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linux/lib/tests/stackinit_kunit.c
Arnd Bergmann 8530ea3c9b Kbuild: remove structleak gcc plugin 
gcc-12 and higher support the -ftrivial-auto-var-init= flag, after
gcc-8 is the minimum version, this is half of the supported ones, and
the vast majority of the versions that users are actually likely to
have, so it seems like a good time to stop having the fallback
plugin implementation

Older toolchains are still able to build kernels normally without
this plugin, but won't be able to use variable initialization..

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
2025-04-30 21:57:09 +02:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Test cases for compiler-based stack variable zeroing via
* -ftrivial-auto-var-init={zero,pattern}.
* For example, see:
* "Running tests with kunit_tool" at Documentation/dev-tools/kunit/start.rst
* ./tools/testing/kunit/kunit.py run stackinit [--raw_output] \
* --make_option LLVM=1 \
* --kconfig_add CONFIG_INIT_STACK_ALL_ZERO=y
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <kunit/test.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/string.h>
/* Exfiltration buffer. */
#define MAX_VAR_SIZE 128
static u8 check_buf[MAX_VAR_SIZE];
/* Character array to trigger stack protector in all functions. */
#define VAR_BUFFER 32
/* Volatile mask to convince compiler to copy memory with 0xff. */
static volatile u8 forced_mask = 0xff;
/* Location and size tracking to validate fill and test are colocated. */
static void *fill_start, *target_start;
static size_t fill_size, target_size;
static bool stackinit_range_contains(char *haystack_start, size_t haystack_size,
char *needle_start, size_t needle_size)
{
if (needle_start >= haystack_start &&
needle_start + needle_size <= haystack_start + haystack_size)
return true;
return false;
}
/* Whether the test is expected to fail. */
#define WANT_SUCCESS 0
#define XFAIL 1
#define DO_NOTHING_TYPE_SCALAR(var_type) var_type
#define DO_NOTHING_TYPE_STRING(var_type) void
#define DO_NOTHING_TYPE_STRUCT(var_type) void
#define DO_NOTHING_TYPE_UNION(var_type) void
#define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)
#define DO_NOTHING_RETURN_STRING(ptr) /**/
#define DO_NOTHING_RETURN_STRUCT(ptr) /**/
#define DO_NOTHING_RETURN_UNION(ptr) /**/
#define DO_NOTHING_CALL_SCALAR(var, name) \
(var) = do_nothing_ ## name(&(var))
#define DO_NOTHING_CALL_STRING(var, name) \
do_nothing_ ## name(var)
#define DO_NOTHING_CALL_STRUCT(var, name) \
do_nothing_ ## name(&(var))
#define DO_NOTHING_CALL_UNION(var, name) \
do_nothing_ ## name(&(var))
#define FETCH_ARG_SCALAR(var) &var
#define FETCH_ARG_STRING(var) var
#define FETCH_ARG_STRUCT(var) &var
#define FETCH_ARG_UNION(var) &var
/*
* On m68k, if the leaf function test variable is longer than 8 bytes,
* the start of the stack frame moves. 8 is sufficiently large to
* test m68k char arrays, but leave it at 16 for other architectures.
*/
#ifdef CONFIG_M68K
#define FILL_SIZE_STRING 8
#define FILL_SIZE_ARRAY 2
#else
#define FILL_SIZE_STRING 16
#define FILL_SIZE_ARRAY 8
#endif
#define INIT_CLONE_SCALAR /**/
#define INIT_CLONE_STRING [FILL_SIZE_STRING]
#define INIT_CLONE_STRUCT /**/
#define INIT_CLONE_UNION /**/
#define ZERO_CLONE_SCALAR(zero) memset(&(zero), 0x00, sizeof(zero))
#define ZERO_CLONE_STRING(zero) memset(&(zero), 0x00, sizeof(zero))
/*
* For the struct, intentionally poison padding to see if it gets
* copied out in direct assignments.
* */
#define ZERO_CLONE_STRUCT(zero) \
do { \
memset(&(zero), 0xFF, sizeof(zero)); \
zero.one = 0; \
zero.two = 0; \
zero.three = 0; \
zero.four = 0; \
} while (0)
#define ZERO_CLONE_UNION(zero) ZERO_CLONE_STRUCT(zero)
#define INIT_SCALAR_none(var_type) /**/
#define INIT_SCALAR_zero(var_type) = 0
#define INIT_STRING_none(var_type) [FILL_SIZE_STRING] /**/
#define INIT_STRING_zero(var_type) [FILL_SIZE_STRING] = { }
#define INIT_STRUCT_none(var_type) /**/
#define INIT_STRUCT_zero(var_type) = { }
#define INIT_STRUCT_old_zero(var_type) = { 0 }
#define __static_partial { .two = 0, }
#define __static_all { .one = 0, \
.two = 0, \
.three = 0, \
.four = 0, \
}
#define __dynamic_partial { .two = arg->two, }
#define __dynamic_all { .one = arg->one, \
.two = arg->two, \
.three = arg->three, \
.four = arg->four, \
}
#define __runtime_partial var.two = 0
#define __runtime_all var.one = 0; \
var.two = 0; \
var.three = 0; \
var.four = 0
#define INIT_STRUCT_static_partial(var_type) \
= __static_partial
#define INIT_STRUCT_static_all(var_type) \
= __static_all
#define INIT_STRUCT_dynamic_partial(var_type) \
= __dynamic_partial
#define INIT_STRUCT_dynamic_all(var_type) \
= __dynamic_all
#define INIT_STRUCT_runtime_partial(var_type) \
; __runtime_partial
#define INIT_STRUCT_runtime_all(var_type) \
; __runtime_all
#define INIT_STRUCT_assigned_static_partial(var_type) \
; var = (var_type)__static_partial
#define INIT_STRUCT_assigned_static_all(var_type) \
; var = (var_type)__static_all
#define INIT_STRUCT_assigned_dynamic_partial(var_type) \
; var = (var_type)__dynamic_partial
#define INIT_STRUCT_assigned_dynamic_all(var_type) \
; var = (var_type)__dynamic_all
#define INIT_STRUCT_assigned_copy(var_type) \
; var = *(arg)
/* Union initialization is the same as structs. */
#define INIT_UNION_none(var_type) INIT_STRUCT_none(var_type)
#define INIT_UNION_zero(var_type) INIT_STRUCT_zero(var_type)
#define INIT_UNION_old_zero(var_type) INIT_STRUCT_old_zero(var_type)
#define INIT_UNION_static_partial(var_type) \
INIT_STRUCT_static_partial(var_type)
#define INIT_UNION_static_all(var_type) \
INIT_STRUCT_static_all(var_type)
#define INIT_UNION_dynamic_partial(var_type) \
INIT_STRUCT_dynamic_partial(var_type)
#define INIT_UNION_dynamic_all(var_type) \
INIT_STRUCT_dynamic_all(var_type)
#define INIT_UNION_runtime_partial(var_type) \
INIT_STRUCT_runtime_partial(var_type)
#define INIT_UNION_runtime_all(var_type) \
INIT_STRUCT_runtime_all(var_type)
#define INIT_UNION_assigned_static_partial(var_type) \
INIT_STRUCT_assigned_static_partial(var_type)
#define INIT_UNION_assigned_static_all(var_type) \
INIT_STRUCT_assigned_static_all(var_type)
#define INIT_UNION_assigned_dynamic_partial(var_type) \
INIT_STRUCT_assigned_dynamic_partial(var_type)
#define INIT_UNION_assigned_dynamic_all(var_type) \
INIT_STRUCT_assigned_dynamic_all(var_type)
#define INIT_UNION_assigned_copy(var_type) \
INIT_STRUCT_assigned_copy(var_type)
/*
* The "did we actually fill the stack?" check value needs
* to be neither 0 nor any of the "pattern" bytes. The
* pattern bytes are compiler, architecture, and type based,
* so we have to pick a value that never appears for those
* combinations. Use 0x99 which is not 0xFF, 0xFE, nor 0xAA.
*/
#define FILL_BYTE 0x99
/*
* @name: unique string name for the test
* @var_type: type to be tested for zeroing initialization
* @which: is this a SCALAR, STRING, or STRUCT type?
* @init_level: what kind of initialization is performed
* @xfail: is this test expected to fail?
*/
#define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \
/* Returns 0 on success, 1 on failure. */ \
static noinline void test_ ## name (struct kunit *test) \
{ \
var_type zero INIT_CLONE_ ## which; \
int ignored; \
u8 sum = 0, i; \
\
/* Notice when a new test is larger than expected. */ \
BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \
\
/* Fill clone type with zero for per-field init. */ \
ZERO_CLONE_ ## which(zero); \
/* Clear entire check buffer for 0xFF overlap test. */ \
memset(check_buf, 0x00, sizeof(check_buf)); \
/* Fill stack with FILL_BYTE. */ \
ignored = leaf_ ##name((unsigned long)&ignored, 1, \
FETCH_ARG_ ## which(zero)); \
/* Verify all bytes overwritten with FILL_BYTE. */ \
for (sum = 0, i = 0; i < target_size; i++) \
sum += (check_buf[i] != FILL_BYTE); \
/* Clear entire check buffer for later bit tests. */ \
memset(check_buf, 0x00, sizeof(check_buf)); \
/* Extract stack-defined variable contents. */ \
ignored = leaf_ ##name((unsigned long)&ignored, 0, \
FETCH_ARG_ ## which(zero)); \
/* \
* Delay the sum test to here to do as little as \
* possible between the two leaf function calls. \
*/ \
KUNIT_ASSERT_EQ_MSG(test, sum, 0, \
"leaf fill was not 0x%02X!?\n", \
FILL_BYTE); \
\
/* Validate that compiler lined up fill and target. */ \
KUNIT_ASSERT_TRUE_MSG(test, \
stackinit_range_contains(fill_start, fill_size, \
target_start, target_size), \
"stackframe was not the same between calls!? " \
"(fill %zu wide, target offset by %d)\n", \
fill_size, \
(int)((ssize_t)(uintptr_t)fill_start - \
(ssize_t)(uintptr_t)target_start)); \
\
/* Validate check region has no FILL_BYTE bytes. */ \
for (sum = 0, i = 0; i < target_size; i++) \
sum += (check_buf[i] == FILL_BYTE); \
\
if (sum != 0 && xfail) \
kunit_skip(test, \
"XFAIL uninit bytes: %d\n", \
sum); \
KUNIT_ASSERT_EQ_MSG(test, sum, 0, \
"uninit bytes: %d\n", sum); \
}
#define DEFINE_TEST(name, var_type, which, init_level, xfail) \
/* no-op to force compiler into ignoring "uninitialized" vars */\
static noinline DO_NOTHING_TYPE_ ## which(var_type) \
do_nothing_ ## name(var_type *ptr) \
{ \
OPTIMIZER_HIDE_VAR(ptr); \
/* Will always be true, but compiler doesn't know. */ \
if ((unsigned long)ptr > 0x2) \
return DO_NOTHING_RETURN_ ## which(ptr); \
else \
return DO_NOTHING_RETURN_ ## which(ptr + 1); \
} \
static noinline int leaf_ ## name(unsigned long sp, bool fill, \
var_type *arg) \
{ \
char buf[VAR_BUFFER]; \
var_type var \
INIT_ ## which ## _ ## init_level(var_type); \
\
target_start = &var; \
target_size = sizeof(var); \
/* \
* Keep this buffer around to make sure we've got a \
* stack frame of SOME kind... \
*/ \
memset(buf, (char)(sp & 0xff), sizeof(buf)); \
/* Fill variable with FILL_BYTE. */ \
if (fill) { \
fill_start = &var; \
fill_size = sizeof(var); \
memset(fill_start, \
FILL_BYTE & forced_mask, \
fill_size); \
} \
\
/* Silence "never initialized" warnings. */ \
DO_NOTHING_CALL_ ## which(var, name); \
\
/* Exfiltrate "var". */ \
memcpy(check_buf, target_start, target_size); \
\
return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \
} \
DEFINE_TEST_DRIVER(name, var_type, which, xfail)
/* Structure with no padding. */
struct test_packed {
unsigned long one;
unsigned long two;
unsigned long three;
unsigned long four;
};
/* Simple structure with padding likely to be covered by compiler. */
struct test_small_hole {
size_t one;
char two;
/* 3 byte padding hole here. */
int three;
unsigned long four;
};
/* Trigger unhandled padding in a structure. */
struct test_big_hole {
u8 one;
u8 two;
u8 three;
/* 61 byte padding hole here. */
u8 four __aligned(64);
} __aligned(64);
struct test_trailing_hole {
char *one;
char *two;
char *three;
char four;
/* "sizeof(unsigned long) - 1" byte padding hole here. */
};
/* Test if STRUCTLEAK is clearing structs with __user fields. */
struct test_user {
u8 one;
unsigned long two;
char __user *three;
unsigned long four;
};
/* No padding: all members are the same size. */
union test_same_sizes {
unsigned long one;
unsigned long two;
unsigned long three;
unsigned long four;
};
/* Mismatched sizes, with one and two being small */
union test_small_start {
char one:1;
char two;
short three;
unsigned long four;
struct big_struct {
unsigned long array[FILL_SIZE_ARRAY];
} big;
};
/* Mismatched sizes, with three and four being small */
union test_small_end {
short one;
unsigned long two;
char three:1;
char four;
};
#define ALWAYS_PASS WANT_SUCCESS
#define ALWAYS_FAIL XFAIL
#ifdef CONFIG_INIT_STACK_NONE
# define USER_PASS XFAIL
# define BYREF_PASS XFAIL
# define STRONG_PASS XFAIL
#else
# define USER_PASS WANT_SUCCESS
# define BYREF_PASS WANT_SUCCESS
# define STRONG_PASS WANT_SUCCESS
#endif
#define DEFINE_SCALAR_TEST(name, init, xfail) \
DEFINE_TEST(name ## _ ## init, name, SCALAR, \
init, xfail)
#define DEFINE_SCALAR_TESTS(init, xfail) \
DEFINE_SCALAR_TEST(u8, init, xfail); \
DEFINE_SCALAR_TEST(u16, init, xfail); \
DEFINE_SCALAR_TEST(u32, init, xfail); \
DEFINE_SCALAR_TEST(u64, init, xfail); \
DEFINE_TEST(char_array_ ## init, unsigned char, \
STRING, init, xfail)
#define DEFINE_STRUCT_TEST(name, init, xfail) \
DEFINE_TEST(name ## _ ## init, \
struct test_ ## name, STRUCT, init, \
xfail)
#define DEFINE_UNION_TEST(name, init, xfail) \
DEFINE_TEST(name ## _ ## init, \
union test_ ## name, STRUCT, init, \
xfail)
#define DEFINE_STRUCT_TESTS(init, xfail) \
DEFINE_STRUCT_TEST(small_hole, init, xfail); \
DEFINE_STRUCT_TEST(big_hole, init, xfail); \
DEFINE_STRUCT_TEST(trailing_hole, init, xfail); \
DEFINE_STRUCT_TEST(packed, init, xfail)
#define DEFINE_STRUCT_INITIALIZER_TESTS(base, xfail) \
DEFINE_STRUCT_TESTS(base ## _ ## partial, \
xfail); \
DEFINE_STRUCT_TESTS(base ## _ ## all, xfail)
#define DEFINE_UNION_INITIALIZER_TESTS(base, xfail) \
DEFINE_UNION_TESTS(base ## _ ## partial, \
xfail); \
DEFINE_UNION_TESTS(base ## _ ## all, xfail)
#define DEFINE_UNION_TESTS(init, xfail) \
DEFINE_UNION_TEST(same_sizes, init, xfail); \
DEFINE_UNION_TEST(small_start, init, xfail); \
DEFINE_UNION_TEST(small_end, init, xfail);
/* These should be fully initialized all the time! */
DEFINE_SCALAR_TESTS(zero, ALWAYS_PASS);
DEFINE_STRUCT_TESTS(zero, ALWAYS_PASS);
DEFINE_STRUCT_TESTS(old_zero, ALWAYS_PASS);
DEFINE_UNION_TESTS(zero, ALWAYS_PASS);
DEFINE_UNION_TESTS(old_zero, ALWAYS_PASS);
/* Struct initializers: padding may be left uninitialized. */
DEFINE_STRUCT_INITIALIZER_TESTS(static, STRONG_PASS);
DEFINE_STRUCT_INITIALIZER_TESTS(dynamic, STRONG_PASS);
DEFINE_STRUCT_INITIALIZER_TESTS(runtime, STRONG_PASS);
DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static, STRONG_PASS);
DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS);
DEFINE_STRUCT_TESTS(assigned_copy, ALWAYS_FAIL);
DEFINE_UNION_INITIALIZER_TESTS(static, STRONG_PASS);
DEFINE_UNION_INITIALIZER_TESTS(dynamic, STRONG_PASS);
DEFINE_UNION_INITIALIZER_TESTS(runtime, STRONG_PASS);
DEFINE_UNION_INITIALIZER_TESTS(assigned_static, STRONG_PASS);
DEFINE_UNION_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS);
DEFINE_UNION_TESTS(assigned_copy, ALWAYS_FAIL);
/* No initialization without compiler instrumentation. */
DEFINE_SCALAR_TESTS(none, STRONG_PASS);
DEFINE_STRUCT_TESTS(none, BYREF_PASS);
/* Initialization of members with __user attribute. */
DEFINE_TEST(user, struct test_user, STRUCT, none, USER_PASS);
/*
* Check two uses through a variable declaration outside either path,
* which was noticed as a special case in porting earlier stack init
* compiler logic.
*/
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[10];
case 1:
target_start = &var;
target_size = sizeof(var);
if (fill) {
fill_start = &var;
fill_size = sizeof(var);
memset(fill_start, (forced_mask | 0x55) & FILL_BYTE, fill_size);
}
memcpy(check_buf, target_start, target_size);
break;
case 2:
target_start = &var;
target_size = sizeof(var);
if (fill) {
fill_start = &var;
fill_size = sizeof(var);
memset(fill_start, (forced_mask | 0xaa) & FILL_BYTE, fill_size);
}
memcpy(check_buf, target_start, target_size);
break;
default:
var[1] = 5;
return var[1] & forced_mask;
}
return 0;
}
static noinline int leaf_switch_1_none(unsigned long sp, bool fill,
uint64_t *arg)
{
return __leaf_switch_none(1, fill);
}
static noinline int leaf_switch_2_none(unsigned long sp, bool fill,
uint64_t *arg)
{
return __leaf_switch_none(2, fill);
}
/*
* These are expected to fail for most configurations because neither
* GCC nor Clang have a way to perform initialization of variables in
* non-code areas (i.e. in a switch statement before the first "case").
* https://llvm.org/pr44916
*/
DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, ALWAYS_FAIL);
DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, ALWAYS_FAIL);
#define KUNIT_test_scalars(init) \
KUNIT_CASE(test_u8_ ## init), \
KUNIT_CASE(test_u16_ ## init), \
KUNIT_CASE(test_u32_ ## init), \
KUNIT_CASE(test_u64_ ## init), \
KUNIT_CASE(test_char_array_ ## init)
#define KUNIT_test_structs(init) \
KUNIT_CASE(test_small_hole_ ## init), \
KUNIT_CASE(test_big_hole_ ## init), \
KUNIT_CASE(test_trailing_hole_ ## init),\
KUNIT_CASE(test_packed_ ## init) \
#define KUNIT_test_unions(init) \
KUNIT_CASE(test_same_sizes_ ## init), \
KUNIT_CASE(test_small_start_ ## init), \
KUNIT_CASE(test_small_end_ ## init) \
static struct kunit_case stackinit_test_cases[] = {
/* These are explicitly initialized and should always pass. */
KUNIT_test_scalars(zero),
KUNIT_test_structs(zero),
KUNIT_test_structs(old_zero),
KUNIT_test_unions(zero),
KUNIT_test_unions(old_zero),
/* Padding here appears to be accidentally always initialized? */
KUNIT_test_structs(dynamic_partial),
KUNIT_test_structs(assigned_dynamic_partial),
KUNIT_test_unions(dynamic_partial),
KUNIT_test_unions(assigned_dynamic_partial),
/* Padding initialization depends on compiler behaviors. */
KUNIT_test_structs(static_partial),
KUNIT_test_structs(static_all),
KUNIT_test_structs(dynamic_all),
KUNIT_test_structs(runtime_partial),
KUNIT_test_structs(runtime_all),
KUNIT_test_structs(assigned_static_partial),
KUNIT_test_structs(assigned_static_all),
KUNIT_test_structs(assigned_dynamic_all),
KUNIT_test_unions(static_partial),
KUNIT_test_unions(static_all),
KUNIT_test_unions(dynamic_all),
KUNIT_test_unions(runtime_partial),
KUNIT_test_unions(runtime_all),
KUNIT_test_unions(assigned_static_partial),
KUNIT_test_unions(assigned_static_all),
KUNIT_test_unions(assigned_dynamic_all),
/* Everything fails this since it effectively performs a memcpy(). */
KUNIT_test_structs(assigned_copy),
KUNIT_test_unions(assigned_copy),
/* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
KUNIT_test_scalars(none),
KUNIT_CASE(test_switch_1_none),
KUNIT_CASE(test_switch_2_none),
/* STRUCTLEAK_BYREF should cover from here down. */
KUNIT_test_structs(none),
/* STRUCTLEAK will only cover this. */
KUNIT_CASE(test_user),
{}
};
static struct kunit_suite stackinit_test_suite = {
.name = "stackinit",
.test_cases = stackinit_test_cases,
};
kunit_test_suites(&stackinit_test_suite);
MODULE_DESCRIPTION("Test cases for compiler-based stack variable zeroing");
MODULE_LICENSE("GPL");
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