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/stacktrace.h> 11 #include <linux/perf_event.h> 12 #include "percpu_freelist.h" 13 14 struct stack_map_bucket { 15 struct pcpu_freelist_node fnode; 16 u32 hash; 17 u32 nr; 18 u64 ip[]; 19 }; 20 21 struct bpf_stack_map { 22 struct bpf_map map; 23 void *elems; 24 struct pcpu_freelist freelist; 25 u32 n_buckets; 26 struct stack_map_bucket *buckets[]; 27 }; 28 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 34 smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries); 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: 47 bpf_map_area_free(smap->elems); 48 return err; 49 } 50 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 62 if (attr->map_flags) 63 return ERR_PTR(-EINVAL); 64 65 /* check sanity of attributes */ 66 if (attr->max_entries == 0 || attr->key_size != 4 || 67 value_size < 8 || value_size % 8 || 68 value_size / 8 > sysctl_perf_event_max_stack) 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 78 smap = bpf_map_area_alloc(cost); 79 if (!smap) 80 return ERR_PTR(-ENOMEM); 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; 91 smap->n_buckets = n_buckets; 92 smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; 93 94 err = bpf_map_precharge_memlock(smap->map.pages); 95 if (err) 96 goto free_smap; 97 98 err = get_callchain_buffers(sysctl_perf_event_max_stack); 99 if (err) 100 goto free_smap; 101 102 err = prealloc_elems_and_freelist(smap); 103 if (err) 104 goto put_buffers; 105 106 return &smap->map; 107 108 put_buffers: 109 put_callchain_buffers(); 110 free_smap: 111 bpf_map_area_free(smap); 112 return ERR_PTR(err); 113 } 114 115 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, 116 u64, flags) 117 { 118 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); 119 struct perf_callchain_entry *trace; 120 struct stack_map_bucket *bucket, *new_bucket, *old_bucket; 121 u32 max_depth = map->value_size / 8; 122 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */ 123 u32 init_nr = sysctl_perf_event_max_stack - max_depth; 124 u32 skip = flags & BPF_F_SKIP_FIELD_MASK; 125 u32 hash, id, trace_nr, trace_len; 126 bool user = flags & BPF_F_USER_STACK; 127 bool kernel = !user; 128 u64 *ips; 129 130 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | 131 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) 132 return -EINVAL; 133 134 trace = get_perf_callchain(regs, init_nr, kernel, user, 135 sysctl_perf_event_max_stack, false, false); 136 137 if (unlikely(!trace)) 138 /* couldn't fetch the stack trace */ 139 return -EFAULT; 140 141 /* get_perf_callchain() guarantees that trace->nr >= init_nr 142 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth 143 */ 144 trace_nr = trace->nr - init_nr; 145 146 if (trace_nr <= skip) 147 /* skipping more than usable stack trace */ 148 return -EFAULT; 149 150 trace_nr -= skip; 151 trace_len = trace_nr * sizeof(u64); 152 ips = trace->ip + skip + init_nr; 153 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); 154 id = hash & (smap->n_buckets - 1); 155 bucket = READ_ONCE(smap->buckets[id]); 156 157 if (bucket && bucket->hash == hash) { 158 if (flags & BPF_F_FAST_STACK_CMP) 159 return id; 160 if (bucket->nr == trace_nr && 161 memcmp(bucket->ip, ips, trace_len) == 0) 162 return id; 163 } 164 165 /* this call stack is not in the map, try to add it */ 166 if (bucket && !(flags & BPF_F_REUSE_STACKID)) 167 return -EEXIST; 168 169 new_bucket = (struct stack_map_bucket *) 170 pcpu_freelist_pop(&smap->freelist); 171 if (unlikely(!new_bucket)) 172 return -ENOMEM; 173 174 memcpy(new_bucket->ip, ips, trace_len); 175 new_bucket->hash = hash; 176 new_bucket->nr = trace_nr; 177 178 old_bucket = xchg(&smap->buckets[id], new_bucket); 179 if (old_bucket) 180 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); 181 return id; 182 } 183 184 const struct bpf_func_proto bpf_get_stackid_proto = { 185 .func = bpf_get_stackid, 186 .gpl_only = true, 187 .ret_type = RET_INTEGER, 188 .arg1_type = ARG_PTR_TO_CTX, 189 .arg2_type = ARG_CONST_MAP_PTR, 190 .arg3_type = ARG_ANYTHING, 191 }; 192 193 /* Called from eBPF program */ 194 static void *stack_map_lookup_elem(struct bpf_map *map, void *key) 195 { 196 return NULL; 197 } 198 199 /* Called from syscall */ 200 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value) 201 { 202 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); 203 struct stack_map_bucket *bucket, *old_bucket; 204 u32 id = *(u32 *)key, trace_len; 205 206 if (unlikely(id >= smap->n_buckets)) 207 return -ENOENT; 208 209 bucket = xchg(&smap->buckets[id], NULL); 210 if (!bucket) 211 return -ENOENT; 212 213 trace_len = bucket->nr * sizeof(u64); 214 memcpy(value, bucket->ip, trace_len); 215 memset(value + trace_len, 0, map->value_size - trace_len); 216 217 old_bucket = xchg(&smap->buckets[id], bucket); 218 if (old_bucket) 219 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); 220 return 0; 221 } 222 223 static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key) 224 { 225 return -EINVAL; 226 } 227 228 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value, 229 u64 map_flags) 230 { 231 return -EINVAL; 232 } 233 234 /* Called from syscall or from eBPF program */ 235 static int stack_map_delete_elem(struct bpf_map *map, void *key) 236 { 237 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); 238 struct stack_map_bucket *old_bucket; 239 u32 id = *(u32 *)key; 240 241 if (unlikely(id >= smap->n_buckets)) 242 return -E2BIG; 243 244 old_bucket = xchg(&smap->buckets[id], NULL); 245 if (old_bucket) { 246 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); 247 return 0; 248 } else { 249 return -ENOENT; 250 } 251 } 252 253 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */ 254 static void stack_map_free(struct bpf_map *map) 255 { 256 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); 257 258 /* wait for bpf programs to complete before freeing stack map */ 259 synchronize_rcu(); 260 261 bpf_map_area_free(smap->elems); 262 pcpu_freelist_destroy(&smap->freelist); 263 bpf_map_area_free(smap); 264 put_callchain_buffers(); 265 } 266 267 static const struct bpf_map_ops stack_map_ops = { 268 .map_alloc = stack_map_alloc, 269 .map_free = stack_map_free, 270 .map_get_next_key = stack_map_get_next_key, 271 .map_lookup_elem = stack_map_lookup_elem, 272 .map_update_elem = stack_map_update_elem, 273 .map_delete_elem = stack_map_delete_elem, 274 }; 275 276 static struct bpf_map_type_list stack_map_type __ro_after_init = { 277 .ops = &stack_map_ops, 278 .type = BPF_MAP_TYPE_STACK_TRACE, 279 }; 280 281 static int __init register_stack_map(void) 282 { 283 bpf_register_map_type(&stack_map_type); 284 return 0; 285 } 286 late_initcall(register_stack_map); 287