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1/* Copyright (c) 2016 Facebook
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 */
7#include <linux/bpf.h>
8#include <linux/jhash.h>
9#include <linux/filter.h>
10#include <linux/vmalloc.h>
11#include <linux/stacktrace.h>
12#include <linux/perf_event.h>
13#include "percpu_freelist.h"
14
15struct stack_map_bucket {
16 struct pcpu_freelist_node fnode;
17 u32 hash;
18 u32 nr;
19 u64 ip[];
20};
21
22struct bpf_stack_map {
23 struct bpf_map map;
24 void *elems;
25 struct pcpu_freelist freelist;
26 u32 n_buckets;
27 struct stack_map_bucket *buckets[];
28};
29
30static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
31{
32 u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
33 int err;
34
35 smap->elems = vzalloc(elem_size * smap->map.max_entries);
36 if (!smap->elems)
37 return -ENOMEM;
38
39 err = pcpu_freelist_init(&smap->freelist);
40 if (err)
41 goto free_elems;
42
43 pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
44 smap->map.max_entries);
45 return 0;
46
47free_elems:
48 vfree(smap->elems);
49 return err;
50}
51
52/* Called from syscall */
53static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
54{
55 u32 value_size = attr->value_size;
56 struct bpf_stack_map *smap;
57 u64 cost, n_buckets;
58 int err;
59
60 if (!capable(CAP_SYS_ADMIN))
61 return ERR_PTR(-EPERM);
62
63 if (attr->map_flags)
64 return ERR_PTR(-EINVAL);
65
66 /* check sanity of attributes */
67 if (attr->max_entries == 0 || attr->key_size != 4 ||
68 value_size < 8 || value_size % 8 ||
69 value_size / 8 > PERF_MAX_STACK_DEPTH)
70 return ERR_PTR(-EINVAL);
71
72 /* hash table size must be power of 2 */
73 n_buckets = roundup_pow_of_two(attr->max_entries);
74
75 cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
76 if (cost >= U32_MAX - PAGE_SIZE)
77 return ERR_PTR(-E2BIG);
78
79 smap = kzalloc(cost, GFP_USER | __GFP_NOWARN);
80 if (!smap) {
81 smap = vzalloc(cost);
82 if (!smap)
83 return ERR_PTR(-ENOMEM);
84 }
85
86 err = -E2BIG;
87 cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
88 if (cost >= U32_MAX - PAGE_SIZE)
89 goto free_smap;
90
91 smap->map.map_type = attr->map_type;
92 smap->map.key_size = attr->key_size;
93 smap->map.value_size = value_size;
94 smap->map.max_entries = attr->max_entries;
95 smap->n_buckets = n_buckets;
96 smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
97
98 err = bpf_map_precharge_memlock(smap->map.pages);
99 if (err)
100 goto free_smap;
101
102 err = get_callchain_buffers();
103 if (err)
104 goto free_smap;
105
106 err = prealloc_elems_and_freelist(smap);
107 if (err)
108 goto put_buffers;
109
110 return &smap->map;
111
112put_buffers:
113 put_callchain_buffers();
114free_smap:
115 kvfree(smap);
116 return ERR_PTR(err);
117}
118
119static u64 bpf_get_stackid(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5)
120{
121 struct pt_regs *regs = (struct pt_regs *) (long) r1;
122 struct bpf_map *map = (struct bpf_map *) (long) r2;
123 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
124 struct perf_callchain_entry *trace;
125 struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
126 u32 max_depth = map->value_size / 8;
127 /* stack_map_alloc() checks that max_depth <= PERF_MAX_STACK_DEPTH */
128 u32 init_nr = PERF_MAX_STACK_DEPTH - max_depth;
129 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
130 u32 hash, id, trace_nr, trace_len;
131 bool user = flags & BPF_F_USER_STACK;
132 bool kernel = !user;
133 u64 *ips;
134
135 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
136 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
137 return -EINVAL;
138
139 trace = get_perf_callchain(regs, init_nr, kernel, user, false, false);
140
141 if (unlikely(!trace))
142 /* couldn't fetch the stack trace */
143 return -EFAULT;
144
145 /* get_perf_callchain() guarantees that trace->nr >= init_nr
146 * and trace-nr <= PERF_MAX_STACK_DEPTH, so trace_nr <= max_depth
147 */
148 trace_nr = trace->nr - init_nr;
149
150 if (trace_nr <= skip)
151 /* skipping more than usable stack trace */
152 return -EFAULT;
153
154 trace_nr -= skip;
155 trace_len = trace_nr * sizeof(u64);
156 ips = trace->ip + skip + init_nr;
157 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
158 id = hash & (smap->n_buckets - 1);
159 bucket = READ_ONCE(smap->buckets[id]);
160
161 if (bucket && bucket->hash == hash) {
162 if (flags & BPF_F_FAST_STACK_CMP)
163 return id;
164 if (bucket->nr == trace_nr &&
165 memcmp(bucket->ip, ips, trace_len) == 0)
166 return id;
167 }
168
169 /* this call stack is not in the map, try to add it */
170 if (bucket && !(flags & BPF_F_REUSE_STACKID))
171 return -EEXIST;
172
173 new_bucket = (struct stack_map_bucket *)
174 pcpu_freelist_pop(&smap->freelist);
175 if (unlikely(!new_bucket))
176 return -ENOMEM;
177
178 memcpy(new_bucket->ip, ips, trace_len);
179 new_bucket->hash = hash;
180 new_bucket->nr = trace_nr;
181
182 old_bucket = xchg(&smap->buckets[id], new_bucket);
183 if (old_bucket)
184 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
185 return id;
186}
187
188const struct bpf_func_proto bpf_get_stackid_proto = {
189 .func = bpf_get_stackid,
190 .gpl_only = true,
191 .ret_type = RET_INTEGER,
192 .arg1_type = ARG_PTR_TO_CTX,
193 .arg2_type = ARG_CONST_MAP_PTR,
194 .arg3_type = ARG_ANYTHING,
195};
196
197/* Called from eBPF program */
198static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
199{
200 return NULL;
201}
202
203/* Called from syscall */
204int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
205{
206 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
207 struct stack_map_bucket *bucket, *old_bucket;
208 u32 id = *(u32 *)key, trace_len;
209
210 if (unlikely(id >= smap->n_buckets))
211 return -ENOENT;
212
213 bucket = xchg(&smap->buckets[id], NULL);
214 if (!bucket)
215 return -ENOENT;
216
217 trace_len = bucket->nr * sizeof(u64);
218 memcpy(value, bucket->ip, trace_len);
219 memset(value + trace_len, 0, map->value_size - trace_len);
220
221 old_bucket = xchg(&smap->buckets[id], bucket);
222 if (old_bucket)
223 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
224 return 0;
225}
226
227static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
228{
229 return -EINVAL;
230}
231
232static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
233 u64 map_flags)
234{
235 return -EINVAL;
236}
237
238/* Called from syscall or from eBPF program */
239static int stack_map_delete_elem(struct bpf_map *map, void *key)
240{
241 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
242 struct stack_map_bucket *old_bucket;
243 u32 id = *(u32 *)key;
244
245 if (unlikely(id >= smap->n_buckets))
246 return -E2BIG;
247
248 old_bucket = xchg(&smap->buckets[id], NULL);
249 if (old_bucket) {
250 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
251 return 0;
252 } else {
253 return -ENOENT;
254 }
255}
256
257/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
258static void stack_map_free(struct bpf_map *map)
259{
260 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
261
262 /* wait for bpf programs to complete before freeing stack map */
263 synchronize_rcu();
264
265 vfree(smap->elems);
266 pcpu_freelist_destroy(&smap->freelist);
267 kvfree(smap);
268 put_callchain_buffers();
269}
270
271static const struct bpf_map_ops stack_map_ops = {
272 .map_alloc = stack_map_alloc,
273 .map_free = stack_map_free,
274 .map_get_next_key = stack_map_get_next_key,
275 .map_lookup_elem = stack_map_lookup_elem,
276 .map_update_elem = stack_map_update_elem,
277 .map_delete_elem = stack_map_delete_elem,
278};
279
280static struct bpf_map_type_list stack_map_type __read_mostly = {
281 .ops = &stack_map_ops,
282 .type = BPF_MAP_TYPE_STACK_TRACE,
283};
284
285static int __init register_stack_map(void)
286{
287 bpf_register_map_type(&stack_map_type);
288 return 0;
289}
290late_initcall(register_stack_map);
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
20struct stack_map_bucket {
21 struct pcpu_freelist_node fnode;
22 u32 hash;
23 u32 nr;
24 u64 data[];
25};
26
27struct 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 */
36struct stack_map_irq_work {
37 struct irq_work irq_work;
38 struct mm_struct *mm;
39};
40
41static 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
52static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work);
53
54static inline bool stack_map_use_build_id(struct bpf_map *map)
55{
56 return (map->map_flags & BPF_F_STACK_BUILD_ID);
57}
58
59static 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
65static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
66{
67 u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
68 int err;
69
70 smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
71 smap->map.numa_node);
72 if (!smap->elems)
73 return -ENOMEM;
74
75 err = pcpu_freelist_init(&smap->freelist);
76 if (err)
77 goto free_elems;
78
79 pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
80 smap->map.max_entries);
81 return 0;
82
83free_elems:
84 bpf_map_area_free(smap->elems);
85 return err;
86}
87
88/* Called from syscall */
89static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
90{
91 u32 value_size = attr->value_size;
92 struct bpf_stack_map *smap;
93 struct bpf_map_memory mem;
94 u64 cost, n_buckets;
95 int err;
96
97 if (!bpf_capable())
98 return ERR_PTR(-EPERM);
99
100 if (attr->map_flags & ~STACK_CREATE_FLAG_MASK)
101 return ERR_PTR(-EINVAL);
102
103 /* check sanity of attributes */
104 if (attr->max_entries == 0 || attr->key_size != 4 ||
105 value_size < 8 || value_size % 8)
106 return ERR_PTR(-EINVAL);
107
108 BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
109 if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
110 if (value_size % sizeof(struct bpf_stack_build_id) ||
111 value_size / sizeof(struct bpf_stack_build_id)
112 > sysctl_perf_event_max_stack)
113 return ERR_PTR(-EINVAL);
114 } else if (value_size / 8 > sysctl_perf_event_max_stack)
115 return ERR_PTR(-EINVAL);
116
117 /* hash table size must be power of 2 */
118 n_buckets = roundup_pow_of_two(attr->max_entries);
119
120 cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
121 cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
122 err = bpf_map_charge_init(&mem, cost);
123 if (err)
124 return ERR_PTR(err);
125
126 smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
127 if (!smap) {
128 bpf_map_charge_finish(&mem);
129 return ERR_PTR(-ENOMEM);
130 }
131
132 bpf_map_init_from_attr(&smap->map, attr);
133 smap->map.value_size = value_size;
134 smap->n_buckets = n_buckets;
135
136 err = get_callchain_buffers(sysctl_perf_event_max_stack);
137 if (err)
138 goto free_charge;
139
140 err = prealloc_elems_and_freelist(smap);
141 if (err)
142 goto put_buffers;
143
144 bpf_map_charge_move(&smap->map.memory, &mem);
145
146 return &smap->map;
147
148put_buffers:
149 put_callchain_buffers();
150free_charge:
151 bpf_map_charge_finish(&mem);
152 bpf_map_area_free(smap);
153 return ERR_PTR(err);
154}
155
156#define BPF_BUILD_ID 3
157/*
158 * Parse build id from the note segment. This logic can be shared between
159 * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
160 * identical.
161 */
162static inline int stack_map_parse_build_id(void *page_addr,
163 unsigned char *build_id,
164 void *note_start,
165 Elf32_Word note_size)
166{
167 Elf32_Word note_offs = 0, new_offs;
168
169 /* check for overflow */
170 if (note_start < page_addr || note_start + note_size < note_start)
171 return -EINVAL;
172
173 /* only supports note that fits in the first page */
174 if (note_start + note_size > page_addr + PAGE_SIZE)
175 return -EINVAL;
176
177 while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
178 Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
179
180 if (nhdr->n_type == BPF_BUILD_ID &&
181 nhdr->n_namesz == sizeof("GNU") &&
182 nhdr->n_descsz > 0 &&
183 nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
184 memcpy(build_id,
185 note_start + note_offs +
186 ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
187 nhdr->n_descsz);
188 memset(build_id + nhdr->n_descsz, 0,
189 BPF_BUILD_ID_SIZE - nhdr->n_descsz);
190 return 0;
191 }
192 new_offs = note_offs + sizeof(Elf32_Nhdr) +
193 ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
194 if (new_offs <= note_offs) /* overflow */
195 break;
196 note_offs = new_offs;
197 }
198 return -EINVAL;
199}
200
201/* Parse build ID from 32-bit ELF */
202static int stack_map_get_build_id_32(void *page_addr,
203 unsigned char *build_id)
204{
205 Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
206 Elf32_Phdr *phdr;
207 int i;
208
209 /* only supports phdr that fits in one page */
210 if (ehdr->e_phnum >
211 (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
212 return -EINVAL;
213
214 phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
215
216 for (i = 0; i < ehdr->e_phnum; ++i) {
217 if (phdr[i].p_type == PT_NOTE &&
218 !stack_map_parse_build_id(page_addr, build_id,
219 page_addr + phdr[i].p_offset,
220 phdr[i].p_filesz))
221 return 0;
222 }
223 return -EINVAL;
224}
225
226/* Parse build ID from 64-bit ELF */
227static int stack_map_get_build_id_64(void *page_addr,
228 unsigned char *build_id)
229{
230 Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
231 Elf64_Phdr *phdr;
232 int i;
233
234 /* only supports phdr that fits in one page */
235 if (ehdr->e_phnum >
236 (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
237 return -EINVAL;
238
239 phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
240
241 for (i = 0; i < ehdr->e_phnum; ++i) {
242 if (phdr[i].p_type == PT_NOTE &&
243 !stack_map_parse_build_id(page_addr, build_id,
244 page_addr + phdr[i].p_offset,
245 phdr[i].p_filesz))
246 return 0;
247 }
248 return -EINVAL;
249}
250
251/* Parse build ID of ELF file mapped to vma */
252static int stack_map_get_build_id(struct vm_area_struct *vma,
253 unsigned char *build_id)
254{
255 Elf32_Ehdr *ehdr;
256 struct page *page;
257 void *page_addr;
258 int ret;
259
260 /* only works for page backed storage */
261 if (!vma->vm_file)
262 return -EINVAL;
263
264 page = find_get_page(vma->vm_file->f_mapping, 0);
265 if (!page)
266 return -EFAULT; /* page not mapped */
267
268 ret = -EINVAL;
269 page_addr = kmap_atomic(page);
270 ehdr = (Elf32_Ehdr *)page_addr;
271
272 /* compare magic x7f "ELF" */
273 if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
274 goto out;
275
276 /* only support executable file and shared object file */
277 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
278 goto out;
279
280 if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
281 ret = stack_map_get_build_id_32(page_addr, build_id);
282 else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
283 ret = stack_map_get_build_id_64(page_addr, build_id);
284out:
285 kunmap_atomic(page_addr);
286 put_page(page);
287 return ret;
288}
289
290static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
291 u64 *ips, u32 trace_nr, bool user)
292{
293 int i;
294 struct vm_area_struct *vma;
295 bool irq_work_busy = false;
296 struct stack_map_irq_work *work = NULL;
297
298 if (irqs_disabled()) {
299 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
300 work = this_cpu_ptr(&up_read_work);
301 if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY) {
302 /* cannot queue more up_read, fallback */
303 irq_work_busy = true;
304 }
305 } else {
306 /*
307 * PREEMPT_RT does not allow to trylock mmap sem in
308 * interrupt disabled context. Force the fallback code.
309 */
310 irq_work_busy = true;
311 }
312 }
313
314 /*
315 * We cannot do up_read() when the irq is disabled, because of
316 * risk to deadlock with rq_lock. To do build_id lookup when the
317 * irqs are disabled, we need to run up_read() in irq_work. We use
318 * a percpu variable to do the irq_work. If the irq_work is
319 * already used by another lookup, we fall back to report ips.
320 *
321 * Same fallback is used for kernel stack (!user) on a stackmap
322 * with build_id.
323 */
324 if (!user || !current || !current->mm || irq_work_busy ||
325 !mmap_read_trylock_non_owner(current->mm)) {
326 /* cannot access current->mm, fall back to ips */
327 for (i = 0; i < trace_nr; i++) {
328 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
329 id_offs[i].ip = ips[i];
330 memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
331 }
332 return;
333 }
334
335 for (i = 0; i < trace_nr; i++) {
336 vma = find_vma(current->mm, ips[i]);
337 if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {
338 /* per entry fall back to ips */
339 id_offs[i].status = BPF_STACK_BUILD_ID_IP;
340 id_offs[i].ip = ips[i];
341 memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
342 continue;
343 }
344 id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
345 - vma->vm_start;
346 id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
347 }
348
349 if (!work) {
350 mmap_read_unlock_non_owner(current->mm);
351 } else {
352 work->mm = current->mm;
353 irq_work_queue(&work->irq_work);
354 }
355}
356
357static struct perf_callchain_entry *
358get_callchain_entry_for_task(struct task_struct *task, u32 init_nr)
359{
360#ifdef CONFIG_STACKTRACE
361 struct perf_callchain_entry *entry;
362 int rctx;
363
364 entry = get_callchain_entry(&rctx);
365
366 if (!entry)
367 return NULL;
368
369 entry->nr = init_nr +
370 stack_trace_save_tsk(task, (unsigned long *)(entry->ip + init_nr),
371 sysctl_perf_event_max_stack - init_nr, 0);
372
373 /* stack_trace_save_tsk() works on unsigned long array, while
374 * perf_callchain_entry uses u64 array. For 32-bit systems, it is
375 * necessary to fix this mismatch.
376 */
377 if (__BITS_PER_LONG != 64) {
378 unsigned long *from = (unsigned long *) entry->ip;
379 u64 *to = entry->ip;
380 int i;
381
382 /* copy data from the end to avoid using extra buffer */
383 for (i = entry->nr - 1; i >= (int)init_nr; i--)
384 to[i] = (u64)(from[i]);
385 }
386
387 put_callchain_entry(rctx);
388
389 return entry;
390#else /* CONFIG_STACKTRACE */
391 return NULL;
392#endif
393}
394
395static long __bpf_get_stackid(struct bpf_map *map,
396 struct perf_callchain_entry *trace, u64 flags)
397{
398 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
399 struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
400 u32 max_depth = map->value_size / stack_map_data_size(map);
401 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
402 u32 init_nr = sysctl_perf_event_max_stack - max_depth;
403 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
404 u32 hash, id, trace_nr, trace_len;
405 bool user = flags & BPF_F_USER_STACK;
406 u64 *ips;
407 bool hash_matches;
408
409 /* get_perf_callchain() guarantees that trace->nr >= init_nr
410 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
411 */
412 trace_nr = trace->nr - init_nr;
413
414 if (trace_nr <= skip)
415 /* skipping more than usable stack trace */
416 return -EFAULT;
417
418 trace_nr -= skip;
419 trace_len = trace_nr * sizeof(u64);
420 ips = trace->ip + skip + init_nr;
421 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
422 id = hash & (smap->n_buckets - 1);
423 bucket = READ_ONCE(smap->buckets[id]);
424
425 hash_matches = bucket && bucket->hash == hash;
426 /* fast cmp */
427 if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
428 return id;
429
430 if (stack_map_use_build_id(map)) {
431 /* for build_id+offset, pop a bucket before slow cmp */
432 new_bucket = (struct stack_map_bucket *)
433 pcpu_freelist_pop(&smap->freelist);
434 if (unlikely(!new_bucket))
435 return -ENOMEM;
436 new_bucket->nr = trace_nr;
437 stack_map_get_build_id_offset(
438 (struct bpf_stack_build_id *)new_bucket->data,
439 ips, trace_nr, user);
440 trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
441 if (hash_matches && bucket->nr == trace_nr &&
442 memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
443 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
444 return id;
445 }
446 if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
447 pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
448 return -EEXIST;
449 }
450 } else {
451 if (hash_matches && bucket->nr == trace_nr &&
452 memcmp(bucket->data, ips, trace_len) == 0)
453 return id;
454 if (bucket && !(flags & BPF_F_REUSE_STACKID))
455 return -EEXIST;
456
457 new_bucket = (struct stack_map_bucket *)
458 pcpu_freelist_pop(&smap->freelist);
459 if (unlikely(!new_bucket))
460 return -ENOMEM;
461 memcpy(new_bucket->data, ips, trace_len);
462 }
463
464 new_bucket->hash = hash;
465 new_bucket->nr = trace_nr;
466
467 old_bucket = xchg(&smap->buckets[id], new_bucket);
468 if (old_bucket)
469 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
470 return id;
471}
472
473BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
474 u64, flags)
475{
476 u32 max_depth = map->value_size / stack_map_data_size(map);
477 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
478 u32 init_nr = sysctl_perf_event_max_stack - max_depth;
479 bool user = flags & BPF_F_USER_STACK;
480 struct perf_callchain_entry *trace;
481 bool kernel = !user;
482
483 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
484 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
485 return -EINVAL;
486
487 trace = get_perf_callchain(regs, init_nr, kernel, user,
488 sysctl_perf_event_max_stack, false, false);
489
490 if (unlikely(!trace))
491 /* couldn't fetch the stack trace */
492 return -EFAULT;
493
494 return __bpf_get_stackid(map, trace, flags);
495}
496
497const struct bpf_func_proto bpf_get_stackid_proto = {
498 .func = bpf_get_stackid,
499 .gpl_only = true,
500 .ret_type = RET_INTEGER,
501 .arg1_type = ARG_PTR_TO_CTX,
502 .arg2_type = ARG_CONST_MAP_PTR,
503 .arg3_type = ARG_ANYTHING,
504};
505
506static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
507{
508 __u64 nr_kernel = 0;
509
510 while (nr_kernel < trace->nr) {
511 if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
512 break;
513 nr_kernel++;
514 }
515 return nr_kernel;
516}
517
518BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
519 struct bpf_map *, map, u64, flags)
520{
521 struct perf_event *event = ctx->event;
522 struct perf_callchain_entry *trace;
523 bool kernel, user;
524 __u64 nr_kernel;
525 int ret;
526
527 /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
528 if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
529 return bpf_get_stackid((unsigned long)(ctx->regs),
530 (unsigned long) map, flags, 0, 0);
531
532 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
533 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
534 return -EINVAL;
535
536 user = flags & BPF_F_USER_STACK;
537 kernel = !user;
538
539 trace = ctx->data->callchain;
540 if (unlikely(!trace))
541 return -EFAULT;
542
543 nr_kernel = count_kernel_ip(trace);
544
545 if (kernel) {
546 __u64 nr = trace->nr;
547
548 trace->nr = nr_kernel;
549 ret = __bpf_get_stackid(map, trace, flags);
550
551 /* restore nr */
552 trace->nr = nr;
553 } else { /* user */
554 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
555
556 skip += nr_kernel;
557 if (skip > BPF_F_SKIP_FIELD_MASK)
558 return -EFAULT;
559
560 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
561 ret = __bpf_get_stackid(map, trace, flags);
562 }
563 return ret;
564}
565
566const struct bpf_func_proto bpf_get_stackid_proto_pe = {
567 .func = bpf_get_stackid_pe,
568 .gpl_only = false,
569 .ret_type = RET_INTEGER,
570 .arg1_type = ARG_PTR_TO_CTX,
571 .arg2_type = ARG_CONST_MAP_PTR,
572 .arg3_type = ARG_ANYTHING,
573};
574
575static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
576 struct perf_callchain_entry *trace_in,
577 void *buf, u32 size, u64 flags)
578{
579 u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
580 bool user_build_id = flags & BPF_F_USER_BUILD_ID;
581 u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
582 bool user = flags & BPF_F_USER_STACK;
583 struct perf_callchain_entry *trace;
584 bool kernel = !user;
585 int err = -EINVAL;
586 u64 *ips;
587
588 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
589 BPF_F_USER_BUILD_ID)))
590 goto clear;
591 if (kernel && user_build_id)
592 goto clear;
593
594 elem_size = (user && user_build_id) ? sizeof(struct bpf_stack_build_id)
595 : sizeof(u64);
596 if (unlikely(size % elem_size))
597 goto clear;
598
599 /* cannot get valid user stack for task without user_mode regs */
600 if (task && user && !user_mode(regs))
601 goto err_fault;
602
603 num_elem = size / elem_size;
604 if (sysctl_perf_event_max_stack < num_elem)
605 init_nr = 0;
606 else
607 init_nr = sysctl_perf_event_max_stack - num_elem;
608
609 if (trace_in)
610 trace = trace_in;
611 else if (kernel && task)
612 trace = get_callchain_entry_for_task(task, init_nr);
613 else
614 trace = get_perf_callchain(regs, init_nr, kernel, user,
615 sysctl_perf_event_max_stack,
616 false, false);
617 if (unlikely(!trace))
618 goto err_fault;
619
620 trace_nr = trace->nr - init_nr;
621 if (trace_nr < skip)
622 goto err_fault;
623
624 trace_nr -= skip;
625 trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
626 copy_len = trace_nr * elem_size;
627 ips = trace->ip + skip + init_nr;
628 if (user && user_build_id)
629 stack_map_get_build_id_offset(buf, ips, trace_nr, user);
630 else
631 memcpy(buf, ips, copy_len);
632
633 if (size > copy_len)
634 memset(buf + copy_len, 0, size - copy_len);
635 return copy_len;
636
637err_fault:
638 err = -EFAULT;
639clear:
640 memset(buf, 0, size);
641 return err;
642}
643
644BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
645 u64, flags)
646{
647 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
648}
649
650const struct bpf_func_proto bpf_get_stack_proto = {
651 .func = bpf_get_stack,
652 .gpl_only = true,
653 .ret_type = RET_INTEGER,
654 .arg1_type = ARG_PTR_TO_CTX,
655 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
656 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
657 .arg4_type = ARG_ANYTHING,
658};
659
660BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
661 u32, size, u64, flags)
662{
663 struct pt_regs *regs = task_pt_regs(task);
664
665 return __bpf_get_stack(regs, task, NULL, buf, size, flags);
666}
667
668BTF_ID_LIST(bpf_get_task_stack_btf_ids)
669BTF_ID(struct, task_struct)
670
671const struct bpf_func_proto bpf_get_task_stack_proto = {
672 .func = bpf_get_task_stack,
673 .gpl_only = false,
674 .ret_type = RET_INTEGER,
675 .arg1_type = ARG_PTR_TO_BTF_ID,
676 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
677 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
678 .arg4_type = ARG_ANYTHING,
679 .btf_id = bpf_get_task_stack_btf_ids,
680};
681
682BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
683 void *, buf, u32, size, u64, flags)
684{
685 struct pt_regs *regs = (struct pt_regs *)(ctx->regs);
686 struct perf_event *event = ctx->event;
687 struct perf_callchain_entry *trace;
688 bool kernel, user;
689 int err = -EINVAL;
690 __u64 nr_kernel;
691
692 if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
693 return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
694
695 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
696 BPF_F_USER_BUILD_ID)))
697 goto clear;
698
699 user = flags & BPF_F_USER_STACK;
700 kernel = !user;
701
702 err = -EFAULT;
703 trace = ctx->data->callchain;
704 if (unlikely(!trace))
705 goto clear;
706
707 nr_kernel = count_kernel_ip(trace);
708
709 if (kernel) {
710 __u64 nr = trace->nr;
711
712 trace->nr = nr_kernel;
713 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
714
715 /* restore nr */
716 trace->nr = nr;
717 } else { /* user */
718 u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
719
720 skip += nr_kernel;
721 if (skip > BPF_F_SKIP_FIELD_MASK)
722 goto clear;
723
724 flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
725 err = __bpf_get_stack(regs, NULL, trace, buf, size, flags);
726 }
727 return err;
728
729clear:
730 memset(buf, 0, size);
731 return err;
732
733}
734
735const struct bpf_func_proto bpf_get_stack_proto_pe = {
736 .func = bpf_get_stack_pe,
737 .gpl_only = true,
738 .ret_type = RET_INTEGER,
739 .arg1_type = ARG_PTR_TO_CTX,
740 .arg2_type = ARG_PTR_TO_UNINIT_MEM,
741 .arg3_type = ARG_CONST_SIZE_OR_ZERO,
742 .arg4_type = ARG_ANYTHING,
743};
744
745/* Called from eBPF program */
746static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
747{
748 return ERR_PTR(-EOPNOTSUPP);
749}
750
751/* Called from syscall */
752int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
753{
754 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
755 struct stack_map_bucket *bucket, *old_bucket;
756 u32 id = *(u32 *)key, trace_len;
757
758 if (unlikely(id >= smap->n_buckets))
759 return -ENOENT;
760
761 bucket = xchg(&smap->buckets[id], NULL);
762 if (!bucket)
763 return -ENOENT;
764
765 trace_len = bucket->nr * stack_map_data_size(map);
766 memcpy(value, bucket->data, trace_len);
767 memset(value + trace_len, 0, map->value_size - trace_len);
768
769 old_bucket = xchg(&smap->buckets[id], bucket);
770 if (old_bucket)
771 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
772 return 0;
773}
774
775static int stack_map_get_next_key(struct bpf_map *map, void *key,
776 void *next_key)
777{
778 struct bpf_stack_map *smap = container_of(map,
779 struct bpf_stack_map, map);
780 u32 id;
781
782 WARN_ON_ONCE(!rcu_read_lock_held());
783
784 if (!key) {
785 id = 0;
786 } else {
787 id = *(u32 *)key;
788 if (id >= smap->n_buckets || !smap->buckets[id])
789 id = 0;
790 else
791 id++;
792 }
793
794 while (id < smap->n_buckets && !smap->buckets[id])
795 id++;
796
797 if (id >= smap->n_buckets)
798 return -ENOENT;
799
800 *(u32 *)next_key = id;
801 return 0;
802}
803
804static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
805 u64 map_flags)
806{
807 return -EINVAL;
808}
809
810/* Called from syscall or from eBPF program */
811static int stack_map_delete_elem(struct bpf_map *map, void *key)
812{
813 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
814 struct stack_map_bucket *old_bucket;
815 u32 id = *(u32 *)key;
816
817 if (unlikely(id >= smap->n_buckets))
818 return -E2BIG;
819
820 old_bucket = xchg(&smap->buckets[id], NULL);
821 if (old_bucket) {
822 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
823 return 0;
824 } else {
825 return -ENOENT;
826 }
827}
828
829/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
830static void stack_map_free(struct bpf_map *map)
831{
832 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
833
834 bpf_map_area_free(smap->elems);
835 pcpu_freelist_destroy(&smap->freelist);
836 bpf_map_area_free(smap);
837 put_callchain_buffers();
838}
839
840static int stack_trace_map_btf_id;
841const struct bpf_map_ops stack_trace_map_ops = {
842 .map_alloc = stack_map_alloc,
843 .map_free = stack_map_free,
844 .map_get_next_key = stack_map_get_next_key,
845 .map_lookup_elem = stack_map_lookup_elem,
846 .map_update_elem = stack_map_update_elem,
847 .map_delete_elem = stack_map_delete_elem,
848 .map_check_btf = map_check_no_btf,
849 .map_btf_name = "bpf_stack_map",
850 .map_btf_id = &stack_trace_map_btf_id,
851};
852
853static int __init stack_map_init(void)
854{
855 int cpu;
856 struct stack_map_irq_work *work;
857
858 for_each_possible_cpu(cpu) {
859 work = per_cpu_ptr(&up_read_work, cpu);
860 init_irq_work(&work->irq_work, do_up_read);
861 }
862 return 0;
863}
864subsys_initcall(stack_map_init);