[sanitizer] Restrict clock_gettime workaround to glibc

[MaskRay]

Summary

The hackery is due to glibc clock_gettime crashing from preinit_array (D40679).
32-bit musl architectures do not define __NR_clock_gettime so the code causes a compile error.

Tested on Alpine Linux x86-64 (musl) and FreeBSD x86-64.

[MaskRay]

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[MaskRay]

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[vitalybuka]

Trivial test which just call the function from preinit array and do not crash would be nice

[MaskRay]

In D96925#2607537, @vitalybuka wrote:

Trivial test which just call the function from preinit array and do not crash would be nice

This (clock_gettime in .preinit_array time) has been tested by scudo tests (D40679).
Actually I cannot reproduce the failure (on glibc 2.31) if I delete the SANITIZER_GLIBC guarded code.
Perhaps this is glibc version dependent.

@cryptoad Perhaps we can delete these blocks once the minimum supported glibc does not need these.

Hope this patch makes these places stand out.

compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc

INTERCEPTOR(int, clock_gettime, u32 clk_id, void *tp) {
   // its metadata. See
   // https://github.com/google/sanitizers/issues/321.
   int res = REAL(clock_gettime)(clk_id, tp);
   if (!res) {
     COMMON_INTERCEPTOR_WRITE_RANGE(ctx, tp, struct_timespec_sz);
   }
   return res;
 }
+#if SANITIZER_GLIBC
 namespace __sanitizer {
 extern "C" {
 int real_clock_gettime(u32 clk_id, void *tp) {
   if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
     return internal_clock_gettime(clk_id, tp);
   return REAL(clock_gettime)(clk_id, tp);
 }
 }  // extern "C"
 }  // namespace __sanitizer
+#endif
 INTERCEPTOR(int, clock_settime, u32 clk_id, const void *tp) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, clock_settime, clk_id, tp);
   COMMON_INTERCEPTOR_READ_RANGE(ctx, tp, struct_timespec_sz);
   return REAL(clock_settime)(clk_id, tp);
 }
 #define INIT_CLOCK_GETTIME                  \
   COMMON_INTERCEPT_FUNCTION(clock_getres);  \

compiler-rt/lib/sanitizer_common/sanitizer_linux.h

 
 void ReadProcMaps(ProcSelfMapsBuff *proc_maps);
 
 // Syscall wrappers.
 uptr internal_getdents(fd_t fd, struct linux_dirent *dirp, unsigned int count);
 uptr internal_sigaltstack(const void* ss, void* oss);
 uptr internal_sigprocmask(int how, __sanitizer_sigset_t *set,
     __sanitizer_sigset_t *oldset);
+#if SANITIZER_GLIBC
 uptr internal_clock_gettime(__sanitizer_clockid_t clk_id, void *tp);
+#endif
 
 // Linux-only syscalls.
 #if SANITIZER_LINUX
 uptr internal_prctl(int option, uptr arg2, uptr arg3, uptr arg4, uptr arg5);
 // Used only by sanitizer_stoptheworld. Signal handlers that are actually used
 // (like the process-wide error reporting SEGV handler) must use
 // internal_sigaction instead.
 int internal_sigaction_norestorer(int signum, const void *act, void *oldact);

compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp

#if SANITIZER_FREEBSD
   timeval tv;
 #else
   kernel_timeval tv;
 #endif
   internal_memset(&tv, 0, sizeof(tv));
   internal_syscall(SYSCALL(gettimeofday), &tv, 0);
   return (u64)tv.tv_sec * 1000*1000*1000 + tv.tv_usec * 1000;
 }
+#endif  // !SANITIZER_SOLARIS && !SANITIZER_NETBSD
 
+#if SANITIZER_GLIBC
 uptr internal_clock_gettime(__sanitizer_clockid_t clk_id, void *tp) {
   return internal_syscall(SYSCALL(clock_gettime), clk_id, tp);
 }
-#endif  // !SANITIZER_SOLARIS && !SANITIZER_NETBSD
+#endif  // SANITIZER_GLIBC
 
 // Like getenv, but reads env directly from /proc (on Linux) or parses the
 // 'environ' array (on some others) and does not use libc. This function
 // should be called first inside __asan_init.
 const char *GetEnv(const char *name) {
 #if SANITIZER_FREEBSD || SANITIZER_NETBSD || SANITIZER_SOLARIS
   if (::environ != 0) {
     uptr NameLen = internal_strlen(name);

compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp

 
 void LogMessageOnPrintf(const char *str) {
   if (common_flags()->log_to_syslog && ShouldLogAfterPrintf())
     WriteToSyslog(str);
 }
 
 #endif  // SANITIZER_LINUX
 
-#if SANITIZER_LINUX && !SANITIZER_GO
+#if SANITIZER_GLIBC && !SANITIZER_GO
 // glibc crashes when using clock_gettime from a preinit_array function as the
 // vDSO function pointers haven't been initialized yet. __progname is
 // initialized after the vDSO function pointers, so if it exists, is not null
 // and is not empty, we can use clock_gettime.
 extern "C" SANITIZER_WEAK_ATTRIBUTE char *__progname;
-inline bool CanUseVDSO() {
-  // Bionic is safe, it checks for the vDSO function pointers to be initialized.
-  if (SANITIZER_ANDROID)
-    return true;
-  if (&__progname && __progname && *__progname)
-    return true;
-  return false;
-}
+inline bool CanUseVDSO() { return &__progname && __progname && *__progname; }
 
 // MonotonicNanoTime is a timing function that can leverage the vDSO by calling
 // clock_gettime. real_clock_gettime only exists if clock_gettime is
 // intercepted, so define it weakly and use it if available.
 extern "C" SANITIZER_WEAK_ATTRIBUTE
 int real_clock_gettime(u32 clk_id, void *tp);
 u64 MonotonicNanoTime() {
   timespec ts;
   if (CanUseVDSO()) {
     if (&real_clock_gettime)
       real_clock_gettime(CLOCK_MONOTONIC, &ts);
     else
       clock_gettime(CLOCK_MONOTONIC, &ts);
   } else {
     internal_clock_gettime(CLOCK_MONOTONIC, &ts);
   }
   return (u64)ts.tv_sec * (1000ULL * 1000 * 1000) + ts.tv_nsec;
 }
 #else
-// Non-Linux & Go always use the syscall.
+// Non-Linux & Go always use the regular function.
 u64 MonotonicNanoTime() {
   timespec ts;
-  internal_clock_gettime(CLOCK_MONOTONIC, &ts);
+  clock_gettime(CLOCK_MONOTONIC, &ts);
   return (u64)ts.tv_sec * (1000ULL * 1000 * 1000) + ts.tv_nsec;
 }
 #endif  // SANITIZER_LINUX && !SANITIZER_GO
 
 void ReExec() {
   const char *pathname = "/proc/self/exe";
 
 #if SANITIZER_NETBSD