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Update macho.zig

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This commit is contained in:
Jarred Sumner
2024-12-01 12:39:57 -08:00
parent 413c8232dd
commit 413c46729c
1 changed files with 43 additions and 18 deletions
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61
src/macho.zig
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@@ -98,6 +98,7 @@ pub const MachoFile = struct {
// Look for existing __BUN,__BUN section
var existing_cmd_idx: ?usize = null;
var existing_cmd_offset: ?usize = null;
var original_fileoff: u64 = 0;
outer: for (self.commands.items, 0..) |cmd, i| {
if (cmd.cmd == @intFromEnum(macho.LC.SEGMENT_64)) {
@@ -109,12 +110,17 @@ pub const MachoFile = struct {
if (mem.eql(u8, sect.sectName(), "__BUN")) {
existing_cmd_idx = i;
existing_cmd_offset = cmd.offset;
original_fileoff = sect.offset;
self.seg = command;
self.sec = sect.*;
self.seg.vmsize = alignVmsize(total_size, blob_alignment);
self.seg.filesize = alignVmsize(total_size, blob_alignment);
// Keep the original offset
const new_size = alignVmsize(total_size, blob_alignment);
self.seg.vmsize = new_size;
self.seg.filesize = new_size;
self.sec.size = @intCast(total_size);
self.sec.offset = @intCast(self.linkedit_cmd.fileoff);
// Don't change the offset
self.sec.offset = @intCast(original_fileoff);
break :outer;
}
}
@@ -123,6 +129,10 @@ pub const MachoFile = struct {
}
}
if (existing_cmd_idx == null or existing_cmd_offset == null) {
return error.InvalidObject;
}
var blob_data = try self.allocator.alloc(u8, aligned_size);
@memset(blob_data, 0);
@@ -139,15 +149,12 @@ pub const MachoFile = struct {
// Adjust linkedit offsets only if new size is different
if (old_seg.filesize != self.seg.filesize) {
const size_diff = @as(i64, @intCast(self.seg.filesize)) - @as(i64, @intCast(old_seg.filesize));
self.linkedit_cmd.fileoff = @intCast(@as(i64, @intCast(self.linkedit_cmd.fileoff)) + size_diff);
try self.updateLoadCommandOffsets(old_seg.fileoff, size_diff);
// Only adjust linkedit if we're actually growing
if (size_diff > 0) {
self.linkedit_cmd.fileoff = @intCast(@as(i64, @intCast(self.linkedit_cmd.fileoff)) + size_diff);
try self.updateLoadCommandOffsets(original_fileoff + old_seg.filesize, size_diff);
}
}
} else {
// Add new section
self.linkedit_cmd.vmaddr += self.seg.vmsize;
self.linkedit_cmd.fileoff += self.seg.filesize;
self.header.ncmds += 1;
self.header.sizeofcmds += self.seg.cmdsize;
}
self.sectdata = blob_data;
@@ -228,12 +235,17 @@ pub const MachoFile = struct {
pub fn build(self: *MachoFile, writer: anytype) !void {
try writer.writeAll(mem.asBytes(&self.header));
// Write all load commands
for (self.commands.items) |cmd| {
if (cmd.cmd == @intFromEnum(macho.LC.SEGMENT_64)) {
const segname = self.data.items[cmd.offset..][0..16];
if (mem.eql(u8, segname[0..SEG_LINKEDIT.len], SEG_LINKEDIT)) {
const command = @as(*const macho.segment_command_64, @ptrCast(@alignCast(&self.data.items[cmd.offset]))).*;
if (mem.eql(u8, command.segName(), "__BUN")) {
// Write our modified BUN segment command
try writer.writeAll(mem.asBytes(&self.seg));
try writer.writeAll(mem.asBytes(&self.sec));
continue;
} else if (mem.eql(u8, command.segName(), "__LINKEDIT")) {
// Write our modified LINKEDIT segment
try writer.writeAll(mem.asBytes(&self.linkedit_cmd));
continue;
}
@@ -241,12 +253,16 @@ pub const MachoFile = struct {
try writer.writeAll(self.data.items[cmd.offset..][0..cmd.cmdsize]);
}
var off = self.header.sizeofcmds + @sizeOf(macho.mach_header_64);
const len: u32 = @truncate(self.rest_size - self.seg.cmdsize);
try writer.writeAll(self.data.items[off..][0..len]);
// Write segment data up to our BUN section
var off: usize = self.header.sizeofcmds + @sizeOf(macho.mach_header_64);
off += len;
while (off < self.sec.offset) {
const chunk_size = @min(4096, self.sec.offset - off);
try writer.writeAll(self.data.items[off..][0..chunk_size]);
off += chunk_size;
}
// Write our BUN section data
if (self.sectdata) |sectdata| {
try writer.writeAll(sectdata);
if (self.seg.filesize > sectdata.len) {
@@ -257,7 +273,16 @@ pub const MachoFile = struct {
}
}
try writer.writeAll(self.data.items[off..][0..self.linkedit_cmd.filesize]);
// Write remaining data up to LINKEDIT
off = self.sec.offset + self.seg.filesize;
while (off < self.linkedit_cmd.fileoff) {
const chunk_size = @min(4096, self.linkedit_cmd.fileoff - off);
try writer.writeAll(self.data.items[off..][0..chunk_size]);
off += chunk_size;
}
// Write LINKEDIT data
try writer.writeAll(self.data.items[self.linkedit_cmd.fileoff..][0..self.linkedit_cmd.filesize]);
}
pub fn buildAndSign(self: *MachoFile, writer: anytype) !void {