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![Daniel Borkmann](/assets/img/avatar_default.png)
trie_alloc() always needs to have BPF_F_NO_PREALLOC passed in via
attr->map_flags, since it does not support preallocation yet. We
check the flag, but we never copy the flag into trie->map.map_flags,
which is later on exposed into fdinfo and used by loaders such as
iproute2. Latter uses this in bpf_map_selfcheck_pinned() to test
whether a pinned map has the same spec as the one from the BPF obj
file and if not, bails out, which is currently the case for lpm
since it exposes always 0 as flags.
Also copy over flags in array_map_alloc() and stack_map_alloc().
They always have to be 0 right now, but we should make sure to not
miss to copy them over at a later point in time when we add actual
flags for them to use.
Fixes: b95a5c4db0
("bpf: add a longest prefix match trie map implementation")
Reported-by: Jarno Rajahalme <jarno@covalent.io>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
275 lines
7.1 KiB
C
275 lines
7.1 KiB
C
/* 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/stacktrace.h>
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#include <linux/perf_event.h>
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#include "percpu_freelist.h"
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struct stack_map_bucket {
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struct pcpu_freelist_node fnode;
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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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void *elems;
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struct pcpu_freelist freelist;
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u32 n_buckets;
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struct stack_map_bucket *buckets[];
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};
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static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
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{
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u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
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int err;
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smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries);
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if (!smap->elems)
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return -ENOMEM;
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err = pcpu_freelist_init(&smap->freelist);
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if (err)
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goto free_elems;
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pcpu_freelist_populate(&smap->freelist, smap->elems, elem_size,
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smap->map.max_entries);
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return 0;
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free_elems:
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bpf_map_area_free(smap->elems);
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return err;
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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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if (attr->map_flags)
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return ERR_PTR(-EINVAL);
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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 > sysctl_perf_event_max_stack)
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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 = bpf_map_area_alloc(cost);
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if (!smap)
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return ERR_PTR(-ENOMEM);
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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->map.map_flags = attr->map_flags;
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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 = bpf_map_precharge_memlock(smap->map.pages);
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if (err)
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goto free_smap;
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err = get_callchain_buffers(sysctl_perf_event_max_stack);
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if (err)
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goto free_smap;
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err = prealloc_elems_and_freelist(smap);
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if (err)
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goto put_buffers;
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return &smap->map;
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put_buffers:
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put_callchain_buffers();
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free_smap:
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bpf_map_area_free(smap);
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return ERR_PTR(err);
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}
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BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
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u64, flags)
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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 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 <= sysctl_perf_event_max_stack */
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u32 init_nr = sysctl_perf_event_max_stack - 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,
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sysctl_perf_event_max_stack, 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 <= sysctl_perf_event_max_stack, 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 = READ_ONCE(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 = (struct stack_map_bucket *)
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pcpu_freelist_pop(&smap->freelist);
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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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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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pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
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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 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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return NULL;
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}
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/* Called from syscall */
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int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
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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, *old_bucket;
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u32 id = *(u32 *)key, trace_len;
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if (unlikely(id >= smap->n_buckets))
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return -ENOENT;
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bucket = xchg(&smap->buckets[id], NULL);
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if (!bucket)
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return -ENOENT;
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trace_len = bucket->nr * sizeof(u64);
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memcpy(value, bucket->ip, trace_len);
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memset(value + trace_len, 0, map->value_size - trace_len);
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old_bucket = xchg(&smap->buckets[id], bucket);
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if (old_bucket)
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pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
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return 0;
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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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pcpu_freelist_push(&smap->freelist, &old_bucket->fnode);
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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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/* wait for bpf programs to complete before freeing stack map */
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synchronize_rcu();
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bpf_map_area_free(smap->elems);
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pcpu_freelist_destroy(&smap->freelist);
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bpf_map_area_free(smap);
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put_callchain_buffers();
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}
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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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