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 15 struct stack_map_bucket { 16 struct pcpu_freelist_node fnode; 17 u32 hash; 18 u32 nr; 19 u64 ip[]; 20 }; 21 22 struct 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 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 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 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; 111 112 put_buffers: 113 put_callchain_buffers(); 114 free_smap: 115 kvfree(smap); 116 return ERR_PTR(err); 117 } 118 119 static 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 } 187 188 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 }; 196 197 /* Called from eBPF program */ 198 static void *stack_map_lookup_elem(struct bpf_map *map, void *key) 199 { 200 return NULL; 201 } 202 203 /* Called from syscall */ 204 int 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 } 226 227 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) { 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 */ 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); 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 } 270 271 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); 291