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macho: do not zero-out file if there are no nonzerofill sects

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If the `__DATA` segment comprises of only zerofill sections, do not
accidentally zero out all of file.
This commit is contained in:
Jakub Konka 2022-11-06 00:36:27 +01:00
parent aaaa7df152
commit 76fb3e0621
1 changed files with 7 additions and 10 deletions
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17
src/link/MachO/zld.zig
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@ -4305,24 +4305,21 @@ pub fn linkWithZld(macho_file: *MachO, comp: *Compilation, prog_node: *std.Progr
// segment and the beginning of __LINKEDIT segment is zerofilled as the loader will
// copy-paste this space into memory for quicker zerofill operation.
if (zld.getSegmentByName("__DATA")) |data_seg_id| blk: {
var physical_zerofill_start: u64 = 0;
var physical_zerofill_start: ?u64 = null;
const section_indexes = zld.getSectionIndexes(data_seg_id);
for (zld.sections.items(.header)[section_indexes.start..section_indexes.end]) |header| {
if (header.isZerofill() and header.size > 0) break;
physical_zerofill_start = header.offset + header.size;
} else break :blk;
const start = physical_zerofill_start orelse break :blk;
const linkedit = zld.getLinkeditSegmentPtr();
const physical_zerofill_size = math.cast(usize, linkedit.fileoff - physical_zerofill_start) orelse
return error.Overflow;
if (physical_zerofill_size > 0) {
log.debug("zeroing out zerofill area of length {x} at {x}", .{
physical_zerofill_size,
physical_zerofill_start,
});
var padding = try zld.gpa.alloc(u8, physical_zerofill_size);
const size = math.cast(usize, linkedit.fileoff - start) orelse return error.Overflow;
if (size > 0) {
log.debug("zeroing out zerofill area of length {x} at {x}", .{ size, start });
var padding = try zld.gpa.alloc(u8, size);
defer zld.gpa.free(padding);
mem.set(u8, padding, 0);
try zld.file.pwriteAll(padding, physical_zerofill_start);
try zld.file.pwriteAll(padding, start);
}
}