linux-kernel - RE: Oops with tip/x86/fpu

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Date:	Thu, 26 Mar 2015 22:37:03 +0000
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	Oleg Nesterov <oleg@...hat.com>, Borislav Petkov <bp@...e.de>,
	"Hansen, Dave" <dave.hansen@...el.com>
CC:	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	Andy Lutomirski <luto@...capital.net>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Riikonen <priikone@....fi>,
	"Rik van Riel" <riel@...hat.com>,
	Suresh Siddha <sbsiddha@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: RE: Oops with tip/x86/fpu

> From: Oleg Nesterov [mailto:oleg@...hat.com]
> Sent: Thursday, March 05, 2015 10:22 AM
> 
> On 03/05, Oleg Nesterov wrote:
> >
> 
> Does it trigger something else on your machine?
> 
> Oleg.
> 
> #include <stdio.h>
> #include <signal.h>
> #include <unistd.h>
> #include <ucontext.h>
> 
> void sighup(int sig, siginfo_t *info, void *ctxt) {
> 	struct ucontext *uctxt = ctxt;
> 	struct sigcontext *sctxt = (void*)&uctxt->uc_mcontext;
> 
> 	printf("SIGHUP! %p\n", sctxt->fpstate);
> 	sctxt->fpstate = (void *)1;

sctxt->fpstate=(void *)1 changes the fpstate pointer in the sigcontext. It will generate segfault and bad frame info in kernel.

This is expected behavior, right? Is this still a valid test?

Thanks.

-Fenghua
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