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lib/test_stackinit: Allow building stand-alone

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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: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210723221933.3431999-3-keescook@chromium.org
This commit is contained in:
Kees Cook 2021-07-23 15:19:32 -07:00
parent f9398f1560
commit 1e2cd3084f
1 changed files with 69 additions and 3 deletions
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72
lib/test_stackinit.c
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@ -1,8 +1,13 @@
// 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: