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 #define STACK_CREATE_FLAG_MASK \ 15 (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY) 16 17 struct stack_map_bucket { 18 struct pcpu_freelist_node fnode; 19 u32 hash; 20 u32 nr; 21 u64 ip[]; 22 }; 23 24 struct bpf_stack_map { 25 struct bpf_map map; 26 void *elems; 27 struct pcpu_freelist freelist; 28 u32 n_buckets; 29 struct stack_map_bucket *buckets[]; 30 }; 31 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 37 smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries, 38 smap->map.numa_node); 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: 51 bpf_map_area_free(smap->elems); 52 return err; 53 } 54 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 66 if (attr->map_flags & ~STACK_CREATE_FLAG_MASK) 67 return ERR_PTR(-EINVAL); 68 69 /* check sanity of attributes */ 70 if (attr->max_entries == 0 || attr->key_size != 4 || 71 value_size < 8 || value_size % 8 || 72 value_size / 8 > sysctl_perf_event_max_stack) 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 82 smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr)); 83 if (!smap) 84 return ERR_PTR(-ENOMEM); 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->map.map_flags = attr->map_flags; 96 smap->n_buckets = n_buckets; 97 smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; 98 smap->map.numa_node = bpf_map_attr_numa_node(attr); 99 100 err = bpf_map_precharge_memlock(smap->map.pages); 101 if (err) 102 goto free_smap; 103 104 err = get_callchain_buffers(sysctl_perf_event_max_stack); 105 if (err) 106 goto free_smap; 107 108 err = prealloc_elems_and_freelist(smap); 109 if (err) 110 goto put_buffers; 111 112 return &smap->map; 113 114 put_buffers: 115 put_callchain_buffers(); 116 free_smap: 117 bpf_map_area_free(smap); 118 return ERR_PTR(err); 119 } 120 121 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, 122 u64, flags) 123 { 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; 128 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */ 129 u32 init_nr = sysctl_perf_event_max_stack - max_depth; 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; 139 140 trace = get_perf_callchain(regs, init_nr, kernel, user, 141 sysctl_perf_event_max_stack, false, false); 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 148 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth 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); 161 bucket = READ_ONCE(smap->buckets[id]); 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; 174 175 new_bucket = (struct stack_map_bucket *) 176 pcpu_freelist_pop(&smap->freelist); 177 if (unlikely(!new_bucket)) 178 return -ENOMEM; 179 180 memcpy(new_bucket->ip, ips, trace_len); 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) 186 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); 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 }; 198 199 /* Called from eBPF program */ 200 static void *stack_map_lookup_elem(struct bpf_map *map, void *key) 201 { 202 return NULL; 203 } 204 205 /* Called from syscall */ 206 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value) 207 { 208 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); 209 struct stack_map_bucket *bucket, *old_bucket; 210 u32 id = *(u32 *)key, trace_len; 211 212 if (unlikely(id >= smap->n_buckets)) 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; 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) { 252 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); 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); 263 264 /* wait for bpf programs to complete before freeing stack map */ 265 synchronize_rcu(); 266 267 bpf_map_area_free(smap->elems); 268 pcpu_freelist_destroy(&smap->freelist); 269 bpf_map_area_free(smap); 270 put_callchain_buffers(); 271 } 272 273 const struct bpf_map_ops stack_map_ops = { 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 }; 281