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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Test cases for compiler-based stack variable zeroing via4 * -ftrivial-auto-var-init={zero,pattern} or CONFIG_GCC_PLUGIN_STRUCTLEAK*.5 * For example, see:6 * "Running tests with kunit_tool" at Documentation/dev-tools/kunit/start.rst7 * ./tools/testing/kunit/kunit.py run stackinit [--raw_output] \8 * --make_option LLVM=1 \9 * --kconfig_add CONFIG_INIT_STACK_ALL_ZERO=y10 *11 */12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt13 14#include <kunit/test.h>15#include <linux/init.h>16#include <linux/kernel.h>17#include <linux/module.h>18#include <linux/string.h>19 20/* Exfiltration buffer. */21#define MAX_VAR_SIZE 12822static u8 check_buf[MAX_VAR_SIZE];23 24/* Character array to trigger stack protector in all functions. */25#define VAR_BUFFER 3226 27/* Volatile mask to convince compiler to copy memory with 0xff. */28static volatile u8 forced_mask = 0xff;29 30/* Location and size tracking to validate fill and test are colocated. */31static void *fill_start, *target_start;32static size_t fill_size, target_size;33 34static bool stackinit_range_contains(char *haystack_start, size_t haystack_size,35 char *needle_start, size_t needle_size)36{37 if (needle_start >= haystack_start &&38 needle_start + needle_size <= haystack_start + haystack_size)39 return true;40 return false;41}42 43/* Whether the test is expected to fail. */44#define WANT_SUCCESS 045#define XFAIL 146 47#define DO_NOTHING_TYPE_SCALAR(var_type) var_type48#define DO_NOTHING_TYPE_STRING(var_type) void49#define DO_NOTHING_TYPE_STRUCT(var_type) void50 51#define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)52#define DO_NOTHING_RETURN_STRING(ptr) /**/53#define DO_NOTHING_RETURN_STRUCT(ptr) /**/54 55#define DO_NOTHING_CALL_SCALAR(var, name) \56 (var) = do_nothing_ ## name(&(var))57#define DO_NOTHING_CALL_STRING(var, name) \58 do_nothing_ ## name(var)59#define DO_NOTHING_CALL_STRUCT(var, name) \60 do_nothing_ ## name(&(var))61 62#define FETCH_ARG_SCALAR(var) &var63#define FETCH_ARG_STRING(var) var64#define FETCH_ARG_STRUCT(var) &var65 66/*67 * On m68k, if the leaf function test variable is longer than 8 bytes,68 * the start of the stack frame moves. 8 is sufficiently large to69 * test m68k char arrays, but leave it at 16 for other architectures.70 */71#ifdef CONFIG_M68K72#define FILL_SIZE_STRING 873#else74#define FILL_SIZE_STRING 1675#endif76 77#define INIT_CLONE_SCALAR /**/78#define INIT_CLONE_STRING [FILL_SIZE_STRING]79#define INIT_CLONE_STRUCT /**/80 81#define ZERO_CLONE_SCALAR(zero) memset(&(zero), 0x00, sizeof(zero))82#define ZERO_CLONE_STRING(zero) memset(&(zero), 0x00, sizeof(zero))83/*84 * For the struct, intentionally poison padding to see if it gets85 * copied out in direct assignments.86 * */87#define ZERO_CLONE_STRUCT(zero) \88 do { \89 memset(&(zero), 0xFF, sizeof(zero)); \90 zero.one = 0; \91 zero.two = 0; \92 zero.three = 0; \93 zero.four = 0; \94 } while (0)95 96#define INIT_SCALAR_none(var_type) /**/97#define INIT_SCALAR_zero(var_type) = 098 99#define INIT_STRING_none(var_type) [FILL_SIZE_STRING] /**/100#define INIT_STRING_zero(var_type) [FILL_SIZE_STRING] = { }101 102#define INIT_STRUCT_none(var_type) /**/103#define INIT_STRUCT_zero(var_type) = { }104 105 106#define __static_partial { .two = 0, }107#define __static_all { .one = 0, \108 .two = 0, \109 .three = 0, \110 .four = 0, \111 }112#define __dynamic_partial { .two = arg->two, }113#define __dynamic_all { .one = arg->one, \114 .two = arg->two, \115 .three = arg->three, \116 .four = arg->four, \117 }118#define __runtime_partial var.two = 0119#define __runtime_all var.one = 0; \120 var.two = 0; \121 var.three = 0; \122 var.four = 0123 124#define INIT_STRUCT_static_partial(var_type) \125 = __static_partial126#define INIT_STRUCT_static_all(var_type) \127 = __static_all128#define INIT_STRUCT_dynamic_partial(var_type) \129 = __dynamic_partial130#define INIT_STRUCT_dynamic_all(var_type) \131 = __dynamic_all132#define INIT_STRUCT_runtime_partial(var_type) \133 ; __runtime_partial134#define INIT_STRUCT_runtime_all(var_type) \135 ; __runtime_all136 137#define INIT_STRUCT_assigned_static_partial(var_type) \138 ; var = (var_type)__static_partial139#define INIT_STRUCT_assigned_static_all(var_type) \140 ; var = (var_type)__static_all141#define INIT_STRUCT_assigned_dynamic_partial(var_type) \142 ; var = (var_type)__dynamic_partial143#define INIT_STRUCT_assigned_dynamic_all(var_type) \144 ; var = (var_type)__dynamic_all145 146#define INIT_STRUCT_assigned_copy(var_type) \147 ; var = *(arg)148 149/*150 * @name: unique string name for the test151 * @var_type: type to be tested for zeroing initialization152 * @which: is this a SCALAR, STRING, or STRUCT type?153 * @init_level: what kind of initialization is performed154 * @xfail: is this test expected to fail?155 */156#define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \157/* Returns 0 on success, 1 on failure. */ \158static noinline void test_ ## name (struct kunit *test) \159{ \160 var_type zero INIT_CLONE_ ## which; \161 int ignored; \162 u8 sum = 0, i; \163 \164 /* Notice when a new test is larger than expected. */ \165 BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \166 \167 /* Fill clone type with zero for per-field init. */ \168 ZERO_CLONE_ ## which(zero); \169 /* Clear entire check buffer for 0xFF overlap test. */ \170 memset(check_buf, 0x00, sizeof(check_buf)); \171 /* Fill stack with 0xFF. */ \172 ignored = leaf_ ##name((unsigned long)&ignored, 1, \173 FETCH_ARG_ ## which(zero)); \174 /* Verify all bytes overwritten with 0xFF. */ \175 for (sum = 0, i = 0; i < target_size; i++) \176 sum += (check_buf[i] != 0xFF); \177 /* Clear entire check buffer for later bit tests. */ \178 memset(check_buf, 0x00, sizeof(check_buf)); \179 /* Extract stack-defined variable contents. */ \180 ignored = leaf_ ##name((unsigned long)&ignored, 0, \181 FETCH_ARG_ ## which(zero)); \182 /* \183 * Delay the sum test to here to do as little as \184 * possible between the two leaf function calls. \185 */ \186 KUNIT_ASSERT_EQ_MSG(test, sum, 0, \187 "leaf fill was not 0xFF!?\n"); \188 \189 /* Validate that compiler lined up fill and target. */ \190 KUNIT_ASSERT_TRUE_MSG(test, \191 stackinit_range_contains(fill_start, fill_size, \192 target_start, target_size), \193 "stackframe was not the same between calls!? " \194 "(fill %zu wide, target offset by %d)\n", \195 fill_size, \196 (int)((ssize_t)(uintptr_t)fill_start - \197 (ssize_t)(uintptr_t)target_start)); \198 \199 /* Look for any bytes still 0xFF in check region. */ \200 for (sum = 0, i = 0; i < target_size; i++) \201 sum += (check_buf[i] == 0xFF); \202 \203 if (sum != 0 && xfail) \204 kunit_skip(test, \205 "XFAIL uninit bytes: %d\n", \206 sum); \207 KUNIT_ASSERT_EQ_MSG(test, sum, 0, \208 "uninit bytes: %d\n", sum); \209}210#define DEFINE_TEST(name, var_type, which, init_level, xfail) \211/* no-op to force compiler into ignoring "uninitialized" vars */\212static noinline DO_NOTHING_TYPE_ ## which(var_type) \213do_nothing_ ## name(var_type *ptr) \214{ \215 /* Will always be true, but compiler doesn't know. */ \216 if ((unsigned long)ptr > 0x2) \217 return DO_NOTHING_RETURN_ ## which(ptr); \218 else \219 return DO_NOTHING_RETURN_ ## which(ptr + 1); \220} \221static noinline int leaf_ ## name(unsigned long sp, bool fill, \222 var_type *arg) \223{ \224 char buf[VAR_BUFFER]; \225 var_type var \226 INIT_ ## which ## _ ## init_level(var_type); \227 \228 target_start = &var; \229 target_size = sizeof(var); \230 /* \231 * Keep this buffer around to make sure we've got a \232 * stack frame of SOME kind... \233 */ \234 memset(buf, (char)(sp & 0xff), sizeof(buf)); \235 /* Fill variable with 0xFF. */ \236 if (fill) { \237 fill_start = &var; \238 fill_size = sizeof(var); \239 memset(fill_start, \240 (char)((sp & 0xff) | forced_mask), \241 fill_size); \242 } \243 \244 /* Silence "never initialized" warnings. */ \245 DO_NOTHING_CALL_ ## which(var, name); \246 \247 /* Exfiltrate "var". */ \248 memcpy(check_buf, target_start, target_size); \249 \250 return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \251} \252DEFINE_TEST_DRIVER(name, var_type, which, xfail)253 254/* Structure with no padding. */255struct test_packed {256 unsigned long one;257 unsigned long two;258 unsigned long three;259 unsigned long four;260};261 262/* Simple structure with padding likely to be covered by compiler. */263struct test_small_hole {264 size_t one;265 char two;266 /* 3 byte padding hole here. */267 int three;268 unsigned long four;269};270 271/* Trigger unhandled padding in a structure. */272struct test_big_hole {273 u8 one;274 u8 two;275 u8 three;276 /* 61 byte padding hole here. */277 u8 four __aligned(64);278} __aligned(64);279 280struct test_trailing_hole {281 char *one;282 char *two;283 char *three;284 char four;285 /* "sizeof(unsigned long) - 1" byte padding hole here. */286};287 288/* Test if STRUCTLEAK is clearing structs with __user fields. */289struct test_user {290 u8 one;291 unsigned long two;292 char __user *three;293 unsigned long four;294};295 296#define ALWAYS_PASS WANT_SUCCESS297#define ALWAYS_FAIL XFAIL298 299#ifdef CONFIG_INIT_STACK_NONE300# define USER_PASS XFAIL301# define BYREF_PASS XFAIL302# define STRONG_PASS XFAIL303#elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER)304# define USER_PASS WANT_SUCCESS305# define BYREF_PASS XFAIL306# define STRONG_PASS XFAIL307#elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF)308# define USER_PASS WANT_SUCCESS309# define BYREF_PASS WANT_SUCCESS310# define STRONG_PASS XFAIL311#else312# define USER_PASS WANT_SUCCESS313# define BYREF_PASS WANT_SUCCESS314# define STRONG_PASS WANT_SUCCESS315#endif316 317#define DEFINE_SCALAR_TEST(name, init, xfail) \318 DEFINE_TEST(name ## _ ## init, name, SCALAR, \319 init, xfail)320 321#define DEFINE_SCALAR_TESTS(init, xfail) \322 DEFINE_SCALAR_TEST(u8, init, xfail); \323 DEFINE_SCALAR_TEST(u16, init, xfail); \324 DEFINE_SCALAR_TEST(u32, init, xfail); \325 DEFINE_SCALAR_TEST(u64, init, xfail); \326 DEFINE_TEST(char_array_ ## init, unsigned char, \327 STRING, init, xfail)328 329#define DEFINE_STRUCT_TEST(name, init, xfail) \330 DEFINE_TEST(name ## _ ## init, \331 struct test_ ## name, STRUCT, init, \332 xfail)333 334#define DEFINE_STRUCT_TESTS(init, xfail) \335 DEFINE_STRUCT_TEST(small_hole, init, xfail); \336 DEFINE_STRUCT_TEST(big_hole, init, xfail); \337 DEFINE_STRUCT_TEST(trailing_hole, init, xfail); \338 DEFINE_STRUCT_TEST(packed, init, xfail)339 340#define DEFINE_STRUCT_INITIALIZER_TESTS(base, xfail) \341 DEFINE_STRUCT_TESTS(base ## _ ## partial, \342 xfail); \343 DEFINE_STRUCT_TESTS(base ## _ ## all, xfail)344 345/* These should be fully initialized all the time! */346DEFINE_SCALAR_TESTS(zero, ALWAYS_PASS);347DEFINE_STRUCT_TESTS(zero, ALWAYS_PASS);348/* Struct initializers: padding may be left uninitialized. */349DEFINE_STRUCT_INITIALIZER_TESTS(static, STRONG_PASS);350DEFINE_STRUCT_INITIALIZER_TESTS(dynamic, STRONG_PASS);351DEFINE_STRUCT_INITIALIZER_TESTS(runtime, STRONG_PASS);352DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static, STRONG_PASS);353DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS);354DEFINE_STRUCT_TESTS(assigned_copy, ALWAYS_FAIL);355/* No initialization without compiler instrumentation. */356DEFINE_SCALAR_TESTS(none, STRONG_PASS);357DEFINE_STRUCT_TESTS(none, BYREF_PASS);358/* Initialization of members with __user attribute. */359DEFINE_TEST(user, struct test_user, STRUCT, none, USER_PASS);360 361/*362 * Check two uses through a variable declaration outside either path,363 * which was noticed as a special case in porting earlier stack init364 * compiler logic.365 */366static int noinline __leaf_switch_none(int path, bool fill)367{368 switch (path) {369 /*370 * This is intentionally unreachable. To silence the371 * warning, build with -Wno-switch-unreachable372 */373 uint64_t var[10];374 375 case 1:376 target_start = &var;377 target_size = sizeof(var);378 if (fill) {379 fill_start = &var;380 fill_size = sizeof(var);381 382 memset(fill_start, forced_mask | 0x55, fill_size);383 }384 memcpy(check_buf, target_start, target_size);385 break;386 case 2:387 target_start = &var;388 target_size = sizeof(var);389 if (fill) {390 fill_start = &var;391 fill_size = sizeof(var);392 393 memset(fill_start, forced_mask | 0xaa, fill_size);394 }395 memcpy(check_buf, target_start, target_size);396 break;397 default:398 var[1] = 5;399 return var[1] & forced_mask;400 }401 return 0;402}403 404static noinline int leaf_switch_1_none(unsigned long sp, bool fill,405 uint64_t *arg)406{407 return __leaf_switch_none(1, fill);408}409 410static noinline int leaf_switch_2_none(unsigned long sp, bool fill,411 uint64_t *arg)412{413 return __leaf_switch_none(2, fill);414}415 416/*417 * These are expected to fail for most configurations because neither418 * GCC nor Clang have a way to perform initialization of variables in419 * non-code areas (i.e. in a switch statement before the first "case").420 * https://llvm.org/pr44916421 */422DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, ALWAYS_FAIL);423DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, ALWAYS_FAIL);424 425#define KUNIT_test_scalars(init) \426 KUNIT_CASE(test_u8_ ## init), \427 KUNIT_CASE(test_u16_ ## init), \428 KUNIT_CASE(test_u32_ ## init), \429 KUNIT_CASE(test_u64_ ## init), \430 KUNIT_CASE(test_char_array_ ## init)431 432#define KUNIT_test_structs(init) \433 KUNIT_CASE(test_small_hole_ ## init), \434 KUNIT_CASE(test_big_hole_ ## init), \435 KUNIT_CASE(test_trailing_hole_ ## init),\436 KUNIT_CASE(test_packed_ ## init) \437 438static struct kunit_case stackinit_test_cases[] = {439 /* These are explicitly initialized and should always pass. */440 KUNIT_test_scalars(zero),441 KUNIT_test_structs(zero),442 /* Padding here appears to be accidentally always initialized? */443 KUNIT_test_structs(dynamic_partial),444 KUNIT_test_structs(assigned_dynamic_partial),445 /* Padding initialization depends on compiler behaviors. */446 KUNIT_test_structs(static_partial),447 KUNIT_test_structs(static_all),448 KUNIT_test_structs(dynamic_all),449 KUNIT_test_structs(runtime_partial),450 KUNIT_test_structs(runtime_all),451 KUNIT_test_structs(assigned_static_partial),452 KUNIT_test_structs(assigned_static_all),453 KUNIT_test_structs(assigned_dynamic_all),454 /* Everything fails this since it effectively performs a memcpy(). */455 KUNIT_test_structs(assigned_copy),456 /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */457 KUNIT_test_scalars(none),458 KUNIT_CASE(test_switch_1_none),459 KUNIT_CASE(test_switch_2_none),460 /* STRUCTLEAK_BYREF should cover from here down. */461 KUNIT_test_structs(none),462 /* STRUCTLEAK will only cover this. */463 KUNIT_CASE(test_user),464 {}465};466 467static struct kunit_suite stackinit_test_suite = {468 .name = "stackinit",469 .test_cases = stackinit_test_cases,470};471 472kunit_test_suites(&stackinit_test_suite);473 474MODULE_DESCRIPTION("Test cases for compiler-based stack variable zeroing");475MODULE_LICENSE("GPL");476