struct perf_callchain_entry *
perf_callchain(struct perf_event *event, struct pt_regs *regs)
{
bool kernel = !event->attr.exclude_callchain_kernel;
bool user = !event->attr.exclude_callchain_user;
/* Disallow cross-task user callchains. */
bool crosstask = event->ctx->task && event->ctx->task != current;
if (!kernel && !user)
return NULL;
return get_perf_callchain(regs, 0, kernel, user, sysctl_perf_event_max_stack, crosstask, true);
}
BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
u64, flags)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct perf_callchain_entry *trace;
struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
u32 max_depth = map->value_size / 8;
/* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
u32 init_nr = sysctl_perf_event_max_stack - max_depth;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
u32 hash, id, trace_nr, trace_len;
bool user = flags & BPF_F_USER_STACK;
bool kernel = !user;
u64 *ips;
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
return -EINVAL;
trace = get_perf_callchain(regs, init_nr, kernel, user,
sysctl_perf_event_max_stack, false, false);
if (unlikely(!trace))
/* couldn't fetch the stack trace */
return -EFAULT;
/* get_perf_callchain() guarantees that trace->nr >= init_nr
* and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
*/
trace_nr = trace->nr - init_nr;
if (trace_nr <= skip)
/* skipping more than usable stack trace */
return -EFAULT;
trace_nr -= skip;
trace_len = trace_nr * sizeof(u64);
ips = trace->ip + skip + init_nr;
hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
id = hash & (smap->n_buckets - 1);
bucket = READ_ONCE(smap->buckets[id]);
if (bucket && bucket->hash == hash) {
if (flags & BPF_F_FAST_STACK_CMP)
return id;
if (bucket->nr == trace_nr &&
memcmp(bucket->ip, ips, trace_len) == 0)
return id;
}
/* this call stack is not in the map, try to add it */
if (bucket && !(flags & BPF_F_REUSE_STACKID))
return -EEXIST;
new_bucket = (struct stack_map_bucket *)
pcpu_freelist_pop(&smap->freelist);
if (unlikely(!new_bucket))
return -ENOMEM;
memcpy(new_bucket->ip, ips, trace_len);
new_bucket->hash = hash;
new_bucket->nr = trace_nr;
old_bucket = xchg(&smap->buckets[id], new_bucket);
if (old_bucket)
pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
return id;
}
