[DFSan] Add wrapper for getentropy().

[morehouse]

compiler-rt/test/dfsan/custom.cpp

956

__GLIBC_PREREQ might be cleaner.

[browneee]

Address comment.

compiler-rt/lib/dfsan/dfsan_custom.cpp

 }
 
 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfso_get_current_dir_name(dfsan_label *ret_label,
                                   dfsan_origin *ret_origin) {
   return __dfsw_get_current_dir_name(ret_label);
 }
 
+// This function is only available for glibc 2.25 or newer.  Mark it weak so
+// linking succeeds with older glibcs.
+SANITIZER_WEAK_ATTRIBUTE int getentropy(void *buffer, size_t length);
+
+SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_getentropy(void *buffer, size_t length,
+                                                    dfsan_label buffer_label,
+                                                    dfsan_label length_label,
+                                                    dfsan_label *ret_label) {
+  int ret = getentropy(buffer, length);
+  if (ret == 0) {
+    dfsan_set_label(0, buffer, length);
+  }
+  *ret_label = 0;
+  return ret;
+}
+
+SANITIZER_INTERFACE_ATTRIBUTE int __dfso_getentropy(void *buffer, size_t length,
+                                                    dfsan_label buffer_label,
+                                                    dfsan_label length_label,
+                                                    dfsan_label *ret_label,
+                                                    dfsan_origin buffer_origin,
+                                                    dfsan_origin length_origin,
+                                                    dfsan_origin *ret_origin) {
+  return __dfsw_getentropy(buffer, length, buffer_label, length_label,
+                           ret_label);
+}
+
 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_gethostname(char *name, size_t len, dfsan_label name_label,
                        dfsan_label len_label, dfsan_label *ret_label) {
   int ret = gethostname(name, len);
   if (ret == 0) {
     dfsan_set_label(0, name, strlen(name) + 1);
   }
   *ret_label = 0;

compiler-rt/lib/dfsan/done_abilist.txt

 fun:_dl_get_tls_static_info=custom
 fun:clock_gettime=custom
 fun:dlopen=custom
 fun:epoll_wait=custom
 fun:fgets=custom
 fun:fstat=custom
 fun:getcwd=custom
 fun:get_current_dir_name=custom
+fun:getentropy=custom
 fun:gethostname=custom
 fun:getpeername=custom
 fun:getrlimit=custom
 fun:getrusage=custom
 fun:getsockname=custom
 fun:getsockopt=custom
 fun:nanosleep=custom
 fun:pread=custom

compiler-rt/lib/dfsan/libc_ubuntu1404_abilist.txt

 fun:getdate=uninstrumented
 fun:getdate_r=uninstrumented
 fun:getdelim=uninstrumented
 fun:getdirentries=uninstrumented
 fun:getdirentries64=uninstrumented
 fun:getdomainname=uninstrumented
 fun:getdtablesize=uninstrumented
 fun:getegid=uninstrumented
+fun:getentropy=uninstrumented
 fun:getenv=uninstrumented
 fun:geteuid=uninstrumented
 fun:getfsent=uninstrumented
 fun:getfsfile=uninstrumented
 fun:getfsspec=uninstrumented
 fun:getgid=uninstrumented
 fun:getgrent=uninstrumented
 fun:getgrent_r=uninstrumented

compiler-rt/test/dfsan/custom.cpp

 #ifdef ORIGIN_TRACKING
 #define ASSERT_SAVED_N_ORIGINS(val, n) \
   for (int i = 0; i < n; ++i)          \
     ASSERT_ORIGIN(val[i], val##_o[i]);
 #else
 #define ASSERT_SAVED_N_ORIGINS(val, n)
 #endif
 
+#if !defined(__GLIBC_PREREQ)
+#  define __GLIBC_PREREQ(a, b) 0
+#endif
+
 void test_stat() {
   int i = 1;
   dfsan_set_label(i_label, &i, sizeof(i));
 
   struct stat s;
   s.st_dev = i;
   DEFINE_AND_SAVE_ORIGINS(s)
   int ret = stat("/", &s);

 void test_get_current_dir_name() {
   char* ret = get_current_dir_name();
   assert(ret);
   assert(ret[0] == '/');
   ASSERT_READ_ZERO_LABEL(ret, strlen(ret) + 1);
   ASSERT_ZERO_LABEL(ret);
 }
 
+void test_getentropy() {
+  char buf[64];
+  dfsan_set_label(i_label, buf + 2, 2);
+  DEFINE_AND_SAVE_ORIGINS(buf)
+#if __GLIBC_PREREQ(2, 25)
+  // glibc >= 2.25 has getentropy()
+  int ret = getentropy(buf, sizeof(buf));
+  ASSERT_ZERO_LABEL(ret);
+  if (ret == 0) {
+    ASSERT_READ_ZERO_LABEL(buf + 2, 2);
+    ASSERT_SAVED_ORIGINS(buf)
+  }
+#endif
+}
+
 void test_gethostname() {
   char buf[1024];
   dfsan_set_label(i_label, buf + 2, 2);
   DEFINE_AND_SAVE_ORIGINS(buf)
   int ret = gethostname(buf, sizeof(buf));
   assert(ret == 0);
   ASSERT_ZERO_LABEL(ret);
   ASSERT_READ_ZERO_LABEL(buf + 2, 2);
int main(void) {
   test_dl_iterate_phdr();
   test_dlopen();
   test_epoll_wait();
   test_fgets();
   test_fork();
   test_fstat();
   test_get_current_dir_name();
   test_getcwd();
+  test_getentropy();
   test_gethostname();
   test_getpeername();
   test_getpwuid_r();
   test_getrlimit();
   test_getrusage();
   test_getsockname();
   test_getsockopt();
   test_gettimeofday();