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zld: fix handling of section alignment

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This commit is contained in:
Jakub Konka 2021-02-28 11:36:39 +01:00
parent 7c22f4f851
commit 44ebf48631
1 changed files with 54 additions and 43 deletions
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97
src/link/MachO/Zld.zig
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@ -264,8 +264,8 @@ pub fn link(self: *Zld, files: []const []const u8, out_path: []const u8) !void {
try self.populateMetadata();
try self.parseInputFiles(files);
try self.resolveImports();
self.allocateTextSegment();
self.allocateDataSegment();
try self.allocateTextSegment();
try self.allocateDataSegment();
self.allocateLinkeditSegment();
try self.writeStubHelperCommon();
try self.resolveSymbols();
@ -349,6 +349,7 @@ fn parseObjectFile(self: *Zld, object: *const Object) !void {
};
}
const dest_sect = &seg.sections.items[res.entry.value.sect_index];
dest_sect.@"align" = math.max(dest_sect.@"align", sect.@"align");
dest_sect.size += sect.size;
seg.inner.filesize += sect.size;
}
@ -441,10 +442,14 @@ fn resolveImports(self: *Zld) !void {
});
}
fn allocateTextSegment(self: *Zld) void {
fn allocateTextSegment(self: *Zld) !void {
const seg = &self.load_commands.items[self.text_segment_cmd_index.?].Segment;
const nexterns = @intCast(u32, self.lazy_imports.items().len);
const base_vmaddr = self.load_commands.items[self.pagezero_segment_cmd_index.?].Segment.inner.vmsize;
seg.inner.fileoff = 0;
seg.inner.vmaddr = base_vmaddr;
// Set stubs and stub_helper sizes
const stubs = &seg.sections.items[self.stubs_section_index.?];
const stub_helper = &seg.sections.items[self.stub_helper_section_index.?];
@ -462,19 +467,41 @@ fn allocateTextSegment(self: *Zld) void {
sizeofcmds += lc.cmdsize();
}
self.allocateSegment(
self.text_segment_cmd_index.?,
0,
sizeofcmds,
true,
);
try self.allocateSegment(self.text_segment_cmd_index.?, sizeofcmds);
// Shift all sections to the back to minimize jump size between __TEXT and __DATA segments.
var min_alignment: u32 = 0;
for (seg.sections.items) |sect| {
const alignment = try math.powi(u32, 2, sect.@"align");
min_alignment = math.max(min_alignment, alignment);
}
assert(min_alignment > 0);
const last_sect_idx = seg.sections.items.len - 1;
const last_sect = seg.sections.items[last_sect_idx];
const shift: u32 = blk: {
const diff = seg.inner.filesize - last_sect.offset - last_sect.size;
const factor = @divTrunc(diff, min_alignment);
break :blk @intCast(u32, factor * min_alignment);
};
if (shift > 0) {
for (seg.sections.items) |*sect| {
sect.offset += shift;
sect.addr += shift;
}
}
}
fn allocateDataSegment(self: *Zld) void {
fn allocateDataSegment(self: *Zld) !void {
const seg = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
const nonlazy = @intCast(u32, self.nonlazy_imports.items().len);
const lazy = @intCast(u32, self.lazy_imports.items().len);
const text_seg = self.load_commands.items[self.text_segment_cmd_index.?].Segment;
seg.inner.fileoff = text_seg.inner.fileoff + text_seg.inner.filesize;
seg.inner.vmaddr = text_seg.inner.vmaddr + text_seg.inner.vmsize;
// Set got size
const got = &seg.sections.items[self.got_section_index.?];
got.size += nonlazy * @sizeOf(u64);
@ -485,50 +512,34 @@ fn allocateDataSegment(self: *Zld) void {
la_symbol_ptr.size += lazy * @sizeOf(u64);
data.size += @sizeOf(u64); // TODO when do we need more?
const text_seg = self.load_commands.items[self.text_segment_cmd_index.?].Segment;
const offset = text_seg.inner.fileoff + text_seg.inner.filesize;
self.allocateSegment(self.data_segment_cmd_index.?, offset, 0, false);
try self.allocateSegment(self.data_segment_cmd_index.?, 0);
}
fn allocateLinkeditSegment(self: *Zld) void {
const seg = &self.load_commands.items[self.linkedit_segment_cmd_index.?].Segment;
const data_seg = self.load_commands.items[self.data_segment_cmd_index.?].Segment;
const offset = data_seg.inner.fileoff + data_seg.inner.filesize;
self.allocateSegment(self.linkedit_segment_cmd_index.?, offset, 0, false);
seg.inner.fileoff = data_seg.inner.fileoff + data_seg.inner.filesize;
seg.inner.vmaddr = data_seg.inner.vmaddr + data_seg.inner.vmsize;
}
fn allocateSegment(self: *Zld, index: u16, offset: u64, start: u64, reverse: bool) void {
fn allocateSegment(self: *Zld, index: u16, offset: u64) !void {
const base_vmaddr = self.load_commands.items[self.pagezero_segment_cmd_index.?].Segment.inner.vmsize;
const seg = &self.load_commands.items[index].Segment;
// Calculate segment size
var total_size = start;
for (seg.sections.items) |sect| {
total_size += sect.size;
// Allocate the sections according to their alignment at the beginning of the segment.
var start: u64 = offset;
for (seg.sections.items) |*sect| {
const alignment = try math.powi(u32, 2, sect.@"align");
const start_aligned = mem.alignForwardGeneric(u64, start, alignment);
const end_aligned = mem.alignForwardGeneric(u64, start_aligned + sect.size, alignment);
sect.offset = @intCast(u32, seg.inner.fileoff + start_aligned);
sect.addr = seg.inner.vmaddr + start_aligned;
start = end_aligned;
}
const aligned_size = mem.alignForwardGeneric(u64, total_size, self.page_size.?);
seg.inner.vmaddr = base_vmaddr + offset;
seg.inner.vmsize = aligned_size;
seg.inner.fileoff = offset;
seg.inner.filesize = aligned_size;
// Allocate section offsets
if (reverse) {
var end_off: u64 = seg.inner.fileoff + seg.inner.filesize;
var count: usize = seg.sections.items.len;
while (count > 0) : (count -= 1) {
const sec = &seg.sections.items[count - 1];
end_off -= mem.alignForwardGeneric(u64, sec.size, @alignOf(u128)); // TODO is 8-byte aligned correct?
sec.offset = @intCast(u32, end_off);
sec.addr = base_vmaddr + end_off;
}
} else {
var next_off: u64 = seg.inner.fileoff + start;
for (seg.sections.items) |*sect| {
sect.offset = @intCast(u32, next_off);
sect.addr = base_vmaddr + next_off;
next_off += mem.alignForwardGeneric(u64, sect.size, @alignOf(u128)); // TODO is 8-byte aligned correct?
}
}
const seg_size_aligned = mem.alignForwardGeneric(u64, start, self.page_size.?);
seg.inner.filesize = seg_size_aligned;
seg.inner.vmsize = seg_size_aligned;
}
fn writeStubHelperCommon(self: *Zld) !void {