treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206
[muen/linux.git] / kernel / bpf / stackmap.c
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/stacktrace.h>
8 #include <linux/perf_event.h>
9 #include <linux/elf.h>
10 #include <linux/pagemap.h>
11 #include <linux/irq_work.h>
12 #include "percpu_freelist.h"
13
14 #define STACK_CREATE_FLAG_MASK                                  \
15         (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY |        \
16          BPF_F_STACK_BUILD_ID)
17
18 struct stack_map_bucket {
19         struct pcpu_freelist_node fnode;
20         u32 hash;
21         u32 nr;
22         u64 data[];
23 };
24
25 struct bpf_stack_map {
26         struct bpf_map map;
27         void *elems;
28         struct pcpu_freelist freelist;
29         u32 n_buckets;
30         struct stack_map_bucket *buckets[];
31 };
32
33 /* irq_work to run up_read() for build_id lookup in nmi context */
34 struct stack_map_irq_work {
35         struct irq_work irq_work;
36         struct rw_semaphore *sem;
37 };
38
39 static void do_up_read(struct irq_work *entry)
40 {
41         struct stack_map_irq_work *work;
42
43         work = container_of(entry, struct stack_map_irq_work, irq_work);
44         up_read_non_owner(work->sem);
45         work->sem = NULL;
46 }
47
48 static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
49
50 static inline bool stack_map_use_build_id(struct bpf_map *map)
51 {
52         return (map->map_flags & BPF_F_STACK_BUILD_ID);
53 }
54
55 static inline int stack_map_data_size(struct bpf_map *map)
56 {
57         return stack_map_use_build_id(map) ?
58                 sizeof(struct bpf_stack_build_id) : sizeof(u64);
59 }
60
61 static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
62 {
63         u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
64         int err;
65
66         smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
67                                          smap->map.numa_node);
68         if (!smap->elems)
69                 return -ENOMEM;
70
71         err = pcpu_freelist_init(&smap->freelist);
72         if (err)
73                 goto free_elems;
74
75         pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
76                                smap->map.max_entries);
77         return 0;
78
79 free_elems:
80         bpf_map_area_free(smap->elems);
81         return err;
82 }
83
84 /* Called from syscall */
85 static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
86 {
87         u32 value_size = attr->value_size;
88         struct bpf_stack_map *smap;
89         u64 cost, n_buckets;
90         int err;
91
92         if (!capable(CAP_SYS_ADMIN))
93                 return ERR_PTR(-EPERM);
94
95         if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
96                 return ERR_PTR(-EINVAL);
97
98         /* check sanity of attributes */
99         if (attr->max_entries == 0 || attr->key_size != 4 ||
100             value_size < 8 || value_size % 8)
101                 return ERR_PTR(-EINVAL);
102
103         BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
104         if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
105                 if (value_size % sizeof(struct bpf_stack_build_id) ||
106                     value_size / sizeof(struct bpf_stack_build_id)
107                     > sysctl_perf_event_max_stack)
108                         return ERR_PTR(-EINVAL);
109         } else if (value_size / 8 > sysctl_perf_event_max_stack)
110                 return ERR_PTR(-EINVAL);
111
112         /* hash table size must be power of 2 */
113         n_buckets = roundup_pow_of_two(attr->max_entries);
114
115         cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
116         if (cost >= U32_MAX - PAGE_SIZE)
117                 return ERR_PTR(-E2BIG);
118
119         smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
120         if (!smap)
121                 return ERR_PTR(-ENOMEM);
122
123         err = -E2BIG;
124         cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
125         if (cost >= U32_MAX - PAGE_SIZE)
126                 goto free_smap;
127
128         bpf_map_init_from_attr(&smap->map, attr);
129         smap->map.value_size = value_size;
130         smap->n_buckets = n_buckets;
131         smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
132
133         err = bpf_map_precharge_memlock(smap->map.pages);
134         if (err)
135                 goto free_smap;
136
137         err = get_callchain_buffers(sysctl_perf_event_max_stack);
138         if (err)
139                 goto free_smap;
140
141         err = prealloc_elems_and_freelist(smap);
142         if (err)
143                 goto put_buffers;
144
145         return &smap->map;
146
147 put_buffers:
148         put_callchain_buffers();
149 free_smap:
150         bpf_map_area_free(smap);
151         return ERR_PTR(err);
152 }
153
154 #define BPF_BUILD_ID 3
155 /*
156  * Parse build id from the note segment. This logic can be shared between
157  * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
158  * identical.
159  */
160 static inline int stack_map_parse_build_id(void *page_addr,
161                                            unsigned char *build_id,
162                                            void *note_start,
163                                            Elf32_Word note_size)
164 {
165         Elf32_Word note_offs = 0, new_offs;
166
167         /* check for overflow */
168         if (note_start < page_addr || note_start + note_size < note_start)
169                 return -EINVAL;
170
171         /* only supports note that fits in the first page */
172         if (note_start + note_size > page_addr + PAGE_SIZE)
173                 return -EINVAL;
174
175         while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
176                 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
177
178                 if (nhdr->n_type == BPF_BUILD_ID &&
179                     nhdr->n_namesz == sizeof("GNU") &&
180                     nhdr->n_descsz > 0 &&
181                     nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
182                         memcpy(build_id,
183                                note_start + note_offs +
184                                ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
185                                nhdr->n_descsz);
186                         memset(build_id + nhdr->n_descsz, 0,
187                                BPF_BUILD_ID_SIZE - nhdr->n_descsz);
188                         return 0;
189                 }
190                 new_offs = note_offs + sizeof(Elf32_Nhdr) +
191                         ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
192                 if (new_offs <= note_offs)  /* overflow */
193                         break;
194                 note_offs = new_offs;
195         }
196         return -EINVAL;
197 }
198
199 /* Parse build ID from 32-bit ELF */
200 static int stack_map_get_build_id_32(void *page_addr,
201                                      unsigned char *build_id)
202 {
203         Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
204         Elf32_Phdr *phdr;
205         int i;
206
207         /* only supports phdr that fits in one page */
208         if (ehdr->e_phnum >
209             (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
210                 return -EINVAL;
211
212         phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
213
214         for (i = 0; i < ehdr->e_phnum; ++i)
215                 if (phdr[i].p_type == PT_NOTE)
216                         return stack_map_parse_build_id(page_addr, build_id,
217                                         page_addr + phdr[i].p_offset,
218                                         phdr[i].p_filesz);
219         return -EINVAL;
220 }
221
222 /* Parse build ID from 64-bit ELF */
223 static int stack_map_get_build_id_64(void *page_addr,
224                                      unsigned char *build_id)
225 {
226         Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
227         Elf64_Phdr *phdr;
228         int i;
229
230         /* only supports phdr that fits in one page */
231         if (ehdr->e_phnum >
232             (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
233                 return -EINVAL;
234
235         phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
236
237         for (i = 0; i < ehdr->e_phnum; ++i)
238                 if (phdr[i].p_type == PT_NOTE)
239                         return stack_map_parse_build_id(page_addr, build_id,
240                                         page_addr + phdr[i].p_offset,
241                                         phdr[i].p_filesz);
242         return -EINVAL;
243 }
244
245 /* Parse build ID of ELF file mapped to vma */
246 static int stack_map_get_build_id(struct vm_area_struct *vma,
247                                   unsigned char *build_id)
248 {
249         Elf32_Ehdr *ehdr;
250         struct page *page;
251         void *page_addr;
252         int ret;
253
254         /* only works for page backed storage  */
255         if (!vma->vm_file)
256                 return -EINVAL;
257
258         page = find_get_page(vma->vm_file->f_mapping, 0);
259         if (!page)
260                 return -EFAULT; /* page not mapped */
261
262         ret = -EINVAL;
263         page_addr = kmap_atomic(page);
264         ehdr = (Elf32_Ehdr *)page_addr;
265
266         /* compare magic x7f "ELF" */
267         if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
268                 goto out;
269
270         /* only support executable file and shared object file */
271         if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
272                 goto out;
273
274         if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
275                 ret = stack_map_get_build_id_32(page_addr, build_id);
276         else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
277                 ret = stack_map_get_build_id_64(page_addr, build_id);
278 out:
279         kunmap_atomic(page_addr);
280         put_page(page);
281         return ret;
282 }
283
284 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
285                                           u64 *ips, u32 trace_nr, bool user)
286 {
287         int i;
288         struct vm_area_struct *vma;
289         bool irq_work_busy = false;
290         struct stack_map_irq_work *work = NULL;
291
292         if (in_nmi()) {
293                 work = this_cpu_ptr(&up_read_work);
294                 if (work->irq_work.flags & IRQ_WORK_BUSY)
295                         /* cannot queue more up_read, fallback */
296                         irq_work_busy = true;
297         }
298
299         /*
300          * We cannot do up_read() in nmi context. To do build_id lookup
301          * in nmi context, we need to run up_read() in irq_work. We use
302          * a percpu variable to do the irq_work. If the irq_work is
303          * already used by another lookup, we fall back to report ips.
304          *
305          * Same fallback is used for kernel stack (!user) on a stackmap
306          * with build_id.
307          */
308         if (!user || !current || !current->mm || irq_work_busy ||
309             down_read_trylock(&current->mm->mmap_sem) == 0) {
310                 /* cannot access current->mm, fall back to ips */
311                 for (i = 0; i < trace_nr; i++) {
312                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
313                         id_offs[i].ip = ips[i];
314                         memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
315                 }
316                 return;
317         }
318
319         for (i = 0; i < trace_nr; i++) {
320                 vma = find_vma(current->mm, ips[i]);
321                 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
322                         /* per entry fall back to ips */
323                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
324                         id_offs[i].ip = ips[i];
325                         memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
326                         continue;
327                 }
328                 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
329                         - vma->vm_start;
330                 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
331         }
332
333         if (!work) {
334                 up_read(&current->mm->mmap_sem);
335         } else {
336                 work->sem = &current->mm->mmap_sem;
337                 irq_work_queue(&work->irq_work);
338                 /*
339                  * The irq_work will release the mmap_sem with
340                  * up_read_non_owner(). The rwsem_release() is called
341                  * here to release the lock from lockdep's perspective.
342                  */
343                 rwsem_release(&current->mm->mmap_sem.dep_map, 1, _RET_IP_);
344         }
345 }
346
347 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
348            u64, flags)
349 {
350         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
351         struct perf_callchain_entry *trace;
352         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
353         u32 max_depth = map->value_size / stack_map_data_size(map);
354         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
355         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
356         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
357         u32 hash, id, trace_nr, trace_len;
358         bool user = flags & BPF_F_USER_STACK;
359         bool kernel = !user;
360         u64 *ips;
361         bool hash_matches;
362
363         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
364                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
365                 return -EINVAL;
366
367         trace = get_perf_callchain(regs, init_nr, kernel, user,
368                                    sysctl_perf_event_max_stack, false, false);
369
370         if (unlikely(!trace))
371                 /* couldn't fetch the stack trace */
372                 return -EFAULT;
373
374         /* get_perf_callchain() guarantees that trace->nr >= init_nr
375          * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
376          */
377         trace_nr = trace->nr - init_nr;
378
379         if (trace_nr <= skip)
380                 /* skipping more than usable stack trace */
381                 return -EFAULT;
382
383         trace_nr -= skip;
384         trace_len = trace_nr * sizeof(u64);
385         ips = trace->ip + skip + init_nr;
386         hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
387         id = hash & (smap->n_buckets - 1);
388         bucket = READ_ONCE(smap->buckets[id]);
389
390         hash_matches = bucket && bucket->hash == hash;
391         /* fast cmp */
392         if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
393                 return id;
394
395         if (stack_map_use_build_id(map)) {
396                 /* for build_id+offset, pop a bucket before slow cmp */
397                 new_bucket = (struct stack_map_bucket *)
398                         pcpu_freelist_pop(&smap->freelist);
399                 if (unlikely(!new_bucket))
400                         return -ENOMEM;
401                 new_bucket->nr = trace_nr;
402                 stack_map_get_build_id_offset(
403                         (struct bpf_stack_build_id *)new_bucket->data,
404                         ips, trace_nr, user);
405                 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
406                 if (hash_matches && bucket->nr == trace_nr &&
407                     memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
408                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
409                         return id;
410                 }
411                 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
412                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
413                         return -EEXIST;
414                 }
415         } else {
416                 if (hash_matches && bucket->nr == trace_nr &&
417                     memcmp(bucket->data, ips, trace_len) == 0)
418                         return id;
419                 if (bucket && !(flags & BPF_F_REUSE_STACKID))
420                         return -EEXIST;
421
422                 new_bucket = (struct stack_map_bucket *)
423                         pcpu_freelist_pop(&smap->freelist);
424                 if (unlikely(!new_bucket))
425                         return -ENOMEM;
426                 memcpy(new_bucket->data, ips, trace_len);
427         }
428
429         new_bucket->hash = hash;
430         new_bucket->nr = trace_nr;
431
432         old_bucket = xchg(&smap->buckets[id], new_bucket);
433         if (old_bucket)
434                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
435         return id;
436 }
437
438 const struct bpf_func_proto bpf_get_stackid_proto = {
439         .func           = bpf_get_stackid,
440         .gpl_only       = true,
441         .ret_type       = RET_INTEGER,
442         .arg1_type      = ARG_PTR_TO_CTX,
443         .arg2_type      = ARG_CONST_MAP_PTR,
444         .arg3_type      = ARG_ANYTHING,
445 };
446
447 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
448            u64, flags)
449 {
450         u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
451         bool user_build_id = flags & BPF_F_USER_BUILD_ID;
452         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
453         bool user = flags & BPF_F_USER_STACK;
454         struct perf_callchain_entry *trace;
455         bool kernel = !user;
456         int err = -EINVAL;
457         u64 *ips;
458
459         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
460                                BPF_F_USER_BUILD_ID)))
461                 goto clear;
462         if (kernel && user_build_id)
463                 goto clear;
464
465         elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
466                                             : sizeof(u64);
467         if (unlikely(size % elem_size))
468                 goto clear;
469
470         num_elem = size / elem_size;
471         if (sysctl_perf_event_max_stack < num_elem)
472                 init_nr = 0;
473         else
474                 init_nr = sysctl_perf_event_max_stack - num_elem;
475         trace = get_perf_callchain(regs, init_nr, kernel, user,
476                                    sysctl_perf_event_max_stack, false, false);
477         if (unlikely(!trace))
478                 goto err_fault;
479
480         trace_nr = trace->nr - init_nr;
481         if (trace_nr < skip)
482                 goto err_fault;
483
484         trace_nr -= skip;
485         trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
486         copy_len = trace_nr * elem_size;
487         ips = trace->ip + skip + init_nr;
488         if (user && user_build_id)
489                 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
490         else
491                 memcpy(buf, ips, copy_len);
492
493         if (size > copy_len)
494                 memset(buf + copy_len, 0, size - copy_len);
495         return copy_len;
496
497 err_fault:
498         err = -EFAULT;
499 clear:
500         memset(buf, 0, size);
501         return err;
502 }
503
504 const struct bpf_func_proto bpf_get_stack_proto = {
505         .func           = bpf_get_stack,
506         .gpl_only       = true,
507         .ret_type       = RET_INTEGER,
508         .arg1_type      = ARG_PTR_TO_CTX,
509         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
510         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
511         .arg4_type      = ARG_ANYTHING,
512 };
513
514 /* Called from eBPF program */
515 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
516 {
517         return ERR_PTR(-EOPNOTSUPP);
518 }
519
520 /* Called from syscall */
521 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
522 {
523         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
524         struct stack_map_bucket *bucket, *old_bucket;
525         u32 id = *(u32 *)key, trace_len;
526
527         if (unlikely(id >= smap->n_buckets))
528                 return -ENOENT;
529
530         bucket = xchg(&smap->buckets[id], NULL);
531         if (!bucket)
532                 return -ENOENT;
533
534         trace_len = bucket->nr * stack_map_data_size(map);
535         memcpy(value, bucket->data, trace_len);
536         memset(value + trace_len, 0, map->value_size - trace_len);
537
538         old_bucket = xchg(&smap->buckets[id], bucket);
539         if (old_bucket)
540                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
541         return 0;
542 }
543
544 static int stack_map_get_next_key(struct bpf_map *map, void *key,
545                                   void *next_key)
546 {
547         struct bpf_stack_map *smap = container_of(map,
548                                                   struct bpf_stack_map, map);
549         u32 id;
550
551         WARN_ON_ONCE(!rcu_read_lock_held());
552
553         if (!key) {
554                 id = 0;
555         } else {
556                 id = *(u32 *)key;
557                 if (id >= smap->n_buckets || !smap->buckets[id])
558                         id = 0;
559                 else
560                         id++;
561         }
562
563         while (id < smap->n_buckets && !smap->buckets[id])
564                 id++;
565
566         if (id >= smap->n_buckets)
567                 return -ENOENT;
568
569         *(u32 *)next_key = id;
570         return 0;
571 }
572
573 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
574                                  u64 map_flags)
575 {
576         return -EINVAL;
577 }
578
579 /* Called from syscall or from eBPF program */
580 static int stack_map_delete_elem(struct bpf_map *map, void *key)
581 {
582         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
583         struct stack_map_bucket *old_bucket;
584         u32 id = *(u32 *)key;
585
586         if (unlikely(id >= smap->n_buckets))
587                 return -E2BIG;
588
589         old_bucket = xchg(&smap->buckets[id], NULL);
590         if (old_bucket) {
591                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
592                 return 0;
593         } else {
594                 return -ENOENT;
595         }
596 }
597
598 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
599 static void stack_map_free(struct bpf_map *map)
600 {
601         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
602
603         /* wait for bpf programs to complete before freeing stack map */
604         synchronize_rcu();
605
606         bpf_map_area_free(smap->elems);
607         pcpu_freelist_destroy(&smap->freelist);
608         bpf_map_area_free(smap);
609         put_callchain_buffers();
610 }
611
612 const struct bpf_map_ops stack_trace_map_ops = {
613         .map_alloc = stack_map_alloc,
614         .map_free = stack_map_free,
615         .map_get_next_key = stack_map_get_next_key,
616         .map_lookup_elem = stack_map_lookup_elem,
617         .map_update_elem = stack_map_update_elem,
618         .map_delete_elem = stack_map_delete_elem,
619         .map_check_btf = map_check_no_btf,
620 };
621
622 static int __init stack_map_init(void)
623 {
624         int cpu;
625         struct stack_map_irq_work *work;
626
627         for_each_possible_cpu(cpu) {
628                 work = per_cpu_ptr(&up_read_work, cpu);
629                 init_irq_work(&work->irq_work, do_up_read);
630         }
631         return 0;
632 }
633 subsys_initcall(stack_map_init);