]>
Commit | Line | Data |
---|---|---|
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> | |
13 | ||
14 | struct stack_map_bucket { | |
15 | struct rcu_head rcu; | |
16 | u32 hash; | |
17 | u32 nr; | |
18 | u64 ip[]; | |
19 | }; | |
20 | ||
21 | struct bpf_stack_map { | |
22 | struct bpf_map map; | |
23 | u32 n_buckets; | |
24 | struct stack_map_bucket __rcu *buckets[]; | |
25 | }; | |
26 | ||
27 | /* Called from syscall */ | |
28 | static struct bpf_map *stack_map_alloc(union bpf_attr *attr) | |
29 | { | |
30 | u32 value_size = attr->value_size; | |
31 | struct bpf_stack_map *smap; | |
32 | u64 cost, n_buckets; | |
33 | int err; | |
34 | ||
35 | if (!capable(CAP_SYS_ADMIN)) | |
36 | return ERR_PTR(-EPERM); | |
37 | ||
38 | /* check sanity of attributes */ | |
39 | if (attr->max_entries == 0 || attr->key_size != 4 || | |
40 | value_size < 8 || value_size % 8 || | |
41 | value_size / 8 > PERF_MAX_STACK_DEPTH) | |
42 | return ERR_PTR(-EINVAL); | |
43 | ||
44 | /* hash table size must be power of 2 */ | |
45 | n_buckets = roundup_pow_of_two(attr->max_entries); | |
46 | ||
47 | cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap); | |
48 | if (cost >= U32_MAX - PAGE_SIZE) | |
49 | return ERR_PTR(-E2BIG); | |
50 | ||
51 | smap = kzalloc(cost, GFP_USER | __GFP_NOWARN); | |
52 | if (!smap) { | |
53 | smap = vzalloc(cost); | |
54 | if (!smap) | |
55 | return ERR_PTR(-ENOMEM); | |
56 | } | |
57 | ||
58 | err = -E2BIG; | |
59 | cost += n_buckets * (value_size + sizeof(struct stack_map_bucket)); | |
60 | if (cost >= U32_MAX - PAGE_SIZE) | |
61 | goto free_smap; | |
62 | ||
63 | smap->map.map_type = attr->map_type; | |
64 | smap->map.key_size = attr->key_size; | |
65 | smap->map.value_size = value_size; | |
66 | smap->map.max_entries = attr->max_entries; | |
67 | smap->n_buckets = n_buckets; | |
68 | smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; | |
69 | ||
70 | err = get_callchain_buffers(); | |
71 | if (err) | |
72 | goto free_smap; | |
73 | ||
74 | return &smap->map; | |
75 | ||
76 | free_smap: | |
77 | kvfree(smap); | |
78 | return ERR_PTR(err); | |
79 | } | |
80 | ||
81 | static u64 bpf_get_stackid(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5) | |
82 | { | |
83 | struct pt_regs *regs = (struct pt_regs *) (long) r1; | |
84 | struct bpf_map *map = (struct bpf_map *) (long) r2; | |
85 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
86 | struct perf_callchain_entry *trace; | |
87 | struct stack_map_bucket *bucket, *new_bucket, *old_bucket; | |
88 | u32 max_depth = map->value_size / 8; | |
89 | /* stack_map_alloc() checks that max_depth <= PERF_MAX_STACK_DEPTH */ | |
90 | u32 init_nr = PERF_MAX_STACK_DEPTH - max_depth; | |
91 | u32 skip = flags & BPF_F_SKIP_FIELD_MASK; | |
92 | u32 hash, id, trace_nr, trace_len; | |
93 | bool user = flags & BPF_F_USER_STACK; | |
94 | bool kernel = !user; | |
95 | u64 *ips; | |
96 | ||
97 | if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | | |
98 | BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) | |
99 | return -EINVAL; | |
100 | ||
101 | trace = get_perf_callchain(regs, init_nr, kernel, user, false, false); | |
102 | ||
103 | if (unlikely(!trace)) | |
104 | /* couldn't fetch the stack trace */ | |
105 | return -EFAULT; | |
106 | ||
107 | /* get_perf_callchain() guarantees that trace->nr >= init_nr | |
108 | * and trace-nr <= PERF_MAX_STACK_DEPTH, so trace_nr <= max_depth | |
109 | */ | |
110 | trace_nr = trace->nr - init_nr; | |
111 | ||
112 | if (trace_nr <= skip) | |
113 | /* skipping more than usable stack trace */ | |
114 | return -EFAULT; | |
115 | ||
116 | trace_nr -= skip; | |
117 | trace_len = trace_nr * sizeof(u64); | |
118 | ips = trace->ip + skip + init_nr; | |
119 | hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); | |
120 | id = hash & (smap->n_buckets - 1); | |
121 | bucket = rcu_dereference(smap->buckets[id]); | |
122 | ||
123 | if (bucket && bucket->hash == hash) { | |
124 | if (flags & BPF_F_FAST_STACK_CMP) | |
125 | return id; | |
126 | if (bucket->nr == trace_nr && | |
127 | memcmp(bucket->ip, ips, trace_len) == 0) | |
128 | return id; | |
129 | } | |
130 | ||
131 | /* this call stack is not in the map, try to add it */ | |
132 | if (bucket && !(flags & BPF_F_REUSE_STACKID)) | |
133 | return -EEXIST; | |
134 | ||
135 | new_bucket = kmalloc(sizeof(struct stack_map_bucket) + map->value_size, | |
136 | GFP_ATOMIC | __GFP_NOWARN); | |
137 | if (unlikely(!new_bucket)) | |
138 | return -ENOMEM; | |
139 | ||
140 | memcpy(new_bucket->ip, ips, trace_len); | |
141 | memset(new_bucket->ip + trace_len / 8, 0, map->value_size - trace_len); | |
142 | new_bucket->hash = hash; | |
143 | new_bucket->nr = trace_nr; | |
144 | ||
145 | old_bucket = xchg(&smap->buckets[id], new_bucket); | |
146 | if (old_bucket) | |
147 | kfree_rcu(old_bucket, rcu); | |
148 | return id; | |
149 | } | |
150 | ||
151 | const struct bpf_func_proto bpf_get_stackid_proto = { | |
152 | .func = bpf_get_stackid, | |
153 | .gpl_only = true, | |
154 | .ret_type = RET_INTEGER, | |
155 | .arg1_type = ARG_PTR_TO_CTX, | |
156 | .arg2_type = ARG_CONST_MAP_PTR, | |
157 | .arg3_type = ARG_ANYTHING, | |
158 | }; | |
159 | ||
160 | /* Called from syscall or from eBPF program */ | |
161 | static void *stack_map_lookup_elem(struct bpf_map *map, void *key) | |
162 | { | |
163 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
164 | struct stack_map_bucket *bucket; | |
165 | u32 id = *(u32 *)key; | |
166 | ||
167 | if (unlikely(id >= smap->n_buckets)) | |
168 | return NULL; | |
169 | bucket = rcu_dereference(smap->buckets[id]); | |
170 | return bucket ? bucket->ip : NULL; | |
171 | } | |
172 | ||
173 | static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key) | |
174 | { | |
175 | return -EINVAL; | |
176 | } | |
177 | ||
178 | static int stack_map_update_elem(struct bpf_map *map, void *key, void *value, | |
179 | u64 map_flags) | |
180 | { | |
181 | return -EINVAL; | |
182 | } | |
183 | ||
184 | /* Called from syscall or from eBPF program */ | |
185 | static int stack_map_delete_elem(struct bpf_map *map, void *key) | |
186 | { | |
187 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
188 | struct stack_map_bucket *old_bucket; | |
189 | u32 id = *(u32 *)key; | |
190 | ||
191 | if (unlikely(id >= smap->n_buckets)) | |
192 | return -E2BIG; | |
193 | ||
194 | old_bucket = xchg(&smap->buckets[id], NULL); | |
195 | if (old_bucket) { | |
196 | kfree_rcu(old_bucket, rcu); | |
197 | return 0; | |
198 | } else { | |
199 | return -ENOENT; | |
200 | } | |
201 | } | |
202 | ||
203 | /* Called when map->refcnt goes to zero, either from workqueue or from syscall */ | |
204 | static void stack_map_free(struct bpf_map *map) | |
205 | { | |
206 | struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); | |
207 | int i; | |
208 | ||
209 | synchronize_rcu(); | |
210 | ||
211 | for (i = 0; i < smap->n_buckets; i++) | |
212 | if (smap->buckets[i]) | |
213 | kfree_rcu(smap->buckets[i], rcu); | |
214 | kvfree(smap); | |
215 | put_callchain_buffers(); | |
216 | } | |
217 | ||
218 | static const struct bpf_map_ops stack_map_ops = { | |
219 | .map_alloc = stack_map_alloc, | |
220 | .map_free = stack_map_free, | |
221 | .map_get_next_key = stack_map_get_next_key, | |
222 | .map_lookup_elem = stack_map_lookup_elem, | |
223 | .map_update_elem = stack_map_update_elem, | |
224 | .map_delete_elem = stack_map_delete_elem, | |
225 | }; | |
226 | ||
227 | static struct bpf_map_type_list stack_map_type __read_mostly = { | |
228 | .ops = &stack_map_ops, | |
229 | .type = BPF_MAP_TYPE_STACK_TRACE, | |
230 | }; | |
231 | ||
232 | static int __init register_stack_map(void) | |
233 | { | |
234 | bpf_register_map_type(&stack_map_type); | |
235 | return 0; | |
236 | } | |
237 | late_initcall(register_stack_map); |