61 lines
1.8 KiB
C
61 lines
1.8 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* bpf-script-example.c
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* Test basic LLVM building
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*/
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#ifndef LINUX_VERSION_CODE
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# error Need LINUX_VERSION_CODE
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# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
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#endif
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#define BPF_ANY 0
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#define BPF_MAP_TYPE_ARRAY 2
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#define BPF_FUNC_map_lookup_elem 1
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#define BPF_FUNC_map_update_elem 2
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static void *(*bpf_map_lookup_elem)(void *map, void *key) =
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(void *) BPF_FUNC_map_lookup_elem;
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static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) =
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(void *) BPF_FUNC_map_update_elem;
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/*
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* Following macros are taken from tools/lib/bpf/bpf_helpers.h,
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* and are used to create BTF defined maps. It is easier to take
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* 2 simple macros, than being able to include above header in
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* runtime.
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*
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* __uint - defines integer attribute of BTF map definition,
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* Such attributes are represented using a pointer to an array,
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* in which dimensionality of array encodes specified integer
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* value.
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*
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* __type - defines pointer variable with typeof(val) type for
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* attributes like key or value, which will be defined by the
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* size of the type.
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*/
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#define __uint(name, val) int (*name)[val]
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#define __type(name, val) typeof(val) *name
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#define SEC(NAME) __attribute__((section(NAME), used))
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struct {
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__uint(type, BPF_MAP_TYPE_ARRAY);
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__uint(max_entries, 1);
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__type(key, int);
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__type(value, int);
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} flip_table SEC(".maps");
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SEC("syscalls:sys_enter_epoll_pwait")
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int bpf_func__SyS_epoll_pwait(void *ctx)
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{
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int ind =0;
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int *flag = bpf_map_lookup_elem(&flip_table, &ind);
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int new_flag;
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if (!flag)
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return 0;
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/* flip flag and store back */
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new_flag = !*flag;
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bpf_map_update_elem(&flip_table, &ind, &new_flag, BPF_ANY);
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return new_flag;
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}
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char _license[] SEC("license") = "GPL";
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int _version SEC("version") = LINUX_VERSION_CODE;
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