linux-kernel - Re: perf test BPF failing on 4.15.0-rc6

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Date:   Thu, 4 Jan 2018 09:37:35 +0800
From:   "Wangnan (F)" <wangnan0@...wei.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
CC:     Adrian Hunter <adrian.hunter@...el.com>,
        David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: perf test BPF failing on 4.15.0-rc6



On 2018/1/4 4:13, Arnaldo Carvalho de Melo wrote:
> Em Wed, Jan 03, 2018 at 03:33:07PM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Wed, Jan 03, 2018 at 03:27:01PM -0300, Arnaldo Carvalho de Melo escreveu:
>>>> Continuing investigation...
>>> After applying the fallback patch to allow new tools to work with older
>>> kernels:
>>>
>>> [root@...icio ~]# perf test bpf
>>> 39: BPF filter                                            :
>>> 39.1: Basic BPF filtering                                 : Ok
>>> 39.2: BPF pinning                                         : Ok
>>> 39.3: BPF prologue generation                             : Ok
>>> 39.4: BPF relocation checker                              : Ok
>>> [root@...icio ~]# uname -a
>>> Linux felicio.ghostprotocols.net 4.13.0-rc7+ #1 SMP Mon Sep 11 13:56:18 -03 2017 x86_64 x86_64 x86_64 GNU/Linux
>>> [root@...icio ~]# rpm -q glibc
>>> glibc-2.17-157.el7_3.2.x86_64
>>> [root@...icio ~]#
>>>
>>> After applying the patch below I get to, which is what I am trying to
>>> fix now:
>>>
>>> [root@...et ~]# perf test bpf
>>> 39: BPF filter                                            :
>>> 39.1: Basic BPF filtering                                 : Ok
>>> 39.2: BPF pinning                                         : Ok
>>> 39.3: BPF prologue generation                             : FAILED!
>>> 39.4: BPF relocation checker                              : Skip
>>> [root@...et ~]#
>> Update the patch to the one at the end of this message to make it work
>> with older glibcs, so that we ask for epoll_pwait() and hook into that
>> as well().
>>
>> Now checking why 39.3 fails...
> Couldn't reproduce after fixing up some kernel build problems, the patch
> below is all I need to have this working with both Fedora 27 and RHEL7,
> please take a look and see if it continues to work on your systems,

It works for me. Thank you.

Since we test epoll_pwait, we'd better correct function names:


diff --git a/tools/perf/tests/bpf-script-example.c 
b/tools/perf/tests/bpf-script-example.c
index 268e5f8..e4123c1 100644
--- a/tools/perf/tests/bpf-script-example.c
+++ b/tools/perf/tests/bpf-script-example.c
@@ -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);
diff --git a/tools/perf/tests/bpf.c b/tools/perf/tests/bpf.c
index 34c22cd..a8f9095 100644
--- a/tools/perf/tests/bpf.c
+++ b/tools/perf/tests/bpf.c
@@ -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 {
          "[basic_bpf_test]",
          "fix 'perf test LLVM' first",
          "load bpf object failed",
-        &epoll_wait_loop,
+        &epoll_pwait_loop,
          (NR_ITERS + 1) / 2,
          false,
      },
@@ -78,7 +78,7 @@ static struct {
          "[bpf_pinning]",
          "fix kbuild first",
          "check your vmlinux setting?",
-        &epoll_wait_loop,
+        &epoll_pwait_loop,
          (NR_ITERS + 1) / 2,
          true,
      },