test: fuzz: Add framework for fuzzing

Add the basic infrastructure for declaring fuzz tests and a command to
invoke them.

Signed-off-by: Andrew Scull <ascull@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

Kconfig

@@ -161,6 +161,15 @@ config ASAN
 	  Enables AddressSanitizer to discover out-of-bounds accesses,
 	  use-after-free, double-free and memory leaks.
 
+config FUZZ
+	bool "Enable fuzzing"
+	depends on CC_IS_CLANG
+	depends on DM_FUZZING_ENGINE
+	select ASAN
+	help
+	  Enables the fuzzing infrastructure to generate fuzzing data and run
+          fuzz tests.
+
 config CC_HAS_ASM_INLINE
 	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
 

include/test/fuzz.h

@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2022 Google, Inc.
+ * Written by Andrew Scull <ascull@google.com>
+ */
+
+#ifndef __TEST_FUZZ_H
+#define __TEST_FUZZ_H
+
+#include <linker_lists.h>
+#include <linux/types.h>
+
+/**
+ * struct fuzz_test - Information about a fuzz test
+ *
+ * @name: Name of fuzz test
+ * @func: Function to call to perform fuzz test on an input
+ * @flags: Flags indicate pre-conditions for fuzz test
+ */
+struct fuzz_test {
+	const char *name;
+	int (*func)(const uint8_t * data, size_t size);
+	int flags;
+};
+
+/**
+ * FUZZ_TEST() - register a fuzz test
+ *
+ * The fuzz test function must return 0 as other values are reserved for future
+ * use.
+ *
+ * @_name:	the name of the fuzz test function
+ * @_flags:	an integer field that can be evaluated by the fuzzer
+ * 		implementation
+ */
+#define FUZZ_TEST(_name, _flags)					\
+	ll_entry_declare(struct fuzz_test, _name, fuzz_tests) = {	\
+		.name = #_name,						\
+		.func = _name,						\
+		.flags = _flags,					\
+	}
+
+/** Get the start of the list of fuzz tests */
+#define FUZZ_TEST_START() \
+	ll_entry_start(struct fuzz_test, fuzz_tests)
+
+/** Get the number of elements in the list of fuzz tests */
+#define FUZZ_TEST_COUNT() \
+	ll_entry_count(struct fuzz_test, fuzz_tests)
+
+#endif /* __TEST_FUZZ_H */

test/Makefile

@@ -16,6 +16,7 @@ obj-$(CONFIG_$(SPL_)CMDLINE) += cmd_ut.o
 obj-$(CONFIG_$(SPL_)CMDLINE) += command_ut.o
 obj-$(CONFIG_$(SPL_)UT_COMPRESSION) += compression.o
 obj-y += dm/
+obj-$(CONFIG_FUZZ) += fuzz/
 obj-$(CONFIG_$(SPL_)CMDLINE) += print_ut.o
 obj-$(CONFIG_$(SPL_)CMDLINE) += str_ut.o
 obj-$(CONFIG_UT_TIME) += time_ut.o

test/fuzz/Makefile

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright (c) 2022 Google, Inc.
+# Written by Andrew Scull <ascull@google.com>
+#
+
+obj-$(CONFIG_$(SPL_)CMDLINE) += cmd_fuzz.o

test/fuzz/cmd_fuzz.c

@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2022 Google, Inc.
+ * Written by Andrew Scull <ascull@google.com>
+ */
+
+#include <command.h>
+#include <common.h>
+#include <dm.h>
+#include <fuzzing_engine.h>
+#include <test/fuzz.h>
+
+static struct fuzz_test *find_fuzz_test(const char *name)
+{
+	struct fuzz_test *fuzzer = FUZZ_TEST_START();
+	size_t count = FUZZ_TEST_COUNT();
+	size_t i;
+
+	for (i = 0; i < count; ++i) {
+		if (strcmp(name, fuzzer->name) == 0)
+			return fuzzer;
+		++fuzzer;
+	}
+
+	return NULL;
+}
+
+static struct udevice *find_fuzzing_engine(void)
+{
+	struct udevice *dev;
+
+	if (uclass_first_device(UCLASS_FUZZING_ENGINE, &dev))
+		return NULL;
+
+	return dev;
+}
+
+static int do_fuzz(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
+{
+	struct fuzz_test *fuzzer;
+	struct udevice *dev;
+
+	if (argc != 2)
+		return CMD_RET_USAGE;
+
+	fuzzer = find_fuzz_test(argv[1]);
+	if (!fuzzer) {
+		printf("Could not find fuzzer: %s\n", argv[1]);
+		return 1;
+	}
+
+	dev = find_fuzzing_engine();
+	if (!dev) {
+		puts("No fuzzing engine available\n");
+		return 1;
+	}
+
+	while (1) {
+		const uint8_t *data;
+		size_t size;
+
+		if (dm_fuzzing_engine_get_input(dev, &data, &size)) {
+			puts("Fuzzing engine failed\n");
+			return 1;
+		}
+
+		fuzzer->func(data, size);
+	}
+
+	return 1;
+}
+
+#ifdef CONFIG_SYS_LONGHELP
+static char fuzz_help_text[] =
+	"[fuzz-test-name] - execute the named fuzz test\n"
+	;
+#endif /* CONFIG_SYS_LONGHELP */
+
+U_BOOT_CMD(
+	fuzz, CONFIG_SYS_MAXARGS, 1, do_fuzz,
+	"fuzz tests", fuzz_help_text
+);