Commit 3ca0f18bfe2e8a47c38b05fffea97146476e938c | 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 15:07:21+02:00
log	3ca0f18bfe2e8a47c38b05fffea97146476e938c
tree	14a8898c20d18e157f45b8357c50b2388755fa4a
parent	a8844ab3bc18762026bd2ff7b7085e0abb6fdf36
signature	Signed by SSH key SHA256:7B/LJ7bpR1eX8aCXSr4mtd5M45VMPKcx9zY8e95b5QM

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];