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 smap->map.numa_node); 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 bpf_map_area_free(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 & ~BPF_F_NUMA_NODE) 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 > sysctl_perf_event_max_stack) 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 = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr)); 80 if (!smap) 81 return ERR_PTR(-ENOMEM); 82 83 err = -E2BIG; 84 cost += n_buckets * (value_size + sizeof(struct stack_map_bucket)); 85 if (cost >= U32_MAX - PAGE_SIZE) 86 goto free_smap; 87 88 smap->map.map_type = attr->map_type; 89 smap->map.key_size = attr->key_size; 90 smap->map.value_size = value_size; 91 smap->map.max_entries = attr->max_entries; 92 smap->map.map_flags = attr->map_flags; 93 smap->n_buckets = n_buckets; 94 smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; 95 smap->map.numa_node = bpf_map_attr_numa_node(attr); 96 97 err = bpf_map_precharge_memlock(smap->map.pages); 98 if (err) 99 goto free_smap; 100 101 err = get_callchain_buffers(sysctl_perf_event_max_stack); 102 if (err) 103 goto free_smap; 104 105 err = prealloc_elems_and_freelist(smap); 106 if (err) 107 goto put_buffers; 108 109 return &smap->map; 110 111 put_buffers: 112 put_callchain_buffers(); 113 free_smap: 114 bpf_map_area_free(smap); 115 return ERR_PTR(err); 116 } 117 118 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, 119 u64, flags) 120 { 121 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); 122 struct perf_callchain_entry *trace; 123 struct stack_map_bucket *bucket, *new_bucket, *old_bucket; 124 u32 max_depth = map->value_size / 8; 125 /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */ 126 u32 init_nr = sysctl_perf_event_max_stack - max_depth; 127 u32 skip = flags & BPF_F_SKIP_FIELD_MASK; 128 u32 hash, id, trace_nr, trace_len; 129 bool user = flags & BPF_F_USER_STACK; 130 bool kernel = !user; 131 u64 *ips; 132 133 if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | 134 BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) 135 return -EINVAL; 136 137 trace = get_perf_callchain(regs, init_nr, kernel, user, 138 sysctl_perf_event_max_stack, false, false); 139 140 if (unlikely(!trace)) 141 /* couldn't fetch the stack trace */ 142 return -EFAULT; 143 144 /* get_perf_callchain() guarantees that trace->nr >= init_nr 145 * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth 146 */ 147 trace_nr = trace->nr - init_nr; 148 149 if (trace_nr <= skip) 150 /* skipping more than usable stack trace */ 151 return -EFAULT; 152 153 trace_nr -= skip; 154 trace_len = trace_nr * sizeof(u64); 155 ips = trace->ip + skip + init_nr; 156 hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); 157 id = hash & (smap->n_buckets - 1); 158 bucket = READ_ONCE(smap->buckets[id]); 159 160 if (bucket && bucket->hash == hash) { 161 if (flags & BPF_F_FAST_STACK_CMP) 162 return id; 163 if (bucket->nr == trace_nr && 164 memcmp(bucket->ip, ips, trace_len) == 0) 165 return id; 166 } 167 168 /* this call stack is not in the map, try to add it */ 169 if (bucket && !(flags & BPF_F_REUSE_STACKID)) 170 return -EEXIST; 171 172 new_bucket = (struct stack_map_bucket *) 173 pcpu_freelist_pop(&smap->freelist); 174 if (unlikely(!new_bucket)) 175 return -ENOMEM; 176 177 memcpy(new_bucket->ip, ips, trace_len); 178 new_bucket->hash = hash; 179 new_bucket->nr = trace_nr; 180 181 old_bucket = xchg(&smap->buckets[id], new_bucket); 182 if (old_bucket) 183 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); 184 return id; 185 } 186 187 const struct bpf_func_proto bpf_get_stackid_proto = { 188 .func = bpf_get_stackid, 189 .gpl_only = true, 190 .ret_type = RET_INTEGER, 191 .arg1_type = ARG_PTR_TO_CTX, 192 .arg2_type = ARG_CONST_MAP_PTR, 193 .arg3_type = ARG_ANYTHING, 194 }; 195 196 /* Called from eBPF program */ 197 static void *stack_map_lookup_elem(struct bpf_map *map, void *key) 198 { 199 return NULL; 200 } 201 202 /* Called from syscall */ 203 int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value) 204 { 205 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); 206 struct stack_map_bucket *bucket, *old_bucket; 207 u32 id = *(u32 *)key, trace_len; 208 209 if (unlikely(id >= smap->n_buckets)) 210 return -ENOENT; 211 212 bucket = xchg(&smap->buckets[id], NULL); 213 if (!bucket) 214 return -ENOENT; 215 216 trace_len = bucket->nr * sizeof(u64); 217 memcpy(value, bucket->ip, trace_len); 218 memset(value + trace_len, 0, map->value_size - trace_len); 219 220 old_bucket = xchg(&smap->buckets[id], bucket); 221 if (old_bucket) 222 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); 223 return 0; 224 } 225 226 static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key) 227 { 228 return -EINVAL; 229 } 230 231 static int stack_map_update_elem(struct bpf_map *map, void *key, void *value, 232 u64 map_flags) 233 { 234 return -EINVAL; 235 } 236 237 /* Called from syscall or from eBPF program */ 238 static int stack_map_delete_elem(struct bpf_map *map, void *key) 239 { 240 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); 241 struct stack_map_bucket *old_bucket; 242 u32 id = *(u32 *)key; 243 244 if (unlikely(id >= smap->n_buckets)) 245 return -E2BIG; 246 247 old_bucket = xchg(&smap->buckets[id], NULL); 248 if (old_bucket) { 249 pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); 250 return 0; 251 } else { 252 return -ENOENT; 253 } 254 } 255 256 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */ 257 static void stack_map_free(struct bpf_map *map) 258 { 259 struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); 260 261 /* wait for bpf programs to complete before freeing stack map */ 262 synchronize_rcu(); 263 264 bpf_map_area_free(smap->elems); 265 pcpu_freelist_destroy(&smap->freelist); 266 bpf_map_area_free(smap); 267 put_callchain_buffers(); 268 } 269 270 const struct bpf_map_ops stack_map_ops = { 271 .map_alloc = stack_map_alloc, 272 .map_free = stack_map_free, 273 .map_get_next_key = stack_map_get_next_key, 274 .map_lookup_elem = stack_map_lookup_elem, 275 .map_update_elem = stack_map_update_elem, 276 .map_delete_elem = stack_map_delete_elem, 277 }; 278