Add weak definitions of trace-cmp hooks to dfsan

[kcc]

Summary

This allows to build and link the code with e.g.
-fsanitize=dataflow -fsanitize-coverage=trace-pc-guard,pc-table,func,trace-cmp
w/o providing (all) the definitions of trace-cmp hooks.

This is similar to dummy hooks provided by asan/ubsan/msan for the same purpose,
except that some of the hooks need to have the __dfsw_ prefix
since we need dfsan to replace them.

[pcc]

LGTM

lib/dfsan/dfsan_custom.cc

int __dfsw_snprintf(char *str, size_t size, const char *format,
                     dfsan_label format_label, dfsan_label *va_labels,
                     dfsan_label *ret_label, ...) {
   va_list ap;
   va_start(ap, ret_label);
   int ret = format_buffer(str, size, format, va_labels, ret_label, ap);
   va_end(ap);
   return ret;
 }
-} // extern "C"
+
+// Default empty implementations (weak). Users should redefine them.
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard, u32 *) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard_init, u32 *,
+                             u32 *) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_pcs_init, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_indir, void) {}
+
+SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_cmp, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_cmp1, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_cmp2, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_cmp4, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_cmp8, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_const_cmp1,
+                             void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_const_cmp2,
+                             void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_const_cmp4,
+                             void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_const_cmp8,
+                             void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_switch, void) {}
+}  // extern "C"

lib/dfsan/scripts/check_custom_wrappers.sh

 }
 
 # Ignore __sanitizer_cov_trace* because they are implemented elsewhere.
 trap on_exit EXIT
 grep -E "^fun:.*=custom" ${DFSAN_ABI_LIST} \
   | grep -v "dfsan_get_label\|__sanitizer_cov_trace" \
   | sed "s/^fun:\(.*\)=custom.*/\1/" | sort > $DIFF_A
 grep -E "__dfsw.*\(" ${DFSAN_CUSTOM_WRAPPERS} \
+  | grep -v "__sanitizer_cov_trace" \
   | sed "s/.*__dfsw_\(.*\)(.*/\1/" | sort > $DIFF_B
 diff -u $DIFF_A $DIFF_B > ${DIFFOUT}
 if [ $? -ne 0 ]
 then
   echo -n "The following differences between the ABI list and ">> ${ERRORLOG}
   echo "the implemented custom wrappers have been found:" >> ${ERRORLOG}
   cat ${DIFFOUT} >> ${ERRORLOG}
 fi
 
 grep -E __dfsw_ ${DFSAN_CUSTOM_WRAPPERS} \
+  | grep -v "__sanitizer_cov_trace" \
   | sed "s/.*__dfsw_\([^(]*\).*/\1/" | sort > $DIFF_A
 grep -E "^[[:space:]]*test_.*\(\);" ${DFSAN_CUSTOM_TESTS} \
   | sed "s/.*test_\(.*\)();/\1/" | sort > $DIFF_B
 diff -u $DIFF_A $DIFF_B > ${DIFFOUT}
 if [ $? -ne 0 ]
 then
   echo -n "The following differences between the implemented " >> ${ERRORLOG}
   echo "custom wrappers and the tests have been found:" >> ${ERRORLOG}

test/dfsan/trace-cmp.c

+// Checks that dfsan works with trace-cmp instrumentation, even if some hooks
+// are not defined (relies on week hooks implemented in dfsan).
+//
+// RUN: %clang_dfsan -fsanitize-coverage=trace-pc-guard,pc-table,func,trace-cmp %s -o %t
+// RUN: %run %t 2>&1 | FileCheck %s
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <sanitizer/dfsan_interface.h>
+
+uint32_t a4, b4;
+uint64_t a8, b8;
+
+// Define just two hooks, and leave others undefined.
+void __dfsw___sanitizer_cov_trace_const_cmp4(uint8_t a, uint8_t b,
+                                             dfsan_label l1, dfsan_label l2) {
+  printf("const_cmp4 %d %d\n", a, b);
+}
+void __dfsw___sanitizer_cov_trace_cmp8(uint8_t a, uint8_t b, dfsan_label l1,
+                                       dfsan_label l2) {
+  printf("cmp8 %d %d\n", a, b);
+}
+
+int main(int argc, char **argv) {
+  printf("MAIN\n");
+  // CHECK: MAIN
+
+  if (a4 != b4) abort();
+  if (a4 == 42) abort();
+  // CHECK: const_cmp4 42 0
+  if (a8 != b8) abort();
+  // CHECK: cmp8 0 0
+  if (a8 == 66) abort();
+
+  switch (10 / (a4 + 2)) {
+    case 1: abort();
+    case 2: exit(1);
+    case 5:
+            printf("SWITCH OK\n");
+            break;
+  }
+  // CHECK: SWITCH OK
+
+
+  printf("DONE\n");
+  // CHECK: DONE
+  return 0;
+}