![Eric Dumazet](/assets/img/avatar_default.png)
[ upstream commit32fff239de
] syszbot managed to trigger RCU detected stalls in bpf_array_free_percpu() It takes time to allocate a huge percpu map, but even more time to free it. Since we run in process context, use cond_resched() to yield cpu if needed. Fixes:a10423b87a
("bpf: introduce BPF_MAP_TYPE_PERCPU_ARRAY map") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
689 lines
18 KiB
C
689 lines
18 KiB
C
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
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* Copyright (c) 2016,2017 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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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include <linux/bpf.h>
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#include <linux/err.h>
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#include <linux/slab.h>
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#include <linux/mm.h>
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#include <linux/filter.h>
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#include <linux/perf_event.h>
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#include "map_in_map.h"
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static void bpf_array_free_percpu(struct bpf_array *array)
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{
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int i;
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for (i = 0; i < array->map.max_entries; i++) {
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free_percpu(array->pptrs[i]);
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cond_resched();
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}
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}
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static int bpf_array_alloc_percpu(struct bpf_array *array)
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{
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void __percpu *ptr;
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int i;
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for (i = 0; i < array->map.max_entries; i++) {
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ptr = __alloc_percpu_gfp(array->elem_size, 8,
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GFP_USER | __GFP_NOWARN);
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if (!ptr) {
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bpf_array_free_percpu(array);
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return -ENOMEM;
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}
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array->pptrs[i] = ptr;
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cond_resched();
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}
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return 0;
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}
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/* Called from syscall */
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static struct bpf_map *array_map_alloc(union bpf_attr *attr)
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{
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bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_ARRAY;
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int ret, numa_node = bpf_map_attr_numa_node(attr);
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u32 elem_size, index_mask, max_entries;
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bool unpriv = !capable(CAP_SYS_ADMIN);
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u64 cost, array_size, mask64;
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struct bpf_array *array;
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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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attr->value_size == 0 || attr->map_flags & ~BPF_F_NUMA_NODE ||
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(percpu && numa_node != NUMA_NO_NODE))
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return ERR_PTR(-EINVAL);
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if (attr->value_size > KMALLOC_MAX_SIZE)
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/* if value_size is bigger, the user space won't be able to
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* access the elements.
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*/
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return ERR_PTR(-E2BIG);
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elem_size = round_up(attr->value_size, 8);
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max_entries = attr->max_entries;
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/* On 32 bit archs roundup_pow_of_two() with max_entries that has
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* upper most bit set in u32 space is undefined behavior due to
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* resulting 1U << 32, so do it manually here in u64 space.
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*/
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mask64 = fls_long(max_entries - 1);
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mask64 = 1ULL << mask64;
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mask64 -= 1;
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index_mask = mask64;
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if (unpriv) {
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/* round up array size to nearest power of 2,
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* since cpu will speculate within index_mask limits
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*/
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max_entries = index_mask + 1;
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/* Check for overflows. */
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if (max_entries < attr->max_entries)
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return ERR_PTR(-E2BIG);
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}
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array_size = sizeof(*array);
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if (percpu)
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array_size += (u64) max_entries * sizeof(void *);
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else
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array_size += (u64) max_entries * elem_size;
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/* make sure there is no u32 overflow later in round_up() */
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cost = array_size;
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if (cost >= U32_MAX - PAGE_SIZE)
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return ERR_PTR(-ENOMEM);
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if (percpu) {
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cost += (u64)attr->max_entries * elem_size * num_possible_cpus();
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if (cost >= U32_MAX - PAGE_SIZE)
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return ERR_PTR(-ENOMEM);
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}
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cost = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
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ret = bpf_map_precharge_memlock(cost);
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if (ret < 0)
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return ERR_PTR(ret);
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/* allocate all map elements and zero-initialize them */
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array = bpf_map_area_alloc(array_size, numa_node);
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if (!array)
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return ERR_PTR(-ENOMEM);
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array->index_mask = index_mask;
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array->map.unpriv_array = unpriv;
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/* copy mandatory map attributes */
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array->map.map_type = attr->map_type;
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array->map.key_size = attr->key_size;
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array->map.value_size = attr->value_size;
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array->map.max_entries = attr->max_entries;
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array->map.map_flags = attr->map_flags;
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array->map.numa_node = numa_node;
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array->map.pages = cost;
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array->elem_size = elem_size;
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if (percpu && bpf_array_alloc_percpu(array)) {
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bpf_map_area_free(array);
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return ERR_PTR(-ENOMEM);
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}
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return &array->map;
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}
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/* Called from syscall or from eBPF program */
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static void *array_map_lookup_elem(struct bpf_map *map, void *key)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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u32 index = *(u32 *)key;
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if (unlikely(index >= array->map.max_entries))
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return NULL;
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return array->value + array->elem_size * (index & array->index_mask);
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}
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/* emit BPF instructions equivalent to C code of array_map_lookup_elem() */
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static u32 array_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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struct bpf_insn *insn = insn_buf;
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u32 elem_size = round_up(map->value_size, 8);
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const int ret = BPF_REG_0;
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const int map_ptr = BPF_REG_1;
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const int index = BPF_REG_2;
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*insn++ = BPF_ALU64_IMM(BPF_ADD, map_ptr, offsetof(struct bpf_array, value));
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*insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
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if (map->unpriv_array) {
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*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 4);
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*insn++ = BPF_ALU32_IMM(BPF_AND, ret, array->index_mask);
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} else {
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*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 3);
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}
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if (is_power_of_2(elem_size)) {
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*insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(elem_size));
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} else {
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*insn++ = BPF_ALU64_IMM(BPF_MUL, ret, elem_size);
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}
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*insn++ = BPF_ALU64_REG(BPF_ADD, ret, map_ptr);
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*insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
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*insn++ = BPF_MOV64_IMM(ret, 0);
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return insn - insn_buf;
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}
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/* Called from eBPF program */
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static void *percpu_array_map_lookup_elem(struct bpf_map *map, void *key)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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u32 index = *(u32 *)key;
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if (unlikely(index >= array->map.max_entries))
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return NULL;
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return this_cpu_ptr(array->pptrs[index & array->index_mask]);
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}
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int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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u32 index = *(u32 *)key;
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void __percpu *pptr;
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int cpu, off = 0;
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u32 size;
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if (unlikely(index >= array->map.max_entries))
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return -ENOENT;
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/* per_cpu areas are zero-filled and bpf programs can only
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* access 'value_size' of them, so copying rounded areas
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* will not leak any kernel data
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*/
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size = round_up(map->value_size, 8);
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rcu_read_lock();
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pptr = array->pptrs[index & array->index_mask];
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for_each_possible_cpu(cpu) {
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bpf_long_memcpy(value + off, per_cpu_ptr(pptr, cpu), size);
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off += size;
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}
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rcu_read_unlock();
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return 0;
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}
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/* Called from syscall */
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static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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u32 index = key ? *(u32 *)key : U32_MAX;
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u32 *next = (u32 *)next_key;
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if (index >= array->map.max_entries) {
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*next = 0;
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return 0;
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}
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if (index == array->map.max_entries - 1)
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return -ENOENT;
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*next = index + 1;
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return 0;
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}
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/* Called from syscall or from eBPF program */
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static int array_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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struct bpf_array *array = container_of(map, struct bpf_array, map);
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u32 index = *(u32 *)key;
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if (unlikely(map_flags > BPF_EXIST))
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/* unknown flags */
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return -EINVAL;
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if (unlikely(index >= array->map.max_entries))
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/* all elements were pre-allocated, cannot insert a new one */
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return -E2BIG;
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if (unlikely(map_flags == BPF_NOEXIST))
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/* all elements already exist */
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return -EEXIST;
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if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
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memcpy(this_cpu_ptr(array->pptrs[index & array->index_mask]),
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value, map->value_size);
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else
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memcpy(array->value +
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array->elem_size * (index & array->index_mask),
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value, map->value_size);
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return 0;
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}
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int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
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u64 map_flags)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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u32 index = *(u32 *)key;
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void __percpu *pptr;
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int cpu, off = 0;
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u32 size;
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if (unlikely(map_flags > BPF_EXIST))
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/* unknown flags */
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return -EINVAL;
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if (unlikely(index >= array->map.max_entries))
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/* all elements were pre-allocated, cannot insert a new one */
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return -E2BIG;
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if (unlikely(map_flags == BPF_NOEXIST))
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/* all elements already exist */
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return -EEXIST;
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/* the user space will provide round_up(value_size, 8) bytes that
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* will be copied into per-cpu area. bpf programs can only access
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* value_size of it. During lookup the same extra bytes will be
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* returned or zeros which were zero-filled by percpu_alloc,
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* so no kernel data leaks possible
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*/
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size = round_up(map->value_size, 8);
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rcu_read_lock();
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pptr = array->pptrs[index & array->index_mask];
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for_each_possible_cpu(cpu) {
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bpf_long_memcpy(per_cpu_ptr(pptr, cpu), value + off, size);
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off += size;
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}
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rcu_read_unlock();
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return 0;
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}
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/* Called from syscall or from eBPF program */
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static int array_map_delete_elem(struct bpf_map *map, void *key)
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{
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return -EINVAL;
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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 array_map_free(struct bpf_map *map)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
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* so the programs (can be more than one that used this map) were
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* disconnected from events. Wait for outstanding programs to complete
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* and free the array
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*/
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synchronize_rcu();
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if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
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bpf_array_free_percpu(array);
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bpf_map_area_free(array);
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}
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const struct bpf_map_ops array_map_ops = {
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.map_alloc = array_map_alloc,
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.map_free = array_map_free,
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.map_get_next_key = array_map_get_next_key,
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.map_lookup_elem = array_map_lookup_elem,
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.map_update_elem = array_map_update_elem,
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.map_delete_elem = array_map_delete_elem,
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.map_gen_lookup = array_map_gen_lookup,
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};
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const struct bpf_map_ops percpu_array_map_ops = {
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.map_alloc = array_map_alloc,
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.map_free = array_map_free,
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.map_get_next_key = array_map_get_next_key,
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.map_lookup_elem = percpu_array_map_lookup_elem,
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.map_update_elem = array_map_update_elem,
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.map_delete_elem = array_map_delete_elem,
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};
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static struct bpf_map *fd_array_map_alloc(union bpf_attr *attr)
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{
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/* only file descriptors can be stored in this type of map */
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if (attr->value_size != sizeof(u32))
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return ERR_PTR(-EINVAL);
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return array_map_alloc(attr);
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}
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static void fd_array_map_free(struct bpf_map *map)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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int i;
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synchronize_rcu();
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/* make sure it's empty */
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for (i = 0; i < array->map.max_entries; i++)
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BUG_ON(array->ptrs[i] != NULL);
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bpf_map_area_free(array);
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}
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static void *fd_array_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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/* only called from syscall */
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int bpf_fd_array_map_lookup_elem(struct bpf_map *map, void *key, u32 *value)
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{
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void **elem, *ptr;
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int ret = 0;
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if (!map->ops->map_fd_sys_lookup_elem)
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return -ENOTSUPP;
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rcu_read_lock();
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elem = array_map_lookup_elem(map, key);
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if (elem && (ptr = READ_ONCE(*elem)))
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*value = map->ops->map_fd_sys_lookup_elem(ptr);
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else
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ret = -ENOENT;
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rcu_read_unlock();
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return ret;
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}
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/* only called from syscall */
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int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file,
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void *key, void *value, u64 map_flags)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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void *new_ptr, *old_ptr;
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u32 index = *(u32 *)key, ufd;
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if (map_flags != BPF_ANY)
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return -EINVAL;
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if (index >= array->map.max_entries)
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return -E2BIG;
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ufd = *(u32 *)value;
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new_ptr = map->ops->map_fd_get_ptr(map, map_file, ufd);
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if (IS_ERR(new_ptr))
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return PTR_ERR(new_ptr);
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old_ptr = xchg(array->ptrs + index, new_ptr);
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if (old_ptr)
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map->ops->map_fd_put_ptr(old_ptr);
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return 0;
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}
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static int fd_array_map_delete_elem(struct bpf_map *map, void *key)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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void *old_ptr;
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u32 index = *(u32 *)key;
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if (index >= array->map.max_entries)
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return -E2BIG;
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old_ptr = xchg(array->ptrs + index, NULL);
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if (old_ptr) {
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map->ops->map_fd_put_ptr(old_ptr);
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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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static void *prog_fd_array_get_ptr(struct bpf_map *map,
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struct file *map_file, int fd)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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struct bpf_prog *prog = bpf_prog_get(fd);
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if (IS_ERR(prog))
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return prog;
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if (!bpf_prog_array_compatible(array, prog)) {
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bpf_prog_put(prog);
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return ERR_PTR(-EINVAL);
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}
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return prog;
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}
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static void prog_fd_array_put_ptr(void *ptr)
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{
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bpf_prog_put(ptr);
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}
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static u32 prog_fd_array_sys_lookup_elem(void *ptr)
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{
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return ((struct bpf_prog *)ptr)->aux->id;
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}
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/* decrement refcnt of all bpf_progs that are stored in this map */
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void bpf_fd_array_map_clear(struct bpf_map *map)
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{
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struct bpf_array *array = container_of(map, struct bpf_array, map);
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int i;
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for (i = 0; i < array->map.max_entries; i++)
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fd_array_map_delete_elem(map, &i);
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}
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const struct bpf_map_ops prog_array_map_ops = {
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.map_alloc = fd_array_map_alloc,
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.map_free = fd_array_map_free,
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.map_get_next_key = array_map_get_next_key,
|
|
.map_lookup_elem = fd_array_map_lookup_elem,
|
|
.map_delete_elem = fd_array_map_delete_elem,
|
|
.map_fd_get_ptr = prog_fd_array_get_ptr,
|
|
.map_fd_put_ptr = prog_fd_array_put_ptr,
|
|
.map_fd_sys_lookup_elem = prog_fd_array_sys_lookup_elem,
|
|
};
|
|
|
|
static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
|
|
struct file *map_file)
|
|
{
|
|
struct bpf_event_entry *ee;
|
|
|
|
ee = kzalloc(sizeof(*ee), GFP_ATOMIC);
|
|
if (ee) {
|
|
ee->event = perf_file->private_data;
|
|
ee->perf_file = perf_file;
|
|
ee->map_file = map_file;
|
|
}
|
|
|
|
return ee;
|
|
}
|
|
|
|
static void __bpf_event_entry_free(struct rcu_head *rcu)
|
|
{
|
|
struct bpf_event_entry *ee;
|
|
|
|
ee = container_of(rcu, struct bpf_event_entry, rcu);
|
|
fput(ee->perf_file);
|
|
kfree(ee);
|
|
}
|
|
|
|
static void bpf_event_entry_free_rcu(struct bpf_event_entry *ee)
|
|
{
|
|
call_rcu(&ee->rcu, __bpf_event_entry_free);
|
|
}
|
|
|
|
static void *perf_event_fd_array_get_ptr(struct bpf_map *map,
|
|
struct file *map_file, int fd)
|
|
{
|
|
struct bpf_event_entry *ee;
|
|
struct perf_event *event;
|
|
struct file *perf_file;
|
|
u64 value;
|
|
|
|
perf_file = perf_event_get(fd);
|
|
if (IS_ERR(perf_file))
|
|
return perf_file;
|
|
|
|
ee = ERR_PTR(-EOPNOTSUPP);
|
|
event = perf_file->private_data;
|
|
if (perf_event_read_local(event, &value) == -EOPNOTSUPP)
|
|
goto err_out;
|
|
|
|
ee = bpf_event_entry_gen(perf_file, map_file);
|
|
if (ee)
|
|
return ee;
|
|
ee = ERR_PTR(-ENOMEM);
|
|
err_out:
|
|
fput(perf_file);
|
|
return ee;
|
|
}
|
|
|
|
static void perf_event_fd_array_put_ptr(void *ptr)
|
|
{
|
|
bpf_event_entry_free_rcu(ptr);
|
|
}
|
|
|
|
static void perf_event_fd_array_release(struct bpf_map *map,
|
|
struct file *map_file)
|
|
{
|
|
struct bpf_array *array = container_of(map, struct bpf_array, map);
|
|
struct bpf_event_entry *ee;
|
|
int i;
|
|
|
|
rcu_read_lock();
|
|
for (i = 0; i < array->map.max_entries; i++) {
|
|
ee = READ_ONCE(array->ptrs[i]);
|
|
if (ee && ee->map_file == map_file)
|
|
fd_array_map_delete_elem(map, &i);
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
const struct bpf_map_ops perf_event_array_map_ops = {
|
|
.map_alloc = fd_array_map_alloc,
|
|
.map_free = fd_array_map_free,
|
|
.map_get_next_key = array_map_get_next_key,
|
|
.map_lookup_elem = fd_array_map_lookup_elem,
|
|
.map_delete_elem = fd_array_map_delete_elem,
|
|
.map_fd_get_ptr = perf_event_fd_array_get_ptr,
|
|
.map_fd_put_ptr = perf_event_fd_array_put_ptr,
|
|
.map_release = perf_event_fd_array_release,
|
|
};
|
|
|
|
#ifdef CONFIG_CGROUPS
|
|
static void *cgroup_fd_array_get_ptr(struct bpf_map *map,
|
|
struct file *map_file /* not used */,
|
|
int fd)
|
|
{
|
|
return cgroup_get_from_fd(fd);
|
|
}
|
|
|
|
static void cgroup_fd_array_put_ptr(void *ptr)
|
|
{
|
|
/* cgroup_put free cgrp after a rcu grace period */
|
|
cgroup_put(ptr);
|
|
}
|
|
|
|
static void cgroup_fd_array_free(struct bpf_map *map)
|
|
{
|
|
bpf_fd_array_map_clear(map);
|
|
fd_array_map_free(map);
|
|
}
|
|
|
|
const struct bpf_map_ops cgroup_array_map_ops = {
|
|
.map_alloc = fd_array_map_alloc,
|
|
.map_free = cgroup_fd_array_free,
|
|
.map_get_next_key = array_map_get_next_key,
|
|
.map_lookup_elem = fd_array_map_lookup_elem,
|
|
.map_delete_elem = fd_array_map_delete_elem,
|
|
.map_fd_get_ptr = cgroup_fd_array_get_ptr,
|
|
.map_fd_put_ptr = cgroup_fd_array_put_ptr,
|
|
};
|
|
#endif
|
|
|
|
static struct bpf_map *array_of_map_alloc(union bpf_attr *attr)
|
|
{
|
|
struct bpf_map *map, *inner_map_meta;
|
|
|
|
inner_map_meta = bpf_map_meta_alloc(attr->inner_map_fd);
|
|
if (IS_ERR(inner_map_meta))
|
|
return inner_map_meta;
|
|
|
|
map = fd_array_map_alloc(attr);
|
|
if (IS_ERR(map)) {
|
|
bpf_map_meta_free(inner_map_meta);
|
|
return map;
|
|
}
|
|
|
|
map->inner_map_meta = inner_map_meta;
|
|
|
|
return map;
|
|
}
|
|
|
|
static void array_of_map_free(struct bpf_map *map)
|
|
{
|
|
/* map->inner_map_meta is only accessed by syscall which
|
|
* is protected by fdget/fdput.
|
|
*/
|
|
bpf_map_meta_free(map->inner_map_meta);
|
|
bpf_fd_array_map_clear(map);
|
|
fd_array_map_free(map);
|
|
}
|
|
|
|
static void *array_of_map_lookup_elem(struct bpf_map *map, void *key)
|
|
{
|
|
struct bpf_map **inner_map = array_map_lookup_elem(map, key);
|
|
|
|
if (!inner_map)
|
|
return NULL;
|
|
|
|
return READ_ONCE(*inner_map);
|
|
}
|
|
|
|
static u32 array_of_map_gen_lookup(struct bpf_map *map,
|
|
struct bpf_insn *insn_buf)
|
|
{
|
|
struct bpf_array *array = container_of(map, struct bpf_array, map);
|
|
u32 elem_size = round_up(map->value_size, 8);
|
|
struct bpf_insn *insn = insn_buf;
|
|
const int ret = BPF_REG_0;
|
|
const int map_ptr = BPF_REG_1;
|
|
const int index = BPF_REG_2;
|
|
|
|
*insn++ = BPF_ALU64_IMM(BPF_ADD, map_ptr, offsetof(struct bpf_array, value));
|
|
*insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
|
|
if (map->unpriv_array) {
|
|
*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 6);
|
|
*insn++ = BPF_ALU32_IMM(BPF_AND, ret, array->index_mask);
|
|
} else {
|
|
*insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 5);
|
|
}
|
|
if (is_power_of_2(elem_size))
|
|
*insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(elem_size));
|
|
else
|
|
*insn++ = BPF_ALU64_IMM(BPF_MUL, ret, elem_size);
|
|
*insn++ = BPF_ALU64_REG(BPF_ADD, ret, map_ptr);
|
|
*insn++ = BPF_LDX_MEM(BPF_DW, ret, ret, 0);
|
|
*insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 1);
|
|
*insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
|
|
*insn++ = BPF_MOV64_IMM(ret, 0);
|
|
|
|
return insn - insn_buf;
|
|
}
|
|
|
|
const struct bpf_map_ops array_of_maps_map_ops = {
|
|
.map_alloc = array_of_map_alloc,
|
|
.map_free = array_of_map_free,
|
|
.map_get_next_key = array_map_get_next_key,
|
|
.map_lookup_elem = array_of_map_lookup_elem,
|
|
.map_delete_elem = fd_array_map_delete_elem,
|
|
.map_fd_get_ptr = bpf_map_fd_get_ptr,
|
|
.map_fd_put_ptr = bpf_map_fd_put_ptr,
|
|
.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
|
|
.map_gen_lookup = array_of_map_gen_lookup,
|
|
};
|