linux-kernel - Re: [PATCH] perf tools: Fix object code reading for PTI entry trampolines

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Date:   Tue, 5 Jun 2018 10:41:42 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf tools: Fix object code reading for PTI entry
 trampolines

Em Tue, Jun 05, 2018 at 10:30:00AM +0300, Adrian Hunter escreveu:
> Fix object code reading and the "Object code reading" test for PTI entry
> trampolines.
> 
> perf tools uses map__rip_2objdump() to calculate objdump virtual addresses.
> map__rip_2objdump() needs to be amended to deal with PTI entry trampolines.
> Also the "Object code reading" test will not create maps for the PTI entry
> trampolines unless the machine environment exists to show that the arch is
> x86_64.

So, I split it into two patches, right at the "Also" part in your
description:

[acme@...enth perf]$ git log --oneline -2
36800a71b000 (HEAD -> perf/core) perf map: Consider PTI entry trampolines in rip_2objdump()
2f6777b74f6d perf test code-reading: Fix perf_env setup for PTI entry trampolines
[acme@...enth perf]$

https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/log/?h=perf/core

And this test fails way less often, but still does, for instance:

# while true ; do perf test -v object 2>out.txt ; grep -i fail out.txt && break ; done
dso__data_read_offset failed
Object code reading: FAILED!
#
[root@...enth ~]# tail out.txt 
File is: /proc/kcore
On file address is: 0x7fff892300df
kcore map tested already - skipping
Reading object code for memory address: 0x4a020f
File is: /home/acme/bin/perf (deleted)
On file address is: 0xa020f
dso__data_read_offset failed
test child finished with -1
---- end ----
Object code reading: FAILED!
[root@...enth ~]#

I start that loop and then try running 'make -C tools/perf O=/tmp/build/perf install-bin',
to generate some load.

But now at least on a quiet system it works.

- Arnaldo