1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Test cases for compiler-based stack variable zeroing via
4 * -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.rst
7 *	./tools/testing/kunit/kunit.py run stackinit [--raw_output] \
8 *		--make_option LLVM=1 \
9 *		--kconfig_add CONFIG_INIT_STACK_ALL_ZERO=y
10 *
11 */
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13
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	128
22static u8 check_buf[MAX_VAR_SIZE];
23
24/* Character array to trigger stack protector in all functions. */
25#define VAR_BUFFER	 32
26
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				0
45#define XFAIL					1
46
47#define DO_NOTHING_TYPE_SCALAR(var_type)	var_type
48#define DO_NOTHING_TYPE_STRING(var_type)	void
49#define DO_NOTHING_TYPE_STRUCT(var_type)	void
50
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)		&var
63#define FETCH_ARG_STRING(var)		var
64#define FETCH_ARG_STRUCT(var)		&var
65
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 to
69 * test m68k char arrays, but leave it at 16 for other architectures.
70 */
71#ifdef CONFIG_M68K
72#define FILL_SIZE_STRING		8
73#else
74#define FILL_SIZE_STRING		16
75#endif
76
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 gets
85 * 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)	= 0
98
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 = 0
119#define __runtime_all			var.one = 0;			\
120					var.two = 0;			\
121					var.three = 0;			\
122					var.four = 0
123
124#define INIT_STRUCT_static_partial(var_type)				\
125					= __static_partial
126#define INIT_STRUCT_static_all(var_type)				\
127					= __static_all
128#define INIT_STRUCT_dynamic_partial(var_type)				\
129					= __dynamic_partial
130#define INIT_STRUCT_dynamic_all(var_type)				\
131					= __dynamic_all
132#define INIT_STRUCT_runtime_partial(var_type)				\
133					; __runtime_partial
134#define INIT_STRUCT_runtime_all(var_type)				\
135					; __runtime_all
136
137#define INIT_STRUCT_assigned_static_partial(var_type)			\
138					; var = (var_type)__static_partial
139#define INIT_STRUCT_assigned_static_all(var_type)			\
140					; var = (var_type)__static_all
141#define INIT_STRUCT_assigned_dynamic_partial(var_type)			\
142					; var = (var_type)__dynamic_partial
143#define INIT_STRUCT_assigned_dynamic_all(var_type)			\
144					; var = (var_type)__dynamic_all
145
146#define INIT_STRUCT_assigned_copy(var_type)				\
147					; var = *(arg)
148
149/*
150 * @name: unique string name for the test
151 * @var_type: type to be tested for zeroing initialization
152 * @which: is this a SCALAR, STRING, or STRUCT type?
153 * @init_level: what kind of initialization is performed
154 * @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_SUCCESS
297#define ALWAYS_FAIL	XFAIL
298
299#ifdef CONFIG_INIT_STACK_NONE
300# define USER_PASS	XFAIL
301# define BYREF_PASS	XFAIL
302# define STRONG_PASS	XFAIL
303#elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER)
304# define USER_PASS	WANT_SUCCESS
305# define BYREF_PASS	XFAIL
306# define STRONG_PASS	XFAIL
307#elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF)
308# define USER_PASS	WANT_SUCCESS
309# define BYREF_PASS	WANT_SUCCESS
310# define STRONG_PASS	XFAIL
311#else
312# define USER_PASS	WANT_SUCCESS
313# define BYREF_PASS	WANT_SUCCESS
314# define STRONG_PASS	WANT_SUCCESS
315#endif
316
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 init
364 * 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 the
371		 * warning, build with -Wno-switch-unreachable
372		 */
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 neither
418 * GCC nor Clang have a way to perform initialization of variables in
419 * non-code areas (i.e. in a switch statement before the first "case").
420 * https://llvm.org/pr44916
421 */
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_LICENSE("GPL");
475