mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-08-05 16:54:27 +00:00
c7db4873fb
Regular BPF hash map is not mmap-able from user space. However, map-in-map with outer map of type BPF_MAP_TYPE_HASH_OF_MAPS and mmap-able array as inner map can perform similar operations as a mmap-able hash map. This can be used by applications that benefit from fast accesses to some local data. Add a selftest to show this use case. Signed-off-by: Song Liu <song@kernel.org> Link: https://lore.kernel.org/r/20240723051455.1589192-1-song@kernel.org Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
57 lines
1.2 KiB
C
57 lines
1.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
|
|
|
|
#include "vmlinux.h"
|
|
#include <bpf/bpf_helpers.h>
|
|
|
|
#include "bpf_misc.h"
|
|
|
|
char _license[] SEC("license") = "GPL";
|
|
|
|
struct inner_array_type {
|
|
__uint(type, BPF_MAP_TYPE_ARRAY);
|
|
__uint(map_flags, BPF_F_MMAPABLE);
|
|
__type(key, __u32);
|
|
__type(value, __u64);
|
|
__uint(max_entries, 1);
|
|
} inner_array SEC(".maps");
|
|
|
|
struct {
|
|
__uint(type, BPF_MAP_TYPE_HASH_OF_MAPS);
|
|
__uint(key_size, 4);
|
|
__uint(value_size, 4);
|
|
__uint(max_entries, 1);
|
|
__array(values, struct inner_array_type);
|
|
} outer_map SEC(".maps");
|
|
|
|
int pid = 0;
|
|
__u64 match_value = 0x13572468;
|
|
bool done = false;
|
|
bool pid_match = false;
|
|
bool outer_map_match = false;
|
|
|
|
SEC("fentry/" SYS_PREFIX "sys_nanosleep")
|
|
int add_to_list_in_inner_array(void *ctx)
|
|
{
|
|
__u32 curr_pid, zero = 0;
|
|
struct bpf_map *map;
|
|
__u64 *value;
|
|
|
|
curr_pid = (u32)bpf_get_current_pid_tgid();
|
|
if (done || curr_pid != pid)
|
|
return 0;
|
|
|
|
pid_match = true;
|
|
map = bpf_map_lookup_elem(&outer_map, &curr_pid);
|
|
if (!map)
|
|
return 0;
|
|
|
|
outer_map_match = true;
|
|
value = bpf_map_lookup_elem(map, &zero);
|
|
if (!value)
|
|
return 0;
|
|
|
|
*value = match_value;
|
|
done = true;
|
|
return 0;
|
|
}
|