test: host_command_fuzz: fuzzing test

Writing fuzzing tests is a little tricky, as clang takes over the main
function. Instead, we start the test main function in a thread, and
have LLVMFuzzerTestOneInput prepare the host command buffer, and
wake the TEST_RUNNER task.

To make fuzzing faster, we only send somehow correctly formed requests,
with a valid checksum and length (this can be disabled with an option).

We also make sure that the emulator does not hibernate, reboot or jump
to a different image when fuzzing is enabled.

BRANCH=none
BUG=chromium:854975
TEST=make buildfuzztests -j
     ASAN_OPTIONS="log_path=stderr" \
         build/host/host_command_fuzz/host_command_fuzz.exe -timeout=5

Change-Id: I27b25e44c405f118dfc1296247479245e15e54b4
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1107523
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Jonathan Metzman <metzman@chromium.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/chip/host/system.c b/chip/host/system.c
index 69ed1c83a1..cc0c307d95 100644
--- a/chip/host/system.c
+++ b/chip/host/system.c
@@ -173,6 +173,15 @@ test_mockable int system_is_locked(void)
 	return 0;
 }
 
+#ifdef TEST_FUZZ
+/* When fuzzing, do not allow sysjumps. */
+int system_run_image_copy(enum system_image_copy_t copy)
+{
+	ccprints("Emulator would sysjump here. Fuzzing: doing nothing.");
+	return EC_ERROR_UNKNOWN;
+}
+#endif
+
 const char *system_get_chip_vendor(void)
 {
 	return "chromeos";