linux-kernel - Re: [PATCH] perf, x86: Disable sanity check

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4F904C6C.7020407@fb.com>
Date:	Thu, 19 Apr 2012 10:33:32 -0700
From:	Arun Sharma <asharma@...com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	<linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	"Arnaldo Carvalho de Melo" <acme@...hat.com>,
	Mike Galbraith <efault@....de>,
	"Paul Mackerras" <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"Stephane Eranian" <eranian@...gle.com>,
	Namhyung Kim <namhyung.kim@....com>,
	"Tom Zanussi" <tzanussi@...il.com>,
	<linux-perf-users@...r.kernel.org>
Subject: Re: [PATCH] perf, x86: Disable sanity check

On 4/18/12 10:22 PM, Frederic Weisbecker wrote:

> So rbp is part of the JIT stack but not rsp?
> Do you have a practical example of that? I must confess I don't know
> much about JIT stack.

Nothing specific to JITs here. Any time an app has two stacks S1 and S2 
(with S1 at a lower address and S2 at a higher address) and %rsp at the 
time of a perf event is pointing to S2, we don't get traces beyond S2.

               |                 |
               |                 |
               |   0x1000000     |  <-- %rbp
               |                 |
               |                 |
S2: 0x2000000 |                 |  <-- %rsp
               |                 |
               |                 |
               |                 |
               |    frame3       |
               |                 |
               |    frame2       |
               |                 |
S1: 0x1000000 |    frame1       |
               |                 |
               |                 |
               |                 |
               |                 |

gdb is able to show:

(gdb) bt
<frame at 0x2000000>
frame1
frame2
frame3
frame4
..

just fine.

In our use case, there may be multiple transitions between S1 and S2. 
For eg: frame4 could be on S2 (i.e 0x2xxxxxx range).

  -Arun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/