[RFC PATCH 1/2] fuzz: Add basic fuzz testing target.

[Josh Steadmon <steadmon@google.com>]

Signed-off-by: Josh Steadmon <steadmon@google.com>
---
 .gitignore          |  2 ++
 Makefile            | 30 +++++++++++++++++++++++++++++-
 fuzz-pack-headers.c | 14 ++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 fuzz-pack-headers.c

diff --git a/.gitignore b/.gitignore
index 9d1363a1eb..87a28b3115 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
+/fuzz_corpora
+/fuzz-pack-headers
 /GIT-BUILD-OPTIONS
 /GIT-CFLAGS
 /GIT-LDFLAGS
diff --git a/Makefile b/Makefile
index 13e1c52478..10bb82b115 100644
--- a/Makefile
+++ b/Makefile
@@ -590,6 +590,8 @@ XDIFF_OBJS =
 VCSSVN_OBJS =
 GENERATED_H =
 EXTRA_CPPFLAGS =
+FUZZ_OBJS =
+FUZZ_PROGRAMS =
 LIB_OBJS =
 PROGRAM_OBJS =
 PROGRAMS =
@@ -682,6 +684,10 @@ SCRIPTS = $(SCRIPT_SH_INS) \
 
 ETAGS_TARGET = TAGS
 
+FUZZ_OBJS += fuzz-pack-headers.o
+
+FUZZ_PROGRAMS += $(patsubst %.o,%,$(FUZZ_OBJS))
+
 # Empty...
 EXTRA_PROGRAMS =
 
@@ -2250,6 +2256,7 @@ TEST_OBJS := $(patsubst %$X,%.o,$(TEST_PROGRAMS)) $(patsubst %,t/helper/%,$(TEST
 OBJECTS := $(LIB_OBJS) $(BUILTIN_OBJS) $(PROGRAM_OBJS) $(TEST_OBJS) \
 	$(XDIFF_OBJS) \
 	$(VCSSVN_OBJS) \
+	$(FUZZ_OBJS) \
 	common-main.o \
 	git.o
 ifndef NO_CURL
@@ -2931,7 +2938,7 @@ profile-clean:
 cocciclean:
 	$(RM) contrib/coccinelle/*.cocci.patch*
 
-clean: profile-clean coverage-clean cocciclean
+clean: profile-clean coverage-clean cocciclean fuzz-clean
 	$(RM) *.res
 	$(RM) $(OBJECTS)
 	$(RM) $(LIB_FILE) $(XDIFF_LIB) $(VCSSVN_LIB)
@@ -3061,3 +3068,24 @@ cover_db: coverage-report
 cover_db_html: cover_db
 	cover -report html -outputdir cover_db_html cover_db
 
+
+### Fuzz testing
+#
+.PHONY: fuzz-clean fuzz-objs fuzz-compile
+
+FUZZ_CFLAGS = $(CFLAGS) -fsanitize-coverage=trace-pc-guard -fsanitize=address
+FUZZ_LDFLAGS = $(FUZZ_CFLAGS)
+
+
+fuzz-clean:
+	$(RM) $(FUZZ_PROGRAMS) $(FUZZ_OBJS)
+
+fuzz-objs: $(FUZZ_OBJS)
+
+fuzz-compile:
+	$(MAKE) CC=clang LD=clang CFLAGS="$(FUZZ_CFLAGS)" \
+		LDFLAGS="$(FUZZ_LDFLAGS)" all fuzz-objs
+
+$(FUZZ_PROGRAMS): fuzz-compile
+	clang++ $(FUZZ_LDFLAGS) $(LIB_OBJS) $(BUILTIN_OBJS) $(XDIFF_OBJS) \
+		$(EXTLIBS) git.o $@.o /usr/lib/llvm-4.0/lib/libFuzzer.a -o $@
diff --git a/fuzz-pack-headers.c b/fuzz-pack-headers.c
new file mode 100644
index 0000000000..99da1d0fd3
--- /dev/null
+++ b/fuzz-pack-headers.c
@@ -0,0 +1,14 @@
+#include "packfile.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+	enum object_type type;
+	unsigned long len;
+
+	unpack_object_header_buffer((const unsigned char *)data,
+				    (unsigned long)size, &type, &len);
+
+	return 0;
+}
-- 
2.19.0.605.g01d371f741-goog