Commit | Line | Data |
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1802d0be | 1 | // SPDX-License-Identifier: GPL-2.0-only |
cd11016e AP |
2 | /* |
3 | * Generic stack depot for storing stack traces. | |
4 | * | |
5 | * Some debugging tools need to save stack traces of certain events which can | |
6 | * be later presented to the user. For example, KASAN needs to safe alloc and | |
7 | * free stacks for each object, but storing two stack traces per object | |
8 | * requires too much memory (e.g. SLUB_DEBUG needs 256 bytes per object for | |
9 | * that). | |
10 | * | |
11 | * Instead, stack depot maintains a hashtable of unique stacktraces. Since alloc | |
12 | * and free stacks repeat a lot, we save about 100x space. | |
13 | * Stacks are never removed from depot, so we store them contiguously one after | |
9dbbc3b9 | 14 | * another in a contiguous memory allocation. |
cd11016e AP |
15 | * |
16 | * Author: Alexander Potapenko <glider@google.com> | |
17 | * Copyright (C) 2016 Google, Inc. | |
18 | * | |
19 | * Based on code by Dmitry Chernenkov. | |
cd11016e AP |
20 | */ |
21 | ||
4a6b5314 AK |
22 | #define pr_fmt(fmt) "stackdepot: " fmt |
23 | ||
cd11016e AP |
24 | #include <linux/gfp.h> |
25 | #include <linux/jhash.h> | |
26 | #include <linux/kernel.h> | |
27 | #include <linux/mm.h> | |
2dba5eb1 | 28 | #include <linux/mutex.h> |
cd11016e AP |
29 | #include <linux/percpu.h> |
30 | #include <linux/printk.h> | |
31 | #include <linux/slab.h> | |
32 | #include <linux/stacktrace.h> | |
33 | #include <linux/stackdepot.h> | |
34 | #include <linux/string.h> | |
35 | #include <linux/types.h> | |
e1fdc403 | 36 | #include <linux/memblock.h> |
f9987921 | 37 | #include <linux/kasan-enabled.h> |
cd11016e AP |
38 | |
39 | #define DEPOT_STACK_BITS (sizeof(depot_stack_handle_t) * 8) | |
40 | ||
7c31190b | 41 | #define STACK_ALLOC_NULL_PROTECTION_BITS 1 |
cd11016e AP |
42 | #define STACK_ALLOC_ORDER 2 /* 'Slab' size order for stack depot, 4 pages */ |
43 | #define STACK_ALLOC_SIZE (1LL << (PAGE_SHIFT + STACK_ALLOC_ORDER)) | |
44 | #define STACK_ALLOC_ALIGN 4 | |
45 | #define STACK_ALLOC_OFFSET_BITS (STACK_ALLOC_ORDER + PAGE_SHIFT - \ | |
46 | STACK_ALLOC_ALIGN) | |
7c31190b | 47 | #define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - \ |
83a4f1ef AP |
48 | STACK_ALLOC_NULL_PROTECTION_BITS - \ |
49 | STACK_ALLOC_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS) | |
02754e0a | 50 | #define STACK_ALLOC_SLABS_CAP 8192 |
cd11016e AP |
51 | #define STACK_ALLOC_MAX_SLABS \ |
52 | (((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \ | |
53 | (1LL << (STACK_ALLOC_INDEX_BITS)) : STACK_ALLOC_SLABS_CAP) | |
54 | ||
55 | /* The compact structure to store the reference to stacks. */ | |
56 | union handle_parts { | |
57 | depot_stack_handle_t handle; | |
58 | struct { | |
59 | u32 slabindex : STACK_ALLOC_INDEX_BITS; | |
60 | u32 offset : STACK_ALLOC_OFFSET_BITS; | |
7c31190b | 61 | u32 valid : STACK_ALLOC_NULL_PROTECTION_BITS; |
83a4f1ef | 62 | u32 extra : STACK_DEPOT_EXTRA_BITS; |
cd11016e AP |
63 | }; |
64 | }; | |
65 | ||
66 | struct stack_record { | |
67 | struct stack_record *next; /* Link in the hashtable */ | |
68 | u32 hash; /* Hash in the hastable */ | |
69 | u32 size; /* Number of frames in the stack */ | |
70 | union handle_parts handle; | |
3a2b67e6 | 71 | unsigned long entries[]; /* Variable-sized array of entries. */ |
cd11016e AP |
72 | }; |
73 | ||
a5f1783b VB |
74 | static bool __stack_depot_want_early_init __initdata = IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT); |
75 | static bool __stack_depot_early_init_passed __initdata; | |
76 | ||
cd11016e AP |
77 | static void *stack_slabs[STACK_ALLOC_MAX_SLABS]; |
78 | ||
79 | static int depot_index; | |
80 | static int next_slab_inited; | |
81 | static size_t depot_offset; | |
78564b94 | 82 | static DEFINE_RAW_SPINLOCK(depot_lock); |
cd11016e | 83 | |
f9987921 VB |
84 | /* one hash table bucket entry per 16kB of memory */ |
85 | #define STACK_HASH_SCALE 14 | |
86 | /* limited between 4k and 1M buckets */ | |
87 | #define STACK_HASH_ORDER_MIN 12 | |
88 | #define STACK_HASH_ORDER_MAX 20 | |
cd11016e AP |
89 | #define STACK_HASH_SEED 0x9747b28c |
90 | ||
f9987921 VB |
91 | static unsigned int stack_hash_order; |
92 | static unsigned int stack_hash_mask; | |
93 | ||
e1fdc403 VJ |
94 | static bool stack_depot_disable; |
95 | static struct stack_record **stack_table; | |
96 | ||
97 | static int __init is_stack_depot_disabled(char *str) | |
98 | { | |
64427985 VJ |
99 | int ret; |
100 | ||
101 | ret = kstrtobool(str, &stack_depot_disable); | |
102 | if (!ret && stack_depot_disable) { | |
4a6b5314 | 103 | pr_info("disabled\n"); |
e1fdc403 VJ |
104 | stack_table = NULL; |
105 | } | |
106 | return 0; | |
107 | } | |
108 | early_param("stack_depot_disable", is_stack_depot_disabled); | |
109 | ||
a5f1783b VB |
110 | void __init stack_depot_want_early_init(void) |
111 | { | |
112 | /* Too late to request early init now */ | |
113 | WARN_ON(__stack_depot_early_init_passed); | |
114 | ||
115 | __stack_depot_want_early_init = true; | |
116 | } | |
117 | ||
118 | int __init stack_depot_early_init(void) | |
119 | { | |
f9987921 | 120 | unsigned long entries = 0; |
a5f1783b VB |
121 | |
122 | /* This is supposed to be called only once, from mm_init() */ | |
123 | if (WARN_ON(__stack_depot_early_init_passed)) | |
124 | return 0; | |
125 | ||
126 | __stack_depot_early_init_passed = true; | |
127 | ||
f9987921 VB |
128 | if (kasan_enabled() && !stack_hash_order) |
129 | stack_hash_order = STACK_HASH_ORDER_MAX; | |
130 | ||
a5f1783b VB |
131 | if (!__stack_depot_want_early_init || stack_depot_disable) |
132 | return 0; | |
133 | ||
f9987921 VB |
134 | if (stack_hash_order) |
135 | entries = 1UL << stack_hash_order; | |
136 | stack_table = alloc_large_system_hash("stackdepot", | |
137 | sizeof(struct stack_record *), | |
138 | entries, | |
139 | STACK_HASH_SCALE, | |
140 | HASH_EARLY | HASH_ZERO, | |
141 | NULL, | |
142 | &stack_hash_mask, | |
143 | 1UL << STACK_HASH_ORDER_MIN, | |
144 | 1UL << STACK_HASH_ORDER_MAX); | |
a5f1783b VB |
145 | |
146 | if (!stack_table) { | |
4a6b5314 | 147 | pr_err("hash table allocation failed, disabling\n"); |
a5f1783b VB |
148 | stack_depot_disable = true; |
149 | return -ENOMEM; | |
150 | } | |
151 | ||
152 | return 0; | |
153 | } | |
154 | ||
155 | int stack_depot_init(void) | |
e1fdc403 | 156 | { |
2dba5eb1 | 157 | static DEFINE_MUTEX(stack_depot_init_mutex); |
a5f1783b | 158 | int ret = 0; |
2dba5eb1 VB |
159 | |
160 | mutex_lock(&stack_depot_init_mutex); | |
161 | if (!stack_depot_disable && !stack_table) { | |
f9987921 VB |
162 | unsigned long entries; |
163 | int scale = STACK_HASH_SCALE; | |
164 | ||
165 | if (stack_hash_order) { | |
166 | entries = 1UL << stack_hash_order; | |
167 | } else { | |
168 | entries = nr_free_buffer_pages(); | |
169 | entries = roundup_pow_of_two(entries); | |
170 | ||
171 | if (scale > PAGE_SHIFT) | |
172 | entries >>= (scale - PAGE_SHIFT); | |
173 | else | |
174 | entries <<= (PAGE_SHIFT - scale); | |
175 | } | |
176 | ||
177 | if (entries < 1UL << STACK_HASH_ORDER_MIN) | |
178 | entries = 1UL << STACK_HASH_ORDER_MIN; | |
179 | if (entries > 1UL << STACK_HASH_ORDER_MAX) | |
180 | entries = 1UL << STACK_HASH_ORDER_MAX; | |
181 | ||
4a6b5314 | 182 | pr_info("allocating hash table of %lu entries with kvcalloc\n", |
f9987921 VB |
183 | entries); |
184 | stack_table = kvcalloc(entries, sizeof(struct stack_record *), GFP_KERNEL); | |
a5f1783b | 185 | if (!stack_table) { |
4a6b5314 | 186 | pr_err("hash table allocation failed, disabling\n"); |
2dba5eb1 | 187 | stack_depot_disable = true; |
a5f1783b | 188 | ret = -ENOMEM; |
2dba5eb1 | 189 | } |
f9987921 | 190 | stack_hash_mask = entries - 1; |
e1fdc403 | 191 | } |
2dba5eb1 | 192 | mutex_unlock(&stack_depot_init_mutex); |
a5f1783b | 193 | return ret; |
e1fdc403 | 194 | } |
2dba5eb1 | 195 | EXPORT_SYMBOL_GPL(stack_depot_init); |
cd11016e | 196 | |
15ef6a98 AK |
197 | static bool init_stack_slab(void **prealloc) |
198 | { | |
199 | if (!*prealloc) | |
200 | return false; | |
201 | /* | |
202 | * This smp_load_acquire() pairs with smp_store_release() to | |
203 | * |next_slab_inited| below and in depot_alloc_stack(). | |
204 | */ | |
205 | if (smp_load_acquire(&next_slab_inited)) | |
206 | return true; | |
207 | if (stack_slabs[depot_index] == NULL) { | |
208 | stack_slabs[depot_index] = *prealloc; | |
209 | *prealloc = NULL; | |
210 | } else { | |
211 | /* If this is the last depot slab, do not touch the next one. */ | |
212 | if (depot_index + 1 < STACK_ALLOC_MAX_SLABS) { | |
213 | stack_slabs[depot_index + 1] = *prealloc; | |
214 | *prealloc = NULL; | |
215 | } | |
216 | /* | |
217 | * This smp_store_release pairs with smp_load_acquire() from | |
218 | * |next_slab_inited| above and in stack_depot_save(). | |
219 | */ | |
220 | smp_store_release(&next_slab_inited, 1); | |
221 | } | |
222 | return true; | |
223 | } | |
224 | ||
225 | /* Allocation of a new stack in raw storage */ | |
226 | static struct stack_record * | |
227 | depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) | |
228 | { | |
229 | struct stack_record *stack; | |
230 | size_t required_size = struct_size(stack, entries, size); | |
231 | ||
232 | required_size = ALIGN(required_size, 1 << STACK_ALLOC_ALIGN); | |
233 | ||
234 | if (unlikely(depot_offset + required_size > STACK_ALLOC_SIZE)) { | |
235 | if (unlikely(depot_index + 1 >= STACK_ALLOC_MAX_SLABS)) { | |
236 | WARN_ONCE(1, "Stack depot reached limit capacity"); | |
237 | return NULL; | |
238 | } | |
239 | depot_index++; | |
240 | depot_offset = 0; | |
241 | /* | |
242 | * smp_store_release() here pairs with smp_load_acquire() from | |
243 | * |next_slab_inited| in stack_depot_save() and | |
244 | * init_stack_slab(). | |
245 | */ | |
246 | if (depot_index + 1 < STACK_ALLOC_MAX_SLABS) | |
247 | smp_store_release(&next_slab_inited, 0); | |
248 | } | |
249 | init_stack_slab(prealloc); | |
250 | if (stack_slabs[depot_index] == NULL) | |
251 | return NULL; | |
252 | ||
253 | stack = stack_slabs[depot_index] + depot_offset; | |
254 | ||
255 | stack->hash = hash; | |
256 | stack->size = size; | |
257 | stack->handle.slabindex = depot_index; | |
258 | stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN; | |
259 | stack->handle.valid = 1; | |
260 | stack->handle.extra = 0; | |
261 | memcpy(stack->entries, entries, flex_array_size(stack, entries, size)); | |
262 | depot_offset += required_size; | |
263 | ||
264 | return stack; | |
265 | } | |
266 | ||
cd11016e AP |
267 | /* Calculate hash for a stack */ |
268 | static inline u32 hash_stack(unsigned long *entries, unsigned int size) | |
269 | { | |
270 | return jhash2((u32 *)entries, | |
180644f8 GS |
271 | array_size(size, sizeof(*entries)) / sizeof(u32), |
272 | STACK_HASH_SEED); | |
cd11016e AP |
273 | } |
274 | ||
a571b272 AP |
275 | /* Use our own, non-instrumented version of memcmp(). |
276 | * | |
277 | * We actually don't care about the order, just the equality. | |
278 | */ | |
279 | static inline | |
280 | int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2, | |
281 | unsigned int n) | |
282 | { | |
283 | for ( ; n-- ; u1++, u2++) { | |
284 | if (*u1 != *u2) | |
285 | return 1; | |
286 | } | |
287 | return 0; | |
288 | } | |
289 | ||
cd11016e AP |
290 | /* Find a stack that is equal to the one stored in entries in the hash */ |
291 | static inline struct stack_record *find_stack(struct stack_record *bucket, | |
292 | unsigned long *entries, int size, | |
293 | u32 hash) | |
294 | { | |
295 | struct stack_record *found; | |
296 | ||
297 | for (found = bucket; found; found = found->next) { | |
298 | if (found->hash == hash && | |
299 | found->size == size && | |
a571b272 | 300 | !stackdepot_memcmp(entries, found->entries, size)) |
cd11016e | 301 | return found; |
cd11016e AP |
302 | } |
303 | return NULL; | |
304 | } | |
305 | ||
cd11016e | 306 | /** |
11ac25c6 | 307 | * __stack_depot_save - Save a stack trace from an array |
c0cfc337 TG |
308 | * |
309 | * @entries: Pointer to storage array | |
310 | * @nr_entries: Size of the storage array | |
83a4f1ef | 311 | * @extra_bits: Flags to store in unused bits of depot_stack_handle_t |
c0cfc337 | 312 | * @alloc_flags: Allocation gfp flags |
11ac25c6 ME |
313 | * @can_alloc: Allocate stack slabs (increased chance of failure if false) |
314 | * | |
315 | * Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is | |
316 | * %true, is allowed to replenish the stack slab pool in case no space is left | |
317 | * (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids | |
318 | * any allocations and will fail if no space is left to store the stack trace. | |
319 | * | |
e9400660 ME |
320 | * If the stack trace in @entries is from an interrupt, only the portion up to |
321 | * interrupt entry is saved. | |
322 | * | |
83a4f1ef AP |
323 | * Additional opaque flags can be passed in @extra_bits, stored in the unused |
324 | * bits of the stack handle, and retrieved using stack_depot_get_extra_bits() | |
325 | * without calling stack_depot_fetch(). | |
326 | * | |
11ac25c6 ME |
327 | * Context: Any context, but setting @can_alloc to %false is required if |
328 | * alloc_pages() cannot be used from the current context. Currently | |
329 | * this is the case from contexts where neither %GFP_ATOMIC nor | |
330 | * %GFP_NOWAIT can be used (NMI, raw_spin_lock). | |
cd11016e | 331 | * |
11ac25c6 | 332 | * Return: The handle of the stack struct stored in depot, 0 on failure. |
cd11016e | 333 | */ |
11ac25c6 ME |
334 | depot_stack_handle_t __stack_depot_save(unsigned long *entries, |
335 | unsigned int nr_entries, | |
83a4f1ef | 336 | unsigned int extra_bits, |
11ac25c6 | 337 | gfp_t alloc_flags, bool can_alloc) |
cd11016e | 338 | { |
cd11016e | 339 | struct stack_record *found = NULL, **bucket; |
83a4f1ef | 340 | union handle_parts retval = { .handle = 0 }; |
cd11016e AP |
341 | struct page *page = NULL; |
342 | void *prealloc = NULL; | |
c0cfc337 TG |
343 | unsigned long flags; |
344 | u32 hash; | |
cd11016e | 345 | |
e9400660 ME |
346 | /* |
347 | * If this stack trace is from an interrupt, including anything before | |
348 | * interrupt entry usually leads to unbounded stackdepot growth. | |
349 | * | |
350 | * Because use of filter_irq_stacks() is a requirement to ensure | |
351 | * stackdepot can efficiently deduplicate interrupt stacks, always | |
352 | * filter_irq_stacks() to simplify all callers' use of stackdepot. | |
353 | */ | |
354 | nr_entries = filter_irq_stacks(entries, nr_entries); | |
355 | ||
e1fdc403 | 356 | if (unlikely(nr_entries == 0) || stack_depot_disable) |
cd11016e AP |
357 | goto fast_exit; |
358 | ||
c0cfc337 | 359 | hash = hash_stack(entries, nr_entries); |
f9987921 | 360 | bucket = &stack_table[hash & stack_hash_mask]; |
cd11016e AP |
361 | |
362 | /* | |
363 | * Fast path: look the stack trace up without locking. | |
364 | * The smp_load_acquire() here pairs with smp_store_release() to | |
365 | * |bucket| below. | |
366 | */ | |
c0cfc337 TG |
367 | found = find_stack(smp_load_acquire(bucket), entries, |
368 | nr_entries, hash); | |
cd11016e AP |
369 | if (found) |
370 | goto exit; | |
371 | ||
372 | /* | |
373 | * Check if the current or the next stack slab need to be initialized. | |
374 | * If so, allocate the memory - we won't be able to do that under the | |
375 | * lock. | |
376 | * | |
377 | * The smp_load_acquire() here pairs with smp_store_release() to | |
378 | * |next_slab_inited| in depot_alloc_stack() and init_stack_slab(). | |
379 | */ | |
11ac25c6 | 380 | if (unlikely(can_alloc && !smp_load_acquire(&next_slab_inited))) { |
cd11016e AP |
381 | /* |
382 | * Zero out zone modifiers, as we don't have specific zone | |
383 | * requirements. Keep the flags related to allocation in atomic | |
384 | * contexts and I/O. | |
385 | */ | |
386 | alloc_flags &= ~GFP_ZONEMASK; | |
387 | alloc_flags &= (GFP_ATOMIC | GFP_KERNEL); | |
87cc271d | 388 | alloc_flags |= __GFP_NOWARN; |
cd11016e AP |
389 | page = alloc_pages(alloc_flags, STACK_ALLOC_ORDER); |
390 | if (page) | |
391 | prealloc = page_address(page); | |
392 | } | |
393 | ||
78564b94 | 394 | raw_spin_lock_irqsave(&depot_lock, flags); |
cd11016e | 395 | |
c0cfc337 | 396 | found = find_stack(*bucket, entries, nr_entries, hash); |
cd11016e | 397 | if (!found) { |
7f2b8818 ME |
398 | struct stack_record *new = depot_alloc_stack(entries, nr_entries, hash, &prealloc); |
399 | ||
cd11016e AP |
400 | if (new) { |
401 | new->next = *bucket; | |
402 | /* | |
403 | * This smp_store_release() pairs with | |
404 | * smp_load_acquire() from |bucket| above. | |
405 | */ | |
406 | smp_store_release(bucket, new); | |
407 | found = new; | |
408 | } | |
409 | } else if (prealloc) { | |
410 | /* | |
411 | * We didn't need to store this stack trace, but let's keep | |
412 | * the preallocated memory for the future. | |
413 | */ | |
414 | WARN_ON(!init_stack_slab(&prealloc)); | |
415 | } | |
416 | ||
78564b94 | 417 | raw_spin_unlock_irqrestore(&depot_lock, flags); |
cd11016e AP |
418 | exit: |
419 | if (prealloc) { | |
420 | /* Nobody used this memory, ok to free it. */ | |
421 | free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER); | |
422 | } | |
423 | if (found) | |
83a4f1ef | 424 | retval.handle = found->handle.handle; |
cd11016e | 425 | fast_exit: |
83a4f1ef AP |
426 | retval.extra = extra_bits; |
427 | ||
428 | return retval.handle; | |
cd11016e | 429 | } |
11ac25c6 ME |
430 | EXPORT_SYMBOL_GPL(__stack_depot_save); |
431 | ||
432 | /** | |
433 | * stack_depot_save - Save a stack trace from an array | |
434 | * | |
435 | * @entries: Pointer to storage array | |
436 | * @nr_entries: Size of the storage array | |
437 | * @alloc_flags: Allocation gfp flags | |
438 | * | |
439 | * Context: Contexts where allocations via alloc_pages() are allowed. | |
440 | * See __stack_depot_save() for more details. | |
441 | * | |
442 | * Return: The handle of the stack struct stored in depot, 0 on failure. | |
443 | */ | |
444 | depot_stack_handle_t stack_depot_save(unsigned long *entries, | |
445 | unsigned int nr_entries, | |
446 | gfp_t alloc_flags) | |
447 | { | |
83a4f1ef | 448 | return __stack_depot_save(entries, nr_entries, 0, alloc_flags, true); |
11ac25c6 | 449 | } |
c0cfc337 | 450 | EXPORT_SYMBOL_GPL(stack_depot_save); |
15ef6a98 AK |
451 | |
452 | /** | |
453 | * stack_depot_fetch - Fetch stack entries from a depot | |
454 | * | |
455 | * @handle: Stack depot handle which was returned from | |
456 | * stack_depot_save(). | |
457 | * @entries: Pointer to store the entries address | |
458 | * | |
459 | * Return: The number of trace entries for this depot. | |
460 | */ | |
461 | unsigned int stack_depot_fetch(depot_stack_handle_t handle, | |
462 | unsigned long **entries) | |
463 | { | |
464 | union handle_parts parts = { .handle = handle }; | |
465 | void *slab; | |
466 | size_t offset = parts.offset << STACK_ALLOC_ALIGN; | |
467 | struct stack_record *stack; | |
468 | ||
469 | *entries = NULL; | |
470 | if (!handle) | |
471 | return 0; | |
472 | ||
473 | if (parts.slabindex > depot_index) { | |
474 | WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n", | |
475 | parts.slabindex, depot_index, handle); | |
476 | return 0; | |
477 | } | |
478 | slab = stack_slabs[parts.slabindex]; | |
479 | if (!slab) | |
480 | return 0; | |
481 | stack = slab + offset; | |
482 | ||
483 | *entries = stack->entries; | |
484 | return stack->size; | |
485 | } | |
486 | EXPORT_SYMBOL_GPL(stack_depot_fetch); | |
487 | ||
488 | /** | |
489 | * stack_depot_print - print stack entries from a depot | |
490 | * | |
491 | * @stack: Stack depot handle which was returned from | |
492 | * stack_depot_save(). | |
493 | * | |
494 | */ | |
495 | void stack_depot_print(depot_stack_handle_t stack) | |
496 | { | |
497 | unsigned long *entries; | |
498 | unsigned int nr_entries; | |
499 | ||
500 | nr_entries = stack_depot_fetch(stack, &entries); | |
501 | if (nr_entries > 0) | |
502 | stack_trace_print(entries, nr_entries, 0); | |
503 | } | |
504 | EXPORT_SYMBOL_GPL(stack_depot_print); | |
505 | ||
506 | /** | |
507 | * stack_depot_snprint - print stack entries from a depot into a buffer | |
508 | * | |
509 | * @handle: Stack depot handle which was returned from | |
510 | * stack_depot_save(). | |
511 | * @buf: Pointer to the print buffer | |
512 | * | |
513 | * @size: Size of the print buffer | |
514 | * | |
515 | * @spaces: Number of leading spaces to print | |
516 | * | |
517 | * Return: Number of bytes printed. | |
518 | */ | |
519 | int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size, | |
520 | int spaces) | |
521 | { | |
522 | unsigned long *entries; | |
523 | unsigned int nr_entries; | |
524 | ||
525 | nr_entries = stack_depot_fetch(handle, &entries); | |
526 | return nr_entries ? stack_trace_snprint(buf, size, entries, nr_entries, | |
527 | spaces) : 0; | |
528 | } | |
529 | EXPORT_SYMBOL_GPL(stack_depot_snprint); | |
530 | ||
531 | unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle) | |
532 | { | |
533 | union handle_parts parts = { .handle = handle }; | |
534 | ||
535 | return parts.extra; | |
536 | } | |
537 | EXPORT_SYMBOL(stack_depot_get_extra_bits); |