From 2d10c52b3cfac9516f5548b04528bb7c31a0a6e7 Mon Sep 17 00:00:00 2001
From: Jakub Konka <kubkon@jakubkonka.com>
Date: Sat, 21 Aug 2021 11:51:50 +0200
Subject: [PATCH] macho: create an explicit symbol and atom for dyld entry in
 __data

This way, we will be able to refer to that atom dynamically via
relocations rather than requiring hardcoded addressing upfront.
---
 src/link/MachO.zig | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/src/link/MachO.zig b/src/link/MachO.zig
index f17ecb5a09..947279a37f 100644
--- a/src/link/MachO.zig
+++ b/src/link/MachO.zig
@@ -143,6 +143,7 @@ unresolved: std.AutoArrayHashMapUnmanaged(u32, void) = .{},
 locals_free_list: std.ArrayListUnmanaged(u32) = .{},
 globals_free_list: std.ArrayListUnmanaged(u32) = .{},
 
+dyld_private_sym_index: ?u32 = null,
 dyld_stub_binder_index: ?u32 = null,
 
 stub_helper_stubs_start_off: ?u64 = null,
@@ -758,6 +759,7 @@ pub fn flush(self: *MachO, comp: *Compilation) !void {
         try self.parseLibs(libs.items, self.base.options.sysroot);
         try self.resolveSymbols();
         try self.resolveDyldStubBinder();
+        try self.createDyldPrivateAtom();
 
         if (!use_stage1) {
             // TODO this should be made common when I figure out how to prealloc space for traditional linker path.
@@ -1963,7 +1965,31 @@ fn createEmptyAtom(
     return block;
 }
 
+fn createDyldPrivateAtom(self: *MachO) !void {
+    if (self.dyld_private_sym_index != null) return;
+
+    const match = MatchingSection{
+        .seg = self.data_segment_cmd_index.?,
+        .sect = self.data_section_index.?,
+    };
+    const local_sym_index = @intCast(u32, self.locals.items.len);
+    try self.locals.append(self.base.allocator, .{
+        .n_strx = try self.makeString("dyld_private"),
+        .n_type = macho.N_SECT,
+        .n_sect = 0,
+        .n_desc = 0,
+        .n_value = 0,
+    });
+    _ = try self.createEmptyAtom(match, local_sym_index, @sizeOf(u64), 3);
+
+    self.dyld_private_sym_index = local_sym_index;
+}
+
 // fn createStubHelperPreambleAtom(self: *MachO) !void {
+//     const match = MatchingSection{
+//         .seg = self.text_segment_cmd_index.?,
+//         .sect = self.stub_helper_section_index.?,
+//     };
 //     switch (self.base.options.target.cpu.arch) {
 //         .x86_64 => {
 //             const code_size = 15;