macho: addend for unsigned needs to be written to code buffer

src/MachO/Atom.zig

@@ -684,12 +684,13 @@ pub fn calcNumRelocs(self: Atom, macho_file: *MachO) u32 {
     }
 }
 
-pub fn writeRelocs(self: Atom, macho_file: *MachO, buffer: *std.ArrayList(macho.relocation_info)) !void {
+pub fn writeRelocs(self: Atom, macho_file: *MachO, code: []u8, buffer: *std.ArrayList(macho.relocation_info)) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
     const cpu_arch = macho_file.options.cpu_arch.?;
     const relocs = self.getRelocs(macho_file);
+    var stream = std.io.fixedBufferStream(code);
 
     for (relocs) |rel| {
         const rel_offset = rel.offset - self.off;
@@ -704,9 +705,15 @@ pub fn writeRelocs(self: Atom, macho_file: *MachO, buffer: *std.ArrayList(macho.
         const r_extern = rel.tag == .@"extern";
         const addend = rel.addend + rel.getRelocAddend(cpu_arch);
 
+        try stream.seekTo(rel_offset);
+
         switch (cpu_arch) {
             .aarch64 => {
-                if (addend > 0 and rel.type != .unsigned) {
+                if (rel.type == .unsigned) switch (rel.meta.length) {
+                    0, 1 => unreachable,
+                    2 => try stream.writer().writeInt(i32, @truncate(addend), .little),
+                    3 => try stream.writer().writeInt(i64, addend, .little),
+                } else if (addend > 0) {
                     buffer.appendAssumeCapacity(.{
                         .r_address = r_address,
                         .r_symbolnum = @bitCast(math.cast(i24, addend) orelse return error.Overflow),

src/MachO/eh_frame.zig

@@ -459,6 +459,12 @@ pub fn write(macho_file: *MachO, buffer: []u8) void {
     }
 }
 
+pub fn writeRelocs(macho_file: *MachO, relocs: *std.ArrayList(macho.relocation_info)) void {
+    _ = macho_file;
+    _ = relocs;
+    @panic("TODO eh_frame.writeRelocs");
+}
+
 pub const EH_PE = struct {
     pub const absptr = 0x00;
     pub const uleb128 = 0x01;

src/MachO/relocatable.zig

@@ -237,8 +237,7 @@ fn writeAtoms(macho_file: *MachO) !void {
             assert(atom.flags.alive);
             const off = atom.value - header.addr;
             @memcpy(code[off..][0..atom.size], atom.getCode(macho_file));
-
-            try atom.writeRelocs(macho_file, &relocs);
+            try atom.writeRelocs(macho_file, code, &relocs);
         }
 
         // TODO scattered writes?
@@ -274,11 +273,18 @@ fn writeEhFrame(macho_file: *MachO) !void {
     const sect_index = macho_file.eh_frame_sect_index orelse return;
     const gpa = macho_file.base.allocator;
     const header = macho_file.sections.items(.header)[sect_index];
-    const buffer = try gpa.alloc(u8, header.size);
-    defer gpa.free(buffer);
-    eh_frame.write(macho_file, buffer);
-    try macho_file.base.file.pwriteAll(buffer, header.offset);
-    // TODO write relocs
+
+    const code = try gpa.alloc(u8, header.size);
+    defer gpa.free(code);
+    eh_frame.write(macho_file, code);
+
+    var relocs = try std.ArrayList(macho.relocation_info).initCapacity(gpa, header.nreloc);
+    defer relocs.deinit();
+    eh_frame.writeRelocs(macho_file, &relocs);
+
+    // TODO scattered writes?
+    try macho_file.base.file.pwriteAll(code, header.offset);
+    try macho_file.base.file.pwriteAll(mem.sliceAsBytes(relocs.items), header.reloff);
 }
 
 fn writeDataInCode(macho_file: *MachO, off: u32) !u32 {