[compiler-rt] Implement getrandom interception

[akrieger]

Summary

Straightforward implementation of getrandom syscall and libc
hooks.

Test Plan: Local MSAN failures caused by uninstrumented getrandom
calls stop failing.

Patch by Andrew Krieger.

[vitalybuka]

Can you please add some trivial test under compiler-rt/test/sanitizer_common ? You can't check sanitization there, just check that does not crash and return reasonable results

[akrieger]

Rebase, add unit test

[akrieger]

Rename test file after rebase, fix test to not be trivially wrong.

[akrieger]

@vitalybuka thanks for the quick review and accept. I need someone to commit this for me - can you do that or should I find someone else to push this for me?

compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc

#define INIT_SL_INIT                  \
   COMMON_INTERCEPT_FUNCTION(sl_init); \
   COMMON_INTERCEPT_FUNCTION(sl_add);  \
   COMMON_INTERCEPT_FUNCTION(sl_find); \
   COMMON_INTERCEPT_FUNCTION(sl_free);
 #else
 #define INIT_SL_INIT
 #endif
 
+#if SANITIZER_INTERCEPT_GETRANDOM
+INTERCEPTOR(SSIZE_T, getrandom, void* buf, SIZE_T buflen, unsigned int flags) {
+  void* ctx;
+  COMMON_INTERCEPTOR_ENTER(ctx, getrandom, buf, buflen, flags);
+  SSIZE_T n = REAL(getrandom)(buf, buflen, flags);
+  if (n > 0) {
+    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, buf, n);
+  }
+  return n;
+}
+#define INIT_GETRANDOM \
+  COMMON_INTERCEPT_FUNCTION(getrandom)
+#else
+#define INIT_GETRANDOM
+#endif
+
 static void InitializeCommonInterceptors() {
 #if SI_POSIX
   static u64 metadata_mem[sizeof(MetadataHashMap) / sizeof(u64) + 1];
   interceptor_metadata_map =
       new ((void *)&metadata_mem) MetadataHashMap();  // NOLINT
 #endif
 
   INIT_MMAP;
#endif
   INIT_POPEN;
   INIT_POPENVE;
   INIT_PCLOSE;
   INIT_FUNOPEN;
   INIT_FUNOPEN2;
   INIT_FDEVNAME;
   INIT_GETUSERSHELL;
   INIT_SL_INIT;
+  INIT_GETRANDOM;
 
   INIT___PRINTF_CHK;
 }

compiler-rt/lib/sanitizer_common/sanitizer_common_syscalls.inc

 POST_SYSCALL(rt_sigaction)(long res, long signum,
                            const __sanitizer_kernel_sigaction_t *act,
                            __sanitizer_kernel_sigaction_t *oldact, SIZE_T sz) {
   if (res >= 0 && oldact) {
     SIZE_T oldact_sz = ((char *)&oldact->sa_mask) - ((char *)oldact) + sz;
     POST_WRITE(oldact, oldact_sz);
   }
 }
+
+PRE_SYSCALL(getrandom)(void *buf, uptr count, long flags) {
+  if (buf) {
+    PRE_WRITE(buf, count);
+  }
+}
+
+POST_SYSCALL(getrandom)(long res, void *buf, uptr count, long flags) {
+  if (res > 0 && buf) {
+    POST_WRITE(buf, res);
+  }
+}
+
 }  // extern "C"
 
 #undef PRE_SYSCALL
 #undef PRE_READ
 #undef PRE_WRITE
 #undef POST_SYSCALL
 #undef POST_READ
 #undef POST_WRITE
 
 #endif  // SANITIZER_LINUX

compiler-rt/lib/sanitizer_common/sanitizer_platform_interceptors.h

 #define SANITIZER_INTERCEPT_FUNOPEN (SI_NETBSD || SI_FREEBSD)
 #define SANITIZER_INTERCEPT_FUNOPEN2 SI_NETBSD
 #define SANITIZER_INTERCEPT_GETFSENT (SI_FREEBSD || SI_NETBSD || SI_MAC)
 #define SANITIZER_INTERCEPT_ARC4RANDOM (SI_FREEBSD || SI_NETBSD)
 #define SANITIZER_INTERCEPT_FDEVNAME SI_FREEBSD
 #define SANITIZER_INTERCEPT_GETUSERSHELL (SI_POSIX && !SI_POSIX)
 #define SANITIZER_INTERCEPT_SL_INIT (SI_FREEBSD || SI_NETBSD)
 
+#define SANITIZER_INTERCEPT_GETRANDOM SI_LINUX
+
 #endif  // #ifndef SANITIZER_PLATFORM_INTERCEPTORS_H

compiler-rt/test/sanitizer_common/TestCases/Linux/getrandom.cpp

+// RUN: %clangxx -O2 %s -o %t && %run %t
+// UNSUPPORTED: android
+//
+
+#include <sys/types.h>
+
+#if !defined(__GLIBC_PREREQ)
+#define __GLIBC_PREREQ(a, b) 0
+#endif
+
+#if __GLIBC_PREREQ(2, 25)
+#include <sys/random.h>
+#endif
+
+int main() {
+  char buf[16];
+  ssize_t n = 1;
+#if __GLIBC_PREREQ(2, 25)
+  n = getrandom(buf, sizeof(buf), 0);
+#endif
+  return (int)(n <= 0);
+}