locking/lockdep: Remove unused @nested argument from lock_release()
[sfrench/cifs-2.6.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         struct bpf_map_memory mem;
90         u64 cost, n_buckets;
91         int err;
92
93         if (!capable(CAP_SYS_ADMIN))
94                 return ERR_PTR(-EPERM);
95
96         if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
97                 return ERR_PTR(-EINVAL);
98
99         /* check sanity of attributes */
100         if (attr->max_entries == 0 || attr->key_size != 4 ||
101             value_size < 8 || value_size % 8)
102                 return ERR_PTR(-EINVAL);
103
104         BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
105         if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
106                 if (value_size % sizeof(struct bpf_stack_build_id) ||
107                     value_size / sizeof(struct bpf_stack_build_id)
108                     > sysctl_perf_event_max_stack)
109                         return ERR_PTR(-EINVAL);
110         } else if (value_size / 8 > sysctl_perf_event_max_stack)
111                 return ERR_PTR(-EINVAL);
112
113         /* hash table size must be power of 2 */
114         n_buckets = roundup_pow_of_two(attr->max_entries);
115
116         cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
117         cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
118         err = bpf_map_charge_init(&mem, cost);
119         if (err)
120                 return ERR_PTR(err);
121
122         smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
123         if (!smap) {
124                 bpf_map_charge_finish(&mem);
125                 return ERR_PTR(-ENOMEM);
126         }
127
128         bpf_map_init_from_attr(&smap->map, attr);
129         smap->map.value_size = value_size;
130         smap->n_buckets = n_buckets;
131
132         err = get_callchain_buffers(sysctl_perf_event_max_stack);
133         if (err)
134                 goto free_charge;
135
136         err = prealloc_elems_and_freelist(smap);
137         if (err)
138                 goto put_buffers;
139
140         bpf_map_charge_move(&smap->map.memory, &mem);
141
142         return &smap->map;
143
144 put_buffers:
145         put_callchain_buffers();
146 free_charge:
147         bpf_map_charge_finish(&mem);
148         bpf_map_area_free(smap);
149         return ERR_PTR(err);
150 }
151
152 #define BPF_BUILD_ID 3
153 /*
154  * Parse build id from the note segment. This logic can be shared between
155  * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
156  * identical.
157  */
158 static inline int stack_map_parse_build_id(void *page_addr,
159                                            unsigned char *build_id,
160                                            void *note_start,
161                                            Elf32_Word note_size)
162 {
163         Elf32_Word note_offs = 0, new_offs;
164
165         /* check for overflow */
166         if (note_start < page_addr || note_start + note_size < note_start)
167                 return -EINVAL;
168
169         /* only supports note that fits in the first page */
170         if (note_start + note_size > page_addr + PAGE_SIZE)
171                 return -EINVAL;
172
173         while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
174                 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
175
176                 if (nhdr->n_type == BPF_BUILD_ID &&
177                     nhdr->n_namesz == sizeof("GNU") &&
178                     nhdr->n_descsz > 0 &&
179                     nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
180                         memcpy(build_id,
181                                note_start + note_offs +
182                                ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
183                                nhdr->n_descsz);
184                         memset(build_id + nhdr->n_descsz, 0,
185                                BPF_BUILD_ID_SIZE - nhdr->n_descsz);
186                         return 0;
187                 }
188                 new_offs = note_offs + sizeof(Elf32_Nhdr) +
189                         ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
190                 if (new_offs <= note_offs)  /* overflow */
191                         break;
192                 note_offs = new_offs;
193         }
194         return -EINVAL;
195 }
196
197 /* Parse build ID from 32-bit ELF */
198 static int stack_map_get_build_id_32(void *page_addr,
199                                      unsigned char *build_id)
200 {
201         Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
202         Elf32_Phdr *phdr;
203         int i;
204
205         /* only supports phdr that fits in one page */
206         if (ehdr->e_phnum >
207             (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
208                 return -EINVAL;
209
210         phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
211
212         for (i = 0; i < ehdr->e_phnum; ++i)
213                 if (phdr[i].p_type == PT_NOTE)
214                         return stack_map_parse_build_id(page_addr, build_id,
215                                         page_addr + phdr[i].p_offset,
216                                         phdr[i].p_filesz);
217         return -EINVAL;
218 }
219
220 /* Parse build ID from 64-bit ELF */
221 static int stack_map_get_build_id_64(void *page_addr,
222                                      unsigned char *build_id)
223 {
224         Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
225         Elf64_Phdr *phdr;
226         int i;
227
228         /* only supports phdr that fits in one page */
229         if (ehdr->e_phnum >
230             (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
231                 return -EINVAL;
232
233         phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
234
235         for (i = 0; i < ehdr->e_phnum; ++i)
236                 if (phdr[i].p_type == PT_NOTE)
237                         return stack_map_parse_build_id(page_addr, build_id,
238                                         page_addr + phdr[i].p_offset,
239                                         phdr[i].p_filesz);
240         return -EINVAL;
241 }
242
243 /* Parse build ID of ELF file mapped to vma */
244 static int stack_map_get_build_id(struct vm_area_struct *vma,
245                                   unsigned char *build_id)
246 {
247         Elf32_Ehdr *ehdr;
248         struct page *page;
249         void *page_addr;
250         int ret;
251
252         /* only works for page backed storage  */
253         if (!vma->vm_file)
254                 return -EINVAL;
255
256         page = find_get_page(vma->vm_file->f_mapping, 0);
257         if (!page)
258                 return -EFAULT; /* page not mapped */
259
260         ret = -EINVAL;
261         page_addr = kmap_atomic(page);
262         ehdr = (Elf32_Ehdr *)page_addr;
263
264         /* compare magic x7f "ELF" */
265         if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
266                 goto out;
267
268         /* only support executable file and shared object file */
269         if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
270                 goto out;
271
272         if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
273                 ret = stack_map_get_build_id_32(page_addr, build_id);
274         else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
275                 ret = stack_map_get_build_id_64(page_addr, build_id);
276 out:
277         kunmap_atomic(page_addr);
278         put_page(page);
279         return ret;
280 }
281
282 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
283                                           u64 *ips, u32 trace_nr, bool user)
284 {
285         int i;
286         struct vm_area_struct *vma;
287         bool irq_work_busy = false;
288         struct stack_map_irq_work *work = NULL;
289
290         if (in_nmi()) {
291                 work = this_cpu_ptr(&up_read_work);
292                 if (work->irq_work.flags & IRQ_WORK_BUSY)
293                         /* cannot queue more up_read, fallback */
294                         irq_work_busy = true;
295         }
296
297         /*
298          * We cannot do up_read() in nmi context. To do build_id lookup
299          * in nmi context, we need to run up_read() in irq_work. We use
300          * a percpu variable to do the irq_work. If the irq_work is
301          * already used by another lookup, we fall back to report ips.
302          *
303          * Same fallback is used for kernel stack (!user) on a stackmap
304          * with build_id.
305          */
306         if (!user || !current || !current->mm || irq_work_busy ||
307             down_read_trylock(&current->mm->mmap_sem) == 0) {
308                 /* cannot access current->mm, fall back to ips */
309                 for (i = 0; i < trace_nr; i++) {
310                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
311                         id_offs[i].ip = ips[i];
312                         memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
313                 }
314                 return;
315         }
316
317         for (i = 0; i < trace_nr; i++) {
318                 vma = find_vma(current->mm, ips[i]);
319                 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
320                         /* per entry fall back to ips */
321                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
322                         id_offs[i].ip = ips[i];
323                         memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
324                         continue;
325                 }
326                 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
327                         - vma->vm_start;
328                 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
329         }
330
331         if (!work) {
332                 up_read(&current->mm->mmap_sem);
333         } else {
334                 work->sem = &current->mm->mmap_sem;
335                 irq_work_queue(&work->irq_work);
336                 /*
337                  * The irq_work will release the mmap_sem with
338                  * up_read_non_owner(). The rwsem_release() is called
339                  * here to release the lock from lockdep's perspective.
340                  */
341                 rwsem_release(&current->mm->mmap_sem.dep_map, _RET_IP_);
342         }
343 }
344
345 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
346            u64, flags)
347 {
348         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
349         struct perf_callchain_entry *trace;
350         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
351         u32 max_depth = map->value_size / stack_map_data_size(map);
352         /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
353         u32 init_nr = sysctl_perf_event_max_stack - max_depth;
354         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
355         u32 hash, id, trace_nr, trace_len;
356         bool user = flags & BPF_F_USER_STACK;
357         bool kernel = !user;
358         u64 *ips;
359         bool hash_matches;
360
361         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
362                                BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
363                 return -EINVAL;
364
365         trace = get_perf_callchain(regs, init_nr, kernel, user,
366                                    sysctl_perf_event_max_stack, false, false);
367
368         if (unlikely(!trace))
369                 /* couldn't fetch the stack trace */
370                 return -EFAULT;
371
372         /* get_perf_callchain() guarantees that trace->nr >= init_nr
373          * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
374          */
375         trace_nr = trace->nr - init_nr;
376
377         if (trace_nr <= skip)
378                 /* skipping more than usable stack trace */
379                 return -EFAULT;
380
381         trace_nr -= skip;
382         trace_len = trace_nr * sizeof(u64);
383         ips = trace->ip + skip + init_nr;
384         hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
385         id = hash & (smap->n_buckets - 1);
386         bucket = READ_ONCE(smap->buckets[id]);
387
388         hash_matches = bucket && bucket->hash == hash;
389         /* fast cmp */
390         if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
391                 return id;
392
393         if (stack_map_use_build_id(map)) {
394                 /* for build_id+offset, pop a bucket before slow cmp */
395                 new_bucket = (struct stack_map_bucket *)
396                         pcpu_freelist_pop(&smap->freelist);
397                 if (unlikely(!new_bucket))
398                         return -ENOMEM;
399                 new_bucket->nr = trace_nr;
400                 stack_map_get_build_id_offset(
401                         (struct bpf_stack_build_id *)new_bucket->data,
402                         ips, trace_nr, user);
403                 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
404                 if (hash_matches && bucket->nr == trace_nr &&
405                     memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
406                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
407                         return id;
408                 }
409                 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
410                         pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
411                         return -EEXIST;
412                 }
413         } else {
414                 if (hash_matches && bucket->nr == trace_nr &&
415                     memcmp(bucket->data, ips, trace_len) == 0)
416                         return id;
417                 if (bucket && !(flags & BPF_F_REUSE_STACKID))
418                         return -EEXIST;
419
420                 new_bucket = (struct stack_map_bucket *)
421                         pcpu_freelist_pop(&smap->freelist);
422                 if (unlikely(!new_bucket))
423                         return -ENOMEM;
424                 memcpy(new_bucket->data, ips, trace_len);
425         }
426
427         new_bucket->hash = hash;
428         new_bucket->nr = trace_nr;
429
430         old_bucket = xchg(&smap->buckets[id], new_bucket);
431         if (old_bucket)
432                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
433         return id;
434 }
435
436 const struct bpf_func_proto bpf_get_stackid_proto = {
437         .func           = bpf_get_stackid,
438         .gpl_only       = true,
439         .ret_type       = RET_INTEGER,
440         .arg1_type      = ARG_PTR_TO_CTX,
441         .arg2_type      = ARG_CONST_MAP_PTR,
442         .arg3_type      = ARG_ANYTHING,
443 };
444
445 BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
446            u64, flags)
447 {
448         u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
449         bool user_build_id = flags & BPF_F_USER_BUILD_ID;
450         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
451         bool user = flags & BPF_F_USER_STACK;
452         struct perf_callchain_entry *trace;
453         bool kernel = !user;
454         int err = -EINVAL;
455         u64 *ips;
456
457         if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
458                                BPF_F_USER_BUILD_ID)))
459                 goto clear;
460         if (kernel && user_build_id)
461                 goto clear;
462
463         elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
464                                             : sizeof(u64);
465         if (unlikely(size % elem_size))
466                 goto clear;
467
468         num_elem = size / elem_size;
469         if (sysctl_perf_event_max_stack < num_elem)
470                 init_nr = 0;
471         else
472                 init_nr = sysctl_perf_event_max_stack - num_elem;
473         trace = get_perf_callchain(regs, init_nr, kernel, user,
474                                    sysctl_perf_event_max_stack, false, false);
475         if (unlikely(!trace))
476                 goto err_fault;
477
478         trace_nr = trace->nr - init_nr;
479         if (trace_nr < skip)
480                 goto err_fault;
481
482         trace_nr -= skip;
483         trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
484         copy_len = trace_nr * elem_size;
485         ips = trace->ip + skip + init_nr;
486         if (user && user_build_id)
487                 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
488         else
489                 memcpy(buf, ips, copy_len);
490
491         if (size > copy_len)
492                 memset(buf + copy_len, 0, size - copy_len);
493         return copy_len;
494
495 err_fault:
496         err = -EFAULT;
497 clear:
498         memset(buf, 0, size);
499         return err;
500 }
501
502 const struct bpf_func_proto bpf_get_stack_proto = {
503         .func           = bpf_get_stack,
504         .gpl_only       = true,
505         .ret_type       = RET_INTEGER,
506         .arg1_type      = ARG_PTR_TO_CTX,
507         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
508         .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
509         .arg4_type      = ARG_ANYTHING,
510 };
511
512 /* Called from eBPF program */
513 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
514 {
515         return ERR_PTR(-EOPNOTSUPP);
516 }
517
518 /* Called from syscall */
519 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
520 {
521         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
522         struct stack_map_bucket *bucket, *old_bucket;
523         u32 id = *(u32 *)key, trace_len;
524
525         if (unlikely(id >= smap->n_buckets))
526                 return -ENOENT;
527
528         bucket = xchg(&smap->buckets[id], NULL);
529         if (!bucket)
530                 return -ENOENT;
531
532         trace_len = bucket->nr * stack_map_data_size(map);
533         memcpy(value, bucket->data, trace_len);
534         memset(value + trace_len, 0, map->value_size - trace_len);
535
536         old_bucket = xchg(&smap->buckets[id], bucket);
537         if (old_bucket)
538                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
539         return 0;
540 }
541
542 static int stack_map_get_next_key(struct bpf_map *map, void *key,
543                                   void *next_key)
544 {
545         struct bpf_stack_map *smap = container_of(map,
546                                                   struct bpf_stack_map, map);
547         u32 id;
548
549         WARN_ON_ONCE(!rcu_read_lock_held());
550
551         if (!key) {
552                 id = 0;
553         } else {
554                 id = *(u32 *)key;
555                 if (id >= smap->n_buckets || !smap->buckets[id])
556                         id = 0;
557                 else
558                         id++;
559         }
560
561         while (id < smap->n_buckets && !smap->buckets[id])
562                 id++;
563
564         if (id >= smap->n_buckets)
565                 return -ENOENT;
566
567         *(u32 *)next_key = id;
568         return 0;
569 }
570
571 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
572                                  u64 map_flags)
573 {
574         return -EINVAL;
575 }
576
577 /* Called from syscall or from eBPF program */
578 static int stack_map_delete_elem(struct bpf_map *map, void *key)
579 {
580         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
581         struct stack_map_bucket *old_bucket;
582         u32 id = *(u32 *)key;
583
584         if (unlikely(id >= smap->n_buckets))
585                 return -E2BIG;
586
587         old_bucket = xchg(&smap->buckets[id], NULL);
588         if (old_bucket) {
589                 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
590                 return 0;
591         } else {
592                 return -ENOENT;
593         }
594 }
595
596 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
597 static void stack_map_free(struct bpf_map *map)
598 {
599         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
600
601         /* wait for bpf programs to complete before freeing stack map */
602         synchronize_rcu();
603
604         bpf_map_area_free(smap->elems);
605         pcpu_freelist_destroy(&smap->freelist);
606         bpf_map_area_free(smap);
607         put_callchain_buffers();
608 }
609
610 const struct bpf_map_ops stack_trace_map_ops = {
611         .map_alloc = stack_map_alloc,
612         .map_free = stack_map_free,
613         .map_get_next_key = stack_map_get_next_key,
614         .map_lookup_elem = stack_map_lookup_elem,
615         .map_update_elem = stack_map_update_elem,
616         .map_delete_elem = stack_map_delete_elem,
617         .map_check_btf = map_check_no_btf,
618 };
619
620 static int __init stack_map_init(void)
621 {
622         int cpu;
623         struct stack_map_irq_work *work;
624
625         for_each_possible_cpu(cpu) {
626                 work = per_cpu_ptr(&up_read_work, cpu);
627                 init_irq_work(&work->irq_work, do_up_read);
628         }
629         return 0;
630 }
631 subsys_initcall(stack_map_init);