authorgravatar for 28024277+tjog@users.noreply.github.comtjog <28024277+tjog@users.noreply.github.com> 2025-04-21 17:44:31+02:00
committergravatar for alex@alexrp.comAlex Rønne Petersen <alex@alexrp.com> 2025-04-26 14:35:03+02:00
log2e35fdd032035203b588fa229585c3ee6702f2d4
tree8b157df67860eea2db6d298be83c94469ba43339
parent69007f096177143086e28da0dc1a0eff4efcc52c

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+23-8
......@@ -468,27 +468,42 @@ export fn fuzzer_init(cache_dir_struct: Fuzzer.Slice) void {
468468 // Linkers are expected to automatically add `__start_<section>` and
469469 // `__stop_<section>` symbols when section names are valid C identifiers.
470470
471 const ofmt = builtin.object_format;
472
473 const start_symbol_prefix: []const u8 = if (ofmt == .macho)
474 "\x01section$start$__DATA$__"
475 else
476 "__start___";
477 const end_symbol_prefix: []const u8 = if (ofmt == .macho)
478 "\x01section$end$__DATA$__"
479 else
480 "__end___";
481
482 const pc_counters_start_name = start_symbol_prefix ++ "sancov_cntrs";
471483 const pc_counters_start = @extern([*]u8, .{
472 .name = "__start___sancov_cntrs",
484 .name = pc_counters_start_name,
473485 .linkage = .weak,
474 }) orelse fatal("missing __start___sancov_cntrs symbol", .{});
486 }) orelse fatal("missing {s} symbol", .{pc_counters_start_name});
475487
488 const pc_counters_end_name = end_symbol_prefix ++ "sancov_cntrs";
476489 const pc_counters_end = @extern([*]u8, .{
477 .name = "__stop___sancov_cntrs",
490 .name = pc_counters_end_name,
478491 .linkage = .weak,
479 }) orelse fatal("missing __stop___sancov_cntrs symbol", .{});
492 }) orelse fatal("missing {s} symbol", .{pc_counters_end_name});
480493
481494 const pc_counters = pc_counters_start[0 .. pc_counters_end - pc_counters_start];
482495
496 const pcs_start_name = start_symbol_prefix ++ "sancov_pcs1";
483497 const pcs_start = @extern([*]usize, .{
484 .name = "__start___sancov_pcs1",
498 .name = pcs_start_name,
485499 .linkage = .weak,
486 }) orelse fatal("missing __start___sancov_pcs1 symbol", .{});
500 }) orelse fatal("missing {s} symbol", .{pcs_start_name});
487501
502 const pcs_end_name = end_symbol_prefix ++ "sancov_pcs1";
488503 const pcs_end = @extern([*]usize, .{
489 .name = "__stop___sancov_pcs1",
504 .name = pcs_end_name,
490505 .linkage = .weak,
491 }) orelse fatal("missing __stop___sancov_pcs1 symbol", .{});
506 }) orelse fatal("missing {s} symbol", .{pcs_end_name});
492507
493508 const pcs = pcs_start[0 .. pcs_end - pcs_start];
494509