[DFSan] Add wrapper for getentropy().

Reviewed By: morehouse

Differential Revision: https://reviews.llvm.org/D108604

Author: browneee

compiler-rt/lib/dfsan/dfsan_custom.cpp

@@ -1026,6 +1026,33 @@ char *__dfso_get_current_dir_name(dfsan_label *ret_label,
   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) {

compiler-rt/lib/dfsan/done_abilist.txt

@@ -218,6 +218,7 @@ 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

compiler-rt/lib/dfsan/libc_ubuntu1404_abilist.txt

@@ -1852,6 +1852,7 @@ fun:getdirentries64=uninstrumented
 fun:getdomainname=uninstrumented
 fun:getdtablesize=uninstrumented
 fun:getegid=uninstrumented
+fun:getentropy=uninstrumented
 fun:getenv=uninstrumented
 fun:geteuid=uninstrumented
 fun:getfsent=uninstrumented

compiler-rt/test/dfsan/custom.cpp

@@ -161,6 +161,10 @@ dfsan_label i_j_label = 0;
 #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));
@@ -944,6 +948,21 @@ void test_get_current_dir_name() {
   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);
@@ -1967,6 +1986,7 @@ int main(void) {
   test_fstat();
   test_get_current_dir_name();
   test_getcwd();
+  test_getentropy();
   test_gethostname();
   test_getpeername();
   test_getpwuid_r();