summaryrefslogtreecommitdiff
path: root/arch/s390/lib/test_unwind.c
blob: eb382ceaa116117f792e59435648b5f5aa73bfe9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Test module for unwind_for_each_frame
 */

#define pr_fmt(fmt) "test_unwind: " fmt
#include <asm/unwind.h>
#include <linux/completion.h>
#include <linux/kallsyms.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/kprobes.h>
#include <linux/wait.h>
#include <asm/irq.h>
#include <asm/delay.h>

#define BT_BUF_SIZE (PAGE_SIZE * 4)

/*
 * To avoid printk line limit split backtrace by lines
 */
static void print_backtrace(char *bt)
{
	char *p;

	while (true) {
		p = strsep(&bt, "\n");
		if (!p)
			break;
		pr_err("%s\n", p);
	}
}

/*
 * Calls unwind_for_each_frame(task, regs, sp) and verifies that the result
 * contains unwindme_func2 followed by unwindme_func1.
 */
static noinline int test_unwind(struct task_struct *task, struct pt_regs *regs,
				unsigned long sp)
{
	int frame_count, prev_is_func2, seen_func2_func1;
	const int max_frames = 128;
	struct unwind_state state;
	size_t bt_pos = 0;
	int ret = 0;
	char *bt;

	bt = kmalloc(BT_BUF_SIZE, GFP_ATOMIC);
	if (!bt) {
		pr_err("failed to allocate backtrace buffer\n");
		return -ENOMEM;
	}
	/* Unwind. */
	frame_count = 0;
	prev_is_func2 = 0;
	seen_func2_func1 = 0;
	unwind_for_each_frame(&state, task, regs, sp) {
		unsigned long addr = unwind_get_return_address(&state);
		char sym[KSYM_SYMBOL_LEN];

		if (frame_count++ == max_frames)
			break;
		if (state.reliable && !addr) {
			pr_err("unwind state reliable but addr is 0\n");
			return -EINVAL;
		}
		sprint_symbol(sym, addr);
		if (bt_pos < BT_BUF_SIZE) {
			bt_pos += snprintf(bt + bt_pos, BT_BUF_SIZE - bt_pos,
					   state.reliable ? " [%-7s%px] %pSR\n" :
							    "([%-7s%px] %pSR)\n",
					   stack_type_name(state.stack_info.type),
					   (void *)state.sp, (void *)state.ip);
			if (bt_pos >= BT_BUF_SIZE)
				pr_err("backtrace buffer is too small\n");
		}
		frame_count += 1;
		if (prev_is_func2 && str_has_prefix(sym, "unwindme_func1"))
			seen_func2_func1 = 1;
		prev_is_func2 = str_has_prefix(sym, "unwindme_func2");
	}

	/* Check the results. */
	if (unwind_error(&state)) {
		pr_err("unwind error\n");
		ret = -EINVAL;
	}
	if (!seen_func2_func1) {
		pr_err("unwindme_func2 and unwindme_func1 not found\n");
		ret = -EINVAL;
	}
	if (frame_count == max_frames) {
		pr_err("Maximum number of frames exceeded\n");
		ret = -EINVAL;
	}
	if (ret)
		print_backtrace(bt);
	kfree(bt);
	return ret;
}

/* State of the task being unwound. */
struct unwindme {
	int flags;
	int ret;
	struct task_struct *task;
	struct completion task_ready;
	wait_queue_head_t task_wq;
	unsigned long sp;
};

static struct unwindme *unwindme;

/* Values of unwindme.flags. */
#define UWM_DEFAULT		0x0
#define UWM_THREAD		0x1	/* Unwind a separate task. */
#define UWM_REGS		0x2	/* Pass regs to test_unwind(). */
#define UWM_SP			0x4	/* Pass sp to test_unwind(). */
#define UWM_CALLER		0x8	/* Unwind starting from caller. */
#define UWM_SWITCH_STACK	0x10	/* Use CALL_ON_STACK. */
#define UWM_IRQ			0x20	/* Unwind from irq context. */
#define UWM_PGM			0x40	/* Unwind from program check handler. */

static __always_inline unsigned long get_psw_addr(void)
{
	unsigned long psw_addr;

	asm volatile(
		"basr	%[psw_addr],0\n"
		: [psw_addr] "=d" (psw_addr));
	return psw_addr;
}

#ifdef CONFIG_KPROBES
static int pgm_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
	struct unwindme *u = unwindme;

	u->ret = test_unwind(NULL, (u->flags & UWM_REGS) ? regs : NULL,
			     (u->flags & UWM_SP) ? u->sp : 0);
	return 0;
}
#endif

/* This function may or may not appear in the backtrace. */
static noinline int unwindme_func4(struct unwindme *u)
{
	if (!(u->flags & UWM_CALLER))
		u->sp = current_frame_address();
	if (u->flags & UWM_THREAD) {
		complete(&u->task_ready);
		wait_event(u->task_wq, kthread_should_park());
		kthread_parkme();
		return 0;
#ifdef CONFIG_KPROBES
	} else if (u->flags & UWM_PGM) {
		struct kprobe kp;
		int ret;

		unwindme = u;
		memset(&kp, 0, sizeof(kp));
		kp.symbol_name = "do_report_trap";
		kp.pre_handler = pgm_pre_handler;
		ret = register_kprobe(&kp);
		if (ret < 0) {
			pr_err("register_kprobe failed %d\n", ret);
			return -EINVAL;
		}

		/*
		 * trigger specification exception
		 */
		asm volatile(
			"	mvcl	%%r1,%%r1\n"
			"0:	nopr	%%r7\n"
			EX_TABLE(0b, 0b)
			:);

		unregister_kprobe(&kp);
		unwindme = NULL;
		return u->ret;
#endif
	} else {
		struct pt_regs regs;

		memset(&regs, 0, sizeof(regs));
		regs.psw.addr = get_psw_addr();
		regs.gprs[15] = current_stack_pointer();
		return test_unwind(NULL,
				   (u->flags & UWM_REGS) ? &regs : NULL,
				   (u->flags & UWM_SP) ? u->sp : 0);
	}
}

/* This function may or may not appear in the backtrace. */
static noinline int unwindme_func3(struct unwindme *u)
{
	u->sp = current_frame_address();
	return unwindme_func4(u);
}

/* This function must appear in the backtrace. */
static noinline int unwindme_func2(struct unwindme *u)
{
	int rc;

	if (u->flags & UWM_SWITCH_STACK) {
		preempt_disable();
		rc = CALL_ON_STACK(unwindme_func3, S390_lowcore.nodat_stack, 1, u);
		preempt_enable();
		return rc;
	} else {
		return unwindme_func3(u);
	}
}

/* This function must follow unwindme_func2 in the backtrace. */
static noinline int unwindme_func1(void *u)
{
	return unwindme_func2((struct unwindme *)u);
}

static void unwindme_irq_handler(struct ext_code ext_code,
				       unsigned int param32,
				       unsigned long param64)
{
	struct unwindme *u = READ_ONCE(unwindme);

	if (u && u->task == current) {
		unwindme = NULL;
		u->task = NULL;
		u->ret = unwindme_func1(u);
	}
}

static int test_unwind_irq(struct unwindme *u)
{
	preempt_disable();
	if (register_external_irq(EXT_IRQ_CLK_COMP, unwindme_irq_handler)) {
		pr_info("Couldn't register external interrupt handler");
		return -1;
	}
	u->task = current;
	unwindme = u;
	udelay(1);
	unregister_external_irq(EXT_IRQ_CLK_COMP, unwindme_irq_handler);
	preempt_enable();
	return u->ret;
}

/* Spawns a task and passes it to test_unwind(). */
static int test_unwind_task(struct unwindme *u)
{
	struct task_struct *task;
	int ret;

	/* Initialize thread-related fields. */
	init_completion(&u->task_ready);
	init_waitqueue_head(&u->task_wq);

	/*
	 * Start the task and wait until it reaches unwindme_func4() and sleeps
	 * in (task_ready, unwind_done] range.
	 */
	task = kthread_run(unwindme_func1, u, "%s", __func__);
	if (IS_ERR(task)) {
		pr_err("kthread_run() failed\n");
		return PTR_ERR(task);
	}
	/*
	 * Make sure task reaches unwindme_func4 before parking it,
	 * we might park it before kthread function has been executed otherwise
	 */
	wait_for_completion(&u->task_ready);
	kthread_park(task);
	/* Unwind. */
	ret = test_unwind(task, NULL, (u->flags & UWM_SP) ? u->sp : 0);
	kthread_stop(task);
	return ret;
}

static int test_unwind_flags(int flags)
{
	struct unwindme u;

	u.flags = flags;
	if (u.flags & UWM_THREAD)
		return test_unwind_task(&u);
	else if (u.flags & UWM_IRQ)
		return test_unwind_irq(&u);
	else
		return unwindme_func1(&u);
}

static int test_unwind_init(void)
{
	int ret = 0;

#define TEST(flags)							\
do {									\
	pr_info("[ RUN      ] " #flags "\n");				\
	if (!test_unwind_flags((flags))) {				\
		pr_info("[       OK ] " #flags "\n");			\
	} else {							\
		pr_err("[  FAILED  ] " #flags "\n");			\
		ret = -EINVAL;						\
	}								\
} while (0)

	TEST(UWM_DEFAULT);
	TEST(UWM_SP);
	TEST(UWM_REGS);
	TEST(UWM_SWITCH_STACK);
	TEST(UWM_SP | UWM_REGS);
	TEST(UWM_CALLER | UWM_SP);
	TEST(UWM_CALLER | UWM_SP | UWM_REGS);
	TEST(UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK);
	TEST(UWM_THREAD);
	TEST(UWM_THREAD | UWM_SP);
	TEST(UWM_THREAD | UWM_CALLER | UWM_SP);
	TEST(UWM_IRQ);
	TEST(UWM_IRQ | UWM_SWITCH_STACK);
	TEST(UWM_IRQ | UWM_SP);
	TEST(UWM_IRQ | UWM_REGS);
	TEST(UWM_IRQ | UWM_SP | UWM_REGS);
	TEST(UWM_IRQ | UWM_CALLER | UWM_SP);
	TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS);
	TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK);
#ifdef CONFIG_KPROBES
	TEST(UWM_PGM);
	TEST(UWM_PGM | UWM_SP);
	TEST(UWM_PGM | UWM_REGS);
	TEST(UWM_PGM | UWM_SP | UWM_REGS);
#endif
#undef TEST

	return ret;
}

static void test_unwind_exit(void)
{
}

module_init(test_unwind_init);
module_exit(test_unwind_exit);
MODULE_LICENSE("GPL");