From ed180465182fb95424f1c08793b529d5ec577018 Mon Sep 17 00:00:00 2001
From: Jakub Konka <kubkon@jakubkonka.com>
Date: Tue, 1 Dec 2020 18:02:12 +0100
Subject: [PATCH] macho: dynamically calculate code signature padding

---
 src/link/MachO.zig               | 6 +++---
 src/link/MachO/CodeSignature.zig | 8 ++++++++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/link/MachO.zig b/src/link/MachO.zig
index 921c49763d..cbc63b10eb 100644
--- a/src/link/MachO.zig
+++ b/src/link/MachO.zig
@@ -733,7 +733,8 @@ fn linkWithLLD(self: *MachO, comp: *Compilation) !void {
             // Pad out space for code signature
             const text_cmd = parser.load_commands.items[parser.text_cmd_index.?].Segment.inner;
             const dataoff = @intCast(u32, mem.alignForward(parser.end_pos.?, @sizeOf(u64)));
-            const datasize = 0x400000;
+            const emit = self.base.options.emit.?;
+            const datasize = CodeSignature.calcCodeSignaturePadding(emit.sub_path, dataoff);
             const code_sig = macho.linkedit_data_command{
                 .cmd = macho.LC_CODE_SIGNATURE,
                 .cmdsize = @sizeOf(macho.linkedit_data_command),
@@ -772,7 +773,6 @@ fn linkWithLLD(self: *MachO, comp: *Compilation) !void {
             // Generate adhoc code signature
             var signature = CodeSignature.init(self.base.allocator);
             defer signature.deinit();
-            const emit = self.base.options.emit.?;
             try signature.calcAdhocSignature(
                 out_file,
                 emit.sub_path,
@@ -1723,7 +1723,7 @@ fn writeSymbolTable(self: *MachO) !void {
 fn writeCodeSignaturePadding(self: *MachO) !void {
     const code_sig_cmd = &self.load_commands.items[self.code_signature_cmd_index.?].LinkeditData;
     const fileoff = self.linkedit_segment_next_offset.?;
-    const datasize: u32 = 0x1000; // TODO Calculate the expected size of the signature.
+    const datasize = CodeSignature.calcCodeSignaturePadding(self.base.options.emit.?.sub_path, fileoff);
     code_sig_cmd.dataoff = fileoff;
     code_sig_cmd.datasize = datasize;
 
diff --git a/src/link/MachO/CodeSignature.zig b/src/link/MachO/CodeSignature.zig
index c7cfdfcb44..442132dac1 100644
--- a/src/link/MachO/CodeSignature.zig
+++ b/src/link/MachO/CodeSignature.zig
@@ -179,3 +179,11 @@ test "CodeSignature header" {
     const expected = &[_]u8{ 0xfa, 0xde, 0x0c, 0xc0, 0x0, 0x0, 0x0, 0xc, 0x0, 0x0, 0x0, 0x0 };
     testing.expect(mem.eql(u8, expected[0..], buffer[0..]));
 }
+
+pub fn calcCodeSignaturePadding(id: []const u8, file_size: u64) u32 {
+    const ident_size = id.len + 1;
+    const total_pages = mem.alignForwardGeneric(u64, file_size, page_size) / page_size;
+    const hashed_size = total_pages * hash_size;
+    const codesig_header = @sizeOf(macho.SuperBlob) + @sizeOf(macho.BlobIndex) + @sizeOf(macho.CodeDirectory);
+    return @intCast(u32, mem.alignForwardGeneric(u64, codesig_header + ident_size + hashed_size, @sizeOf(u64)));
+}