[DFSan] Add bcmp wrapper.

[morehouse]

• Restructure bcmp and memcmp wrapper to please check_custom_wrappers.sh

compiler-rt/lib/dfsan/dfsan_custom.cpp

if (s[i] == c || s[i] == 0) {
       if (s[i] == 0 && c != 0) {
         return nullptr;
       }
       return const_cast<char *>(s + i);
     }
   }
 }
 
-DECLARE_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_memcmp, uptr caller_pc,
-                              const void *s1, const void *s2, size_t n,
-                              dfsan_label s1_label, dfsan_label s2_label,
-                              dfsan_label n_label)
-
-SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_memcmp(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) {
-  CALL_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_memcmp, GET_CALLER_PC(), s1, s2, n,
-                             s1_label, s2_label, n_label);
+static int dfsan_memcmp_bcmp(const void *s1, const void *s2, size_t n,
+                             dfsan_label n_label, dfsan_label *ret_label) {
   const char *cs1 = (const char *) s1, *cs2 = (const char *) s2;
   for (size_t i = 0; i != n; ++i) {
     if (cs1[i] != cs2[i]) {
       if (flags().strict_data_dependencies) {
         *ret_label = 0;
       } else {
         *ret_label = dfsan_union(dfsan_read_label(cs1, i + 1),
                                  dfsan_read_label(cs2, i + 1));
       }
       return cs1[i] - cs2[i];
     }
   }
 
   if (flags().strict_data_dependencies) {
     *ret_label = 0;
   } else {
     *ret_label = dfsan_union(dfsan_read_label(cs1, n),
                              dfsan_read_label(cs2, n));
   }
   return 0;
 }
 
+DECLARE_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_memcmp, uptr caller_pc,
+                              const void *s1, const void *s2, size_t n,
+                              dfsan_label s1_label, dfsan_label s2_label,
+                              dfsan_label n_label)
+
+SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_memcmp(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) {
+  CALL_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_memcmp, GET_CALLER_PC(), s1, s2, n,
+                             s1_label, s2_label, n_label);
+  return dfsan_memcmp_bcmp(s1, s2, n, s1_label, s2_label, n_label, ret_label);
+}
+
+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 dfsan_memcmp_bcmp(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)
 
 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_strcmp(const char *s1, const char *s2,
                                                 dfsan_label s1_label,
                                                 dfsan_label s2_label,
                                                 dfsan_label *ret_label) {

compiler-rt/lib/dfsan/done_abilist.txt

 fun:strtod=custom
 fun:strtol=custom
 fun:strtoll=custom
 fun:strtoul=custom
 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
 fun:strchr=custom
 fun:strcmp=custom
 fun:strlen=custom
 fun:strncasecmp=custom
 fun:strncmp=custom

compiler-rt/test/dfsan/custom.cpp

 #include <assert.h>
 #include <fcntl.h>
 #include <link.h>
 #include <poll.h>
 #include <pthread.h>
 #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>
 #include <time.h>
 #include <unistd.h>
 
 dfsan_label i_label = 0;
 dfsan_label j_label = 0;
void test_memcmp() {
   assert(rv < 0);
 #ifdef STRICT_DATA_DEPENDENCIES
   ASSERT_ZERO_LABEL(rv);
 #else
   ASSERT_LABEL(rv, i_j_label);
 #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)];
   dfsan_set_label(i_label, &str1[3], 1);
 
   ASSERT_ZERO_LABEL(memcpy(str2, str1, sizeof(str1)));
   assert(0 == memcmp(str2, str1, sizeof(str1)));
   ASSERT_ZERO_LABEL(str2[0]);
#else
   j_label = dfsan_create_label("j", 0);
   k_label = dfsan_create_label("k", 0);
 #endif
   i_j_label = dfsan_union(i_label, j_label);
   assert(i_j_label != i_label);
   assert(i_j_label != j_label);
   assert(i_j_label != k_label);
 
+  test_bcmp();
   test_calloc();
   test_clock_gettime();
   test_ctime_r();
   test_dfsan_set_write_callback();
   test_dl_iterate_phdr();
   test_dlopen();
   test_fgets();
   test_fstat();