[DFSan] Add bcmp wrapper.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D87801

compiler-rt/lib/dfsan/dfsan_custom.cpp

@@ -129,6 +129,14 @@ SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_memcmp(const void *s1, const void *s2,
   return 0;
 }
 
+SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_bcmp(const void *s1, const void *s2,
+                                              size_t n, dfsan_label s1_label,
+                                              dfsan_label s2_label,
+                                              dfsan_label n_label,
+                                              dfsan_label *ret_label) {
+  return __dfsw_memcmp(s1, s2, n, s1_label, s2_label, n_label, ret_label);
+}
+
 DECLARE_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_strcmp, uptr caller_pc,
                               const char *s1, const char *s2,
                               dfsan_label s1_label, dfsan_label s2_label)

compiler-rt/lib/dfsan/done_abilist.txt

@@ -183,6 +183,7 @@ fun:strtoull=custom
 
 # Functions that produce an output that is computed from the input, but is not
 # necessarily data dependent.
+fun:bcmp=custom
 fun:memchr=custom
 fun:memcmp=custom
 fun:strcasecmp=custom

compiler-rt/test/dfsan/custom.cpp

@@ -17,12 +17,13 @@
 #include <pwd.h>
 #include <sched.h>
 #include <signal.h>
-#include <stdio.h>
 #include <stdint.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <sys/select.h>
+#include <strings.h>
 #include <sys/resource.h>
+#include <sys/select.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
@@ -86,6 +87,24 @@ void test_memcmp() {
 #endif
 }
 
+void test_bcmp() {
+  char str1[] = "str1", str2[] = "str2";
+  dfsan_set_label(i_label, &str1[3], 1);
+  dfsan_set_label(j_label, &str2[3], 1);
+
+  int rv = bcmp(str1, str2, sizeof(str1));
+  assert(rv != 0);
+#ifdef STRICT_DATA_DEPENDENCIES
+  ASSERT_ZERO_LABEL(rv);
+#else
+  ASSERT_LABEL(rv, i_j_label);
+#endif
+
+  rv = bcmp(str1, str2, sizeof(str1) - 2);
+  assert(rv == 0);
+  ASSERT_ZERO_LABEL(rv);
+}
+
 void test_memcpy() {
   char str1[] = "str1";
   char str2[sizeof(str1)];
@@ -967,6 +986,7 @@ int main(void) {
   assert(i_j_label != j_label);
   assert(i_j_label != k_label);
 
+  test_bcmp();
   test_calloc();
   test_clock_gettime();
   test_ctime_r();