tsan: Refine conditions to intercept pthread_cond_t functions #154268

MaskRay · 2025-08-19T04:59:26Z

On glibc x86-64, functions like pthread_cond_init exist in two versions:
2.2 (older pthread_cond_t) and 2.3.2 (newer pthread_cond_t). In glibc
versions prior to 2.36, using an unversioned interceptor
(dlsym(RTLD_NEXT, "pthread_cond_init")) retrieves the older 2.2
symbol, which is not desired
(https://sourceware.org/bugzilla/show_bug.cgi?id=14932).

For newer architectures, such as aarch64 (introduced in glibc 2.17) and
riscv64 (introduced in glibc 2.27), a versioned interceptor is
unnecessary.

Created using spr 1.3.5-bogner

llvmbot · 2025-08-19T04:59:59Z

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Fangrui Song (MaskRay)

Changes

On glibc x86-64, functions like pthread_cond_init exist in two versions:
2.2 (older pthread_cond_t) and 2.3.2 (newer pthread_cond_t). In glibc
versions prior to 2.36, using an unversioned interceptor
(dlsym(RTLD_NEXT, "pthread_cond_init")) retrieves the older 2.2
symbol, which is not desired
(https://sourceware.org/bugzilla/show_bug.cgi?id=14932).

For newer architectures, such as aarch64 (introduced in glibc 2.17) and
riscv64 (introduced in glibc 2.27), a versioned interceptor is
unnecessary.

Full diff: https://github.com/llvm/llvm-project/pull/154268.diff

1 Files Affected:

(modified) compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp (+15-16)

diff --git a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
index e9f8d311bbce1..1e05c00ca85a6 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
@@ -79,17 +79,6 @@ struct ucontext_t {
 };
 #endif
 
-#if defined(__x86_64__) || defined(__mips__) || SANITIZER_PPC64V1 || \
-    defined(__s390x__)
-#define PTHREAD_ABI_BASE  "GLIBC_2.3.2"
-#elif defined(__aarch64__) || SANITIZER_PPC64V2
-#define PTHREAD_ABI_BASE  "GLIBC_2.17"
-#elif SANITIZER_LOONGARCH64
-#define PTHREAD_ABI_BASE  "GLIBC_2.36"
-#elif SANITIZER_RISCV64
-#  define PTHREAD_ABI_BASE "GLIBC_2.27"
-#endif
-
 extern "C" int pthread_attr_init(void *attr);
 extern "C" int pthread_attr_destroy(void *attr);
 DECLARE_REAL(int, pthread_attr_getdetachstate, void *, void *)
@@ -341,11 +330,6 @@ void ScopedInterceptor::DisableIgnoresImpl() {
 }
 
 #define TSAN_INTERCEPT(func) INTERCEPT_FUNCTION(func)
-#if SANITIZER_FREEBSD || SANITIZER_NETBSD
-#  define TSAN_INTERCEPT_VER(func, ver) INTERCEPT_FUNCTION(func)
-#else
-#  define TSAN_INTERCEPT_VER(func, ver) INTERCEPT_FUNCTION_VER(func, ver)
-#endif
 #if SANITIZER_FREEBSD
 #  define TSAN_MAYBE_INTERCEPT_FREEBSD_ALIAS(func) \
     INTERCEPT_FUNCTION(_pthread_##func)
@@ -3041,12 +3025,27 @@ void InitializeInterceptors() {
   TSAN_INTERCEPT(pthread_timedjoin_np);
   #endif
 
+  // In glibc versions older than 2.36, dlsym(RTLD_NEXT, "pthread_cond_init")
+  // may return an outdated symbol (max(2.2,base_version)) if the port was
+  // introduced before 2.3.2 (when the new pthread_cond_t was introduced).
+#if SANITIZER_GLIBC && !__GLIBC_PREREQ(2, 36) &&                      \
+    (defined(__x86_64__) || defined(__mips__) || SANITIZER_PPC64V1 || \
+     defined(__s390x__))
+#  define PTHREAD_ABI_BASE "GLIBC_2.3.2"
   TSAN_INTERCEPT_VER(pthread_cond_init, PTHREAD_ABI_BASE);
   TSAN_INTERCEPT_VER(pthread_cond_signal, PTHREAD_ABI_BASE);
   TSAN_INTERCEPT_VER(pthread_cond_broadcast, PTHREAD_ABI_BASE);
   TSAN_INTERCEPT_VER(pthread_cond_wait, PTHREAD_ABI_BASE);
   TSAN_INTERCEPT_VER(pthread_cond_timedwait, PTHREAD_ABI_BASE);
   TSAN_INTERCEPT_VER(pthread_cond_destroy, PTHREAD_ABI_BASE);
+#else
+  TSAN_INTERCEPT(pthread_cond_init);
+  TSAN_INTERCEPT(pthread_cond_signal);
+  TSAN_INTERCEPT(pthread_cond_broadcast);
+  TSAN_INTERCEPT(pthread_cond_wait);
+  TSAN_INTERCEPT(pthread_cond_timedwait);
+  TSAN_INTERCEPT(pthread_cond_destroy);
+#endif
 
   TSAN_MAYBE_PTHREAD_COND_CLOCKWAIT;

Created using spr 1.3.5-bogner

thurstond · 2025-08-19T16:39:56Z

compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp

-#if SANITIZER_FREEBSD || SANITIZER_NETBSD
-#  define TSAN_INTERCEPT_VER(func, ver) INTERCEPT_FUNCTION(func)
-#else
-#  define TSAN_INTERCEPT_VER(func, ver) INTERCEPT_FUNCTION_VER(func, ver)
-#endif


Why can these be deleted? Where else would TSAN_INTERCEPT_VER be defined?

TSAN_INTERCEPT_VER is only used by these pthread_cond_* functions and is removed as it's no longer used.

Aren't they still used in lines 3034-3039 of this file?

You are right. Fixed:)

cjappl

Seems reasonable to me - I'll follow this pattern in rtsan when it's merged

Created using spr 1.3.5-bogner

vitalybuka · 2025-08-19T16:56:45Z

compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp

+  // may return an outdated symbol (max(2.2,base_version)) if the port was
+  // introduced before 2.3.2 (when the new pthread_cond_t was introduced).
+#if SANITIZER_GLIBC && !__GLIBC_PREREQ(2, 36) &&                      \
+    (defined(__x86_64__) || defined(__mips__) || SANITIZER_PPC64V1 || \


why CPUs make a difference?

The new pthread_cond symbols were introduced at 2.3.2. If a port (arch) was introduced after 2.3.2, the compatibility symbol (of non-default version) would not compiled, and there will only be one pthread_cond_init symbol, no need for dlvsym.

On glibc x86-64, functions like pthread_cond_init exist in two versions: 2.2 (older pthread_cond_t) and 2.3.2 (newer pthread_cond_t). In glibc versions prior to 2.36, using an unversioned interceptor (`dlsym(RTLD_NEXT, "pthread_cond_init")`) retrieves the older 2.2 symbol, which is not desired (https://sourceware.org/bugzilla/show_bug.cgi?id=14932). For newer architectures, such as aarch64 (introduced in glibc 2.17) and riscv64 (introduced in glibc 2.27), a versioned interceptor is unnecessary. Pull Request: llvm/llvm-project#154268

kongy · 2025-08-20T08:10:06Z

This change broke our musl build:

FAILED: compiler-rt/lib/tsan/dd/CMakeFiles/RTDD.x86_64.dir/dd_interceptors.cpp.o 
/b/f/w/src/git/out/stage2/./bin/clang++ --target=x86_64-unknown-linux-musl --sysroot=/b/f/w/src/git/prebuilts/build-tools/sysroots/x86_64-unknown-linux-musl -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/b/f/w/src/git/out/llvm-project/compiler-rt/lib/tsan/dd/../.. -march=x86-64-v2 --target=x86_64-unknown-linux-musl -D_LIBCPP_HAS_MUSL_LIBC -D_LARGEFILE64_SOURCE=1 -include stdc-predef.h  -Wno-unused-command-line-argument -D_LIBCPP_AVAILABILITY_HAS_NO_VERBOSE_ABORT=1 -mllvm -regalloc-enable-advisor=release  -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -Wall -Wno-unused-parameter -O3 -DNDEBUG -fPIC -fPIC -fno-builtin -fno-exceptions -fomit-frame-pointer -funwind-tables -fno-stack-protector -fno-sanitize=safe-stack -fvisibility=hidden -fno-lto -Wthread-safety -Wthread-safety-reference -Wthread-safety-beta -O3 -gline-tables-only -Wno-gnu -Wno-variadic-macros -Wno-c99-extensions -ftrivial-auto-var-init=pattern -nostdinc++ -fno-rtti -std=c++17 -MD -MT compiler-rt/lib/tsan/dd/CMakeFiles/RTDD.x86_64.dir/dd_interceptors.cpp.o -MF compiler-rt/lib/tsan/dd/CMakeFiles/RTDD.x86_64.dir/dd_interceptors.cpp.o.d -o compiler-rt/lib/tsan/dd/CMakeFiles/RTDD.x86_64.dir/dd_interceptors.cpp.o -c /b/f/w/src/git/out/llvm-project/compiler-rt/lib/tsan/dd/dd_interceptors.cpp
b/f/w/src/git/out/llvm-project/compiler-rt/lib/tsan/dd/dd_interceptors.cpp:31639: error: token is not a valid binary operator in a preprocessor subexpression
  316 | #if SANITIZER_GLIBC && !__GLIBC_PREREQ(2, 36) &&                      \
      |                        ~~~~~~~~~~~~~~~^
1 error generated.

The change in PR #154268 introduced a dependency on the `__GLIBC_PREREQ` macro, which is not defined in musl libc. This caused the build to fail in environments using musl. This patch fixes the build by including `sanitizer_common/sanitizer_glibc_version.h`. This header provides a fallback definition for `__GLIBC_PREREQ` when LLVM is built against non-glibc C libraries, resolving the compilation error.

[𝘀𝗽𝗿] initial version

f8bf9da

Created using spr 1.3.5-bogner

MaskRay requested a review from thurstond August 19, 2025 04:59

llvmbot added compiler-rt compiler-rt:tsan Thread sanitizer compiler-rt:sanitizer labels Aug 19, 2025

MaskRay requested review from fmayer and vitalybuka August 19, 2025 04:59

.

216bee2

Created using spr 1.3.5-bogner

MaskRay mentioned this pull request Aug 19, 2025

[rtsan] Support legacy pthread_cond variables #152947

Merged

thurstond reviewed Aug 19, 2025

View reviewed changes

MaskRay requested a review from thurstond August 19, 2025 16:43

cjappl approved these changes Aug 19, 2025

View reviewed changes

fix INTERCEPT_FUNCTION_VER

61c597d

Created using spr 1.3.5-bogner

vitalybuka reviewed Aug 19, 2025

View reviewed changes

thurstond approved these changes Aug 19, 2025

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vitalybuka approved these changes Aug 19, 2025

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MaskRay merged commit c940c24 into main Aug 20, 2025
9 checks passed

MaskRay deleted the users/MaskRay/spr/tsan-refine-conditions-to-intercept-pthread_cond_t-functions branch August 20, 2025 03:07

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