Commit 2e35fdd032035203b588fa229585c3ee6702f2d4 | zig

author	tjog <28024277+tjog@users.noreply.github.com> 2025-04-21 17:44:31+02:00
committer	Alex Rønne Petersen <alex@alexrp.com> 2025-04-26 14:35:03+02:00
log	2e35fdd032035203b588fa229585c3ee6702f2d4
tree	8b157df67860eea2db6d298be83c94469ba43339
parent	69007f096177143086e28da0dc1a0eff4efcc52c

fuzz: fix expected section start/end symbol name on MacOS when linking libfuzzer

Not only is the section name when adding the sancov variables different.

The linker symbol ending up in the binary is also different.

Reference: https://github.com/llvm/llvm-project/blob/60105ac6bab130c2694fc7f5b7b6a5fddaaab752/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp#L1076-L1104

1 files changed, 23 insertions(+), 8 deletions(-)

lib
- fuzzer.zig

lib/fuzzer.zig+23-8

 @@ -468,27 +468,42 @@ export fn fuzzer_init(cache_dir_struct: Fuzzer.Slice) void {
     // Linkers are expected to automatically add `__start_<section>` and
     // `__stop_<section>` symbols when section names are valid C identifiers.
+    const ofmt = builtin.object_format;
+    const start_symbol_prefix: []const u8 = if (ofmt == .macho)
+        "\x01section$start$__DATA$__"
+    else
+        "__start___";
+    const end_symbol_prefix: []const u8 = if (ofmt == .macho)
+        "\x01section$end$__DATA$__"
+    else
+        "__end___";
+    const pc_counters_start_name = start_symbol_prefix ++ "sancov_cntrs";
     const pc_counters_start = @extern([*]u8, .{
-        .name = "__start___sancov_cntrs",
+        .name = pc_counters_start_name,
         .linkage = .weak,
-    }) orelse fatal("missing __start___sancov_cntrs symbol", .{});
+    }) orelse fatal("missing {s} symbol", .{pc_counters_start_name});
+    const pc_counters_end_name = end_symbol_prefix ++ "sancov_cntrs";
     const pc_counters_end = @extern([*]u8, .{
-        .name = "__stop___sancov_cntrs",
+        .name = pc_counters_end_name,
         .linkage = .weak,
-    }) orelse fatal("missing __stop___sancov_cntrs symbol", .{});
+    }) orelse fatal("missing {s} symbol", .{pc_counters_end_name});
     const pc_counters = pc_counters_start[0 .. pc_counters_end - pc_counters_start];
+    const pcs_start_name = start_symbol_prefix ++ "sancov_pcs1";
     const pcs_start = @extern([*]usize, .{
-        .name = "__start___sancov_pcs1",
+        .name = pcs_start_name,
         .linkage = .weak,
-    }) orelse fatal("missing __start___sancov_pcs1 symbol", .{});
+    }) orelse fatal("missing {s} symbol", .{pcs_start_name});
+    const pcs_end_name = end_symbol_prefix ++ "sancov_pcs1";
     const pcs_end = @extern([*]usize, .{
-        .name = "__stop___sancov_pcs1",
+        .name = pcs_end_name,
         .linkage = .weak,
-    }) orelse fatal("missing __stop___sancov_pcs1 symbol", .{});
+    }) orelse fatal("missing {s} symbol", .{pcs_end_name});
     const pcs = pcs_start[0 .. pcs_end - pcs_start];