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Commit e0337f4f authored by Arnaldo Carvalho de Melo's avatar Arnaldo Carvalho de Melo
Browse files

perf test bpf: Hook on epoll_pwait() 



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: default avatarWang 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 13cb2d0f

tools/perf/tests/bpf-script-example.c

+2 −2
Original line number Diff line number Diff line
@@ -31,8 +31,8 @@ struct bpf_map_def SEC("maps") flip_table = { 
	.max_entries = 1,

};



SEC("func=SyS_epoll_wait")

int bpf_func__SyS_epoll_wait(void *ctx)

SEC("func=SyS_epoll_pwait")

int bpf_func__SyS_epoll_pwait(void *ctx)

{

	int ind =0;

	int *flag = bpf_map_lookup_elem(&flip_table, &ind);

tools/perf/tests/bpf.c

+4 −4
Original line number Diff line number Diff line
@@ -19,13 +19,13 @@ 


#ifdef HAVE_LIBBPF_SUPPORT



static int epoll_wait_loop(void)

static int epoll_pwait_loop(void)

{

	int i;



	/* Should fail NR_ITERS times */

	for (i = 0; i < NR_ITERS; i++)

		epoll_wait(-(i + 1), NULL, 0, 0);

		epoll_pwait(-(i + 1), NULL, 0, 0, NULL);

	return 0;

}
@@ -68,7 +68,7 @@ static struct { 
		.name		  = "[basic_bpf_test]",

		.msg_compile_fail = "fix 'perf test LLVM' first",

		.msg_load_fail	  = "load bpf object failed",

		.target_func	  = &epoll_wait_loop,

		.target_func	  = &epoll_pwait_loop,

		.expect_result	  = (NR_ITERS + 1) / 2,

	},

	{
@@ -77,7 +77,7 @@ static struct { 
		.name		  = "[bpf_pinning]",

		.msg_compile_fail = "fix kbuild first",

		.msg_load_fail	  = "check your vmlinux setting?",

		.target_func	  = &epoll_wait_loop,

		.target_func	  = &epoll_pwait_loop,

		.expect_result	  = (NR_ITERS + 1) / 2,

		.pin 		  = true,

	},