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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> | |
d5a3b1f6 AS |
10 | #include <linux/stacktrace.h> |
11 | #include <linux/perf_event.h> | |
557c0c6e | 12 | #include "percpu_freelist.h" |
d5a3b1f6 AS |
13 | |
14 | struct stack_map_bucket { | |
557c0c6e | 15 | struct pcpu_freelist_node fnode; |
d5a3b1f6 AS |
16 | u32 hash; |
17 | u32 nr; | |
18 | u64 ip[]; | |
19 | }; | |
20 | ||
21 | struct bpf_stack_map { | |
22 | struct bpf_map map; | |
557c0c6e AS |
23 | void *elems; |
24 | struct pcpu_freelist freelist; | |
d5a3b1f6 | 25 | u32 n_buckets; |
557c0c6e | 26 | struct stack_map_bucket *buckets[]; |
d5a3b1f6 AS |
27 | }; |
28 | ||
557c0c6e AS |
29 | static int prealloc_elems_and_freelist(struct bpf_stack_map *smap) |
30 | { | |
31 | u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size; | |
32 | int err; | |
33 | ||
d407bd25 | 34 | smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries); |
557c0c6e AS |
35 | if (!smap->elems) |
36 | return -ENOMEM; | |
37 | ||
38 | err = pcpu_freelist_init(&smap->freelist); | |
39 | if (err) | |
40 | goto free_elems; | |
41 | ||
42 | pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size, | |
43 | smap->map.max_entries); | |
44 | return 0; | |
45 | ||
46 | free_elems: | |
d407bd25 | 47 | bpf_map_area_free(smap->elems); |
557c0c6e AS |
48 | return err; |
49 | } | |
50 | ||
d5a3b1f6 AS |
51 | /* Called from syscall */ |
52 | static struct bpf_map *stack_map_alloc(union bpf_attr *attr) | |
53 | { | |
54 | u32 value_size = attr->value_size; | |
55 | struct bpf_stack_map *smap; | |
56 | u64 cost, n_buckets; | |
57 | int err; | |
58 | ||
59 | if (!capable(CAP_SYS_ADMIN)) | |
60 | return ERR_PTR(-EPERM); | |
61 | ||
823707b6 AS |
62 | if (attr->map_flags) |
63 | return ERR_PTR(-EINVAL); | |
64 | ||
d5a3b1f6 AS |
65 | /* check sanity of attributes */ |
66 | if (attr->max_entries == 0 || attr->key_size != 4 || | |
67 | value_size < 8 || value_size % 8 || | |
c5dfd78e | 68 | value_size / 8 > sysctl_perf_event_max_stack) |
d5a3b1f6 AS |
69 | return ERR_PTR(-EINVAL); |
70 | ||
71 | /* hash table size must be power of 2 */ | |
72 | n_buckets = roundup_pow_of_two(attr->max_entries); | |
73 | ||
74 | cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap); | |
75 | if (cost >= U32_MAX - PAGE_SIZE) | |
76 | return ERR_PTR(-E2BIG); | |
77 | ||
d407bd25 DB |
78 | smap = bpf_map_area_alloc(cost); |
79 | if (!smap) | |
80 | return ERR_PTR(-ENOMEM); | |
d5a3b1f6 AS |
81 | |
82 | err = -E2BIG; | |
83 | cost += n_buckets * (value_size + sizeof(struct stack_map_bucket)); | |
84 | if (cost >= U32_MAX - PAGE_SIZE) | |
85 | goto free_smap; | |
86 | ||
87 | smap->map.map_type = attr->map_type; | |
88 | smap->map.key_size = attr->key_size; | |
89 | smap->map.value_size = value_size; | |
90 | smap->map.max_entries = attr->max_entries; | |
a316338c | 91 | smap->map.map_flags = attr->map_flags; |
d5a3b1f6 AS |
92 | smap->n_buckets = n_buckets; |
93 | smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; | |
94 | ||
557c0c6e AS |
95 | err = bpf_map_precharge_memlock(smap->map.pages); |
96 | if (err) | |
97 | goto free_smap; | |
98 | ||
97c79a38 | 99 | err = get_callchain_buffers(sysctl_perf_event_max_stack); |
d5a3b1f6 AS |
100 | if (err) |
101 | goto free_smap; | |
102 | ||
557c0c6e AS |
103 | err = prealloc_elems_and_freelist(smap); |
104 | if (err) | |
105 | goto put_buffers; | |
106 | ||
d5a3b1f6 AS |
107 | return &smap->map; |
108 | ||
557c0c6e AS |
109 | put_buffers: |
110 | put_callchain_buffers(); | |
d5a3b1f6 | 111 | free_smap: |
d407bd25 | 112 | bpf_map_area_free(smap); |
d5a3b1f6 AS |
113 | return ERR_PTR(err); |
114 | } | |
115 | ||
f3694e00 DB |
116 | BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, |
117 | u64, flags) | |
d5a3b1f6 | 118 | { |
d5a3b1f6 AS |
119 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); |
120 | struct perf_callchain_entry *trace; | |
121 | struct stack_map_bucket *bucket, *new_bucket, *old_bucket; | |
122 | u32 max_depth = map->value_size / 8; | |
c5dfd78e ACM |
123 | /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */ |
124 | u32 init_nr = sysctl_perf_event_max_stack - max_depth; | |
d5a3b1f6 AS |
125 | u32 skip = flags & BPF_F_SKIP_FIELD_MASK; |
126 | u32 hash, id, trace_nr, trace_len; | |
127 | bool user = flags & BPF_F_USER_STACK; | |
128 | bool kernel = !user; | |
129 | u64 *ips; | |
130 | ||
131 | if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | | |
132 | BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) | |
133 | return -EINVAL; | |
134 | ||
cfbcf468 ACM |
135 | trace = get_perf_callchain(regs, init_nr, kernel, user, |
136 | sysctl_perf_event_max_stack, false, false); | |
d5a3b1f6 AS |
137 | |
138 | if (unlikely(!trace)) | |
139 | /* couldn't fetch the stack trace */ | |
140 | return -EFAULT; | |
141 | ||
142 | /* get_perf_callchain() guarantees that trace->nr >= init_nr | |
c5dfd78e | 143 | * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth |
d5a3b1f6 AS |
144 | */ |
145 | trace_nr = trace->nr - init_nr; | |
146 | ||
147 | if (trace_nr <= skip) | |
148 | /* skipping more than usable stack trace */ | |
149 | return -EFAULT; | |
150 | ||
151 | trace_nr -= skip; | |
152 | trace_len = trace_nr * sizeof(u64); | |
153 | ips = trace->ip + skip + init_nr; | |
154 | hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); | |
155 | id = hash & (smap->n_buckets - 1); | |
557c0c6e | 156 | bucket = READ_ONCE(smap->buckets[id]); |
d5a3b1f6 AS |
157 | |
158 | if (bucket && bucket->hash == hash) { | |
159 | if (flags & BPF_F_FAST_STACK_CMP) | |
160 | return id; | |
161 | if (bucket->nr == trace_nr && | |
162 | memcmp(bucket->ip, ips, trace_len) == 0) | |
163 | return id; | |
164 | } | |
165 | ||
166 | /* this call stack is not in the map, try to add it */ | |
167 | if (bucket && !(flags & BPF_F_REUSE_STACKID)) | |
168 | return -EEXIST; | |
169 | ||
557c0c6e AS |
170 | new_bucket = (struct stack_map_bucket *) |
171 | pcpu_freelist_pop(&smap->freelist); | |
d5a3b1f6 AS |
172 | if (unlikely(!new_bucket)) |
173 | return -ENOMEM; | |
174 | ||
175 | memcpy(new_bucket->ip, ips, trace_len); | |
d5a3b1f6 AS |
176 | new_bucket->hash = hash; |
177 | new_bucket->nr = trace_nr; | |
178 | ||
179 | old_bucket = xchg(&smap->buckets[id], new_bucket); | |
180 | if (old_bucket) | |
557c0c6e | 181 | pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); |
d5a3b1f6 AS |
182 | return id; |
183 | } | |
184 | ||
185 | const struct bpf_func_proto bpf_get_stackid_proto = { | |
186 | .func = bpf_get_stackid, | |
187 | .gpl_only = true, | |
188 | .ret_type = RET_INTEGER, | |
189 | .arg1_type = ARG_PTR_TO_CTX, | |
190 | .arg2_type = ARG_CONST_MAP_PTR, | |
191 | .arg3_type = ARG_ANYTHING, | |
192 | }; | |
193 | ||
557c0c6e | 194 | /* Called from eBPF program */ |
d5a3b1f6 | 195 | static void *stack_map_lookup_elem(struct bpf_map *map, void *key) |
557c0c6e AS |
196 | { |
197 | return NULL; | |
198 | } | |
199 | ||
200 | /* Called from syscall */ | |
201 | int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value) | |
d5a3b1f6 AS |
202 | { |
203 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
557c0c6e AS |
204 | struct stack_map_bucket *bucket, *old_bucket; |
205 | u32 id = *(u32 *)key, trace_len; | |
d5a3b1f6 AS |
206 | |
207 | if (unlikely(id >= smap->n_buckets)) | |
557c0c6e AS |
208 | return -ENOENT; |
209 | ||
210 | bucket = xchg(&smap->buckets[id], NULL); | |
211 | if (!bucket) | |
212 | return -ENOENT; | |
213 | ||
214 | trace_len = bucket->nr * sizeof(u64); | |
215 | memcpy(value, bucket->ip, trace_len); | |
216 | memset(value + trace_len, 0, map->value_size - trace_len); | |
217 | ||
218 | old_bucket = xchg(&smap->buckets[id], bucket); | |
219 | if (old_bucket) | |
220 | pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); | |
221 | return 0; | |
d5a3b1f6 AS |
222 | } |
223 | ||
224 | static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key) | |
225 | { | |
226 | return -EINVAL; | |
227 | } | |
228 | ||
229 | static int stack_map_update_elem(struct bpf_map *map, void *key, void *value, | |
230 | u64 map_flags) | |
231 | { | |
232 | return -EINVAL; | |
233 | } | |
234 | ||
235 | /* Called from syscall or from eBPF program */ | |
236 | static int stack_map_delete_elem(struct bpf_map *map, void *key) | |
237 | { | |
238 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
239 | struct stack_map_bucket *old_bucket; | |
240 | u32 id = *(u32 *)key; | |
241 | ||
242 | if (unlikely(id >= smap->n_buckets)) | |
243 | return -E2BIG; | |
244 | ||
245 | old_bucket = xchg(&smap->buckets[id], NULL); | |
246 | if (old_bucket) { | |
557c0c6e | 247 | pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); |
d5a3b1f6 AS |
248 | return 0; |
249 | } else { | |
250 | return -ENOENT; | |
251 | } | |
252 | } | |
253 | ||
254 | /* Called when map->refcnt goes to zero, either from workqueue or from syscall */ | |
255 | static void stack_map_free(struct bpf_map *map) | |
256 | { | |
257 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
d5a3b1f6 | 258 | |
557c0c6e | 259 | /* wait for bpf programs to complete before freeing stack map */ |
d5a3b1f6 AS |
260 | synchronize_rcu(); |
261 | ||
d407bd25 | 262 | bpf_map_area_free(smap->elems); |
557c0c6e | 263 | pcpu_freelist_destroy(&smap->freelist); |
d407bd25 | 264 | bpf_map_area_free(smap); |
d5a3b1f6 AS |
265 | put_callchain_buffers(); |
266 | } | |
267 | ||
40077e0c | 268 | const struct bpf_map_ops stack_map_ops = { |
d5a3b1f6 AS |
269 | .map_alloc = stack_map_alloc, |
270 | .map_free = stack_map_free, | |
271 | .map_get_next_key = stack_map_get_next_key, | |
272 | .map_lookup_elem = stack_map_lookup_elem, | |
273 | .map_update_elem = stack_map_update_elem, | |
274 | .map_delete_elem = stack_map_delete_elem, | |
275 | }; |