linux-kernel - [PATCH v2 0/2] perf probe: Support debuginfod client

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Message-Id: <160041608027.912668.13169810485938551658.stgit@devnote2>
Date:   Fri, 18 Sep 2020 17:01:20 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:     "Frank Ch . Eigler" <fche@...hat.com>,
        Aaron Merey <amerey@...hat.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/2] perf probe: Support debuginfod client

Hi,

Here is the 2nd version of a series to enable debuginfod support on
perf probe command. This allows users to access debuginfo binary
from remote device. 

In this version I fixed a build error when libdebuginfod is not
installed ([2/2]).


Since the perf-probe heavily depends on the debuginfo, debuginfod
gives us many benefits on the perf probe command on remote
machine, especially for the embedded devices.

Here is an example (copied from [2/2])

1. at first you need to start debuginfod on the host machine.
   -F option scans local debuginfo binary. (You don't need to pass
   the source tree, but you must keep the source tree untouched)

  (host) $ cd PATH/TO/KBUILD/DIR/
  (host) $ debuginfod -F .
  ...

2. In the remote machine, you need to set DEBUGINFOD_URLS.
   debuginfod uses 8002 tcp port.

  (remote) # export DEBUGINFOD_URLS="http://$HOST_IP:8002/"

3. Then you can use the perf probe (it can refer the source code)

  (remote) # perf probe -L vfs_read
  <vfs_read@...>
        0  ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
           {
        2         ssize_t ret;

                  if (!(file->f_mode & FMODE_READ))
                          return -EBADF;
        6         if (!(file->f_mode & FMODE_CAN_READ))
                          return -EINVAL;
        8         if (unlikely(!access_ok(buf, count)))
                          return -EFAULT;

       11         ret = rw_verify_area(READ, file, pos, count);
       12         if (ret)
                          return ret;
                  if (count > MAX_RW_COUNT)
  ...

  (remote) # perf probe -a "vfs_read count"
  Added new event:
    probe:vfs_read       (on vfs_read with count)

  (remote) # perf probe -l
    probe:vfs_read       (on vfs_read@...c/linux/fs/read_write.c with count)



Thank you,

---

Masami Hiramatsu (2):
      perf probe: Fix to adjust symbol address with correct reloc_sym address
      perf probe: Fall back to debuginfod query if debuginfo and source not found


 tools/perf/util/probe-event.c  |   66 ++++++++++++++++++++++++++++++++++++++--
 tools/perf/util/probe-finder.c |   61 ++++++++++++++++++++++++++++++++++---
 tools/perf/util/probe-finder.h |    7 +++-
 3 files changed, 123 insertions(+), 11 deletions(-)

--
Masami Hiramatsu (Linaro) <mhiramat@...nel.org>