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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 | 13 | |
6e71b04a CF |
14 | #define STACK_CREATE_FLAG_MASK \ |
15 | (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY) | |
16 | ||
d5a3b1f6 | 17 | struct stack_map_bucket { |
557c0c6e | 18 | struct pcpu_freelist_node fnode; |
d5a3b1f6 AS |
19 | u32 hash; |
20 | u32 nr; | |
21 | u64 ip[]; | |
22 | }; | |
23 | ||
24 | struct bpf_stack_map { | |
25 | struct bpf_map map; | |
557c0c6e AS |
26 | void *elems; |
27 | struct pcpu_freelist freelist; | |
d5a3b1f6 | 28 | u32 n_buckets; |
557c0c6e | 29 | struct stack_map_bucket *buckets[]; |
d5a3b1f6 AS |
30 | }; |
31 | ||
557c0c6e AS |
32 | static int prealloc_elems_and_freelist(struct bpf_stack_map *smap) |
33 | { | |
34 | u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size; | |
35 | int err; | |
36 | ||
96eabe7a MKL |
37 | smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries, |
38 | smap->map.numa_node); | |
557c0c6e AS |
39 | if (!smap->elems) |
40 | return -ENOMEM; | |
41 | ||
42 | err = pcpu_freelist_init(&smap->freelist); | |
43 | if (err) | |
44 | goto free_elems; | |
45 | ||
46 | pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size, | |
47 | smap->map.max_entries); | |
48 | return 0; | |
49 | ||
50 | free_elems: | |
d407bd25 | 51 | bpf_map_area_free(smap->elems); |
557c0c6e AS |
52 | return err; |
53 | } | |
54 | ||
d5a3b1f6 AS |
55 | /* Called from syscall */ |
56 | static struct bpf_map *stack_map_alloc(union bpf_attr *attr) | |
57 | { | |
58 | u32 value_size = attr->value_size; | |
59 | struct bpf_stack_map *smap; | |
60 | u64 cost, n_buckets; | |
61 | int err; | |
62 | ||
63 | if (!capable(CAP_SYS_ADMIN)) | |
64 | return ERR_PTR(-EPERM); | |
65 | ||
6e71b04a | 66 | if (attr->map_flags & ~STACK_CREATE_FLAG_MASK) |
823707b6 AS |
67 | return ERR_PTR(-EINVAL); |
68 | ||
d5a3b1f6 AS |
69 | /* check sanity of attributes */ |
70 | if (attr->max_entries == 0 || attr->key_size != 4 || | |
71 | value_size < 8 || value_size % 8 || | |
c5dfd78e | 72 | value_size / 8 > sysctl_perf_event_max_stack) |
d5a3b1f6 AS |
73 | return ERR_PTR(-EINVAL); |
74 | ||
75 | /* hash table size must be power of 2 */ | |
76 | n_buckets = roundup_pow_of_two(attr->max_entries); | |
77 | ||
78 | cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap); | |
79 | if (cost >= U32_MAX - PAGE_SIZE) | |
80 | return ERR_PTR(-E2BIG); | |
81 | ||
96eabe7a | 82 | smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr)); |
d407bd25 DB |
83 | if (!smap) |
84 | return ERR_PTR(-ENOMEM); | |
d5a3b1f6 AS |
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; | |
a316338c | 95 | smap->map.map_flags = attr->map_flags; |
d5a3b1f6 AS |
96 | smap->n_buckets = n_buckets; |
97 | smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; | |
96eabe7a | 98 | smap->map.numa_node = bpf_map_attr_numa_node(attr); |
d5a3b1f6 | 99 | |
557c0c6e AS |
100 | err = bpf_map_precharge_memlock(smap->map.pages); |
101 | if (err) | |
102 | goto free_smap; | |
103 | ||
97c79a38 | 104 | err = get_callchain_buffers(sysctl_perf_event_max_stack); |
d5a3b1f6 AS |
105 | if (err) |
106 | goto free_smap; | |
107 | ||
557c0c6e AS |
108 | err = prealloc_elems_and_freelist(smap); |
109 | if (err) | |
110 | goto put_buffers; | |
111 | ||
d5a3b1f6 AS |
112 | return &smap->map; |
113 | ||
557c0c6e AS |
114 | put_buffers: |
115 | put_callchain_buffers(); | |
d5a3b1f6 | 116 | free_smap: |
d407bd25 | 117 | bpf_map_area_free(smap); |
d5a3b1f6 AS |
118 | return ERR_PTR(err); |
119 | } | |
120 | ||
f3694e00 DB |
121 | BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, |
122 | u64, flags) | |
d5a3b1f6 | 123 | { |
d5a3b1f6 AS |
124 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); |
125 | struct perf_callchain_entry *trace; | |
126 | struct stack_map_bucket *bucket, *new_bucket, *old_bucket; | |
127 | u32 max_depth = map->value_size / 8; | |
c5dfd78e ACM |
128 | /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */ |
129 | u32 init_nr = sysctl_perf_event_max_stack - max_depth; | |
d5a3b1f6 AS |
130 | u32 skip = flags & BPF_F_SKIP_FIELD_MASK; |
131 | u32 hash, id, trace_nr, trace_len; | |
132 | bool user = flags & BPF_F_USER_STACK; | |
133 | bool kernel = !user; | |
134 | u64 *ips; | |
135 | ||
136 | if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | | |
137 | BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) | |
138 | return -EINVAL; | |
139 | ||
cfbcf468 ACM |
140 | trace = get_perf_callchain(regs, init_nr, kernel, user, |
141 | sysctl_perf_event_max_stack, false, false); | |
d5a3b1f6 AS |
142 | |
143 | if (unlikely(!trace)) | |
144 | /* couldn't fetch the stack trace */ | |
145 | return -EFAULT; | |
146 | ||
147 | /* get_perf_callchain() guarantees that trace->nr >= init_nr | |
c5dfd78e | 148 | * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth |
d5a3b1f6 AS |
149 | */ |
150 | trace_nr = trace->nr - init_nr; | |
151 | ||
152 | if (trace_nr <= skip) | |
153 | /* skipping more than usable stack trace */ | |
154 | return -EFAULT; | |
155 | ||
156 | trace_nr -= skip; | |
157 | trace_len = trace_nr * sizeof(u64); | |
158 | ips = trace->ip + skip + init_nr; | |
159 | hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); | |
160 | id = hash & (smap->n_buckets - 1); | |
557c0c6e | 161 | bucket = READ_ONCE(smap->buckets[id]); |
d5a3b1f6 AS |
162 | |
163 | if (bucket && bucket->hash == hash) { | |
164 | if (flags & BPF_F_FAST_STACK_CMP) | |
165 | return id; | |
166 | if (bucket->nr == trace_nr && | |
167 | memcmp(bucket->ip, ips, trace_len) == 0) | |
168 | return id; | |
169 | } | |
170 | ||
171 | /* this call stack is not in the map, try to add it */ | |
172 | if (bucket && !(flags & BPF_F_REUSE_STACKID)) | |
173 | return -EEXIST; | |
174 | ||
557c0c6e AS |
175 | new_bucket = (struct stack_map_bucket *) |
176 | pcpu_freelist_pop(&smap->freelist); | |
d5a3b1f6 AS |
177 | if (unlikely(!new_bucket)) |
178 | return -ENOMEM; | |
179 | ||
180 | memcpy(new_bucket->ip, ips, trace_len); | |
d5a3b1f6 AS |
181 | new_bucket->hash = hash; |
182 | new_bucket->nr = trace_nr; | |
183 | ||
184 | old_bucket = xchg(&smap->buckets[id], new_bucket); | |
185 | if (old_bucket) | |
557c0c6e | 186 | pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); |
d5a3b1f6 AS |
187 | return id; |
188 | } | |
189 | ||
190 | const struct bpf_func_proto bpf_get_stackid_proto = { | |
191 | .func = bpf_get_stackid, | |
192 | .gpl_only = true, | |
193 | .ret_type = RET_INTEGER, | |
194 | .arg1_type = ARG_PTR_TO_CTX, | |
195 | .arg2_type = ARG_CONST_MAP_PTR, | |
196 | .arg3_type = ARG_ANYTHING, | |
197 | }; | |
198 | ||
557c0c6e | 199 | /* Called from eBPF program */ |
d5a3b1f6 | 200 | static void *stack_map_lookup_elem(struct bpf_map *map, void *key) |
557c0c6e AS |
201 | { |
202 | return NULL; | |
203 | } | |
204 | ||
205 | /* Called from syscall */ | |
206 | int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value) | |
d5a3b1f6 AS |
207 | { |
208 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
557c0c6e AS |
209 | struct stack_map_bucket *bucket, *old_bucket; |
210 | u32 id = *(u32 *)key, trace_len; | |
d5a3b1f6 AS |
211 | |
212 | if (unlikely(id >= smap->n_buckets)) | |
557c0c6e AS |
213 | return -ENOENT; |
214 | ||
215 | bucket = xchg(&smap->buckets[id], NULL); | |
216 | if (!bucket) | |
217 | return -ENOENT; | |
218 | ||
219 | trace_len = bucket->nr * sizeof(u64); | |
220 | memcpy(value, bucket->ip, trace_len); | |
221 | memset(value + trace_len, 0, map->value_size - trace_len); | |
222 | ||
223 | old_bucket = xchg(&smap->buckets[id], bucket); | |
224 | if (old_bucket) | |
225 | pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); | |
226 | return 0; | |
d5a3b1f6 AS |
227 | } |
228 | ||
229 | static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key) | |
230 | { | |
231 | return -EINVAL; | |
232 | } | |
233 | ||
234 | static int stack_map_update_elem(struct bpf_map *map, void *key, void *value, | |
235 | u64 map_flags) | |
236 | { | |
237 | return -EINVAL; | |
238 | } | |
239 | ||
240 | /* Called from syscall or from eBPF program */ | |
241 | static int stack_map_delete_elem(struct bpf_map *map, void *key) | |
242 | { | |
243 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
244 | struct stack_map_bucket *old_bucket; | |
245 | u32 id = *(u32 *)key; | |
246 | ||
247 | if (unlikely(id >= smap->n_buckets)) | |
248 | return -E2BIG; | |
249 | ||
250 | old_bucket = xchg(&smap->buckets[id], NULL); | |
251 | if (old_bucket) { | |
557c0c6e | 252 | pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); |
d5a3b1f6 AS |
253 | return 0; |
254 | } else { | |
255 | return -ENOENT; | |
256 | } | |
257 | } | |
258 | ||
259 | /* Called when map->refcnt goes to zero, either from workqueue or from syscall */ | |
260 | static void stack_map_free(struct bpf_map *map) | |
261 | { | |
262 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
d5a3b1f6 | 263 | |
557c0c6e | 264 | /* wait for bpf programs to complete before freeing stack map */ |
d5a3b1f6 AS |
265 | synchronize_rcu(); |
266 | ||
d407bd25 | 267 | bpf_map_area_free(smap->elems); |
557c0c6e | 268 | pcpu_freelist_destroy(&smap->freelist); |
d407bd25 | 269 | bpf_map_area_free(smap); |
d5a3b1f6 AS |
270 | put_callchain_buffers(); |
271 | } | |
272 | ||
40077e0c | 273 | const struct bpf_map_ops stack_map_ops = { |
d5a3b1f6 AS |
274 | .map_alloc = stack_map_alloc, |
275 | .map_free = stack_map_free, | |
276 | .map_get_next_key = stack_map_get_next_key, | |
277 | .map_lookup_elem = stack_map_lookup_elem, | |
278 | .map_update_elem = stack_map_update_elem, | |
279 | .map_delete_elem = stack_map_delete_elem, | |
280 | }; |