1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Copyright (c) 2016 Facebook
3 */
4 #include <linux/bpf.h>
5 #include <linux/jhash.h>
6 #include <linux/filter.h>
7 #include <linux/kernel.h>
8 #include <linux/stacktrace.h>
9 #include <linux/perf_event.h>
10 #include <linux/elf.h>
11 #include <linux/pagemap.h>
12 #include <linux/irq_work.h>
13 #include <linux/btf_ids.h>
14 #include "percpu_freelist.h"
15
16 #define STACK_CREATE_FLAG_MASK \
17 (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \
18 BPF_F_STACK_BUILD_ID)
19
20 struct stack_map_bucket {
21 struct pcpu_freelist_node fnode;
22 u32 hash;
23 u32 nr;
24 u64 data[];
25 };
26
27 struct bpf_stack_map {
28 struct bpf_map map;
29 void *elems;
30 struct pcpu_freelist freelist;
31 u32 n_buckets;
32 struct stack_map_bucket *buckets[];
33 };
34
35 /* irq_work to run up_read() for build_id lookup in nmi context */
36 struct stack_map_irq_work {
37 struct irq_work irq_work;
38 struct mm_struct *mm;
39 };
40
do_up_read(struct irq_work * entry)41 static void do_up_read(struct irq_work *entry)
42 {
43 struct stack_map_irq_work *work;
44
45 if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
46 return;
47
48 work = container_of(entry, struct stack_map_irq_work, irq_work);
49 mmap_read_unlock_non_owner(work->mm);
50 }
51
52 static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
53
stack_map_use_build_id(struct bpf_map * map)54 static inline bool stack_map_use_build_id(struct bpf_map *map)
55 {
56 return (map->map_flags & BPF_F_STACK_BUILD_ID);
57 }
58
stack_map_data_size(struct bpf_map * map)59 static inline int stack_map_data_size(struct bpf_map *map)
60 {
61 return stack_map_use_build_id(map) ?
62 sizeof(struct bpf_stack_build_id) : sizeof(u64);
63 }
64
prealloc_elems_and_freelist(struct bpf_stack_map * smap)65 static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
66 {
67 u64 elem_size = sizeof(struct stack_map_bucket) +
68 (u64)smap->map.value_size;
69 int err;
70
71 smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
72 smap->map.numa_node);
73 if (!smap->elems)
74 return -ENOMEM;
75
76 err = pcpu_freelist_init(&smap->freelist);
77 if (err)
78 goto free_elems;
79
80 pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
81 smap->map.max_entries);
82 return 0;
83
84 free_elems:
85 bpf_map_area_free(smap->elems);
86 return err;
87 }
88
89 /* Called from syscall */
stack_map_alloc(union bpf_attr * attr)90 static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
91 {
92 u32 value_size = attr->value_size;
93 struct bpf_stack_map *smap;
94 struct bpf_map_memory mem;
95 u64 cost, n_buckets;
96 int err;
97
98 if (!bpf_capable())
99 return ERR_PTR(-EPERM);
100
101 if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
102 return ERR_PTR(-EINVAL);
103
104 /* check sanity of attributes */
105 if (attr->max_entries == 0 || attr->key_size != 4 ||
106 value_size < 8 || value_size % 8)
107 return ERR_PTR(-EINVAL);
108
109 BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
110 if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
111 if (value_size % sizeof(struct bpf_stack_build_id) ||
112 value_size / sizeof(struct bpf_stack_build_id)
113 > sysctl_perf_event_max_stack)
114 return ERR_PTR(-EINVAL);
115 } else if (value_size / 8 > sysctl_perf_event_max_stack)
116 return ERR_PTR(-EINVAL);
117
118 /* hash table size must be power of 2 */
119 n_buckets = roundup_pow_of_two(attr->max_entries);
120 if (!n_buckets)
121 return ERR_PTR(-E2BIG);
122
123 cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
124 err = bpf_map_charge_init(&mem, cost + attr->max_entries *
125 (sizeof(struct stack_map_bucket) + (u64)value_size));
126 if (err)
127 return ERR_PTR(err);
128
129 smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
130 if (!smap) {
131 bpf_map_charge_finish(&mem);
132 return ERR_PTR(-ENOMEM);
133 }
134
135 bpf_map_init_from_attr(&smap->map, attr);
136 smap->map.value_size = value_size;
137 smap->n_buckets = n_buckets;
138
139 err = get_callchain_buffers(sysctl_perf_event_max_stack);
140 if (err)
141 goto free_charge;
142
143 err = prealloc_elems_and_freelist(smap);
144 if (err)
145 goto put_buffers;
146
147 bpf_map_charge_move(&smap->map.memory, &mem);
148
149 return &smap->map;
150
151 put_buffers:
152 put_callchain_buffers();
153 free_charge:
154 bpf_map_charge_finish(&mem);
155 bpf_map_area_free(smap);
156 return ERR_PTR(err);
157 }
158
159 #define BPF_BUILD_ID 3
160 /*
161 * Parse build id from the note segment. This logic can be shared between
162 * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
163 * identical.
164 */
stack_map_parse_build_id(void * page_addr,unsigned char * build_id,void * note_start,Elf32_Word note_size)165 static inline int stack_map_parse_build_id(void *page_addr,
166 unsigned char *build_id,
167 void *note_start,
168 Elf32_Word note_size)
169 {
170 Elf32_Word note_offs = 0, new_offs;
171
172 /* check for overflow */
173 if (note_start < page_addr || note_start + note_size < note_start)
174 return -EINVAL;
175
176 /* only supports note that fits in the first page */
177 if (note_start + note_size > page_addr + PAGE_SIZE)
178 return -EINVAL;
179
180 while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
181 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
182
183 if (nhdr->n_type == BPF_BUILD_ID &&
184 nhdr->n_namesz == sizeof("GNU") &&
185 nhdr->n_descsz > 0 &&
186 nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
187 memcpy(build_id,
188 note_start + note_offs +
189 ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
190 nhdr->n_descsz);
191 memset(build_id + nhdr->n_descsz, 0,
192 BPF_BUILD_ID_SIZE - nhdr->n_descsz);
193 return 0;
194 }
195 new_offs = note_offs + sizeof(Elf32_Nhdr) +
196 ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
197 if (new_offs <= note_offs) /* overflow */
198 break;
199 note_offs = new_offs;
200 }
201 return -EINVAL;
202 }
203
204 /* Parse build ID from 32-bit ELF */
stack_map_get_build_id_32(void * page_addr,unsigned char * build_id)205 static int stack_map_get_build_id_32(void *page_addr,
206 unsigned char *build_id)
207 {
208 Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
209 Elf32_Phdr *phdr;
210 int i;
211
212 /* only supports phdr that fits in one page */
213 if (ehdr->e_phnum >
214 (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
215 return -EINVAL;
216
217 phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
218
219 for (i = 0; i < ehdr->e_phnum; ++i) {
220 if (phdr[i].p_type == PT_NOTE &&
221 !stack_map_parse_build_id(page_addr, build_id,
222 page_addr + phdr[i].p_offset,
223 phdr[i].p_filesz))
224 return 0;
225 }
226 return -EINVAL;
227 }
228
229 /* Parse build ID from 64-bit ELF */
stack_map_get_build_id_64(void * page_addr,unsigned char * build_id)230 static int stack_map_get_build_id_64(void *page_addr,
231 unsigned char *build_id)
232 {
233 Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
234 Elf64_Phdr *phdr;
235 int i;
236
237 /* only supports phdr that fits in one page */
238 if (ehdr->e_phnum >
239 (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
240 return -EINVAL;
241
242 phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
243
244 for (i = 0; i < ehdr->e_phnum; ++i) {
245 if (phdr[i].p_type == PT_NOTE &&
246 !stack_map_parse_build_id(page_addr, build_id,
247 page_addr + phdr[i].p_offset,
248 phdr[i].p_filesz))
249 return 0;
250 }
251 return -EINVAL;
252 }
253
254 /* Parse build ID of ELF file mapped to vma */
stack_map_get_build_id(struct vm_area_struct * vma,unsigned char * build_id)255 static int stack_map_get_build_id(struct vm_area_struct *vma,
256 unsigned char *build_id)
257 {
258 Elf32_Ehdr *ehdr;
259 struct page *page;
260 void *page_addr;
261 int ret;
262
263 /* only works for page backed storage */
264 if (!vma->vm_file)
265 return -EINVAL;
266
267 page = find_get_page(vma->vm_file->f_mapping, 0);
268 if (!page)
269 return -EFAULT; /* page not mapped */
270
271 ret = -EINVAL;
272 page_addr = kmap_atomic(page);
273 ehdr = (Elf32_Ehdr *)page_addr;
274
275 /* compare magic x7f "ELF" */
276 if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
277 goto out;
278
279 /* only support executable file and shared object file */
280 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
281 goto out;
282
283 if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
284 ret = stack_map_get_build_id_32(page_addr, build_id);
285 else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
286 ret = stack_map_get_build_id_64(page_addr, build_id);
287 out:
288 kunmap_atomic(page_addr);
289 put_page(page);
290 return ret;
291 }
292
stack_map_get_build_id_offset(struct bpf_stack_build_id * id_offs,u64 * ips,u32 trace_nr,bool user)293 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
294 u64 *ips, u32 trace_nr, bool user)
295 {
296 int i;
297 struct vm_area_struct *vma;
298 bool irq_work_busy = false;
299 struct stack_map_irq_work *work = NULL;
300
301 if (irqs_disabled()) {
302 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
303 work = this_cpu_ptr(&up_read_work);
304 if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY) {
305 /* cannot queue more up_read, fallback */
306 irq_work_busy = true;
307 }
308 } else {
309 /*
310 * PREEMPT_RT does not allow to trylock mmap sem in
311 * interrupt disabled context. Force the fallback code.
312 */
313 irq_work_busy = true;
314 }
315 }
316
317 /*
318 * We cannot do up_read() when the irq is disabled, because of
319 * risk to deadlock with rq_lock. To do build_id lookup when the
320 * irqs are disabled, we need to run up_read() in irq_work. We use
321 * a percpu variable to do the irq_work. If the irq_work is
322 * already used by another lookup, we fall back to report ips.
323 *
324 * Same fallback is used for kernel stack (!user) on a stackmap
325 * with build_id.
326 */
327 if (!user || !current || !current->mm || irq_work_busy ||
328 !mmap_read_trylock_non_owner(current->mm)) {
329 /* cannot access current->mm, fall back to ips */
330 for (i = 0; i < trace_nr; i++) {
331 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
332 id_offs[i].ip = ips[i];
333 memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
334 }
335 return;
336 }
337
338 for (i = 0; i < trace_nr; i++) {
339 vma = find_vma(current->mm, ips[i]);
340 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
341 /* per entry fall back to ips */
342 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
343 id_offs[i].ip = ips[i];
344 memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
345 continue;
346 }
347 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
348 - vma->vm_start;
349 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
350 }
351
352 if (!work) {
353 mmap_read_unlock_non_owner(current->mm);
354 } else {
355 work->mm = current->mm;
356 irq_work_queue(&work->irq_work);
357 }
358 }
359
360 static struct perf_callchain_entry *
get_callchain_entry_for_task(struct task_struct * task,u32 max_depth)361 get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
362 {
363 #ifdef CONFIG_STACKTRACE
364 struct perf_callchain_entry *entry;
365 int rctx;
366
367 entry = get_callchain_entry(&rctx);
368
369 if (!entry)
370 return NULL;
371
372 entry->nr = stack_trace_save_tsk(task, (unsigned long *)entry->ip,
373 max_depth, 0);
374
375 /* stack_trace_save_tsk() works on unsigned long array, while
376 * perf_callchain_entry uses u64 array. For 32-bit systems, it is
377 * necessary to fix this mismatch.
378 */
379 if (__BITS_PER_LONG != 64) {
380 unsigned long *from = (unsigned long *) entry->ip;
381 u64 *to = entry->ip;
382 int i;
383
384 /* copy data from the end to avoid using extra buffer */
385 for (i = entry->nr - 1; i >= 0; i--)
386 to[i] = (u64)(from[i]);
387 }
388
389 put_callchain_entry(rctx);
390
391 return entry;
392 #else /* CONFIG_STACKTRACE */
393 return NULL;
394 #endif
395 }
396
__bpf_get_stackid(struct bpf_map * map,struct perf_callchain_entry * trace,u64 flags)397 static long __bpf_get_stackid(struct bpf_map *map,
398 struct perf_callchain_entry *trace, u64 flags)
399 {
400 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
401 struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
402 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
403 u32 hash, id, trace_nr, trace_len;
404 bool user = flags & BPF_F_USER_STACK;
405 u64 *ips;
406 bool hash_matches;
407
408 if (trace->nr <= skip)
409 /* skipping more than usable stack trace */
410 return -EFAULT;
411
412 trace_nr = trace->nr - skip;
413 trace_len = trace_nr * sizeof(u64);
414 ips = trace->ip + skip;
415 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
416 id = hash & (smap->n_buckets - 1);
417 bucket = READ_ONCE(smap->buckets[id]);
418
419 hash_matches = bucket && bucket->hash == hash;
420 /* fast cmp */
421 if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
422 return id;
423
424 if (stack_map_use_build_id(map)) {
425 /* for build_id+offset, pop a bucket before slow cmp */
426 new_bucket = (struct stack_map_bucket *)
427 pcpu_freelist_pop(&smap->freelist);
428 if (unlikely(!new_bucket))
429 return -ENOMEM;
430 new_bucket->nr = trace_nr;
431 stack_map_get_build_id_offset(
432 (struct bpf_stack_build_id *)new_bucket->data,
433 ips, trace_nr, user);
434 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
435 if (hash_matches && bucket->nr == trace_nr &&
436 memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
437 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
438 return id;
439 }
440 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
441 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
442 return -EEXIST;
443 }
444 } else {
445 if (hash_matches && bucket->nr == trace_nr &&
446 memcmp(bucket->data, ips, trace_len) == 0)
447 return id;
448 if (bucket && !(flags & BPF_F_REUSE_STACKID))
449 return -EEXIST;
450
451 new_bucket = (struct stack_map_bucket *)
452 pcpu_freelist_pop(&smap->freelist);
453 if (unlikely(!new_bucket))
454 return -ENOMEM;
455 memcpy(new_bucket->data, ips, trace_len);
456 }
457
458 new_bucket->hash = hash;
459 new_bucket->nr = trace_nr;
460
461 old_bucket = xchg(&smap->buckets[id], new_bucket);
462 if (old_bucket)
463 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
464 return id;
465 }
466
BPF_CALL_3(bpf_get_stackid,struct pt_regs *,regs,struct bpf_map *,map,u64,flags)467 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
468 u64, flags)
469 {
470 u32 max_depth = map->value_size / stack_map_data_size(map);
471 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
472 bool user = flags & BPF_F_USER_STACK;
473 struct perf_callchain_entry *trace;
474 bool kernel = !user;
475
476 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
477 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
478 return -EINVAL;
479
480 max_depth += skip;
481 if (max_depth > sysctl_perf_event_max_stack)
482 max_depth = sysctl_perf_event_max_stack;
483
484 trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
485 false, false);
486
487 if (unlikely(!trace))
488 /* couldn't fetch the stack trace */
489 return -EFAULT;
490
491 return __bpf_get_stackid(map, trace, flags);
492 }
493
494 const struct bpf_func_proto bpf_get_stackid_proto = {
495 .func = bpf_get_stackid,
496 .gpl_only = true,
497 .ret_type = RET_INTEGER,
498 .arg1_type = ARG_PTR_TO_CTX,
499 .arg2_type = ARG_CONST_MAP_PTR,
500 .arg3_type = ARG_ANYTHING,
501 };
502
count_kernel_ip(struct perf_callchain_entry * trace)503 static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
504 {
505 __u64 nr_kernel = 0;
506
507 while (nr_kernel < trace->nr) {
508 if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
509 break;
510 nr_kernel++;
511 }
512 return nr_kernel;
513 }
514
BPF_CALL_3(bpf_get_stackid_pe,struct bpf_perf_event_data_kern *,ctx,struct bpf_map *,map,u64,flags)515 BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
516 struct bpf_map *, map, u64, flags)
517 {
518 struct perf_event *event = ctx->event;
519 struct perf_callchain_entry *trace;
520 bool kernel, user;
521 __u64 nr_kernel;
522 int ret;
523
524 /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
525 if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
526 return bpf_get_stackid((unsigned long)(ctx->regs),
527 (unsigned long) map, flags, 0, 0);
528
529 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
530 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
531 return -EINVAL;
532
533 user = flags & BPF_F_USER_STACK;
534 kernel = !user;
535
536 trace = ctx->data->callchain;
537 if (unlikely(!trace))
538 return -EFAULT;
539
540 nr_kernel = count_kernel_ip(trace);
541
542 if (kernel) {
543 __u64 nr = trace->nr;
544
545 trace->nr = nr_kernel;
546 ret = __bpf_get_stackid(map, trace, flags);
547
548 /* restore nr */
549 trace->nr = nr;
550 } else { /* user */
551 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
552
553 skip += nr_kernel;
554 if (skip > BPF_F_SKIP_FIELD_MASK)
555 return -EFAULT;
556
557 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
558 ret = __bpf_get_stackid(map, trace, flags);
559 }
560 return ret;
561 }
562
563 const struct bpf_func_proto bpf_get_stackid_proto_pe = {
564 .func = bpf_get_stackid_pe,
565 .gpl_only = false,
566 .ret_type = RET_INTEGER,
567 .arg1_type = ARG_PTR_TO_CTX,
568 .arg2_type = ARG_CONST_MAP_PTR,
569 .arg3_type = ARG_ANYTHING,
570 };
571
__bpf_get_stack(struct pt_regs * regs,struct task_struct * task,struct perf_callchain_entry * trace_in,void * buf,u32 size,u64 flags)572 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
573 struct perf_callchain_entry *trace_in,
574 void *buf, u32 size, u64 flags)
575 {
576 u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
577 bool user_build_id = flags & BPF_F_USER_BUILD_ID;
578 bool crosstask = task && task != current;
579 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
580 bool user = flags & BPF_F_USER_STACK;
581 struct perf_callchain_entry *trace;
582 bool kernel = !user;
583 int err = -EINVAL;
584 u64 *ips;
585
586 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
587 BPF_F_USER_BUILD_ID)))
588 goto clear;
589 if (kernel && user_build_id)
590 goto clear;
591
592 elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
593 : sizeof(u64);
594 if (unlikely(size % elem_size))
595 goto clear;
596
597 /* cannot get valid user stack for task without user_mode regs */
598 if (task && user && !user_mode(regs))
599 goto err_fault;
600
601 /* get_perf_callchain does not support crosstask user stack walking
602 * but returns an empty stack instead of NULL.
603 */
604 if (crosstask && user) {
605 err = -EOPNOTSUPP;
606 goto clear;
607 }
608
609 num_elem = size / elem_size;
610 max_depth = num_elem + skip;
611 if (sysctl_perf_event_max_stack < max_depth)
612 max_depth = sysctl_perf_event_max_stack;
613
614 if (trace_in)
615 trace = trace_in;
616 else if (kernel && task)
617 trace = get_callchain_entry_for_task(task, max_depth);
618 else
619 trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
620 crosstask, false);
621 if (unlikely(!trace))
622 goto err_fault;
623
624 if (trace->nr < skip)
625 goto err_fault;
626
627 trace_nr = trace->nr - skip;
628 trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
629 copy_len = trace_nr * elem_size;
630
631 ips = trace->ip + skip;
632 if (user && user_build_id)
633 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
634 else
635 memcpy(buf, ips, copy_len);
636
637 if (size > copy_len)
638 memset(buf + copy_len, 0, size - copy_len);
639 return copy_len;
640
641 err_fault:
642 err = -EFAULT;
643 clear:
644 memset(buf, 0, size);
645 return err;
646 }
647
BPF_CALL_4(bpf_get_stack,struct pt_regs *,regs,void *,buf,u32,size,u64,flags)648 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
649 u64, flags)
650 {
651 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
652 }
653
654 const struct bpf_func_proto bpf_get_stack_proto = {
655 .func = bpf_get_stack,
656 .gpl_only = true,
657 .ret_type = RET_INTEGER,
658 .arg1_type = ARG_PTR_TO_CTX,
659 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
660 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
661 .arg4_type = ARG_ANYTHING,
662 };
663
BPF_CALL_4(bpf_get_task_stack,struct task_struct *,task,void *,buf,u32,size,u64,flags)664 BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
665 u32, size, u64, flags)
666 {
667 struct pt_regs *regs;
668 long res = -EINVAL;
669
670 if (!try_get_task_stack(task))
671 return -EFAULT;
672
673 regs = task_pt_regs(task);
674 if (regs)
675 res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
676 put_task_stack(task);
677
678 return res;
679 }
680
681 BTF_ID_LIST_SINGLE(bpf_get_task_stack_btf_ids, struct, task_struct)
682
683 const struct bpf_func_proto bpf_get_task_stack_proto = {
684 .func = bpf_get_task_stack,
685 .gpl_only = false,
686 .ret_type = RET_INTEGER,
687 .arg1_type = ARG_PTR_TO_BTF_ID,
688 .arg1_btf_id = &bpf_get_task_stack_btf_ids[0],
689 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
690 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
691 .arg4_type = ARG_ANYTHING,
692 };
693
BPF_CALL_4(bpf_get_stack_pe,struct bpf_perf_event_data_kern *,ctx,void *,buf,u32,size,u64,flags)694 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
695 void *, buf, u32, size, u64, flags)
696 {
697 struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
698 struct perf_event *event = ctx->event;
699 struct perf_callchain_entry *trace;
700 bool kernel, user;
701 int err = -EINVAL;
702 __u64 nr_kernel;
703
704 if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
705 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
706
707 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
708 BPF_F_USER_BUILD_ID)))
709 goto clear;
710
711 user = flags & BPF_F_USER_STACK;
712 kernel = !user;
713
714 err = -EFAULT;
715 trace = ctx->data->callchain;
716 if (unlikely(!trace))
717 goto clear;
718
719 nr_kernel = count_kernel_ip(trace);
720
721 if (kernel) {
722 __u64 nr = trace->nr;
723
724 trace->nr = nr_kernel;
725 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
726
727 /* restore nr */
728 trace->nr = nr;
729 } else { /* user */
730 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
731
732 skip += nr_kernel;
733 if (skip > BPF_F_SKIP_FIELD_MASK)
734 goto clear;
735
736 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
737 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
738 }
739 return err;
740
741 clear:
742 memset(buf, 0, size);
743 return err;
744
745 }
746
747 const struct bpf_func_proto bpf_get_stack_proto_pe = {
748 .func = bpf_get_stack_pe,
749 .gpl_only = true,
750 .ret_type = RET_INTEGER,
751 .arg1_type = ARG_PTR_TO_CTX,
752 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
753 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
754 .arg4_type = ARG_ANYTHING,
755 };
756
757 /* Called from eBPF program */
stack_map_lookup_elem(struct bpf_map * map,void * key)758 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
759 {
760 return ERR_PTR(-EOPNOTSUPP);
761 }
762
763 /* Called from syscall */
bpf_stackmap_copy(struct bpf_map * map,void * key,void * value)764 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
765 {
766 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
767 struct stack_map_bucket *bucket, *old_bucket;
768 u32 id = *(u32 *)key, trace_len;
769
770 if (unlikely(id >= smap->n_buckets))
771 return -ENOENT;
772
773 bucket = xchg(&smap->buckets[id], NULL);
774 if (!bucket)
775 return -ENOENT;
776
777 trace_len = bucket->nr * stack_map_data_size(map);
778 memcpy(value, bucket->data, trace_len);
779 memset(value + trace_len, 0, map->value_size - trace_len);
780
781 old_bucket = xchg(&smap->buckets[id], bucket);
782 if (old_bucket)
783 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
784 return 0;
785 }
786
stack_map_get_next_key(struct bpf_map * map,void * key,void * next_key)787 static int stack_map_get_next_key(struct bpf_map *map, void *key,
788 void *next_key)
789 {
790 struct bpf_stack_map *smap = container_of(map,
791 struct bpf_stack_map, map);
792 u32 id;
793
794 WARN_ON_ONCE(!rcu_read_lock_held());
795
796 if (!key) {
797 id = 0;
798 } else {
799 id = *(u32 *)key;
800 if (id >= smap->n_buckets || !smap->buckets[id])
801 id = 0;
802 else
803 id++;
804 }
805
806 while (id < smap->n_buckets && !smap->buckets[id])
807 id++;
808
809 if (id >= smap->n_buckets)
810 return -ENOENT;
811
812 *(u32 *)next_key = id;
813 return 0;
814 }
815
stack_map_update_elem(struct bpf_map * map,void * key,void * value,u64 map_flags)816 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
817 u64 map_flags)
818 {
819 return -EINVAL;
820 }
821
822 /* Called from syscall or from eBPF program */
stack_map_delete_elem(struct bpf_map * map,void * key)823 static int stack_map_delete_elem(struct bpf_map *map, void *key)
824 {
825 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
826 struct stack_map_bucket *old_bucket;
827 u32 id = *(u32 *)key;
828
829 if (unlikely(id >= smap->n_buckets))
830 return -E2BIG;
831
832 old_bucket = xchg(&smap->buckets[id], NULL);
833 if (old_bucket) {
834 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
835 return 0;
836 } else {
837 return -ENOENT;
838 }
839 }
840
841 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
stack_map_free(struct bpf_map * map)842 static void stack_map_free(struct bpf_map *map)
843 {
844 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
845
846 bpf_map_area_free(smap->elems);
847 pcpu_freelist_destroy(&smap->freelist);
848 bpf_map_area_free(smap);
849 put_callchain_buffers();
850 }
851
852 static int stack_trace_map_btf_id;
853 const struct bpf_map_ops stack_trace_map_ops = {
854 .map_meta_equal = bpf_map_meta_equal,
855 .map_alloc = stack_map_alloc,
856 .map_free = stack_map_free,
857 .map_get_next_key = stack_map_get_next_key,
858 .map_lookup_elem = stack_map_lookup_elem,
859 .map_update_elem = stack_map_update_elem,
860 .map_delete_elem = stack_map_delete_elem,
861 .map_check_btf = map_check_no_btf,
862 .map_btf_name = "bpf_stack_map",
863 .map_btf_id = &stack_trace_map_btf_id,
864 };
865
stack_map_init(void)866 static int __init stack_map_init(void)
867 {
868 int cpu;
869 struct stack_map_irq_work *work;
870
871 for_each_possible_cpu(cpu) {
872 work = per_cpu_ptr(&up_read_work, cpu);
873 init_irq_work(&work->irq_work, do_up_read);
874 }
875 return 0;
876 }
877 subsys_initcall(stack_map_init);
878