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Date: Sat, 6 Jul 2019 10:44:31 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Yonghong Song <yhs@...com>
Cc: Andrii Nakryiko <andriin@...com>,
"bpf@...r.kernel.org" <bpf@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Alexei Starovoitov <ast@...com>,
"daniel@...earbox.net" <daniel@...earbox.net>,
Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH v6 bpf-next 3/5] selftests/bpf: test perf buffer API
On Sat, Jul 6, 2019 at 10:18 AM Yonghong Song <yhs@...com> wrote:
>
>
>
> On 7/5/19 11:02 PM, Andrii Nakryiko wrote:
> > Add test verifying perf buffer API functionality.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > Acked-by: Song Liu <songliubraving@...com>
> > ---
> > .../selftests/bpf/prog_tests/perf_buffer.c | 94 +++++++++++++++++++
> > .../selftests/bpf/progs/test_perf_buffer.c | 25 +++++
> > 2 files changed, 119 insertions(+)
> > create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_buffer.c
> > create mode 100644 tools/testing/selftests/bpf/progs/test_perf_buffer.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/perf_buffer.c b/tools/testing/selftests/bpf/prog_tests/perf_buffer.c
> > new file mode 100644
> > index 000000000000..64556ab0d1a9
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/perf_buffer.c
> > @@ -0,0 +1,94 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#define _GNU_SOURCE
> > +#include <pthread.h>
> > +#include <sched.h>
> > +#include <sys/socket.h>
> > +#include <test_progs.h>
> > +
> > +static void on_sample(void *ctx, int cpu, void *data, __u32 size)
> > +{
> > + int cpu_data = *(int *)data, duration = 0;
> > + cpu_set_t *cpu_seen = ctx;
> > +
> > + if (cpu_data != cpu)
> > + CHECK(cpu_data != cpu, "check_cpu_data",
> > + "cpu_data %d != cpu %d\n", cpu_data, cpu);
> > +
> > + CPU_SET(cpu, cpu_seen);
> > +}
> > +
> > +void test_perf_buffer(void)
> > +{
> > + int err, prog_fd, nr_cpus, i, duration = 0;
> > + const char *prog_name = "kprobe/sys_nanosleep";
> > + const char *file = "./test_perf_buffer.o";
> > + struct perf_buffer_opts pb_opts = {};
> > + struct bpf_map *perf_buf_map;
> > + cpu_set_t cpu_set, cpu_seen;
> > + struct bpf_program *prog;
> > + struct bpf_object *obj;
> > + struct perf_buffer *pb;
> > + struct bpf_link *link;
> > +
> > + nr_cpus = libbpf_num_possible_cpus();
> > + if (CHECK(nr_cpus < 0, "nr_cpus", "err %d\n", nr_cpus))
> > + return;
> > +
> > + /* load program */
> > + err = bpf_prog_load(file, BPF_PROG_TYPE_KPROBE, &obj, &prog_fd);
> > + if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno))
> > + return;
> > +
> > + prog = bpf_object__find_program_by_title(obj, prog_name);
> > + if (CHECK(!prog, "find_probe", "prog '%s' not found\n", prog_name))
> > + goto out_close;
> > +
> > + /* load map */
> > + perf_buf_map = bpf_object__find_map_by_name(obj, "perf_buf_map");
> > + if (CHECK(!perf_buf_map, "find_perf_buf_map", "not found\n"))
> > + goto out_close;
> > +
> > + /* attach kprobe */
> > + link = bpf_program__attach_kprobe(prog, false /* retprobe */,
> > + "sys_nanosleep");
>
> The attach function "sys_nanosleep" won't work. You can have something
> similar to attach_probe.c.
>
> #ifdef __x86_64__
> #define SYS_KPROBE_NAME "__x64_sys_nanosleep"
> #else
> #define SYS_KPROBE_NAME "sys_nanosleep"
> #endif
>
Yeah, this is going to be a nightmare with those arch-specific names.
I'm wondering if it's worth it to automatically do that in libbpf for
users...
But anyway, will fix in v7, thanks!
>
> > + if (CHECK(IS_ERR(link), "attach_kprobe", "err %ld\n", PTR_ERR(link)))
> > + goto out_close;
> > +
> > + /* set up perf buffer */
> > + pb_opts.sample_cb = on_sample;
> > + pb_opts.ctx = &cpu_seen;
> > + pb = perf_buffer__new(bpf_map__fd(perf_buf_map), 1, &pb_opts);
> > + if (CHECK(IS_ERR(pb), "perf_buf__new", "err %ld\n", PTR_ERR(pb)))
> > + goto out_detach;
> > +
> > + /* trigger kprobe on every CPU */
> > + CPU_ZERO(&cpu_seen);
> > + for (i = 0; i < nr_cpus; i++) {
> > + CPU_ZERO(&cpu_set);
> > + CPU_SET(i, &cpu_set);
> > +
> > + err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set),
> > + &cpu_set);
> > + if (err && CHECK(err, "set_affinity", "cpu #%d, err %d\n",
> > + i, err))
> > + goto out_detach;
> > +
> > + usleep(1);
> > + }
> > +
> > + /* read perf buffer */
> > + err = perf_buffer__poll(pb, 100);
> > + if (CHECK(err < 0, "perf_buffer__poll", "err %d\n", err))
> > + goto out_free_pb;
> > +
> > + if (CHECK(CPU_COUNT(&cpu_seen) != nr_cpus, "seen_cpu_cnt",
> > + "expect %d, seen %d\n", nr_cpus, CPU_COUNT(&cpu_seen)))
> > + goto out_free_pb;
> > +
> > +out_free_pb:
> > + perf_buffer__free(pb);
> > +out_detach:
> > + bpf_link__destroy(link);
> > +out_close:
> > + bpf_object__close(obj);
> > +}
> > diff --git a/tools/testing/selftests/bpf/progs/test_perf_buffer.c b/tools/testing/selftests/bpf/progs/test_perf_buffer.c
> > new file mode 100644
> > index 000000000000..876c27deb65a
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_perf_buffer.c
> > @@ -0,0 +1,25 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +// Copyright (c) 2019 Facebook
> > +
> > +#include <linux/ptrace.h>
> > +#include <linux/bpf.h>
> > +#include "bpf_helpers.h"
> > +
> > +struct {
> > + __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
> > + __uint(key_size, sizeof(int));
> > + __uint(value_size, sizeof(int));
> > +} perf_buf_map SEC(".maps");
> > +
> > +SEC("kprobe/sys_nanosleep")
> > +int handle_sys_nanosleep_entry(struct pt_regs *ctx)
> > +{
> > + int cpu = bpf_get_smp_processor_id();
> > +
> > + bpf_perf_event_output(ctx, &perf_buf_map, BPF_F_CURRENT_CPU,
> > + &cpu, sizeof(cpu));
> > + return 0;
> > +}
> > +
> > +char _license[] SEC("license") = "GPL";
> > +__u32 _version SEC("version") = 1;
> >
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