diff options
| -rw-r--r-- | compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc | 29 |
1 files changed, 2 insertions, 27 deletions
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc b/compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc index 492da16c809..c5578096bc0 100644 --- a/compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc +++ b/compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc @@ -47,30 +47,14 @@ // clone() interface (we want to share the address space with the caller // process, so we prefer clone() over fork()). // -// We avoid the use of libc for two reasons: +// We don't use any libc functions, relying instead on direct syscalls. There +// are two reasons for this: // 1. calling a library function while threads are suspended could cause a // deadlock, if one of the treads happens to be holding a libc lock; // 2. it's generally not safe to call libc functions from the tracer task, // because clone() does not set up a thread-local storage for it. Any // thread-local variables used by libc will be shared between the tracer task // and the thread which spawned it. -// -// We deal with this by replacing libc calls with calls to our own -// implementations defined in sanitizer_libc.h and sanitizer_linux.h. However, -// there are still some libc functions which are used here: -// -// * All of the system calls ultimately go through the libc syscall() function. -// We're operating under the assumption that syscall()'s implementation does -// not acquire any locks or use any thread-local data (except for the errno -// variable, which we handle separately). -// -// * We lack custom implementations of sigfillset() and sigaction(), so we use -// the libc versions instead. The same assumptions as above apply. -// -// * It is safe to call libc functions before the cloned thread is spawned or -// after it has exited. The following functions are used in this manner: -// sigdelset() -// sigprocmask() COMPILER_CHECK(sizeof(SuspendedThreadID) == sizeof(pid_t)); @@ -300,11 +284,6 @@ class ScopedStackSpaceWithGuard { uptr guard_start_; }; -NOINLINE static void WipeStack() { - char arr[256]; - internal_memset(arr, 0, sizeof(arr)); -} - // We have a limitation on the stack frame size, so some stuff had to be moved // into globals. static kernel_sigset_t blocked_sigset; @@ -314,10 +293,6 @@ static kernel_sigaction_t old_sigactions[ARRAY_SIZE(kUnblockedSignals)]; class StopTheWorldScope { public: StopTheWorldScope() { - // Glibc's sigaction() has a side-effect where it copies garbage stack - // values into oldact, which can cause false negatives in LSan. As a quick - // workaround we zero some stack space here. - WipeStack(); // Block all signals that can be blocked safely, and install // default handlers for the remaining signals. // We cannot allow user-defined handlers to run while the ThreadSuspender |
