Add an implementation of LLVMFuzzerTestOneInput() that starts the sandbox on a secondary thread and exposes a function to synchronize the generation of fuzzing inputs with their consumption by the sandbox.
Signed-off-by: Andrew Scull ascull@google.com --- arch/sandbox/config.mk | 3 + arch/sandbox/cpu/os.c | 70 +++++++++++++++++++++++ arch/sandbox/include/asm/fuzzing_engine.h | 25 ++++++++ 3 files changed, 98 insertions(+) create mode 100644 arch/sandbox/include/asm/fuzzing_engine.h
diff --git a/arch/sandbox/config.mk b/arch/sandbox/config.mk index d7ce66fb6c..5fbe1f50e3 100644 --- a/arch/sandbox/config.mk +++ b/arch/sandbox/config.mk @@ -19,6 +19,9 @@ SANITIZERS := ifdef CONFIG_ASAN SANITIZERS += -fsanitize=address endif +ifdef CONFIG_FUZZ +SANITIZERS += -fsanitize=fuzzer +endif KBUILD_CFLAGS += $(SANITIZERS)
cmd_u-boot__ = $(CC) -o $@ -Wl,-T u-boot.lds $(u-boot-init) \ diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c index 5ea4135741..cd45d7b6b6 100644 --- a/arch/sandbox/cpu/os.c +++ b/arch/sandbox/cpu/os.c @@ -8,6 +8,7 @@ #include <dirent.h> #include <errno.h> #include <fcntl.h> +#include <pthread.h> #include <getopt.h> #include <setjmp.h> #include <signal.h> @@ -26,6 +27,7 @@ #include <linux/compiler_attributes.h> #include <linux/types.h>
+#include <asm/fuzzing_engine.h> #include <asm/getopt.h> #include <asm/main.h> #include <asm/sections.h> @@ -1002,7 +1004,75 @@ void os_relaunch(char *argv[]) os_exit(1); }
+ +#ifdef CONFIG_FUZZ +static void *fuzzer_thread(void * ptr) +{ + char cmd[64]; + char *argv[5] = {"./u-boot", "-T", "-c", cmd, NULL}; + const char *fuzz_test; + + /* Find which test to run from an environment variable. */ + fuzz_test = getenv("UBOOT_SB_FUZZ_TEST"); + if (!fuzz_test) + os_abort(); + + snprintf(cmd, sizeof(cmd), "fuzz %s", fuzz_test); + + sandbox_main(4, argv); + os_abort(); + return NULL; +} + +static bool fuzzer_initialized = false; +static pthread_mutex_t fuzzer_mutex = PTHREAD_MUTEX_INITIALIZER; +static pthread_cond_t fuzzer_cond = PTHREAD_COND_INITIALIZER; +static const uint8_t *fuzzer_data; +static size_t fuzzer_size; + +int sandbox_fuzzing_engine_get_input(const uint8_t **data, size_t *size) +{ + if (!fuzzer_initialized) + return -ENOSYS; + + /* Tell the main thread we need new inputs then wait for them. */ + pthread_mutex_lock(&fuzzer_mutex); + pthread_cond_signal(&fuzzer_cond); + pthread_cond_wait(&fuzzer_cond, &fuzzer_mutex); + *data = fuzzer_data; + *size = fuzzer_size; + pthread_mutex_unlock(&fuzzer_mutex); + return 0; +} + +int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) +{ + static pthread_t tid; + + pthread_mutex_lock(&fuzzer_mutex); + + /* Initialize the sandbox on another thread. */ + if (!fuzzer_initialized) { + fuzzer_initialized = true; + if (pthread_create(&tid, NULL, fuzzer_thread, NULL)) + os_abort(); + pthread_cond_wait(&fuzzer_cond, &fuzzer_mutex); + } + + /* Hand over the input. */ + fuzzer_data = data; + fuzzer_size = size; + pthread_cond_signal(&fuzzer_cond); + + /* Wait for the inputs to be finished with. */ + pthread_cond_wait(&fuzzer_cond, &fuzzer_mutex); + pthread_mutex_unlock(&fuzzer_mutex); + + return 0; +} +#else int main(int argc, char *argv[]) { return sandbox_main(argc, argv); } +#endif diff --git a/arch/sandbox/include/asm/fuzzing_engine.h b/arch/sandbox/include/asm/fuzzing_engine.h new file mode 100644 index 0000000000..cf6396363b --- /dev/null +++ b/arch/sandbox/include/asm/fuzzing_engine.h @@ -0,0 +1,25 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Copyright (c) 2022 Google, Inc. + * Written by Andrew Scull ascull@google.com + */ + +#ifndef __ASM_FUZZING_ENGINE_H +#define __ASM_FUZZING_ENGINE_H + +/** Function to get fuzzing engine input data. */ +/** + * sandbox_fuzzing_engine_get_input() - get an input from the sandbox fuzzing + * engine + * + * The function will return a pointer to the input data and the size of the + * data pointed to. The pointer will remain valid until the next invocation of + * this function. + * + * @data: output pointer to input data + * @size output size of input data + * Return: 0 if OK, -ve on error + */ +int sandbox_fuzzing_engine_get_input(const uint8_t **data, size_t *size); + +#endif /* __ASM_FUZZING_ENGINE_H */