[compiler-rt] [rtsan] Support legacy pthread_cond variables (PR #152947)

[Chris Apple via llvm-commits]

https://github.com/cjappl created https://github.com/llvm/llvm-project/pull/152947

(hopefully) fixes #146120 

Follows a pattern put forward in tsan:
https://github.com/llvm/llvm-project/blob/71ffa2a4d3c220c97fbffa6078a446cc17bbaada/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp#L1366-L1371

https://github.com/llvm/llvm-project/blob/71ffa2a4d3c220c97fbffa6078a446cc17bbaada/compiler-rt/lib/tsan/dd/dd_interceptors.cpp#L204-L208

To properly deal with memory corruption on older versions of pthread_cond variables.


I was never able to repro this problem, but I'm hopeful it's in the right direction considering the crash report. Seeing as it's basically behind a feature flag, I think introducing it to see if it fixes the problem is low risk.


>From 5f9843fc919d1b0180c5d68d224e7ceb716f263f Mon Sep 17 00:00:00 2001
From: Chris Apple <cja-private at pm.me>
Date: Sat, 26 Jul 2025 16:03:56 -0700
Subject: [PATCH] [rtsan] Support legacy pthread_cond variables

---
 .../lib/rtsan/rtsan_interceptors_posix.cpp    | 76 +++++++++++++++++--
 1 file changed, 68 insertions(+), 8 deletions(-)

diff --git a/compiler-rt/lib/rtsan/rtsan_interceptors_posix.cpp b/compiler-rt/lib/rtsan/rtsan_interceptors_posix.cpp
index a9d864e9fe926..2f9a80f7ebeda 100644
--- a/compiler-rt/lib/rtsan/rtsan_interceptors_posix.cpp
+++ b/compiler-rt/lib/rtsan/rtsan_interceptors_posix.cpp
@@ -46,12 +46,45 @@
 
 using namespace __sanitizer;
 
+
+#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
+
+DECLARE_REAL_AND_INTERCEPTOR(void *, malloc, usize size)
+DECLARE_REAL_AND_INTERCEPTOR(void, free, void *ptr)
+
 namespace {
 struct DlsymAlloc : public DlSymAllocator<DlsymAlloc> {
   static bool UseImpl() { return !__rtsan_is_initialized(); }
 };
 } // namespace
 
+// See note in tsan or ddsan as to why this is necessary
+static pthread_cond_t *init_cond(pthread_cond_t *c, bool force = false) {
+  if (!common_flags()->legacy_pthread_cond)
+    return c;
+
+  atomic_uintptr_t *p = (atomic_uintptr_t *)c;
+  uptr cond = atomic_load(p, memory_order_acquire);
+  if (!force && cond != 0)
+    return (pthread_cond_t *)cond;
+  void *newcond = WRAP(malloc)(sizeof(pthread_cond_t));
+  internal_memset(newcond, 0, sizeof(pthread_cond_t));
+  if (atomic_compare_exchange_strong(p, &cond, (uptr)newcond,
+                                     memory_order_acq_rel))
+    return (pthread_cond_t *)newcond;
+  WRAP(free)(newcond);
+  return (pthread_cond_t *)cond;
+}
+
 // Filesystem
 
 INTERCEPTOR(int, open, const char *path, int oflag, ...) {
@@ -766,26 +799,49 @@ INTERCEPTOR(int, pthread_join, pthread_t thread, void **value_ptr) {
   return REAL(pthread_join)(thread, value_ptr);
 }
 
+INTERCEPTOR(int, pthread_cond_init, pthread_cond_t *cond,
+            const pthread_condattr_t *a) {
+  __rtsan_notify_intercepted_call("pthread_cond_init");
+  pthread_cond_t *c = init_cond(cond, true);
+  return REAL(pthread_cond_init)(c, a);
+}
+
 INTERCEPTOR(int, pthread_cond_signal, pthread_cond_t *cond) {
   __rtsan_notify_intercepted_call("pthread_cond_signal");
-  return REAL(pthread_cond_signal)(cond);
+  pthread_cond_t *c = init_cond(cond);
+  return REAL(pthread_cond_signal)(c);
 }
 
 INTERCEPTOR(int, pthread_cond_broadcast, pthread_cond_t *cond) {
   __rtsan_notify_intercepted_call("pthread_cond_broadcast");
-  return REAL(pthread_cond_broadcast)(cond);
+  pthread_cond_t *c = init_cond(cond);
+  return REAL(pthread_cond_broadcast)(c);
 }
 
 INTERCEPTOR(int, pthread_cond_wait, pthread_cond_t *cond,
             pthread_mutex_t *mutex) {
   __rtsan_notify_intercepted_call("pthread_cond_wait");
-  return REAL(pthread_cond_wait)(cond, mutex);
+  pthread_cond_t *c = init_cond(cond);
+  return REAL(pthread_cond_wait)(c, mutex);
 }
 
 INTERCEPTOR(int, pthread_cond_timedwait, pthread_cond_t *cond,
             pthread_mutex_t *mutex, const timespec *ts) {
   __rtsan_notify_intercepted_call("pthread_cond_timedwait");
-  return REAL(pthread_cond_timedwait)(cond, mutex, ts);
+  pthread_cond_t *c = init_cond(cond);
+  return REAL(pthread_cond_timedwait)(c, mutex, ts);
+}
+
+INTERCEPTOR(int, pthread_cond_destroy, pthread_cond_t *cond) {
+  __rtsan_notify_intercepted_call("pthread_cond_destroy");
+  pthread_cond_t *c = init_cond(cond);
+  int res = REAL(pthread_cond_destroy)(c);
+  if (common_flags()->legacy_pthread_cond) {
+    // Free our aux cond and zero the pointer to not leave dangling pointers.
+    WRAP(free)(c);
+    atomic_store((atomic_uintptr_t *)c, 0, memory_order_relaxed);
+  }
+  return res;
 }
 
 INTERCEPTOR(int, pthread_rwlock_rdlock, pthread_rwlock_t *lock) {
@@ -1641,10 +1697,14 @@ void __rtsan::InitializeInterceptors() {
   INTERCEPT_FUNCTION(pthread_mutex_lock);
   INTERCEPT_FUNCTION(pthread_mutex_unlock);
   INTERCEPT_FUNCTION(pthread_join);
-  INTERCEPT_FUNCTION(pthread_cond_signal);
-  INTERCEPT_FUNCTION(pthread_cond_broadcast);
-  INTERCEPT_FUNCTION(pthread_cond_wait);
-  INTERCEPT_FUNCTION(pthread_cond_timedwait);
+
+  INTERCEPT_FUNCTION_VER(pthread_cond_init, PTHREAD_ABI_BASE);
+  INTERCEPT_FUNCTION_VER(pthread_cond_signal, PTHREAD_ABI_BASE);
+  INTERCEPT_FUNCTION_VER(pthread_cond_broadcast, PTHREAD_ABI_BASE);
+  INTERCEPT_FUNCTION_VER(pthread_cond_wait, PTHREAD_ABI_BASE);
+  INTERCEPT_FUNCTION_VER(pthread_cond_timedwait, PTHREAD_ABI_BASE);
+  INTERCEPT_FUNCTION_VER(pthread_cond_destroy, PTHREAD_ABI_BASE);
+
   INTERCEPT_FUNCTION(pthread_rwlock_rdlock);
   INTERCEPT_FUNCTION(pthread_rwlock_unlock);
   INTERCEPT_FUNCTION(pthread_rwlock_wrlock);