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Date: Mon, 11 Jan 2021 23:26:23 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Qais Yousef <qais.yousef@....com>
Cc: Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
Alexei Starovoitov <ast@...nel.org>,
Andrii Nakryiko <andrii@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Steven Rostedt <rostedt@...dmis.org>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 2/2] selftests: bpf: Add a new test for bare tracepoints
On Mon, Jan 11, 2021 at 10:20 AM Qais Yousef <qais.yousef@....com> wrote:
>
> Reuse module_attach infrastructure to add a new bare tracepoint to check
> we can attach to it as a raw tracepoint.
>
> Signed-off-by: Qais Yousef <qais.yousef@....com>
> ---
>
> Andrii
>
> I was getting the error below when I was trying to run the test.
> I had to comment out all related fentry* code to be able to test the raw_tp
> stuff. Not sure something I've done wrong or it's broken for some reason.
> I was on v5.11-rc2.
Check that you have all the required Kconfig options from
tools/testing/selftests/bpf/config. And also you will need to build
pahole from master, 1.19 doesn't have some fixes that add kernel
module support. I think pahole is the reasons why you have the failure
below.
>
> $ sudo ./test_progs -v -t module_attach
use -vv when debugging stuff like that with test_progs, it will output
libbpf detailed logs, that often are very helpful
> bpf_testmod.ko is already unloaded.
> Loading bpf_testmod.ko...
> Successfully loaded bpf_testmod.ko.
> test_module_attach:PASS:skel_open 0 nsec
> test_module_attach:PASS:set_attach_target 0 nsec
> test_module_attach:PASS:skel_load 0 nsec
> libbpf: prog 'handle_fentry': failed to attach: ERROR: strerror_r(-524)=22
> libbpf: failed to auto-attach program 'handle_fentry': -524
> test_module_attach:FAIL:skel_attach skeleton attach failed: -524
> #58 module_attach:FAIL
> Successfully unloaded bpf_testmod.ko.
> Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED
>
But even apart from test failure, there seems to be kernel build
failure. See [0] for what fails in kernel-patches CI.
[0] https://travis-ci.com/github/kernel-patches/bpf/builds/212730017
>
> .../selftests/bpf/bpf_testmod/bpf_testmod-events.h | 6 ++++++
> tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c | 2 ++
> tools/testing/selftests/bpf/prog_tests/module_attach.c | 1 +
> tools/testing/selftests/bpf/progs/test_module_attach.c | 10 ++++++++++
> 4 files changed, 19 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h
> index b83ea448bc79..e1ada753f10c 100644
> --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h
> +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h
> @@ -28,6 +28,12 @@ TRACE_EVENT(bpf_testmod_test_read,
> __entry->pid, __entry->comm, __entry->off, __entry->len)
> );
>
> +/* A bare tracepoint with no event associated with it */
> +DECLARE_TRACE(bpf_testmod_test_read_bare,
> + TP_PROTO(struct task_struct *task, struct bpf_testmod_test_read_ctx *ctx),
> + TP_ARGS(task, ctx)
> +);
> +
> #endif /* _BPF_TESTMOD_EVENTS_H */
>
> #undef TRACE_INCLUDE_PATH
> diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> index 2df19d73ca49..d63cebdaca44 100644
> --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> @@ -22,6 +22,8 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj,
> };
>
> trace_bpf_testmod_test_read(current, &ctx);
> + ctx.len++;
> + trace_bpf_testmod_test_read_bare(current, &ctx);
It's kind of boring to have two read tracepoints :) Do you mind adding
a write tracepoint and use bare tracepoint there? You won't need this
ctx.len++ hack as well. Feel free to add identical
bpf_testmod_test_write_ctx (renaming it is more of a pain).
>
> return -EIO; /* always fail */
> }
> diff --git a/tools/testing/selftests/bpf/prog_tests/module_attach.c b/tools/testing/selftests/bpf/prog_tests/module_attach.c
> index 50796b651f72..7085a118f38c 100644
> --- a/tools/testing/selftests/bpf/prog_tests/module_attach.c
> +++ b/tools/testing/selftests/bpf/prog_tests/module_attach.c
> @@ -50,6 +50,7 @@ void test_module_attach(void)
> ASSERT_OK(trigger_module_test_read(READ_SZ), "trigger_read");
>
> ASSERT_EQ(bss->raw_tp_read_sz, READ_SZ, "raw_tp");
> + ASSERT_EQ(bss->raw_tp_bare_read_sz, READ_SZ+1, "raw_tp_bare");
> ASSERT_EQ(bss->tp_btf_read_sz, READ_SZ, "tp_btf");
> ASSERT_EQ(bss->fentry_read_sz, READ_SZ, "fentry");
> ASSERT_EQ(bss->fentry_manual_read_sz, READ_SZ, "fentry_manual");
> diff --git a/tools/testing/selftests/bpf/progs/test_module_attach.c b/tools/testing/selftests/bpf/progs/test_module_attach.c
> index efd1e287ac17..08aa157afa1d 100644
> --- a/tools/testing/selftests/bpf/progs/test_module_attach.c
> +++ b/tools/testing/selftests/bpf/progs/test_module_attach.c
> @@ -17,6 +17,16 @@ int BPF_PROG(handle_raw_tp,
> return 0;
> }
>
> +__u32 raw_tp_bare_read_sz = 0;
> +
> +SEC("raw_tp/bpf_testmod_test_read_bare")
> +int BPF_PROG(handle_raw_tp_bare,
> + struct task_struct *task, struct bpf_testmod_test_read_ctx *read_ctx)
> +{
> + raw_tp_bare_read_sz = BPF_CORE_READ(read_ctx, len);
> + return 0;
> +}
> +
> __u32 tp_btf_read_sz = 0;
>
> SEC("tp_btf/bpf_testmod_test_read")
> --
> 2.25.1
>
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