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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>
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4ast authored and davem330 committed Feb 18, 2016
1 parent 568b329 commit d5a3b1f691865be576c2bffa708549b8cdccda19
Showing with 269 additions and 1 deletion.
  1. +1 −0 include/linux/bpf.h
  2. +21 −0 include/uapi/linux/bpf.h
  3. +3 −0 kernel/bpf/Makefile
  4. +237 −0 kernel/bpf/stackmap.c
  5. +5 −1 kernel/bpf/verifier.c
  6. +2 −0 kernel/trace/bpf_trace.c
@@ -237,6 +237,7 @@ extern const struct bpf_func_proto bpf_get_current_uid_gid_proto;
extern const struct bpf_func_proto bpf_get_current_comm_proto;
extern const struct bpf_func_proto bpf_skb_vlan_push_proto;
extern const struct bpf_func_proto bpf_skb_vlan_pop_proto;
extern const struct bpf_func_proto bpf_get_stackid_proto;
/* Shared helpers among cBPF and eBPF. */
void bpf_user_rnd_init_once(void);
@@ -83,6 +83,7 @@ enum bpf_map_type {
BPF_MAP_TYPE_PERF_EVENT_ARRAY,
BPF_MAP_TYPE_PERCPU_HASH,
BPF_MAP_TYPE_PERCPU_ARRAY,
BPF_MAP_TYPE_STACK_TRACE,
};
enum bpf_prog_type {
@@ -272,6 +273,20 @@ enum bpf_func_id {
*/
BPF_FUNC_perf_event_output,
BPF_FUNC_skb_load_bytes,
/**
* 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
*/
BPF_FUNC_get_stackid,
__BPF_FUNC_MAX_ID,
};
@@ -294,6 +309,12 @@ enum bpf_func_id {
/* BPF_FUNC_skb_set_tunnel_key and BPF_FUNC_skb_get_tunnel_key flags. */
#define BPF_F_TUNINFO_IPV6 (1ULL << 0)
/* BPF_FUNC_get_stackid flags. */
#define BPF_F_SKIP_FIELD_MASK 0xffULL
#define BPF_F_USER_STACK (1ULL << 8)
#define BPF_F_FAST_STACK_CMP (1ULL << 9)
#define BPF_F_REUSE_STACKID (1ULL << 10)
/* user accessible mirror of in-kernel sk_buff.
* new fields can only be added to the end of this structure
*/
@@ -2,3 +2,6 @@ obj-y := core.o
obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o
obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o
ifeq ($(CONFIG_PERF_EVENTS),y)
obj-$(CONFIG_BPF_SYSCALL) += stackmap.o
endif
@@ -0,0 +1,237 @@
/* Copyright (c) 2016 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*/
#include <linux/bpf.h>
#include <linux/jhash.h>
#include <linux/filter.h>
#include <linux/vmalloc.h>
#include <linux/stacktrace.h>
#include <linux/perf_event.h>
struct stack_map_bucket {
struct rcu_head rcu;
u32 hash;
u32 nr;
u64 ip[];
};
struct bpf_stack_map {
struct bpf_map map;
u32 n_buckets;
struct stack_map_bucket __rcu *buckets[];
};
/* Called from syscall */
static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
{
u32 value_size = attr->value_size;
struct bpf_stack_map *smap;
u64 cost, n_buckets;
int err;
if (!capable(CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
/* check sanity of attributes */
if (attr->max_entries == 0 || attr->key_size != 4 ||
value_size < 8 || value_size % 8 ||
value_size / 8 > PERF_MAX_STACK_DEPTH)
return ERR_PTR(-EINVAL);
/* hash table size must be power of 2 */
n_buckets = roundup_pow_of_two(attr->max_entries);
cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
if (cost >= U32_MAX - PAGE_SIZE)
return ERR_PTR(-E2BIG);
smap = kzalloc(cost, GFP_USER | __GFP_NOWARN);
if (!smap) {
smap = vzalloc(cost);
if (!smap)
return ERR_PTR(-ENOMEM);
}
err = -E2BIG;
cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
if (cost >= U32_MAX - PAGE_SIZE)
goto free_smap;
smap->map.map_type = attr->map_type;
smap->map.key_size = attr->key_size;
smap->map.value_size = value_size;
smap->map.max_entries = attr->max_entries;
smap->n_buckets = n_buckets;
smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
err = get_callchain_buffers();
if (err)
goto free_smap;
return &smap->map;
free_smap:
kvfree(smap);
return ERR_PTR(err);
}
static u64 bpf_get_stackid(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5)
{
struct pt_regs *regs = (struct pt_regs *) (long) r1;
struct bpf_map *map = (struct bpf_map *) (long) r2;
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 <= PERF_MAX_STACK_DEPTH */
u32 init_nr = PERF_MAX_STACK_DEPTH - 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, 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 <= PERF_MAX_STACK_DEPTH, 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 = rcu_dereference(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 = kmalloc(sizeof(struct stack_map_bucket) + map->value_size,
GFP_ATOMIC | __GFP_NOWARN);
if (unlikely(!new_bucket))
return -ENOMEM;
memcpy(new_bucket->ip, ips, trace_len);
memset(new_bucket->ip + trace_len / 8, 0, map->value_size - trace_len);
new_bucket->hash = hash;
new_bucket->nr = trace_nr;
old_bucket = xchg(&smap->buckets[id], new_bucket);
if (old_bucket)
kfree_rcu(old_bucket, rcu);
return id;
}
const struct bpf_func_proto bpf_get_stackid_proto = {
.func = bpf_get_stackid,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_CONST_MAP_PTR,
.arg3_type = ARG_ANYTHING,
};
/* Called from syscall or from eBPF program */
static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct stack_map_bucket *bucket;
u32 id = *(u32 *)key;
if (unlikely(id >= smap->n_buckets))
return NULL;
bucket = rcu_dereference(smap->buckets[id]);
return bucket ? bucket->ip : NULL;
}
static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
{
return -EINVAL;
}
static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 map_flags)
{
return -EINVAL;
}
/* Called from syscall or from eBPF program */
static int stack_map_delete_elem(struct bpf_map *map, void *key)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct stack_map_bucket *old_bucket;
u32 id = *(u32 *)key;
if (unlikely(id >= smap->n_buckets))
return -E2BIG;
old_bucket = xchg(&smap->buckets[id], NULL);
if (old_bucket) {
kfree_rcu(old_bucket, rcu);
return 0;
} else {
return -ENOENT;
}
}
/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
static void stack_map_free(struct bpf_map *map)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
int i;
synchronize_rcu();
for (i = 0; i < smap->n_buckets; i++)
if (smap->buckets[i])
kfree_rcu(smap->buckets[i], rcu);
kvfree(smap);
put_callchain_buffers();
}
static const struct bpf_map_ops stack_map_ops = {
.map_alloc = stack_map_alloc,
.map_free = stack_map_free,
.map_get_next_key = stack_map_get_next_key,
.map_lookup_elem = stack_map_lookup_elem,
.map_update_elem = stack_map_update_elem,
.map_delete_elem = stack_map_delete_elem,
};
static struct bpf_map_type_list stack_map_type __read_mostly = {
.ops = &stack_map_ops,
.type = BPF_MAP_TYPE_STACK_TRACE,
};
static int __init register_stack_map(void)
{
bpf_register_map_type(&stack_map_type);
return 0;
}
late_initcall(register_stack_map);
@@ -246,6 +246,7 @@ static const struct {
{BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output},
{BPF_MAP_TYPE_STACK_TRACE, BPF_FUNC_get_stackid},
};
static void print_verifier_state(struct verifier_env *env)
@@ -911,8 +912,11 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
* don't allow any other map type to be passed into
* the special func;
*/
if (bool_func && bool_map != bool_func)
if (bool_func && bool_map != bool_func) {
verbose("cannot pass map_type %d into func %d\n",
map->map_type, func_id);
return -EINVAL;
}
}
return 0;
@@ -299,6 +299,8 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
return &bpf_perf_event_read_proto;
case BPF_FUNC_perf_event_output:
return &bpf_perf_event_output_proto;
case BPF_FUNC_get_stackid:
return &bpf_get_stackid_proto;
default:
return NULL;
}

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