[PATCH 1/2] Add libfuzzer target to fuzz/x86_instruction_emulator

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

This target enables integration into oss-fuzz.

Signed-off-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
---
 tools/fuzz/x86_instruction_emulator/Makefile    | 10 ++++++++--
 tools/fuzz/x86_instruction_emulator/fuzz-emul.c |  6 ++----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/tools/fuzz/x86_instruction_emulator/Makefile 
b/tools/fuzz/x86_instruction_emulator/Makefile
index 1e4c6b37f5..de5f1e7e30 100644
--- a/tools/fuzz/x86_instruction_emulator/Makefile
+++ b/tools/fuzz/x86_instruction_emulator/Makefile
@@ -3,7 +3,7 @@ include $(XEN_ROOT)/tools/Rules.mk
 
 .PHONY: x86-insn-fuzz-all
 ifeq ($(CONFIG_X86_64),y)
-x86-insn-fuzz-all: x86-insn-fuzzer.a fuzz-emul.o afl
+x86-insn-fuzz-all: x86-insn-fuzzer.a fuzz-emul.o afl libfuzzer
 else
 x86-insn-fuzz-all:
 endif
@@ -58,6 +58,9 @@ afl-harness: afl-harness.o $(OBJS) cpuid.o wrappers.o
 afl-harness-cov: afl-harness-cov.o $(patsubst %.o,%-cov.o,$(OBJS)) cpuid.o 
wrappers.o
        $(CC) $(CFLAGS) $(GCOV_FLAGS) $(addprefix 
-Wl$(comma)--wrap=,$(WRAPPED)) $^ -o $@
 
+libfuzzer-harness: $(OBJS) cpuid.o
+       $(CC) $(CFLAGS) $(LIB_FUZZING_ENGINE) -fsanitize=fuzzer $^ -o $@
+
 # Common targets
 .PHONY: all
 all: x86-insn-fuzz-all
@@ -67,7 +70,7 @@ distclean: clean
 
 .PHONY: clean
 clean:
-       rm -f *.a *.o $(DEPS_RM) afl-harness afl-harness-cov *.gcda *.gcno 
*.gcov
+       rm -f *.a *.o $(DEPS_RM) afl-harness afl-harness-cov *.gcda *.gcno 
*.gcov libfuzzer-harness
        rm -rf x86_emulate x86-emulate.c x86-emulate.h wrappers.c cpuid.c
 
 .PHONY: install
@@ -81,4 +84,7 @@ afl: afl-harness
 .PHONY: afl-cov
 afl-cov: afl-harness-cov
 
+.PHONY: libfuzzer
+libfuzzer: libfuzzer-harness
+
 -include $(DEPS_INCLUDE)
diff --git a/tools/fuzz/x86_instruction_emulator/fuzz-emul.c 
b/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
index eeeb6931f4..2ba9ca9e0b 100644
--- a/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
+++ b/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
@@ -906,14 +906,12 @@ int LLVMFuzzerTestOneInput(const uint8_t *data_p, size_t 
size)
 
     if ( size <= DATA_OFFSET )
     {
-        printf("Input too small\n");
-        return 1;
+        return -1;
     }
 
     if ( size > FUZZ_CORPUS_SIZE )
     {
-        printf("Input too large\n");
-        return 1;
+        return -1;
     }
 
     memcpy(&input, data_p, size);
-- 
2.34.1