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Write out LC_DYSYMTAB together with dyld_stub_binder undef symbol

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This commit is contained in:
Jakub Konka 2020-09-29 22:31:12 +02:00
parent a927f24201
commit ccf9bba61f
2 changed files with 75 additions and 3 deletions
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6
lib/std/macho.zig
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@ -1295,3 +1295,9 @@ pub const N_WEAK_REF: u16 = 0x40;
/// another (non-weak) definition for this symbol, the weak definition is ignored. Only symbols in a
/// coalesced section (page 23) can be marked as a weak definition.
pub const N_WEAK_DEF: u16 = 0x80;
/// The N_SYMBOL_RESOLVER bit of the n_desc field indicates that the
/// that the function is actually a resolver function and should
/// be called to get the address of the real function to use.
/// This bit is only available in .o files (MH_OBJECT filetype)
pub const N_SYMBOL_RESOLVER: u16 = 0x100;

72
src/link/MachO.zig
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@ -106,10 +106,14 @@ got_section_index: ?u16 = null,
entry_addr: ?u64 = null,
/// Table of all local symbols used.
/// Table of all local symbols
/// Internally references string table for names (which are optional).
local_symbols: std.ArrayListUnmanaged(macho.nlist_64) = .{},
/// Table of all defined global symbols
global_symbols: std.ArrayListUnmanaged(macho.nlist_64) = .{},
/// Table of all undefined symbols
undef_symbols: std.ArrayListUnmanaged(macho.nlist_64) = .{},
dyld_stub_binder_index: ?u16 = null,
/// Table of symbol names aka the string table.
string_table: std.ArrayListUnmanaged(u8) = .{},
@ -235,10 +239,11 @@ pub fn flushModule(self: *MachO, comp: *Compilation) !void {
// 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();
try self.writeAllUndefSymbols();
{
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
symtab.nsyms = @intCast(u32, self.local_symbols.items.len + self.global_symbols.items.len);
symtab.nsyms = @intCast(u32, self.local_symbols.items.len + self.global_symbols.items.len + self.undef_symbols.items.len);
const allocated_size = self.allocatedSize(symtab.stroff);
const needed_size = self.string_table.items.len;
log.debug("allocated_size = 0x{x}, needed_size = 0x{x}\n", .{ allocated_size, needed_size });
@ -253,6 +258,17 @@ pub fn flushModule(self: *MachO, comp: *Compilation) !void {
try self.base.file.?.pwriteAll(self.string_table.items, symtab.stroff);
}
{
const dysymtab = &self.load_commands.items[self.dysymtab_cmd_index.?].Dysymtab;
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);
dysymtab.nlocalsym = nlocals;
dysymtab.iextdefsym = nlocals;
dysymtab.nextdefsym = nglobals;
dysymtab.iundefsym = nlocals + nglobals;
dysymtab.nundefsym = nundefs;
}
{
var last_cmd_offset: usize = @sizeOf(macho.mach_header_64);
for (self.load_commands.items) |cmd| {
@ -1018,6 +1034,34 @@ pub fn populateMissingMetadata(self: *MachO) !void {
});
self.cmd_table_dirty = true;
}
if (self.dysymtab_cmd_index == null) {
self.dysymtab_cmd_index = @intCast(u16, self.load_commands.items.len);
try self.load_commands.append(self.base.allocator, .{
.Dysymtab = .{
.cmd = macho.LC_DYSYMTAB,
.cmdsize = @sizeOf(macho.dysymtab_command),
.ilocalsym = 0,
.nlocalsym = 0,
.iextdefsym = 0,
.nextdefsym = 0,
.iundefsym = 0,
.nundefsym = 0,
.tocoff = 0,
.ntoc = 0,
.modtaboff = 0,
.nmodtab = 0,
.extrefsymoff = 0,
.nextrefsyms = 0,
.indirectsymoff = 0,
.nindirectsyms = 0,
.extreloff = 0,
.nextrel = 0,
.locreloff = 0,
.nlocrel = 0,
},
});
self.cmd_table_dirty = true;
}
if (self.dylinker_cmd_index == null) {
self.dylinker_cmd_index = @intCast(u16, self.load_commands.items.len);
const cmdsize = commandSize(@sizeOf(macho.dylinker_command) + mem.lenZ(DEFAULT_DYLD_PATH));
@ -1063,6 +1107,17 @@ 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 symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
@ -1296,10 +1351,21 @@ fn writeOffsetTableEntry(self: *MachO, index: usize) !void {
fn writeAllGlobalSymbols(self: *MachO) !void {
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
const off = symtab.symoff + self.local_symbols.items.len * @sizeOf(macho.nlist_64);
log.debug("writing global symbols from 0x{x} to 0x{x}\n", .{ off, self.global_symbols.items.len + off });
const file_size = self.global_symbols.items.len * @sizeOf(macho.nlist_64);
log.debug("writing global symbols from 0x{x} to 0x{x}\n", .{ off, file_size + off });
try self.base.file.?.pwriteAll(mem.sliceAsBytes(self.global_symbols.items), off);
}
fn writeAllUndefSymbols(self: *MachO) !void {
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
const nlocals = self.local_symbols.items.len;
const nglobals = self.global_symbols.items.len;
const off = symtab.symoff + (nlocals + nglobals) * @sizeOf(macho.nlist_64);
const file_size = self.undef_symbols.items.len * @sizeOf(macho.nlist_64);
log.debug("writing undef symbols from 0x{x} to 0x{x}\n", .{ off, file_size + off });
try self.base.file.?.pwriteAll(mem.sliceAsBytes(self.undef_symbols.items), off);
}
/// Writes Mach-O file header.
/// Should be invoked last as it needs up-to-date values of ncmds and sizeof_cmds bookkeeping
/// variables.