bpf: introduce BPF_MAP_TYPE_STACK_TRACE (d5a3b1f6) · Commits · 戴 / test

include/linux/bpf.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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);

include/uapi/linux/bpf.h

+21 −0

Original line number	Diff line number	Diff line
		@@ -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
		*/

kernel/bpf/Makefile

+3 −0

Original line number	Diff line number	Diff line
		@@ -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

kernel/bpf/stackmap.c

0 → 100644

+237 −0

Original line number	Diff line number	Diff line
		/* 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);

kernel/bpf/verifier.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -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)
		@@ -911,9 +912,12 @@ 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;
		}

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