linux-kernel - Re: crashme fault

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Date:	Sat, 15 Sep 2007 16:47:54 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Andi Kleen <andi@...stfloor.org>,
	lkml <linux-kernel@...r.kernel.org>, Andi Kleen <ak@...e.de>
Subject: Re: crashme fault

Linus Torvalds wrote:
> 
> On Sat, 15 Sep 2007, Linus Torvalds wrote:
>> So regardless of whether we want to trust "user_mode(regs)" more than 
>> "error_code & PF_USER", it would definitely be very interesting if you can 
>> give a good "this is where it started happening".
> 
> Also, can you point to good crashme sources, and give the arguments you 
> used to run it when it crashed?

I use http://people.delphiforums.com/gjc/crashme.tgz from
http://people.delphiforums.com/gjc/crashme.html, plus one small patch:

--- gjc-crashme.orig/crashme.c
+++ gjc-crashme/crashme.c
@@ -260,7 +260,8 @@ void my_signal(sig, func)
 #else
  struct sigaction act;
  act.sa_handler = func;
- act.sa_mask = 0;
+ //act.sa_mask = 0;
+ sigemptyset(&act.sa_mask);
 #ifdef linux
  act.sa_restorer = 0;
 #endif /* linux */


Command: ./crashme +2000 666 1000 1:00:00 1

> The original gjc crashme doesn't even do a "mprotect(PROT_EXEC)" by 
> default (nor does it even compile on a modern unix), so it's not going to 
> do anything. I hacked it up, and it appears to work ok for me, but I'm not 
> at all confident that I'm even close to recreating what you are doing.

So I'm missing some mprotect() call also?
Oops.

> (It probably goes without saying that I've not reproduced the oops on my 
> Core 2 Duo. Lots of #GP and #PF errors, but nothing interesting.
> 
> 		Linus

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