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e0337f4f9a
The 'perf test bpf' was hooking a eBPF program on the SyS_epoll_wait() kernel function, that was what the epoll_wait() glibc function ended up calling, but since at least glibc 2.26, the one that comes with, for instance, Fedora 27, glibc ends up calling SyS_epoll_pwait() when epoll_wait() is used, causing this 'perf test' entry to fail. So switch to using epoll_pwait() and hook the eBPF program to the SyS_epoll_pwait() kernel function to make it work on a wider range of glibc and kernel versions. Tested-by: Wang Nan <wangnan0@huawei.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Link: https://lkml.kernel.org/n/tip-zynvquy63er8s5mrgsz65pto@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
49 lines
1.3 KiB
C
49 lines
1.3 KiB
C
/*
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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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struct bpf_map_def {
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unsigned int type;
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unsigned int key_size;
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unsigned int value_size;
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unsigned int max_entries;
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};
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#define SEC(NAME) __attribute__((section(NAME), used))
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struct bpf_map_def SEC("maps") flip_table = {
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.type = BPF_MAP_TYPE_ARRAY,
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.key_size = sizeof(int),
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.value_size = sizeof(int),
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.max_entries = 1,
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};
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SEC("func=SyS_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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