[mirror_ubuntu-zesty-kernel.git] / kernel / bpf / stackmap.c

/* 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/stacktrace.h>
#include <linux/perf_event.h>
#include "percpu_freelist.h"

struct stack_map_bucket {
	struct pcpu_freelist_node fnode;
	u32 hash;
	u32 nr;
	u64 ip[];
};

struct bpf_stack_map {
	struct bpf_map map;
	void *elems;
	struct pcpu_freelist freelist;
	u32 n_buckets;
	struct stack_map_bucket *buckets[];
};

static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
{
	u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
	int err;

	smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries);
	if (!smap->elems)
		return -ENOMEM;

	err = pcpu_freelist_init(&smap->freelist);
	if (err)
		goto free_elems;

	pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
			       smap->map.max_entries);
	return 0;

free_elems:
	bpf_map_area_free(smap->elems);
	return err;
}

/* 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);

	if (attr->map_flags)
		return ERR_PTR(-EINVAL);

	/* check sanity of attributes */
	if (attr->max_entries == 0 || attr->key_size != 4 ||
	    value_size < 8 || value_size % 8 ||
	    value_size / 8 > sysctl_perf_event_max_stack)
		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 = bpf_map_area_alloc(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 = bpf_map_precharge_memlock(smap->map.pages);
	if (err)
		goto free_smap;

	err = get_callchain_buffers(sysctl_perf_event_max_stack);
	if (err)
		goto free_smap;

	err = prealloc_elems_and_freelist(smap);
	if (err)
		goto put_buffers;

	return &smap->map;

put_buffers:
	put_callchain_buffers();
free_smap:
	bpf_map_area_free(smap);
	return ERR_PTR(err);
}

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;
}

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 eBPF program */
static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
{
	return NULL;
}

/* Called from syscall */
int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
{
	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
	struct stack_map_bucket *bucket, *old_bucket;
	u32 id = *(u32 *)key, trace_len;

	if (unlikely(id >= smap->n_buckets))
		return -ENOENT;

	bucket = xchg(&smap->buckets[id], NULL);
	if (!bucket)
		return -ENOENT;

	trace_len = bucket->nr * sizeof(u64);
	memcpy(value, bucket->ip, trace_len);
	memset(value + trace_len, 0, map->value_size - trace_len);

	old_bucket = xchg(&smap->buckets[id], bucket);
	if (old_bucket)
		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
	return 0;
}

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) {
		pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
		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);

	/* wait for bpf programs to complete before freeing stack map */
	synchronize_rcu();

	bpf_map_area_free(smap->elems);
	pcpu_freelist_destroy(&smap->freelist);
	bpf_map_area_free(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);
Commit	Line	Data
d5a3b1f6 AS	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>
d5a3b1f6 AS	10	#include <linux/stacktrace.h>
d5a3b1f6 AS	11	#include <linux/perf_event.h>
557c0c6e	12	#include "percpu_freelist.h"
d5a3b1f6 AS	13
d5a3b1f6 AS	14	struct stack_map_bucket {
557c0c6e	15	struct pcpu_freelist_node fnode;
d5a3b1f6 AS	16	u32 hash;
	17	u32 nr;
	18	u64 ip[];
	19	};
	20
	21	struct bpf_stack_map {
	22	struct bpf_map map;
557c0c6e AS	23	void *elems;
557c0c6e AS	24	struct pcpu_freelist freelist;
d5a3b1f6	25	u32 n_buckets;
557c0c6e	26	struct stack_map_bucket *buckets[];
d5a3b1f6 AS	27	};
d5a3b1f6 AS	28
557c0c6e AS	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
d407bd25	34	smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries);
557c0c6e AS	35	if (!smap->elems)
	36	return -ENOMEM;
	37
	38	err = pcpu_freelist_init(&smap->freelist);
	39	if (err)
	40	goto free_elems;
	41
	42	pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
	43	smap->map.max_entries);
	44	return 0;
	45
	46	free_elems:
d407bd25	47	bpf_map_area_free(smap->elems);
557c0c6e AS	48	return err;
	49	}
	50
d5a3b1f6 AS	51	/* Called from syscall */
	52	static struct bpf_map stack_map_alloc(union bpf_attr attr)
	53	{
	54	u32 value_size = attr->value_size;
	55	struct bpf_stack_map *smap;
	56	u64 cost, n_buckets;
	57	int err;
	58
	59	if (!capable(CAP_SYS_ADMIN))
	60	return ERR_PTR(-EPERM);
	61
823707b6 AS	62	if (attr->map_flags)
	63	return ERR_PTR(-EINVAL);
	64
d5a3b1f6 AS	65	/* check sanity of attributes */
	66	if (attr->max_entries == 0 \|\| attr->key_size != 4 \|\|
	67	value_size < 8 \|\| value_size % 8 \|\|
c5dfd78e	68	value_size / 8 > sysctl_perf_event_max_stack)
d5a3b1f6 AS	69	return ERR_PTR(-EINVAL);
	70
	71	/* hash table size must be power of 2 */
	72	n_buckets = roundup_pow_of_two(attr->max_entries);
	73
	74	cost = n_buckets * sizeof(struct stack_map_bucket ) + sizeof(smap);
	75	if (cost >= U32_MAX - PAGE_SIZE)
	76	return ERR_PTR(-E2BIG);
	77
d407bd25 DB	78	smap = bpf_map_area_alloc(cost);
	79	if (!smap)
	80	return ERR_PTR(-ENOMEM);
d5a3b1f6 AS	81
	82	err = -E2BIG;
	83	cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
	84	if (cost >= U32_MAX - PAGE_SIZE)
	85	goto free_smap;
	86
	87	smap->map.map_type = attr->map_type;
	88	smap->map.key_size = attr->key_size;
	89	smap->map.value_size = value_size;
	90	smap->map.max_entries = attr->max_entries;
	91	smap->n_buckets = n_buckets;
	92	smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
	93
557c0c6e AS	94	err = bpf_map_precharge_memlock(smap->map.pages);
	95	if (err)
	96	goto free_smap;
	97
97c79a38	98	err = get_callchain_buffers(sysctl_perf_event_max_stack);
d5a3b1f6 AS	99	if (err)
	100	goto free_smap;
	101
557c0c6e AS	102	err = prealloc_elems_and_freelist(smap);
	103	if (err)
	104	goto put_buffers;
	105
d5a3b1f6 AS	106	return &smap->map;
d5a3b1f6 AS	107
557c0c6e AS	108	put_buffers:
557c0c6e AS	109	put_callchain_buffers();
d5a3b1f6	110	free_smap:
d407bd25	111	bpf_map_area_free(smap);
d5a3b1f6 AS	112	return ERR_PTR(err);
	113	}
	114
f3694e00 DB	115	BPF_CALL_3(bpf_get_stackid, struct pt_regs , regs, struct bpf_map , map,
f3694e00 DB	116	u64, flags)
d5a3b1f6	117	{
d5a3b1f6 AS	118	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
	119	struct perf_callchain_entry *trace;
	120	struct stack_map_bucket bucket, new_bucket, *old_bucket;
	121	u32 max_depth = map->value_size / 8;
c5dfd78e ACM	122	/* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
c5dfd78e ACM	123	u32 init_nr = sysctl_perf_event_max_stack - max_depth;
d5a3b1f6 AS	124	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
	125	u32 hash, id, trace_nr, trace_len;
	126	bool user = flags & BPF_F_USER_STACK;
	127	bool kernel = !user;
	128	u64 *ips;
	129
	130	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK \| BPF_F_USER_STACK \|
	131	BPF_F_FAST_STACK_CMP \| BPF_F_REUSE_STACKID)))
	132	return -EINVAL;
	133
cfbcf468 ACM	134	trace = get_perf_callchain(regs, init_nr, kernel, user,
cfbcf468 ACM	135	sysctl_perf_event_max_stack, false, false);
d5a3b1f6 AS	136
	137	if (unlikely(!trace))
	138	/* couldn't fetch the stack trace */
	139	return -EFAULT;
	140
	141	/* get_perf_callchain() guarantees that trace->nr >= init_nr
c5dfd78e	142	* and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
d5a3b1f6 AS	143	*/
	144	trace_nr = trace->nr - init_nr;
	145
	146	if (trace_nr <= skip)
	147	/* skipping more than usable stack trace */
	148	return -EFAULT;
	149
	150	trace_nr -= skip;
	151	trace_len = trace_nr * sizeof(u64);
	152	ips = trace->ip + skip + init_nr;
	153	hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
	154	id = hash & (smap->n_buckets - 1);
557c0c6e	155	bucket = READ_ONCE(smap->buckets[id]);
d5a3b1f6 AS	156
	157	if (bucket && bucket->hash == hash) {
	158	if (flags & BPF_F_FAST_STACK_CMP)
	159	return id;
	160	if (bucket->nr == trace_nr &&
	161	memcmp(bucket->ip, ips, trace_len) == 0)
	162	return id;
	163	}
	164
	165	/* this call stack is not in the map, try to add it */
	166	if (bucket && !(flags & BPF_F_REUSE_STACKID))
	167	return -EEXIST;
	168
557c0c6e AS	169	new_bucket = (struct stack_map_bucket *)
557c0c6e AS	170	pcpu_freelist_pop(&smap->freelist);
d5a3b1f6 AS	171	if (unlikely(!new_bucket))
	172	return -ENOMEM;
	173
	174	memcpy(new_bucket->ip, ips, trace_len);
d5a3b1f6 AS	175	new_bucket->hash = hash;
	176	new_bucket->nr = trace_nr;
	177
	178	old_bucket = xchg(&smap->buckets[id], new_bucket);
	179	if (old_bucket)
557c0c6e	180	pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
d5a3b1f6 AS	181	return id;
	182	}
	183
	184	const struct bpf_func_proto bpf_get_stackid_proto = {
	185	.func = bpf_get_stackid,
	186	.gpl_only = true,
	187	.ret_type = RET_INTEGER,
	188	.arg1_type = ARG_PTR_TO_CTX,
	189	.arg2_type = ARG_CONST_MAP_PTR,
	190	.arg3_type = ARG_ANYTHING,
	191	};
	192
557c0c6e	193	/* Called from eBPF program */
d5a3b1f6	194	static void stack_map_lookup_elem(struct bpf_map map, void *key)
557c0c6e AS	195	{
	196	return NULL;
	197	}
	198
	199	/* Called from syscall */
	200	int bpf_stackmap_copy(struct bpf_map map, void key, void *value)
d5a3b1f6 AS	201	{
d5a3b1f6 AS	202	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
557c0c6e AS	203	struct stack_map_bucket bucket, old_bucket;
557c0c6e AS	204	u32 id = (u32 )key, trace_len;
d5a3b1f6 AS	205
d5a3b1f6 AS	206	if (unlikely(id >= smap->n_buckets))
557c0c6e AS	207	return -ENOENT;
	208
	209	bucket = xchg(&smap->buckets[id], NULL);
	210	if (!bucket)
	211	return -ENOENT;
	212
	213	trace_len = bucket->nr * sizeof(u64);
	214	memcpy(value, bucket->ip, trace_len);
	215	memset(value + trace_len, 0, map->value_size - trace_len);
	216
	217	old_bucket = xchg(&smap->buckets[id], bucket);
	218	if (old_bucket)
	219	pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
	220	return 0;
d5a3b1f6 AS	221	}
	222
	223	static int stack_map_get_next_key(struct bpf_map map, void key, void *next_key)
	224	{
	225	return -EINVAL;
	226	}
	227
	228	static int stack_map_update_elem(struct bpf_map map, void key, void *value,
	229	u64 map_flags)
	230	{
	231	return -EINVAL;
	232	}
	233
	234	/* Called from syscall or from eBPF program */
	235	static int stack_map_delete_elem(struct bpf_map map, void key)
	236	{
	237	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
	238	struct stack_map_bucket *old_bucket;
	239	u32 id = (u32 )key;
	240
	241	if (unlikely(id >= smap->n_buckets))
	242	return -E2BIG;
	243
	244	old_bucket = xchg(&smap->buckets[id], NULL);
	245	if (old_bucket) {
557c0c6e	246	pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
d5a3b1f6 AS	247	return 0;
	248	} else {
	249	return -ENOENT;
	250	}
	251	}
	252
	253	/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
	254	static void stack_map_free(struct bpf_map *map)
	255	{
	256	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
d5a3b1f6	257
557c0c6e	258	/* wait for bpf programs to complete before freeing stack map */
d5a3b1f6 AS	259	synchronize_rcu();
d5a3b1f6 AS	260
d407bd25	261	bpf_map_area_free(smap->elems);
557c0c6e	262	pcpu_freelist_destroy(&smap->freelist);
d407bd25	263	bpf_map_area_free(smap);
d5a3b1f6 AS	264	put_callchain_buffers();
	265	}
	266
	267	static const struct bpf_map_ops stack_map_ops = {
	268	.map_alloc = stack_map_alloc,
	269	.map_free = stack_map_free,
	270	.map_get_next_key = stack_map_get_next_key,
	271	.map_lookup_elem = stack_map_lookup_elem,
	272	.map_update_elem = stack_map_update_elem,
	273	.map_delete_elem = stack_map_delete_elem,
	274	};
	275
	276	static struct bpf_map_type_list stack_map_type __read_mostly = {
	277	.ops = &stack_map_ops,
	278	.type = BPF_MAP_TYPE_STACK_TRACE,
	279	};
	280
	281	static int __init register_stack_map(void)
	282	{
	283	bpf_register_map_type(&stack_map_type);
	284	return 0;
	285	}
	286	late_initcall(register_stack_map);