1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Copyright (c) 2016 Facebook
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/btf_ids.h>
11 #include <linux/buildid.h>
12 #include "percpu_freelist.h"
13 #include "mmap_unlock_work.h"
15 #define STACK_CREATE_FLAG_MASK \
16 (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \
19 struct stack_map_bucket {
20 struct pcpu_freelist_node fnode;
26 struct bpf_stack_map {
29 struct pcpu_freelist freelist;
31 struct stack_map_bucket *buckets[];
34 static inline bool stack_map_use_build_id(struct bpf_map *map)
36 return (map->map_flags & BPF_F_STACK_BUILD_ID);
39 static inline int stack_map_data_size(struct bpf_map *map)
41 return stack_map_use_build_id(map) ?
42 sizeof(struct bpf_stack_build_id) : sizeof(u64);
45 static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
47 u64 elem_size = sizeof(struct stack_map_bucket) +
48 (u64)smap->map.value_size;
51 smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
56 err = pcpu_freelist_init(&smap->freelist);
60 pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
61 smap->map.max_entries);
65 bpf_map_area_free(smap->elems);
69 /* Called from syscall */
70 static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
72 u32 value_size = attr->value_size;
73 struct bpf_stack_map *smap;
78 return ERR_PTR(-EPERM);
80 if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
81 return ERR_PTR(-EINVAL);
83 /* check sanity of attributes */
84 if (attr->max_entries == 0 || attr->key_size != 4 ||
85 value_size < 8 || value_size % 8)
86 return ERR_PTR(-EINVAL);
88 BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
89 if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
90 if (value_size % sizeof(struct bpf_stack_build_id) ||
91 value_size / sizeof(struct bpf_stack_build_id)
92 > sysctl_perf_event_max_stack)
93 return ERR_PTR(-EINVAL);
94 } else if (value_size / 8 > sysctl_perf_event_max_stack)
95 return ERR_PTR(-EINVAL);
97 /* hash table size must be power of 2 */
98 n_buckets = roundup_pow_of_two(attr->max_entries);
100 return ERR_PTR(-E2BIG);
102 cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
103 cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
104 smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
106 return ERR_PTR(-ENOMEM);
108 bpf_map_init_from_attr(&smap->map, attr);
109 smap->map.value_size = value_size;
110 smap->n_buckets = n_buckets;
112 err = get_callchain_buffers(sysctl_perf_event_max_stack);
116 err = prealloc_elems_and_freelist(smap);
123 put_callchain_buffers();
125 bpf_map_area_free(smap);
129 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
130 u64 *ips, u32 trace_nr, bool user)
133 struct mmap_unlock_irq_work *work = NULL;
134 bool irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
135 struct vm_area_struct *vma;
137 /* If the irq_work is in use, fall back to report ips. Same
138 * fallback is used for kernel stack (!user) on a stackmap with
141 if (!user || !current || !current->mm || irq_work_busy ||
142 !mmap_read_trylock(current->mm)) {
143 /* cannot access current->mm, fall back to ips */
144 for (i = 0; i < trace_nr; i++) {
145 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
146 id_offs[i].ip = ips[i];
147 memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
152 for (i = 0; i < trace_nr; i++) {
153 vma = find_vma(current->mm, ips[i]);
154 if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
155 /* per entry fall back to ips */
156 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
157 id_offs[i].ip = ips[i];
158 memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
161 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
163 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
165 bpf_mmap_unlock_mm(work, current->mm);
168 static struct perf_callchain_entry *
169 get_callchain_entry_for_task(struct task_struct *task, u32 init_nr)
171 #ifdef CONFIG_STACKTRACE
172 struct perf_callchain_entry *entry;
175 entry = get_callchain_entry(&rctx);
180 entry->nr = init_nr +
181 stack_trace_save_tsk(task, (unsigned long *)(entry->ip + init_nr),
182 sysctl_perf_event_max_stack - init_nr, 0);
184 /* stack_trace_save_tsk() works on unsigned long array, while
185 * perf_callchain_entry uses u64 array. For 32-bit systems, it is
186 * necessary to fix this mismatch.
188 if (__BITS_PER_LONG != 64) {
189 unsigned long *from = (unsigned long *) entry->ip;
193 /* copy data from the end to avoid using extra buffer */
194 for (i = entry->nr - 1; i >= (int)init_nr; i--)
195 to[i] = (u64)(from[i]);
198 put_callchain_entry(rctx);
201 #else /* CONFIG_STACKTRACE */
206 static long __bpf_get_stackid(struct bpf_map *map,
207 struct perf_callchain_entry *trace, u64 flags)
209 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
210 struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
211 u32 max_depth = map->value_size / stack_map_data_size(map);
212 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
213 u32 init_nr = sysctl_perf_event_max_stack - max_depth;
214 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
215 u32 hash, id, trace_nr, trace_len;
216 bool user = flags & BPF_F_USER_STACK;
220 /* get_perf_callchain() guarantees that trace->nr >= init_nr
221 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
223 trace_nr = trace->nr - init_nr;
225 if (trace_nr <= skip)
226 /* skipping more than usable stack trace */
230 trace_len = trace_nr * sizeof(u64);
231 ips = trace->ip + skip + init_nr;
232 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
233 id = hash & (smap->n_buckets - 1);
234 bucket = READ_ONCE(smap->buckets[id]);
236 hash_matches = bucket && bucket->hash == hash;
238 if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
241 if (stack_map_use_build_id(map)) {
242 /* for build_id+offset, pop a bucket before slow cmp */
243 new_bucket = (struct stack_map_bucket *)
244 pcpu_freelist_pop(&smap->freelist);
245 if (unlikely(!new_bucket))
247 new_bucket->nr = trace_nr;
248 stack_map_get_build_id_offset(
249 (struct bpf_stack_build_id *)new_bucket->data,
250 ips, trace_nr, user);
251 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
252 if (hash_matches && bucket->nr == trace_nr &&
253 memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
254 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
257 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
258 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
262 if (hash_matches && bucket->nr == trace_nr &&
263 memcmp(bucket->data, ips, trace_len) == 0)
265 if (bucket && !(flags & BPF_F_REUSE_STACKID))
268 new_bucket = (struct stack_map_bucket *)
269 pcpu_freelist_pop(&smap->freelist);
270 if (unlikely(!new_bucket))
272 memcpy(new_bucket->data, ips, trace_len);
275 new_bucket->hash = hash;
276 new_bucket->nr = trace_nr;
278 old_bucket = xchg(&smap->buckets[id], new_bucket);
280 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
284 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
287 u32 max_depth = map->value_size / stack_map_data_size(map);
288 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
289 u32 init_nr = sysctl_perf_event_max_stack - max_depth;
290 bool user = flags & BPF_F_USER_STACK;
291 struct perf_callchain_entry *trace;
294 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
295 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
298 trace = get_perf_callchain(regs, init_nr, kernel, user,
299 sysctl_perf_event_max_stack, false, false);
301 if (unlikely(!trace))
302 /* couldn't fetch the stack trace */
305 return __bpf_get_stackid(map, trace, flags);
308 const struct bpf_func_proto bpf_get_stackid_proto = {
309 .func = bpf_get_stackid,
311 .ret_type = RET_INTEGER,
312 .arg1_type = ARG_PTR_TO_CTX,
313 .arg2_type = ARG_CONST_MAP_PTR,
314 .arg3_type = ARG_ANYTHING,
317 static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
321 while (nr_kernel < trace->nr) {
322 if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
329 BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
330 struct bpf_map *, map, u64, flags)
332 struct perf_event *event = ctx->event;
333 struct perf_callchain_entry *trace;
338 /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
339 if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
340 return bpf_get_stackid((unsigned long)(ctx->regs),
341 (unsigned long) map, flags, 0, 0);
343 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
344 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
347 user = flags & BPF_F_USER_STACK;
350 trace = ctx->data->callchain;
351 if (unlikely(!trace))
354 nr_kernel = count_kernel_ip(trace);
357 __u64 nr = trace->nr;
359 trace->nr = nr_kernel;
360 ret = __bpf_get_stackid(map, trace, flags);
365 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
368 if (skip > BPF_F_SKIP_FIELD_MASK)
371 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
372 ret = __bpf_get_stackid(map, trace, flags);
377 const struct bpf_func_proto bpf_get_stackid_proto_pe = {
378 .func = bpf_get_stackid_pe,
380 .ret_type = RET_INTEGER,
381 .arg1_type = ARG_PTR_TO_CTX,
382 .arg2_type = ARG_CONST_MAP_PTR,
383 .arg3_type = ARG_ANYTHING,
386 static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
387 struct perf_callchain_entry *trace_in,
388 void *buf, u32 size, u64 flags)
390 u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
391 bool user_build_id = flags & BPF_F_USER_BUILD_ID;
392 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
393 bool user = flags & BPF_F_USER_STACK;
394 struct perf_callchain_entry *trace;
399 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
400 BPF_F_USER_BUILD_ID)))
402 if (kernel && user_build_id)
405 elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
407 if (unlikely(size % elem_size))
410 /* cannot get valid user stack for task without user_mode regs */
411 if (task && user && !user_mode(regs))
414 num_elem = size / elem_size;
415 if (sysctl_perf_event_max_stack < num_elem)
418 init_nr = sysctl_perf_event_max_stack - num_elem;
422 else if (kernel && task)
423 trace = get_callchain_entry_for_task(task, init_nr);
425 trace = get_perf_callchain(regs, init_nr, kernel, user,
426 sysctl_perf_event_max_stack,
428 if (unlikely(!trace))
431 trace_nr = trace->nr - init_nr;
436 trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
437 copy_len = trace_nr * elem_size;
438 ips = trace->ip + skip + init_nr;
439 if (user && user_build_id)
440 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
442 memcpy(buf, ips, copy_len);
445 memset(buf + copy_len, 0, size - copy_len);
451 memset(buf, 0, size);
455 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
458 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
461 const struct bpf_func_proto bpf_get_stack_proto = {
462 .func = bpf_get_stack,
464 .ret_type = RET_INTEGER,
465 .arg1_type = ARG_PTR_TO_CTX,
466 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
467 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
468 .arg4_type = ARG_ANYTHING,
471 BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
472 u32, size, u64, flags)
474 struct pt_regs *regs;
477 if (!try_get_task_stack(task))
480 regs = task_pt_regs(task);
482 res = __bpf_get_stack(regs, task, NULL, buf, size, flags);
483 put_task_stack(task);
488 const struct bpf_func_proto bpf_get_task_stack_proto = {
489 .func = bpf_get_task_stack,
491 .ret_type = RET_INTEGER,
492 .arg1_type = ARG_PTR_TO_BTF_ID,
493 .arg1_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
494 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
495 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
496 .arg4_type = ARG_ANYTHING,
499 BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
500 void *, buf, u32, size, u64, flags)
502 struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
503 struct perf_event *event = ctx->event;
504 struct perf_callchain_entry *trace;
509 if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
510 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
512 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
513 BPF_F_USER_BUILD_ID)))
516 user = flags & BPF_F_USER_STACK;
520 trace = ctx->data->callchain;
521 if (unlikely(!trace))
524 nr_kernel = count_kernel_ip(trace);
527 __u64 nr = trace->nr;
529 trace->nr = nr_kernel;
530 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
535 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
538 if (skip > BPF_F_SKIP_FIELD_MASK)
541 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
542 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
547 memset(buf, 0, size);
552 const struct bpf_func_proto bpf_get_stack_proto_pe = {
553 .func = bpf_get_stack_pe,
555 .ret_type = RET_INTEGER,
556 .arg1_type = ARG_PTR_TO_CTX,
557 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
558 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
559 .arg4_type = ARG_ANYTHING,
562 /* Called from eBPF program */
563 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
565 return ERR_PTR(-EOPNOTSUPP);
568 /* Called from syscall */
569 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
571 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
572 struct stack_map_bucket *bucket, *old_bucket;
573 u32 id = *(u32 *)key, trace_len;
575 if (unlikely(id >= smap->n_buckets))
578 bucket = xchg(&smap->buckets[id], NULL);
582 trace_len = bucket->nr * stack_map_data_size(map);
583 memcpy(value, bucket->data, trace_len);
584 memset(value + trace_len, 0, map->value_size - trace_len);
586 old_bucket = xchg(&smap->buckets[id], bucket);
588 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
592 static int stack_map_get_next_key(struct bpf_map *map, void *key,
595 struct bpf_stack_map *smap = container_of(map,
596 struct bpf_stack_map, map);
599 WARN_ON_ONCE(!rcu_read_lock_held());
605 if (id >= smap->n_buckets || !smap->buckets[id])
611 while (id < smap->n_buckets && !smap->buckets[id])
614 if (id >= smap->n_buckets)
617 *(u32 *)next_key = id;
621 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
627 /* Called from syscall or from eBPF program */
628 static int stack_map_delete_elem(struct bpf_map *map, void *key)
630 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
631 struct stack_map_bucket *old_bucket;
632 u32 id = *(u32 *)key;
634 if (unlikely(id >= smap->n_buckets))
637 old_bucket = xchg(&smap->buckets[id], NULL);
639 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
646 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
647 static void stack_map_free(struct bpf_map *map)
649 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
651 bpf_map_area_free(smap->elems);
652 pcpu_freelist_destroy(&smap->freelist);
653 bpf_map_area_free(smap);
654 put_callchain_buffers();
657 static int stack_trace_map_btf_id;
658 const struct bpf_map_ops stack_trace_map_ops = {
659 .map_meta_equal = bpf_map_meta_equal,
660 .map_alloc = stack_map_alloc,
661 .map_free = stack_map_free,
662 .map_get_next_key = stack_map_get_next_key,
663 .map_lookup_elem = stack_map_lookup_elem,
664 .map_update_elem = stack_map_update_elem,
665 .map_delete_elem = stack_map_delete_elem,
666 .map_check_btf = map_check_no_btf,
667 .map_btf_name = "bpf_stack_map",
668 .map_btf_id = &stack_trace_map_btf_id,