Re: [PATCH 0/2] perf probe: Support debuginfod client

[Arnaldo Carvalho de Melo]

Em Wed, Sep 16, 2020 at 04:17:53PM -0400, Frank Ch. Eigler escreveu:
> Hi -
> 
> > > Nice, even uses the source code fetching part of the webapi!
> > 
> > So, can I take that as an Acked-by or Reviewed-by? 
> 
> Sure.

Thanks, applied both now that the things that made some 'perf probe'
'perf test' entries to fail is out of the way, all passes now with these
patches.

- Arnaldo

Re: [PATCH 0/2] perf probe: Support debuginfod client

[Frank Ch. Eigler]

Hi -

> > > I need to support this in pahole...
> > 
> > pahole/dwarves use elfutils, so it already has automatic support.
> > https://sourceware.org/elfutils/Debuginfod.html
> 
> I'm still not sure that which interface of elfutils I should use
> for this "automatic" debuginfod support. Are there good documentation
> about it?

The libdwfl part of the elfutils API falls back to debuginfod lookups
internally, so e.g. systemtap had to do nothing to benefit.


> Since this series just for the kernel binary, I have to check we
> can do something on user-space binaries.

It should work identically & transparently.  If you're using one of
a few key packages of a few mainstream distros, the public debuginfod
server may already have the material available.


- FChE

Re: [PATCH 0/2] perf probe: Support debuginfod client

[Masami Hiramatsu]

On Wed, 16 Sep 2020 16:17:53 -0400
"Frank Ch. Eigler"  wrote:

> Hi -
> 
> > > Nice, even uses the source code fetching part of the webapi!
> > 
> > So, can I take that as an Acked-by or Reviewed-by? 
> 
> Sure.

Thanks Frank and Arnaldo!

> 
> > I need to support this in pahole...
> 
> pahole/dwarves use elfutils, so it already has automatic support.
> 
> https://sourceware.org/elfutils/Debuginfod.html

I'm still not sure that which interface of elfutils I should use
for this "automatic" debuginfod support. Are there good documentation
about it?
Since this series just for the kernel binary, I have to check we
can do something on user-space binaries.

Thank you,

-- 
Masami Hiramatsu 

[PATCH 0/2] perf probe: Support debuginfod client

[Masami Hiramatsu]

Hi,

Here is a couple of patches to enable debuginfod support on
perf probe command. This allows users to access debuginfo binary
from remote device. 

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
  
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@ksrc/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  |   60 +---
 tools/perf/util/probe-finder.c |   56 ++---
 tools/perf/util/probe-finder.h |7 +++--
 3 files changed, 112 insertions(+), 11 deletions(-)

--
Masami Hiramatsu (Linaro) 

Re: [PATCH 0/2] perf probe: Support debuginfod client

[Frank Ch. Eigler]

Hi -

> > Nice, even uses the source code fetching part of the webapi!
> 
> So, can I take that as an Acked-by or Reviewed-by? 

Sure.

> I need to support this in pahole...

pahole/dwarves use elfutils, so it already has automatic support.

https://sourceware.org/elfutils/Debuginfod.html

- FChE

Re: [PATCH 0/2] perf probe: Support debuginfod client

[Arnaldo Carvalho de Melo]

Em Wed, Sep 16, 2020 at 02:13:07PM -0400, Frank Ch. Eigler escreveu:
> Hi -
> 
> Nice, even uses the source code fetching part of the webapi!

So, can I take that as an Acked-by or Reviewed-by? 

:-)

- Arnaldo

I need to support this in pahole...
 
> - FChE
> 

-- 

- Arnaldo

Re: [PATCH 0/2] perf probe: Support debuginfod client

[Frank Ch. Eigler]

Hi -

Nice, even uses the source code fetching part of the webapi!

- FChE