bpf: introduce BPF_MAP_TYPE_STACK_TRACE
add new map type to store stack traces and corresponding helper
bpf_get_stackid(ctx, map, flags) - walk user or kernel stack and return id
@ctx: struct pt_regs*
@map: pointer to stack_trace map
@flags: bits 0-7 - numer of stack frames to skip
bit 8 - collect user stack instead of kernel
bit 9 - compare stacks by hash only
bit 10 - if two different stacks hash into the same stackid
discard old
other bits - reserved
Return: >= 0 stackid on success or negative error
stackid is a 32-bit integer handle that can be further combined with
other data (including other stackid) and used as a key into maps.
Userspace will access stackmap using standard lookup/delete syscall commands to
retrieve full stack trace for given stackid.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov
David S. Miller
parent
568b329a02
commit
d5a3b1f691
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@ -237,6 +237,7 @@ extern const struct bpf_func_proto bpf_get_current_uid_gid_proto;
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extern const struct bpf_func_proto bpf_get_current_comm_proto;
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extern const struct bpf_func_proto bpf_skb_vlan_push_proto;
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extern const struct bpf_func_proto bpf_skb_vlan_pop_proto;
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extern const struct bpf_func_proto bpf_get_stackid_proto;
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/* Shared helpers among cBPF and eBPF. */
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void bpf_user_rnd_init_once(void);
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@ -83,6 +83,7 @@ enum bpf_map_type {
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BPF_MAP_TYPE_PERF_EVENT_ARRAY,
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BPF_MAP_TYPE_PERCPU_HASH,
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BPF_MAP_TYPE_PERCPU_ARRAY,
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BPF_MAP_TYPE_STACK_TRACE,
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};
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enum bpf_prog_type {
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@ -272,6 +273,20 @@ enum bpf_func_id {
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*/
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BPF_FUNC_perf_event_output,
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BPF_FUNC_skb_load_bytes,
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/**
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* bpf_get_stackid(ctx, map, flags) - walk user or kernel stack and return id
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* @ctx: struct pt_regs*
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* @map: pointer to stack_trace map
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* @flags: bits 0-7 - numer of stack frames to skip
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* bit 8 - collect user stack instead of kernel
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* bit 9 - compare stacks by hash only
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* bit 10 - if two different stacks hash into the same stackid
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* discard old
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* other bits - reserved
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* Return: >= 0 stackid on success or negative error
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*/
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BPF_FUNC_get_stackid,
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__BPF_FUNC_MAX_ID,
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};
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@ -294,6 +309,12 @@ enum bpf_func_id {
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/* BPF_FUNC_skb_set_tunnel_key and BPF_FUNC_skb_get_tunnel_key flags. */
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#define BPF_F_TUNINFO_IPV6 (1ULL << 0)
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/* BPF_FUNC_get_stackid flags. */
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#define BPF_F_SKIP_FIELD_MASK 0xffULL
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#define BPF_F_USER_STACK (1ULL << 8)
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#define BPF_F_FAST_STACK_CMP (1ULL << 9)
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#define BPF_F_REUSE_STACKID (1ULL << 10)
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/* user accessible mirror of in-kernel sk_buff.
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* new fields can only be added to the end of this structure
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*/
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@ -2,3 +2,6 @@ obj-y := core.o
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obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o
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obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o
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ifeq ($(CONFIG_PERF_EVENTS),y)
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obj-$(CONFIG_BPF_SYSCALL) += stackmap.o
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endif
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@ -0,0 +1,237 @@
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/* Copyright (c) 2016 Facebook
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*/
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#include <linux/bpf.h>
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#include <linux/jhash.h>
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#include <linux/filter.h>
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#include <linux/vmalloc.h>
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#include <linux/stacktrace.h>
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#include <linux/perf_event.h>
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struct stack_map_bucket {
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struct rcu_head rcu;
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u32 hash;
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u32 nr;
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u64 ip[];
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};
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struct bpf_stack_map {
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struct bpf_map map;
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u32 n_buckets;
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struct stack_map_bucket __rcu *buckets[];
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};
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/* Called from syscall */
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static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
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{
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u32 value_size = attr->value_size;
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struct bpf_stack_map *smap;
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u64 cost, n_buckets;
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int err;
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if (!capable(CAP_SYS_ADMIN))
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return ERR_PTR(-EPERM);
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/* check sanity of attributes */
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if (attr->max_entries == 0 || attr->key_size != 4 ||
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value_size < 8 || value_size % 8 ||
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value_size / 8 > PERF_MAX_STACK_DEPTH)
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return ERR_PTR(-EINVAL);
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/* hash table size must be power of 2 */
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n_buckets = roundup_pow_of_two(attr->max_entries);
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cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
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if (cost >= U32_MAX - PAGE_SIZE)
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return ERR_PTR(-E2BIG);
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smap = kzalloc(cost, GFP_USER | __GFP_NOWARN);
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if (!smap) {
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smap = vzalloc(cost);
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if (!smap)
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return ERR_PTR(-ENOMEM);
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}
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err = -E2BIG;
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cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
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if (cost >= U32_MAX - PAGE_SIZE)
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goto free_smap;
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smap->map.map_type = attr->map_type;
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smap->map.key_size = attr->key_size;
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smap->map.value_size = value_size;
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smap->map.max_entries = attr->max_entries;
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smap->n_buckets = n_buckets;
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smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
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err = get_callchain_buffers();
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if (err)
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goto free_smap;
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return &smap->map;
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free_smap:
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kvfree(smap);
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return ERR_PTR(err);
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}
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static u64 bpf_get_stackid(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5)
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{
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struct pt_regs *regs = (struct pt_regs *) (long) r1;
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struct bpf_map *map = (struct bpf_map *) (long) r2;
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struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
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struct perf_callchain_entry *trace;
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struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
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u32 max_depth = map->value_size / 8;
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/* stack_map_alloc() checks that max_depth <= PERF_MAX_STACK_DEPTH */
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u32 init_nr = PERF_MAX_STACK_DEPTH - max_depth;
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u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
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u32 hash, id, trace_nr, trace_len;
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bool user = flags & BPF_F_USER_STACK;
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bool kernel = !user;
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u64 *ips;
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if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
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BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
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return -EINVAL;
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trace = get_perf_callchain(regs, init_nr, kernel, user, false, false);
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if (unlikely(!trace))
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/* couldn't fetch the stack trace */
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return -EFAULT;
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/* get_perf_callchain() guarantees that trace->nr >= init_nr
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* and trace-nr <= PERF_MAX_STACK_DEPTH, so trace_nr <= max_depth
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*/
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trace_nr = trace->nr - init_nr;
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if (trace_nr <= skip)
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/* skipping more than usable stack trace */
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return -EFAULT;
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trace_nr -= skip;
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trace_len = trace_nr * sizeof(u64);
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ips = trace->ip + skip + init_nr;
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hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
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id = hash & (smap->n_buckets - 1);
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bucket = rcu_dereference(smap->buckets[id]);
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if (bucket && bucket->hash == hash) {
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if (flags & BPF_F_FAST_STACK_CMP)
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return id;
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if (bucket->nr == trace_nr &&
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memcmp(bucket->ip, ips, trace_len) == 0)
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return id;
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}
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/* this call stack is not in the map, try to add it */
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if (bucket && !(flags & BPF_F_REUSE_STACKID))
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return -EEXIST;
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new_bucket = kmalloc(sizeof(struct stack_map_bucket) + map->value_size,
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GFP_ATOMIC | __GFP_NOWARN);
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if (unlikely(!new_bucket))
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return -ENOMEM;
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memcpy(new_bucket->ip, ips, trace_len);
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memset(new_bucket->ip + trace_len / 8, 0, map->value_size - trace_len);
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new_bucket->hash = hash;
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new_bucket->nr = trace_nr;
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old_bucket = xchg(&smap->buckets[id], new_bucket);
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if (old_bucket)
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kfree_rcu(old_bucket, rcu);
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return id;
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}
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const struct bpf_func_proto bpf_get_stackid_proto = {
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.func = bpf_get_stackid,
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.gpl_only = true,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_PTR_TO_CTX,
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.arg2_type = ARG_CONST_MAP_PTR,
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.arg3_type = ARG_ANYTHING,
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};
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/* Called from syscall or from eBPF program */
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static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
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{
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struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
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struct stack_map_bucket *bucket;
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u32 id = *(u32 *)key;
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if (unlikely(id >= smap->n_buckets))
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return NULL;
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bucket = rcu_dereference(smap->buckets[id]);
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return bucket ? bucket->ip : NULL;
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}
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static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
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{
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return -EINVAL;
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}
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static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
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u64 map_flags)
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{
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return -EINVAL;
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}
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/* Called from syscall or from eBPF program */
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static int stack_map_delete_elem(struct bpf_map *map, void *key)
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{
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struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
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struct stack_map_bucket *old_bucket;
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u32 id = *(u32 *)key;
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if (unlikely(id >= smap->n_buckets))
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return -E2BIG;
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old_bucket = xchg(&smap->buckets[id], NULL);
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if (old_bucket) {
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kfree_rcu(old_bucket, rcu);
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return 0;
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} else {
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return -ENOENT;
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}
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}
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/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
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static void stack_map_free(struct bpf_map *map)
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{
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struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
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int i;
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synchronize_rcu();
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for (i = 0; i < smap->n_buckets; i++)
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if (smap->buckets[i])
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kfree_rcu(smap->buckets[i], rcu);
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kvfree(smap);
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put_callchain_buffers();
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}
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static const struct bpf_map_ops stack_map_ops = {
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.map_alloc = stack_map_alloc,
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.map_free = stack_map_free,
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.map_get_next_key = stack_map_get_next_key,
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.map_lookup_elem = stack_map_lookup_elem,
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.map_update_elem = stack_map_update_elem,
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.map_delete_elem = stack_map_delete_elem,
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};
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static struct bpf_map_type_list stack_map_type __read_mostly = {
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.ops = &stack_map_ops,
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.type = BPF_MAP_TYPE_STACK_TRACE,
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};
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static int __init register_stack_map(void)
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{
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bpf_register_map_type(&stack_map_type);
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return 0;
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}
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late_initcall(register_stack_map);
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@ -246,6 +246,7 @@ static const struct {
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{BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
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{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
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{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output},
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{BPF_MAP_TYPE_STACK_TRACE, BPF_FUNC_get_stackid},
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};
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static void print_verifier_state(struct verifier_env *env)
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@ -911,8 +912,11 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
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* don't allow any other map type to be passed into
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* the special func;
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*/
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if (bool_func && bool_map != bool_func)
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if (bool_func && bool_map != bool_func) {
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verbose("cannot pass map_type %d into func %d\n",
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map->map_type, func_id);
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return -EINVAL;
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}
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}
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return 0;
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@ -299,6 +299,8 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
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return &bpf_perf_event_read_proto;
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case BPF_FUNC_perf_event_output:
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return &bpf_perf_event_output_proto;
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case BPF_FUNC_get_stackid:
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return &bpf_get_stackid_proto;
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default:
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return NULL;
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}
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