1 files changed, 290 insertions, 0 deletions
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
new file mode 100644
index 000000000000..499d9e933f8e
--- /dev/null
+++ b/kernel/bpf/stackmap.c
@@ -0,0 +1,290 @@
+/* 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>
+#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 = vzalloc(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:
+	vfree(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 > 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 = bpf_map_precharge_memlock(smap->map.pages);
+	if (err)
+		goto free_smap;
+
+	err = get_callchain_buffers();
+	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:
+	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 = 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();
+
+	vfree(smap->elems);
+	pcpu_freelist_destroy(&smap->freelist);
+	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);