linux-kernel - Re: [PATCH 2/7] x86, dumpstack: let signr=0 signal no do

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Date:	Wed, 22 Oct 2008 07:01:26 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Alexander van Heukelum <heukelum@...tmail.fm>
Cc:	Ingo Molnar <mingo@...e.hu>, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, vgoyal@...hat.com, hbabu@...ibm.com,
	hpa@...or.com, akpm@...ux-foundation.org, ebiederm@...ssion.com,
	tglx@...utronix.de
Subject: Re: [PATCH 2/7] x86, dumpstack: let signr=0 signal no do_exit

On Wed, Oct 22, 2008 at 12:00:09PM +0200, Alexander van Heukelum wrote:
> Change oops_end such that signr=0 signals that do_exit
> is not to be called.
> 
> Currently, each use of __die is soon followed by a call
> to oops_end and 'regs' is set to NULL if oops_end is expected
> not to call do_exit. Change all such pairs to set signr=0
> instead. On x86_64 oops_end is used 'bare' in die_nmi; use
> signr=0 instead of regs=NULL there, too.
> 
> Signed-off-by: Alexander van Heukelum <heukelum@...tmail.fm>

Acked-by: Neil Horman <nhorman@...driver.com>

> ---
>  arch/x86/kernel/dumpstack_32.c |    7 ++++---
>  arch/x86/kernel/dumpstack_64.c |    9 +++++----
>  arch/x86/mm/fault.c            |   11 +++++++----
>  3 files changed, 16 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
> index 5493d31..7c22f99 100644
> --- a/arch/x86/kernel/dumpstack_32.c
> +++ b/arch/x86/kernel/dumpstack_32.c
> @@ -318,7 +318,7 @@ void __kprobes oops_end(unsigned long flags, struct pt_regs *regs, int signr)
>  	__raw_spin_unlock(&die_lock);
>  	raw_local_irq_restore(flags);
>  
> -	if (!regs)
> +	if (!signr)
>  		return;
>  
>  	if (in_interrupt())
> @@ -371,17 +371,18 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err)
>  void die(const char *str, struct pt_regs *regs, long err)
>  {
>  	unsigned long flags = oops_begin();
> +	int sig = SIGSEGV;
>  
>  	if (die_nest_count < 3) {
>  		report_bug(regs->ip, regs);
>  
>  		if (__die(str, regs, err))
> -			regs = NULL;
> +			sig = 0;
>  	} else {
>  		printk(KERN_EMERG "Recursive die() failure, output suppressed\n");
>  	}
>  
> -	oops_end(flags, regs, SIGSEGV);
> +	oops_end(flags, regs, sig);
>  }
>  
>  static DEFINE_SPINLOCK(nmi_print_lock);
> diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
> index 96a5db7..ffefea6 100644
> --- a/arch/x86/kernel/dumpstack_64.c
> +++ b/arch/x86/kernel/dumpstack_64.c
> @@ -465,7 +465,7 @@ void __kprobes oops_end(unsigned long flags, struct pt_regs *regs, int signr)
>  		/* Nest count reaches zero, release the lock. */
>  		__raw_spin_unlock(&die_lock);
>  	raw_local_irq_restore(flags);
> -	if (!regs) {
> +	if (!signr) {
>  		oops_exit();
>  		return;
>  	}
> @@ -509,13 +509,14 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err)
>  void die(const char *str, struct pt_regs *regs, long err)
>  {
>  	unsigned long flags = oops_begin();
> +	int sig = SIGSEGV;
>  
>  	if (!user_mode(regs))
>  		report_bug(regs->ip, regs);
>  
>  	if (__die(str, regs, err))
> -		regs = NULL;
> -	oops_end(flags, regs, SIGSEGV);
> +		sig = 0;
> +	oops_end(flags, regs, sig);
>  }
>  
>  notrace __kprobes void
> @@ -539,7 +540,7 @@ die_nmi(char *str, struct pt_regs *regs, int do_panic)
>  		crash_kexec(regs);
>  	if (do_panic || panic_on_oops)
>  		panic("Non maskable interrupt");
> -	oops_end(flags, NULL, SIGBUS);
> +	oops_end(flags, regs, 0);
>  	nmi_exit();
>  	local_irq_enable();
>  	do_exit(SIGBUS);
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 8e52e68..ed9ee30 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -415,6 +415,7 @@ static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
>  				 unsigned long error_code)
>  {
>  	unsigned long flags = oops_begin();
> +	int sig = SIGKILL;
>  	struct task_struct *tsk;
>  
>  	printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
> @@ -425,8 +426,8 @@ static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
>  	tsk->thread.trap_no = 14;
>  	tsk->thread.error_code = error_code;
>  	if (__die("Bad pagetable", regs, error_code))
> -		regs = NULL;
> -	oops_end(flags, regs, SIGKILL);
> +		sig = 0;
> +	oops_end(flags, regs, sig);
>  }
>  #endif
>  
> @@ -594,6 +595,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
>  
>  #ifdef CONFIG_X86_64
>  	unsigned long flags;
> +	int sig;
>  #endif
>  
>  	tsk = current;
> @@ -868,11 +870,12 @@ no_context:
>  	bust_spinlocks(0);
>  	do_exit(SIGKILL);
>  #else
> +	sig = SIGKILL;
>  	if (__die("Oops", regs, error_code))
> -		regs = NULL;
> +		sig = 0;
>  	/* Executive summary in case the body of the oops scrolled away */
>  	printk(KERN_EMERG "CR2: %016lx\n", address);
> -	oops_end(flags, regs, SIGKILL);
> +	oops_end(flags, regs, sig);
>  #endif
>  
>  /*
> -- 
> 1.5.4.3
> 
> 

-- 
/****************************************************
 * Neil Horman <nhorman@...driver.com>
 * Software Engineer, Red Hat
 ****************************************************/
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