = @sizeOf(macho.mach_header_64);
@ -375,27 +357,34 @@ pub fn flushModule(self: *MachO, comp: *Compilation) !void {
try self.base.file.?.pwriteAll(mem.spanZ(LIB_SYSTEM_PATH), off); try self.base.file.?.pwriteAll(mem.spanZ(LIB_SYSTEM_PATH), off);
self.libsystem_cmd_dirty = false; self.libsystem_cmd_dirty = false;
} }
// Write export trie.
try self.writeExportTrie();
const linkedit = &self.load_commands.items[self.linkedit_segment_cmd_index.?].Segment;
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
const dyld_info = &self.load_commands.items[self.dyld_info_cmd_index.?].DyldInfo;
linkedit.fileoff = dyld_info.export_off;
symtab.symoff = dyld_info.export_off + dyld_info.export_size;
}, },
.Obj => {}, .Obj => {},
.Lib => return error.TODOImplementWritingLibFiles, .Lib => return error.TODOImplementWritingLibFiles,
} }
{ // Unfortunately these have to be buffered and done at the end because MachO does not allow
// Update symbol table. // mixing local, global and undefined symbols within a symbol table.
const nlocals = @intCast(u32, self.local_symbols.items.len); try self.writeSymbolTable();
const nglobals = @intCast(u32, self.global_symbols.items.len);
const nundefs = @intCast(u32, self.undef_symbols.items.len);
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
symtab.nsyms = nlocals + nglobals + nundefs;
symtab.stroff = symtab.symoff + symtab.nsyms * @sizeOf(macho.nlist_64);
// Extend dynamic linker info until start of symbol table
const dyld_info = &self.load_commands.items[self.dyld_info_cmd_index.?].DyldInfo;
dyld_info.export_size = symtab.symoff - dyld_info.export_off;
}
try self.writeStringTable(); try self.writeStringTable();
{
// TODO rework how we preallocate space for the entire __LINKEDIT segment instead of
// doing dynamic updates like this.
const linkedit = &self.load_commands.items[self.linkedit_segment_cmd_index.?].Segment;
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
const file_size = symtab.stroff + symtab.strsize - linkedit.fileoff;
linkedit.filesize = file_size;
linkedit.vmsize = mem.alignForwardGeneric(u64, file_size, 0x1000);
}
if (self.cmd_table_dirty) { if (self.cmd_table_dirty) {
try self.writeCmdHeaders(); try self.writeCmdHeaders();
try self.writeMachOHeader(); try self.writeMachOHeader();
@ -984,7 +973,7 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
symbol.n_sect = @intCast(u8, self.text_section_index.?) + 1; symbol.n_sect = @intCast(u8, self.text_section_index.?) + 1;
symbol.n_desc = 0; symbol.n_desc = 0;
// TODO this write could be avoided if no fields of the symbol were changed. // TODO this write could be avoided if no fields of the symbol were changed.
try self.writeSymbol(decl.link.macho.local_sym_index); // try self.writeSymbol(decl.link.macho.local_sym_index);
} else { } else {
const decl_name = mem.spanZ(decl.name); const decl_name = mem.spanZ(decl.name);
const name_str_index = try self.makeString(decl_name); const name_str_index = try self.makeString(decl_name);
@ -1001,7 +990,7 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
}; };
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.local_sym_index); // try self.writeSymbol(decl.link.macho.local_sym_index);
try self.writeOffsetTableEntry(decl.link.macho.offset_table_index); try self.writeOffsetTableEntry(decl.link.macho.offset_table_index);
} }
@ -1399,48 +1388,6 @@ pub fn populateMissingMetadata(self: *MachO) !void {
}, },
}); });
} }
{
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;
if (dyld_info.export_off == 0) {
const nsyms = self.base.options.symbol_count_hint;
const file_size = @sizeOf(u64) * nsyms;
const off = @intCast(u32, self.findFreeSpace(file_size, 0x1000));
log.debug("found export trie free space 0x{x} to 0x{x}\n", .{ off, off + file_size });
dyld_info.export_off = off;
dyld_info.export_size = @intCast(u32, file_size);
const segment_size = mem.alignForwardGeneric(u64, file_size, 0x1000);
linkedit.vmsize += segment_size;
linkedit.fileoff = off;
}
}
{
const linkedit = &self.load_commands.items[self.linkedit_segment_cmd_index.?].Segment;
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
if (symtab.symoff == 0) {
const nsyms = self.base.options.symbol_count_hint;
const file_size = @sizeOf(macho.nlist_64) * nsyms;
const off = @intCast(u32, self.findFreeSpace(file_size, 0x1000));
log.debug("found symbol table free space 0x{x} to 0x{x}\n", .{ off, off + file_size });
symtab.symoff = off;
symtab.nsyms = @intCast(u32, nsyms);
const segment_size = mem.alignForwardGeneric(u64, file_size, 0x1000);
linkedit.vmsize += segment_size;
}
if (symtab.stroff == 0) {
try self.string_table.append(self.base.allocator, 0);
const file_size = @intCast(u32, self.string_table.items.len);
const off = @intCast(u32, self.findFreeSpace(file_size, 0x1000));
log.debug("found string table free space 0x{x} to 0x{x}\n", .{ off, off + file_size });
symtab.stroff = off;
symtab.strsize = file_size;
const segment_size = mem.alignForwardGeneric(u64, file_size, 0x1000);
linkedit.vmsize += segment_size;
}
}
if (self.dyld_stub_binder_index == null) { if (self.dyld_stub_binder_index == null) {
self.dyld_stub_binder_index = @intCast(u16, self.undef_symbols.items.len); self.dyld_stub_binder_index = @intCast(u16, self.undef_symbols.items.len);
const name = try self.makeString("dyld_stub_binder"); const name = try self.makeString("dyld_stub_binder");
@ -1687,6 +1634,53 @@ fn writeOffsetTableEntry(self: *MachO, index: usize) !void {
try self.base.file.?.pwriteAll(&buf, off); try self.base.file.?.pwriteAll(&buf, off);
} }
fn writeSymbolTable(self: *MachO) !void {
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
const locals_off = symtab.symoff;
var locals = try self.base.allocator.alloc(macho.nlist_64, self.local_symbols.items.len - 1);
defer self.base.allocator.free(locals);
for (locals) |*sym, i| {
sym.* = .{
.n_strx = self.local_symbols.items[i + 1].n_strx,
.n_type = self.local_symbols.items[i + 1].n_type,
.n_sect = self.local_symbols.items[i + 1].n_sect,
.n_desc = self.local_symbols.items[i + 1].n_desc,
.n_value = self.local_symbols.items[i + 1].n_value,
};
}
const locals_size = locals.len * @sizeOf(macho.nlist_64);
log.debug("writing local symbols from 0x{x} to 0x{x}\n", .{ locals_off, locals_size + locals_off });
try self.base.file.?.pwriteAll(mem.sliceAsBytes(locals), locals_off);
const globals_off = locals_off + locals_size;
const globals_size = self.global_symbols.items.len * @sizeOf(macho.nlist_64);
log.debug("writing global symbols from 0x{x} to 0x{x}\n", .{ globals_off, globals_size + globals_off });
try self.base.file.?.pwriteAll(mem.sliceAsBytes(self.global_symbols.items), globals_off);
const undefs_off = globals_off + globals_size;
const undefs_size = self.undef_symbols.items.len * @sizeOf(macho.nlist_64);
log.debug("writing undef symbols from 0x{x} to 0x{x}\n", .{ undefs_off, undefs_size + undefs_off });
try self.base.file.?.pwriteAll(mem.sliceAsBytes(self.undef_symbols.items), undefs_off);
// Update symbol table.
const nlocals = @intCast(u32, locals.len);
const nglobals = @intCast(u32, self.global_symbols.items.len);
const nundefs = @intCast(u32, self.undef_symbols.items.len);
symtab.nsyms = nlocals + nglobals + nundefs;
symtab.stroff = symtab.symoff + symtab.nsyms * @sizeOf(macho.nlist_64);
// Update dynamic symbol table.
const dysymtab = &self.load_commands.items[self.dysymtab_cmd_index.?].Dysymtab;
dysymtab.nlocalsym = nlocals;
dysymtab.iextdefsym = nlocals;
dysymtab.nextdefsym = nglobals;
dysymtab.iundefsym = nlocals + nglobals;
dysymtab.nundefsym = nundefs;
}
fn writeAllGlobalSymbols(self: *MachO) !void { fn writeAllGlobalSymbols(self: *MachO) !void {
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab; const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
const off = symtab.symoff + self.local_symbols.items.len * @sizeOf(macho.nlist_64); const off = symtab.symoff + self.local_symbols.items.len * @sizeOf(macho.nlist_64);
@ -1728,29 +1722,26 @@ fn writeExportTrie(self: *MachO) !void {
try trie.writeULEB128Mem(self.base.allocator, &buffer); try trie.writeULEB128Mem(self.base.allocator, &buffer);
const data = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
const dyld_info = &self.load_commands.items[self.dyld_info_cmd_index.?].DyldInfo; const dyld_info = &self.load_commands.items[self.dyld_info_cmd_index.?].DyldInfo;
dyld_info.export_off = @intCast(u32, data.fileoff + data.filesize);
dyld_info.export_size = mem.alignForwardGeneric(u32, @intCast(u32, buffer.items.len), @sizeOf(u64));
try self.base.file.?.pwriteAll(buffer.items, dyld_info.export_off); try self.base.file.?.pwriteAll(buffer.items, dyld_info.export_off);
} }
fn writeStringTable(self: *MachO) !void { fn writeStringTable(self: *MachO) !void {
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab; const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
const allocated_size = self.allocatedSize(symtab.stroff); // const allocated_size = self.allocatedSize(symtab.stroff);
const needed_size = self.string_table.items.len; const needed_size = self.string_table.items.len;
if (needed_size > allocated_size) { // if (needed_size > allocated_size) {
symtab.strsize = 0; // symtab.strsize = 0;
symtab.stroff = @intCast(u32, self.findFreeSpace(needed_size, 1)); // symtab.stroff = @intCast(u32, self.findFreeSpace(needed_size, 1));
} // }
symtab.strsize = @intCast(u32, needed_size); symtab.strsize = mem.alignForwardGeneric(u32, @intCast(u32, needed_size), @sizeOf(u64));
try self.base.file.?.pwriteAll(&[_]u8{ 0 }, symtab.stroff + symtab.strsize - 1);
log.debug("writing string table from 0x{x} to 0x{x}\n", .{ symtab.stroff, symtab.stroff + symtab.strsize }); log.debug("writing string table from 0x{x} to 0x{x}\n", .{ symtab.stroff, symtab.stroff + needed_size });
try self.base.file.?.pwriteAll(self.string_table.items, symtab.stroff); try self.base.file.?.pwriteAll(self.string_table.items, symtab.stroff);
// TODO rework how we preallocate space for the entire __LINKEDIT segment instead of
// doing dynamic updates like this.
const linkedit = &self.load_commands.items[self.linkedit_segment_cmd_index.?].Segment;
linkedit.filesize = symtab.stroff + symtab.strsize - linkedit.fileoff;
} }
fn writeCmdHeaders(self: *MachO) !void { fn writeCmdHeaders(self: *MachO) !void {