1
2#include <linux/sched.h>
3#include <linux/sched/task.h>
4#include <linux/sched/task_stack.h>
5#include <linux/interrupt.h>
6#include <asm/sections.h>
7#include <asm/ptrace.h>
8#include <asm/bitops.h>
9#include <asm/stacktrace.h>
10#include <asm/unwind.h>
11
12#define FRAME_HEADER_SIZE (sizeof(long) * 2)
13
14unsigned long unwind_get_return_address(struct unwind_state *state)
15{
16 if (unwind_done(state))
17 return 0;
18
19 return __kernel_text_address(state->ip) ? state->ip : 0;
20}
21EXPORT_SYMBOL_GPL(unwind_get_return_address);
22
23unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
24{
25 if (unwind_done(state))
26 return NULL;
27
28 return state->regs ? &state->regs->ip : state->bp + 1;
29}
30
31static void unwind_dump(struct unwind_state *state)
32{
33 static bool dumped_before = false;
34 bool prev_zero, zero = false;
35 unsigned long word, *sp;
36 struct stack_info stack_info = {0};
37 unsigned long visit_mask = 0;
38
39 if (dumped_before)
40 return;
41
42 dumped_before = true;
43
44 printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
45 state->stack_info.type, state->stack_info.next_sp,
46 state->stack_mask, state->graph_idx);
47
48 for (sp = PTR_ALIGN(state->orig_sp, sizeof(long)); sp;
49 sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
50 if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
51 break;
52
53 for (; sp < stack_info.end; sp++) {
54
55 word = READ_ONCE_NOCHECK(*sp);
56
57 prev_zero = zero;
58 zero = word == 0;
59
60 if (zero) {
61 if (!prev_zero)
62 printk_deferred("%p: %0*x ...\n",
63 sp, BITS_PER_LONG/4, 0);
64 continue;
65 }
66
67 printk_deferred("%p: %0*lx (%pB)\n",
68 sp, BITS_PER_LONG/4, word, (void *)word);
69 }
70 }
71}
72
73static bool in_entry_code(unsigned long ip)
74{
75 char *addr = (char *)ip;
76
77 if (addr >= __entry_text_start && addr < __entry_text_end)
78 return true;
79
80 if (addr >= __irqentry_text_start && addr < __irqentry_text_end)
81 return true;
82
83 return false;
84}
85
86static inline unsigned long *last_frame(struct unwind_state *state)
87{
88 return (unsigned long *)task_pt_regs(state->task) - 2;
89}
90
91static bool is_last_frame(struct unwind_state *state)
92{
93 return state->bp == last_frame(state);
94}
95
96#ifdef CONFIG_X86_32
97#define GCC_REALIGN_WORDS 3
98#else
99#define GCC_REALIGN_WORDS 1
100#endif
101
102static inline unsigned long *last_aligned_frame(struct unwind_state *state)
103{
104 return last_frame(state) - GCC_REALIGN_WORDS;
105}
106
107static bool is_last_aligned_frame(struct unwind_state *state)
108{
109 unsigned long *last_bp = last_frame(state);
110 unsigned long *aligned_bp = last_aligned_frame(state);
111
112
113
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115
116
117
118
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120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135 return (state->bp == aligned_bp && *(aligned_bp + 1) == *(last_bp + 1));
136}
137
138static bool is_last_ftrace_frame(struct unwind_state *state)
139{
140 unsigned long *last_bp = last_frame(state);
141 unsigned long *last_ftrace_bp = last_bp - 3;
142
143
144
145
146
147
148
149
150
151
152
153
154
155 return (state->bp == last_ftrace_bp &&
156 *state->bp == *(state->bp + 2) &&
157 *(state->bp + 1) == *(state->bp + 4));
158}
159
160static bool is_last_task_frame(struct unwind_state *state)
161{
162 return is_last_frame(state) || is_last_aligned_frame(state) ||
163 is_last_ftrace_frame(state);
164}
165
166
167
168
169
170#ifdef CONFIG_X86_64
171static struct pt_regs *decode_frame_pointer(unsigned long *bp)
172{
173 unsigned long regs = (unsigned long)bp;
174
175 if (!(regs & 0x1))
176 return NULL;
177
178 return (struct pt_regs *)(regs & ~0x1);
179}
180#else
181static struct pt_regs *decode_frame_pointer(unsigned long *bp)
182{
183 unsigned long regs = (unsigned long)bp;
184
185 if (regs & 0x80000000)
186 return NULL;
187
188 return (struct pt_regs *)(regs | 0x80000000);
189}
190#endif
191
192static bool update_stack_state(struct unwind_state *state,
193 unsigned long *next_bp)
194{
195 struct stack_info *info = &state->stack_info;
196 enum stack_type prev_type = info->type;
197 struct pt_regs *regs;
198 unsigned long *frame, *prev_frame_end, *addr_p, addr;
199 size_t len;
200
201 if (state->regs)
202 prev_frame_end = (void *)state->regs + sizeof(*state->regs);
203 else
204 prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE;
205
206
207 regs = decode_frame_pointer(next_bp);
208 if (regs) {
209 frame = (unsigned long *)regs;
210 len = sizeof(*regs);
211 state->got_irq = true;
212 } else {
213 frame = next_bp;
214 len = FRAME_HEADER_SIZE;
215 }
216
217
218
219
220
221
222
223
224 while (!on_stack(info, frame, len))
225 if (get_stack_info(info->next_sp, state->task, info,
226 &state->stack_mask))
227 return false;
228
229
230 if (state->orig_sp && state->stack_info.type == prev_type &&
231 frame < prev_frame_end)
232 return false;
233
234
235 if (regs) {
236 state->regs = regs;
237 state->bp = NULL;
238 } else {
239 state->bp = next_bp;
240 state->regs = NULL;
241 }
242
243
244 if (state->regs && user_mode(state->regs))
245 state->ip = 0;
246 else {
247 addr_p = unwind_get_return_address_ptr(state);
248 addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
249 state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
250 addr, addr_p);
251 }
252
253
254 if (!state->orig_sp)
255 state->orig_sp = frame;
256
257 return true;
258}
259
260bool unwind_next_frame(struct unwind_state *state)
261{
262 struct pt_regs *regs;
263 unsigned long *next_bp;
264
265 if (unwind_done(state))
266 return false;
267
268
269 if (state->regs && user_mode(state->regs))
270 goto the_end;
271
272 if (is_last_task_frame(state)) {
273 regs = task_pt_regs(state->task);
274
275
276
277
278
279
280
281
282
283
284
285
286 if (!user_mode(regs))
287 goto the_end;
288
289
290
291
292
293
294 state->regs = regs;
295 state->bp = NULL;
296 state->ip = 0;
297 return true;
298 }
299
300
301 if (state->next_bp) {
302 next_bp = state->next_bp;
303 state->next_bp = NULL;
304 } else if (state->regs) {
305 next_bp = (unsigned long *)state->regs->bp;
306 } else {
307 next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *state->bp);
308 }
309
310
311 if (!update_stack_state(state, next_bp))
312 goto bad_address;
313
314 return true;
315
316bad_address:
317 state->error = true;
318
319
320
321
322
323
324
325
326 if (state->task != current)
327 goto the_end;
328
329
330
331
332
333 if (state->got_irq && in_entry_code(state->ip))
334 goto the_end;
335 if (state->regs &&
336 state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
337 state->regs->sp < (unsigned long)task_pt_regs(state->task))
338 goto the_end;
339
340
341
342
343
344 if (IS_ENABLED(CONFIG_X86_32))
345 goto the_end;
346
347 if (state->task != current)
348 goto the_end;
349
350 if (state->regs) {
351 printk_deferred_once(KERN_WARNING
352 "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
353 state->regs, state->task->comm,
354 state->task->pid, next_bp);
355 unwind_dump(state);
356 } else {
357 printk_deferred_once(KERN_WARNING
358 "WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n",
359 state->bp, state->task->comm,
360 state->task->pid, next_bp);
361 unwind_dump(state);
362 }
363the_end:
364 state->stack_info.type = STACK_TYPE_UNKNOWN;
365 return false;
366}
367EXPORT_SYMBOL_GPL(unwind_next_frame);
368
369void __unwind_start(struct unwind_state *state, struct task_struct *task,
370 struct pt_regs *regs, unsigned long *first_frame)
371{
372 unsigned long *bp;
373
374 memset(state, 0, sizeof(*state));
375 state->task = task;
376 state->got_irq = (regs);
377
378
379 if (regs && user_mode(regs)) {
380 state->stack_info.type = STACK_TYPE_UNKNOWN;
381 return;
382 }
383
384 bp = get_frame_pointer(task, regs);
385
386
387
388
389
390
391
392
393
394
395 if (regs && regs->ip == 0 && (unsigned long *)regs->sp >= first_frame) {
396 state->next_bp = bp;
397 bp = ((unsigned long *)regs->sp) - 1;
398 }
399
400
401 get_stack_info(bp, state->task, &state->stack_info,
402 &state->stack_mask);
403 update_stack_state(state, bp);
404
405
406
407
408
409
410 while (!unwind_done(state) &&
411 (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
412 (state->next_bp == NULL && state->bp < first_frame)))
413 unwind_next_frame(state);
414}
415EXPORT_SYMBOL_GPL(__unwind_start);
416