1 // SPDX-License-Identifier: GPL-2.0-only
3 * Test module for unwind_for_each_frame
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/timer.h>
13 #include <linux/slab.h>
14 #include <linux/string.h>
15 #include <linux/kprobes.h>
16 #include <linux/wait.h>
19 #define BT_BUF_SIZE (PAGE_SIZE * 4)
22 * To avoid printk line limit split backtrace by lines
24 static void print_backtrace(char *bt)
29 p = strsep(&bt, "\n");
37 * Calls unwind_for_each_frame(task, regs, sp) and verifies that the result
38 * contains unwindme_func2 followed by unwindme_func1.
40 static noinline int test_unwind(struct task_struct *task, struct pt_regs *regs,
43 int frame_count, prev_is_func2, seen_func2_func1;
44 const int max_frames = 128;
45 struct unwind_state state;
50 bt = kmalloc(BT_BUF_SIZE, GFP_ATOMIC);
52 pr_err("failed to allocate backtrace buffer\n");
59 unwind_for_each_frame(&state, task, regs, sp) {
60 unsigned long addr = unwind_get_return_address(&state);
61 char sym[KSYM_SYMBOL_LEN];
63 if (frame_count++ == max_frames)
65 if (state.reliable && !addr) {
66 pr_err("unwind state reliable but addr is 0\n");
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" :
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");
81 if (prev_is_func2 && str_has_prefix(sym, "unwindme_func1"))
83 prev_is_func2 = str_has_prefix(sym, "unwindme_func2");
86 /* Check the results. */
87 if (unwind_error(&state)) {
88 pr_err("unwind error\n");
91 if (!seen_func2_func1) {
92 pr_err("unwindme_func2 and unwindme_func1 not found\n");
95 if (frame_count == max_frames) {
96 pr_err("Maximum number of frames exceeded\n");
105 /* State of the task being unwound. */
109 struct task_struct *task;
110 struct completion task_ready;
111 wait_queue_head_t task_wq;
115 static struct unwindme *unwindme;
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. */
127 static __always_inline unsigned long get_psw_addr(void)
129 unsigned long psw_addr;
132 "basr %[psw_addr],0\n"
133 : [psw_addr] "=d" (psw_addr));
137 #ifdef CONFIG_KPROBES
138 static int pgm_pre_handler(struct kprobe *p, struct pt_regs *regs)
140 struct unwindme *u = unwindme;
142 u->ret = test_unwind(NULL, (u->flags & UWM_REGS) ? regs : NULL,
143 (u->flags & UWM_SP) ? u->sp : 0);
148 /* This function may or may not appear in the backtrace. */
149 static noinline int unwindme_func4(struct unwindme *u)
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());
158 #ifdef CONFIG_KPROBES
159 } else if (u->flags & UWM_PGM) {
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);
169 pr_err("register_kprobe failed %d\n", ret);
174 * trigger specification exception
182 unregister_kprobe(&kp);
189 memset(®s, 0, sizeof(regs));
190 regs.psw.addr = get_psw_addr();
191 regs.gprs[15] = current_stack_pointer();
192 return test_unwind(NULL,
193 (u->flags & UWM_REGS) ? ®s : NULL,
194 (u->flags & UWM_SP) ? u->sp : 0);
198 /* This function may or may not appear in the backtrace. */
199 static noinline int unwindme_func3(struct unwindme *u)
201 u->sp = current_frame_address();
202 return unwindme_func4(u);
205 /* This function must appear in the backtrace. */
206 static noinline int unwindme_func2(struct unwindme *u)
211 if (u->flags & UWM_SWITCH_STACK) {
212 local_irq_save(flags);
213 local_mcck_disable();
214 rc = call_on_stack(1, S390_lowcore.nodat_stack,
215 int, unwindme_func3, struct unwindme *, u);
217 local_irq_restore(flags);
220 return unwindme_func3(u);
224 /* This function must follow unwindme_func2 in the backtrace. */
225 static noinline int unwindme_func1(void *u)
227 return unwindme_func2((struct unwindme *)u);
230 static void unwindme_timer_fn(struct timer_list *unused)
232 struct unwindme *u = READ_ONCE(unwindme);
237 u->ret = unwindme_func1(u);
238 complete(&u->task_ready);
242 static struct timer_list unwind_timer;
244 static int test_unwind_irq(struct unwindme *u)
247 init_completion(&u->task_ready);
248 timer_setup(&unwind_timer, unwindme_timer_fn, 0);
249 mod_timer(&unwind_timer, jiffies + 1);
250 wait_for_completion(&u->task_ready);
254 /* Spawns a task and passes it to test_unwind(). */
255 static int test_unwind_task(struct unwindme *u)
257 struct task_struct *task;
260 /* Initialize thread-related fields. */
261 init_completion(&u->task_ready);
262 init_waitqueue_head(&u->task_wq);
265 * Start the task and wait until it reaches unwindme_func4() and sleeps
266 * in (task_ready, unwind_done] range.
268 task = kthread_run(unwindme_func1, u, "%s", __func__);
270 pr_err("kthread_run() failed\n");
271 return PTR_ERR(task);
274 * Make sure task reaches unwindme_func4 before parking it,
275 * we might park it before kthread function has been executed otherwise
277 wait_for_completion(&u->task_ready);
280 ret = test_unwind(task, NULL, (u->flags & UWM_SP) ? u->sp : 0);
285 static int test_unwind_flags(int flags)
290 if (u.flags & UWM_THREAD)
291 return test_unwind_task(&u);
292 else if (u.flags & UWM_IRQ)
293 return test_unwind_irq(&u);
295 return unwindme_func1(&u);
298 static int test_unwind_init(void)
303 #define TEST(flags) \
305 pr_info("[ RUN ] " #flags "\n"); \
307 if (!test_unwind_flags((flags))) { \
308 pr_info("[ OK ] " #flags "\n"); \
310 pr_err("[ FAILED ] " #flags "\n"); \
315 pr_info("running stack unwinder tests");
319 TEST(UWM_SWITCH_STACK);
320 TEST(UWM_SP | UWM_REGS);
321 TEST(UWM_CALLER | UWM_SP);
322 TEST(UWM_CALLER | UWM_SP | UWM_REGS);
323 TEST(UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK);
325 TEST(UWM_THREAD | UWM_SP);
326 TEST(UWM_THREAD | UWM_CALLER | UWM_SP);
328 TEST(UWM_IRQ | UWM_SWITCH_STACK);
329 TEST(UWM_IRQ | UWM_SP);
330 TEST(UWM_IRQ | UWM_REGS);
331 TEST(UWM_IRQ | UWM_SP | UWM_REGS);
332 TEST(UWM_IRQ | UWM_CALLER | UWM_SP);
333 TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS);
334 TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK);
335 #ifdef CONFIG_KPROBES
337 TEST(UWM_PGM | UWM_SP);
338 TEST(UWM_PGM | UWM_REGS);
339 TEST(UWM_PGM | UWM_SP | UWM_REGS);
343 pr_err("%d of %d stack unwinder tests failed", failed, total);
344 WARN(1, "%d of %d stack unwinder tests failed", failed, total);
346 pr_info("all %d stack unwinder tests passed", total);
349 return failed ? -EINVAL : 0;
352 static void test_unwind_exit(void)
356 module_init(test_unwind_init);
357 module_exit(test_unwind_exit);
358 MODULE_LICENSE("GPL");