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

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

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

Reference: 60105ac6ba/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp (L1076-L1104)
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tjog 2025-04-21 17:44:31 +02:00 • committed by Alex Rønne Petersen
parent a8844ab3bc
commit 3ca0f18bfe
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1 changed files with 26 additions and 11 deletions
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37
lib/fuzzer.zig
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@ -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 pc_counters_start = @extern([*]u8, .{
.name = "__start___sancov_cntrs",
.linkage = .weak,
}) orelse fatal("missing __start___sancov_cntrs symbol", .{});
const ofmt = builtin.object_format;
const pc_counters_end = @extern([*]u8, .{
.name = "__stop___sancov_cntrs",
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 = pc_counters_start_name,
.linkage = .weak,
}) orelse fatal("missing __stop___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 = pc_counters_end_name,
.linkage = .weak,
}) 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];