Commit | Line | Data |
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d5a3b1f6 AS |
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> | |
557c0c6e | 13 | #include "percpu_freelist.h" |
d5a3b1f6 AS |
14 | |
15 | struct stack_map_bucket { | |
557c0c6e | 16 | struct pcpu_freelist_node fnode; |
d5a3b1f6 AS |
17 | u32 hash; |
18 | u32 nr; | |
19 | u64 ip[]; | |
20 | }; | |
21 | ||
22 | struct bpf_stack_map { | |
23 | struct bpf_map map; | |
557c0c6e AS |
24 | void *elems; |
25 | struct pcpu_freelist freelist; | |
d5a3b1f6 | 26 | u32 n_buckets; |
557c0c6e | 27 | struct stack_map_bucket *buckets[]; |
d5a3b1f6 AS |
28 | }; |
29 | ||
557c0c6e AS |
30 | static 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 | ||
47 | free_elems: | |
48 | vfree(smap->elems); | |
49 | return err; | |
50 | } | |
51 | ||
d5a3b1f6 AS |
52 | /* Called from syscall */ |
53 | static 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 | ||
823707b6 AS |
63 | if (attr->map_flags) |
64 | return ERR_PTR(-EINVAL); | |
65 | ||
d5a3b1f6 AS |
66 | /* check sanity of attributes */ |
67 | if (attr->max_entries == 0 || attr->key_size != 4 || | |
68 | value_size < 8 || value_size % 8 || | |
c5dfd78e | 69 | value_size / 8 > sysctl_perf_event_max_stack) |
d5a3b1f6 AS |
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 | ||
557c0c6e AS |
98 | err = bpf_map_precharge_memlock(smap->map.pages); |
99 | if (err) | |
100 | goto free_smap; | |
101 | ||
d5a3b1f6 AS |
102 | err = get_callchain_buffers(); |
103 | if (err) | |
104 | goto free_smap; | |
105 | ||
557c0c6e AS |
106 | err = prealloc_elems_and_freelist(smap); |
107 | if (err) | |
108 | goto put_buffers; | |
109 | ||
d5a3b1f6 AS |
110 | return &smap->map; |
111 | ||
557c0c6e AS |
112 | put_buffers: |
113 | put_callchain_buffers(); | |
d5a3b1f6 AS |
114 | free_smap: |
115 | kvfree(smap); | |
116 | return ERR_PTR(err); | |
117 | } | |
118 | ||
9940d67c | 119 | u64 bpf_get_stackid(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5) |
d5a3b1f6 AS |
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; | |
c5dfd78e ACM |
127 | /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */ |
128 | u32 init_nr = sysctl_perf_event_max_stack - max_depth; | |
d5a3b1f6 AS |
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 | |
c5dfd78e | 146 | * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth |
d5a3b1f6 AS |
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); | |
557c0c6e | 159 | bucket = READ_ONCE(smap->buckets[id]); |
d5a3b1f6 AS |
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 | ||
557c0c6e AS |
173 | new_bucket = (struct stack_map_bucket *) |
174 | pcpu_freelist_pop(&smap->freelist); | |
d5a3b1f6 AS |
175 | if (unlikely(!new_bucket)) |
176 | return -ENOMEM; | |
177 | ||
178 | memcpy(new_bucket->ip, ips, trace_len); | |
d5a3b1f6 AS |
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) | |
557c0c6e | 184 | pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); |
d5a3b1f6 AS |
185 | return id; |
186 | } | |
187 | ||
188 | const 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 | ||
557c0c6e | 197 | /* Called from eBPF program */ |
d5a3b1f6 | 198 | static void *stack_map_lookup_elem(struct bpf_map *map, void *key) |
557c0c6e AS |
199 | { |
200 | return NULL; | |
201 | } | |
202 | ||
203 | /* Called from syscall */ | |
204 | int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value) | |
d5a3b1f6 AS |
205 | { |
206 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
557c0c6e AS |
207 | struct stack_map_bucket *bucket, *old_bucket; |
208 | u32 id = *(u32 *)key, trace_len; | |
d5a3b1f6 AS |
209 | |
210 | if (unlikely(id >= smap->n_buckets)) | |
557c0c6e AS |
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; | |
d5a3b1f6 AS |
225 | } |
226 | ||
227 | static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key) | |
228 | { | |
229 | return -EINVAL; | |
230 | } | |
231 | ||
232 | static 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 */ | |
239 | static 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) { | |
557c0c6e | 250 | pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); |
d5a3b1f6 AS |
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 */ | |
258 | static void stack_map_free(struct bpf_map *map) | |
259 | { | |
260 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
d5a3b1f6 | 261 | |
557c0c6e | 262 | /* wait for bpf programs to complete before freeing stack map */ |
d5a3b1f6 AS |
263 | synchronize_rcu(); |
264 | ||
557c0c6e AS |
265 | vfree(smap->elems); |
266 | pcpu_freelist_destroy(&smap->freelist); | |
d5a3b1f6 AS |
267 | kvfree(smap); |
268 | put_callchain_buffers(); | |
269 | } | |
270 | ||
271 | static 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 | ||
280 | static struct bpf_map_type_list stack_map_type __read_mostly = { | |
281 | .ops = &stack_map_ops, | |
282 | .type = BPF_MAP_TYPE_STACK_TRACE, | |
283 | }; | |
284 | ||
285 | static int __init register_stack_map(void) | |
286 | { | |
287 | bpf_register_map_type(&stack_map_type); | |
288 | return 0; | |
289 | } | |
290 | late_initcall(register_stack_map); |