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macho: ensure we zero-out regions after copying them over

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This is to ensure that the loader correctly zeroes-out zerofill
sections when mapping them. For context, Apple's loader dyld
will map the regions where any zerofill would theoretically reside
as belonging to zerofill section.
This commit is contained in:
Jakub Konka 2024-01-21 10:54:03 +01:00
parent 3a6410959c
commit 060406a526
2 changed files with 16 additions and 9 deletions
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4
src/arch/x86_64/Lower.zig
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@ -440,9 +440,7 @@ fn emit(lower: *Lower, prefix: Prefix, mnemonic: Mnemonic, ops: []const Operand)
});
lower.result_insts_len += 1;
emit_mnemonic = .mov;
break :op .{ .mem = Memory.sib(mem_op.sib.ptr_size, .{
.base = .{ .reg = .rax },
}) };
break :op .{ .reg = .rax };
}
_ = lower.reloc(.{ .linker_reloc = sym });

21
src/link/MachO.zig
View File

@ -2346,9 +2346,7 @@ fn allocateSections(self: *MachO) !void {
new_offset + existing_size,
});
const amt = try self.base.file.?.copyRangeAll(header.offset, self.base.file.?, new_offset, existing_size);
// TODO figure out what to about this error condition - how to communicate it up.
if (amt != existing_size) return error.InputOutput;
try self.copyRangeAllZeroOut(header.offset, new_offset, existing_size);
header.offset = @intCast(new_offset);
header.size = existing_size;
@ -3268,6 +3266,19 @@ fn findFreeSpace(self: *MachO, object_size: u64, min_alignment: u32) u64 {
return start;
}
/// Like File.copyRangeAll but also ensures the source region is zeroed out after copy.
/// This is so that we guarantee zeroed out regions for mapping of zerofill sections by the loader.
fn copyRangeAllZeroOut(self: *MachO, old_offset: u64, new_offset: u64, size: u64) !void {
const gpa = self.base.comp.gpa;
const file = self.base.file.?;
const amt = try file.copyRangeAll(old_offset, file, new_offset, size);
if (amt != size) return error.InputOutput;
const zeroes = try gpa.alloc(u8, size);
defer gpa.free(zeroes);
@memset(zeroes, 0);
try file.pwriteAll(zeroes, old_offset);
}
const InitMetadataOptions = struct {
symbol_count_hint: u64,
program_code_size_hint: u64,
@ -3408,9 +3419,7 @@ pub fn growSection(self: *MachO, sect_index: u8, needed_size: u64) !void {
new_offset + existing_size,
});
const amt = try self.base.file.?.copyRangeAll(sect.offset, self.base.file.?, new_offset, existing_size);
// TODO figure out what to about this error condition - how to communicate it up.
if (amt != existing_size) return error.InputOutput;
try self.copyRangeAllZeroOut(sect.offset, new_offset, existing_size);
sect.offset = @intCast(new_offset);
seg.fileoff = new_offset;