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