1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Test module for unwind_for_each_frame
4 */
5
6#define pr_fmt(fmt) "test_unwind: " fmt
7#include <asm/unwind.h>
8#include <linux/completion.h>
9#include <linux/kallsyms.h>
10#include <linux/kthread.h>
11#include <linux/module.h>
12#include <linux/slab.h>
13#include <linux/string.h>
14#include <linux/kprobes.h>
15#include <linux/wait.h>
16#include <asm/irq.h>
17#include <asm/delay.h>
18
19#define BT_BUF_SIZE (PAGE_SIZE * 4)
20
21/*
22 * To avoid printk line limit split backtrace by lines
23 */
24static void print_backtrace(char *bt)
25{
26	char *p;
27
28	while (true) {
29		p = strsep(&bt, "\n");
30		if (!p)
31			break;
32		pr_err("%s\n", p);
33	}
34}
35
36/*
37 * Calls unwind_for_each_frame(task, regs, sp) and verifies that the result
38 * contains unwindme_func2 followed by unwindme_func1.
39 */
40static noinline int test_unwind(struct task_struct *task, struct pt_regs *regs,
41				unsigned long sp)
42{
43	int frame_count, prev_is_func2, seen_func2_func1;
44	const int max_frames = 128;
45	struct unwind_state state;
46	size_t bt_pos = 0;
47	int ret = 0;
48	char *bt;
49
50	bt = kmalloc(BT_BUF_SIZE, GFP_ATOMIC);
51	if (!bt) {
52		pr_err("failed to allocate backtrace buffer\n");
53		return -ENOMEM;
54	}
55	/* Unwind. */
56	frame_count = 0;
57	prev_is_func2 = 0;
58	seen_func2_func1 = 0;
59	unwind_for_each_frame(&state, task, regs, sp) {
60		unsigned long addr = unwind_get_return_address(&state);
61		char sym[KSYM_SYMBOL_LEN];
62
63		if (frame_count++ == max_frames)
64			break;
65		if (state.reliable && !addr) {
66			pr_err("unwind state reliable but addr is 0\n");
67			kfree(bt);
68			return -EINVAL;
69		}
70		sprint_symbol(sym, addr);
71		if (bt_pos < BT_BUF_SIZE) {
72			bt_pos += snprintf(bt + bt_pos, BT_BUF_SIZE - bt_pos,
73					   state.reliable ? " [%-7s%px] %pSR\n" :
74							    "([%-7s%px] %pSR)\n",
75					   stack_type_name(state.stack_info.type),
76					   (void *)state.sp, (void *)state.ip);
77			if (bt_pos >= BT_BUF_SIZE)
78				pr_err("backtrace buffer is too small\n");
79		}
80		frame_count += 1;
81		if (prev_is_func2 && str_has_prefix(sym, "unwindme_func1"))
82			seen_func2_func1 = 1;
83		prev_is_func2 = str_has_prefix(sym, "unwindme_func2");
84	}
85
86	/* Check the results. */
87	if (unwind_error(&state)) {
88		pr_err("unwind error\n");
89		ret = -EINVAL;
90	}
91	if (!seen_func2_func1) {
92		pr_err("unwindme_func2 and unwindme_func1 not found\n");
93		ret = -EINVAL;
94	}
95	if (frame_count == max_frames) {
96		pr_err("Maximum number of frames exceeded\n");
97		ret = -EINVAL;
98	}
99	if (ret)
100		print_backtrace(bt);
101	kfree(bt);
102	return ret;
103}
104
105/* State of the task being unwound. */
106struct unwindme {
107	int flags;
108	int ret;
109	struct task_struct *task;
110	struct completion task_ready;
111	wait_queue_head_t task_wq;
112	unsigned long sp;
113};
114
115static struct unwindme *unwindme;
116
117/* Values of unwindme.flags. */
118#define UWM_DEFAULT		0x0
119#define UWM_THREAD		0x1	/* Unwind a separate task. */
120#define UWM_REGS		0x2	/* Pass regs to test_unwind(). */
121#define UWM_SP			0x4	/* Pass sp to test_unwind(). */
122#define UWM_CALLER		0x8	/* Unwind starting from caller. */
123#define UWM_SWITCH_STACK	0x10	/* Use CALL_ON_STACK. */
124#define UWM_IRQ			0x20	/* Unwind from irq context. */
125#define UWM_PGM			0x40	/* Unwind from program check handler. */
126
127static __always_inline unsigned long get_psw_addr(void)
128{
129	unsigned long psw_addr;
130
131	asm volatile(
132		"basr	%[psw_addr],0\n"
133		: [psw_addr] "=d" (psw_addr));
134	return psw_addr;
135}
136
137#ifdef CONFIG_KPROBES
138static int pgm_pre_handler(struct kprobe *p, struct pt_regs *regs)
139{
140	struct unwindme *u = unwindme;
141
142	u->ret = test_unwind(NULL, (u->flags & UWM_REGS) ? regs : NULL,
143			     (u->flags & UWM_SP) ? u->sp : 0);
144	return 0;
145}
146#endif
147
148/* This function may or may not appear in the backtrace. */
149static noinline int unwindme_func4(struct unwindme *u)
150{
151	if (!(u->flags & UWM_CALLER))
152		u->sp = current_frame_address();
153	if (u->flags & UWM_THREAD) {
154		complete(&u->task_ready);
155		wait_event(u->task_wq, kthread_should_park());
156		kthread_parkme();
157		return 0;
158#ifdef CONFIG_KPROBES
159	} else if (u->flags & UWM_PGM) {
160		struct kprobe kp;
161		int ret;
162
163		unwindme = u;
164		memset(&kp, 0, sizeof(kp));
165		kp.symbol_name = "do_report_trap";
166		kp.pre_handler = pgm_pre_handler;
167		ret = register_kprobe(&kp);
168		if (ret < 0) {
169			pr_err("register_kprobe failed %d\n", ret);
170			return -EINVAL;
171		}
172
173		/*
174		 * Trigger operation exception; use insn notation to bypass
175		 * llvm's integrated assembler sanity checks.
176		 */
177		asm volatile(
178			"	.insn	e,0x0000\n"	/* illegal opcode */
179			"0:	nopr	%%r7\n"
180			EX_TABLE(0b, 0b)
181			:);
182
183		unregister_kprobe(&kp);
184		unwindme = NULL;
185		return u->ret;
186#endif
187	} else {
188		struct pt_regs regs;
189
190		memset(&regs, 0, sizeof(regs));
191		regs.psw.addr = get_psw_addr();
192		regs.gprs[15] = current_stack_pointer();
193		return test_unwind(NULL,
194				   (u->flags & UWM_REGS) ? &regs : NULL,
195				   (u->flags & UWM_SP) ? u->sp : 0);
196	}
197}
198
199/* This function may or may not appear in the backtrace. */
200static noinline int unwindme_func3(struct unwindme *u)
201{
202	u->sp = current_frame_address();
203	return unwindme_func4(u);
204}
205
206/* This function must appear in the backtrace. */
207static noinline int unwindme_func2(struct unwindme *u)
208{
209	unsigned long flags;
210	int rc;
211
212	if (u->flags & UWM_SWITCH_STACK) {
213		local_irq_save(flags);
214		local_mcck_disable();
215		rc = CALL_ON_STACK(unwindme_func3, S390_lowcore.nodat_stack, 1, u);
216		local_mcck_enable();
217		local_irq_restore(flags);
218		return rc;
219	} else {
220		return unwindme_func3(u);
221	}
222}
223
224/* This function must follow unwindme_func2 in the backtrace. */
225static noinline int unwindme_func1(void *u)
226{
227	return unwindme_func2((struct unwindme *)u);
228}
229
230static void unwindme_irq_handler(struct ext_code ext_code,
231				       unsigned int param32,
232				       unsigned long param64)
233{
234	struct unwindme *u = READ_ONCE(unwindme);
235
236	if (u && u->task == current) {
237		unwindme = NULL;
238		u->task = NULL;
239		u->ret = unwindme_func1(u);
240	}
241}
242
243static int test_unwind_irq(struct unwindme *u)
244{
245	preempt_disable();
246	if (register_external_irq(EXT_IRQ_CLK_COMP, unwindme_irq_handler)) {
247		pr_info("Couldn't register external interrupt handler");
248		return -1;
249	}
250	u->task = current;
251	unwindme = u;
252	udelay(1);
253	unregister_external_irq(EXT_IRQ_CLK_COMP, unwindme_irq_handler);
254	preempt_enable();
255	return u->ret;
256}
257
258/* Spawns a task and passes it to test_unwind(). */
259static int test_unwind_task(struct unwindme *u)
260{
261	struct task_struct *task;
262	int ret;
263
264	/* Initialize thread-related fields. */
265	init_completion(&u->task_ready);
266	init_waitqueue_head(&u->task_wq);
267
268	/*
269	 * Start the task and wait until it reaches unwindme_func4() and sleeps
270	 * in (task_ready, unwind_done] range.
271	 */
272	task = kthread_run(unwindme_func1, u, "%s", __func__);
273	if (IS_ERR(task)) {
274		pr_err("kthread_run() failed\n");
275		return PTR_ERR(task);
276	}
277	/*
278	 * Make sure task reaches unwindme_func4 before parking it,
279	 * we might park it before kthread function has been executed otherwise
280	 */
281	wait_for_completion(&u->task_ready);
282	kthread_park(task);
283	/* Unwind. */
284	ret = test_unwind(task, NULL, (u->flags & UWM_SP) ? u->sp : 0);
285	kthread_stop(task);
286	return ret;
287}
288
289static int test_unwind_flags(int flags)
290{
291	struct unwindme u;
292
293	u.flags = flags;
294	if (u.flags & UWM_THREAD)
295		return test_unwind_task(&u);
296	else if (u.flags & UWM_IRQ)
297		return test_unwind_irq(&u);
298	else
299		return unwindme_func1(&u);
300}
301
302static int test_unwind_init(void)
303{
304	int ret = 0;
305
306#define TEST(flags)							\
307do {									\
308	pr_info("[ RUN      ] " #flags "\n");				\
309	if (!test_unwind_flags((flags))) {				\
310		pr_info("[       OK ] " #flags "\n");			\
311	} else {							\
312		pr_err("[  FAILED  ] " #flags "\n");			\
313		ret = -EINVAL;						\
314	}								\
315} while (0)
316
317	TEST(UWM_DEFAULT);
318	TEST(UWM_SP);
319	TEST(UWM_REGS);
320	TEST(UWM_SWITCH_STACK);
321	TEST(UWM_SP | UWM_REGS);
322	TEST(UWM_CALLER | UWM_SP);
323	TEST(UWM_CALLER | UWM_SP | UWM_REGS);
324	TEST(UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK);
325	TEST(UWM_THREAD);
326	TEST(UWM_THREAD | UWM_SP);
327	TEST(UWM_THREAD | UWM_CALLER | UWM_SP);
328	TEST(UWM_IRQ);
329	TEST(UWM_IRQ | UWM_SWITCH_STACK);
330	TEST(UWM_IRQ | UWM_SP);
331	TEST(UWM_IRQ | UWM_REGS);
332	TEST(UWM_IRQ | UWM_SP | UWM_REGS);
333	TEST(UWM_IRQ | UWM_CALLER | UWM_SP);
334	TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS);
335	TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK);
336#ifdef CONFIG_KPROBES
337	TEST(UWM_PGM);
338	TEST(UWM_PGM | UWM_SP);
339	TEST(UWM_PGM | UWM_REGS);
340	TEST(UWM_PGM | UWM_SP | UWM_REGS);
341#endif
342#undef TEST
343
344	return ret;
345}
346
347static void test_unwind_exit(void)
348{
349}
350
351module_init(test_unwind_init);
352module_exit(test_unwind_exit);
353MODULE_LICENSE("GPL");
354