[libFuzzer] implement strncmp hook for data-flow-guided fuzzing (w/ and w/o dfsan), add a test

llvm-svn: 243611

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/lib/Fuzzer/test/StrncmpTest.cpp b/llvm/lib/Fuzzer/test/StrncmpTest.cpp
new file mode 100644
index 00000000000..86b02d091a6
--- /dev/null
+++ b/llvm/lib/Fuzzer/test/StrncmpTest.cpp
@@ -0,0 +1,20 @@
+// Simple test for a fuzzer. The fuzzer must find a particular string.
+#include <cstring>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+
+extern "C" void LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  // TODO: check other sizes.
+  char *S = (char*)Data;
+  if (Size >= 8 && strncmp(S, "01234567", 8) == 0) {
+    if (Size >= 12 && strncmp(S + 8, "ABCD", 4) == 0) {
+      if (Size >= 14 && strncmp(S + 12, "XY", 2) == 0) {
+        if (Size >= 16 && strncmp(S + 14, "KLM", 3) == 0) {
+          fprintf(stderr, "BINGO\n");
+          exit(1);
+        }
+      }
+    }
+  }
+}