Commit 1e2cd308 authored by Kees Cook's avatar Kees Cook
Browse files

lib/test_stackinit: Allow building stand-alone 

Especially now that GCC is developing the -ftrivial-auto-var-init
option[1], it's helpful to have a stand-alone userspace test for stack
variable initialization. Relicense to GPLv2+ (I am the only author),
provide stand-alone kernel macro stubs, and update comments for clarity.

[1] https://gcc.gnu.org/pipermail/gcc-patches/2021-July/575198.html



Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210723221933.3431999-3-keescook@chromium.org
parent f9398f15

lib/test_stackinit.c

+69 −3
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

// SPDX-License-Identifier: GPL-2.0-or-later

/*

 * Test cases for compiler-based stack variable zeroing via future

 * compiler flags or CONFIG_GCC_PLUGIN_STRUCTLEAK*.

 * Test cases for compiler-based stack variable zeroing via

 * -ftrivial-auto-var-init={zero,pattern} or CONFIG_GCC_PLUGIN_STRUCTLEAK*.

 *

 * External build example:

 *	clang -O2 -Wall -ftrivial-auto-var-init=pattern \

 *		-o test_stackinit test_stackinit.c

 */

#ifdef __KERNEL__

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt



#include <linux/init.h>
@@ -10,6 +15,63 @@ 
#include <linux/module.h>

#include <linux/string.h>



#else



/* Userspace headers. */

#include <stdio.h>

#include <stdint.h>

#include <string.h>

#include <stdbool.h>

#include <errno.h>

#include <sys/types.h>



/* Linux kernel-ism stubs for stand-alone userspace build. */

#define KBUILD_MODNAME		"stackinit"

#define pr_fmt(fmt)		KBUILD_MODNAME ": " fmt

#define pr_err(fmt, ...)	fprintf(stderr, pr_fmt(fmt), ##__VA_ARGS__)

#define pr_warn(fmt, ...)	fprintf(stderr, pr_fmt(fmt), ##__VA_ARGS__)

#define pr_info(fmt, ...)	fprintf(stdout, pr_fmt(fmt), ##__VA_ARGS__)

#define __init			/**/

#define __exit			/**/

#define __user			/**/

#define noinline		__attribute__((__noinline__))

#define __aligned(x)		__attribute__((__aligned__(x)))

#ifdef __clang__

# define __compiletime_error(message) /**/

#else

# define __compiletime_error(message) __attribute__((__error__(message)))

#endif

#define __compiletime_assert(condition, msg, prefix, suffix)		\

	do {								\

		extern void prefix ## suffix(void) __compiletime_error(msg); \

		if (!(condition))					\

			prefix ## suffix();				\

	} while (0)

#define _compiletime_assert(condition, msg, prefix, suffix) \

	__compiletime_assert(condition, msg, prefix, suffix)

#define compiletime_assert(condition, msg) \

	_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)

#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)

#define BUILD_BUG_ON(condition) \

	BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)

typedef uint8_t			u8;

typedef uint16_t		u16;

typedef uint32_t		u32;

typedef uint64_t		u64;



#define module_init(func)	static int (*do_init)(void) = func

#define module_exit(func)	static void (*do_exit)(void) = func

#define MODULE_LICENSE(str)	int main(void) {		\

					int rc;			\

					/* License: str */	\

					rc = do_init();		\

					if (rc == 0)		\

						do_exit();	\

					return rc;		\

				}



#endif /* __KERNEL__ */



/* Exfiltration buffer. */

#define MAX_VAR_SIZE	128

static u8 check_buf[MAX_VAR_SIZE];
@@ -279,6 +341,10 @@ DEFINE_TEST(user, struct test_user, STRUCT, none); 
static int noinline __leaf_switch_none(int path, bool fill)

{

	switch (path) {

		/*

		 * This is intentionally unreachable. To silence the

		 * warning, build with -Wno-switch-unreachable

		 */

		uint64_t var;



	case 1: