linux-kernel - Re: [PATCH] [6/50] i386: clean up oops/bug reports

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Date:	Fri, 21 Sep 2007 18:41:53 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	Andi Kleen <ak@...e.de>
CC:	xemul@...nvz.org, patches@...-64.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [6/50] i386: clean up oops/bug reports

On 09/21/2007 06:32 PM, Andi Kleen wrote:
> From: Pavel Emelyanov <xemul@...nvz.org>
> 
> Typically the oops first lines look like this:
> 
> BUG: unable to handle kernel NULL pointer dereference at virtual address 00000000
>  printing eip:
> c049dfbd
> *pde = 00000000
> Oops: 0002 [#1]
> PREEMPT SMP
> ...
> 
> Such output is gained with some ugly if (!nl) printk("\n"); code and
> besides being a waste of lines, this is also annoying to read. The
> following output looks better (and it is how it looks on x86_64):
> 
> BUG: unable to handle kernel NULL pointer dereference at virtual address 00000000
> printing eip: c049dfbd *pde = 00000000
> Oops: 0002 [#1] PREEMPT SMP
> ...
> 
> Signed-off-by: Pavel Emelyanov <xemul@...nvz.org>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Andi Kleen <ak@...e.de>

Reviewed-by: Chuck Ebbert <cebbert@...hat.com>

> 
> ---
> 
>  arch/i386/kernel/traps.c |   16 ++++------------
>  arch/i386/mm/fault.c     |   13 +++++++------
>  2 files changed, 11 insertions(+), 18 deletions(-)
> 
> Index: linux/arch/i386/kernel/traps.c
> ===================================================================
> --- linux.orig/arch/i386/kernel/traps.c
> +++ linux/arch/i386/kernel/traps.c
> @@ -444,31 +444,23 @@ void die(const char * str, struct pt_reg
>  		local_save_flags(flags);
>  
>  	if (++die.lock_owner_depth < 3) {
> -		int nl = 0;
>  		unsigned long esp;
>  		unsigned short ss;
>  
>  		report_bug(regs->eip, regs);
>  
> -		printk(KERN_EMERG "%s: %04lx [#%d]\n", str, err & 0xffff, ++die_counter);
> +		printk(KERN_EMERG "%s: %04lx [#%d] ", str, err & 0xffff, ++die_counter);
>  #ifdef CONFIG_PREEMPT
> -		printk(KERN_EMERG "PREEMPT ");
> -		nl = 1;
> +		printk("PREEMPT ");
>  #endif
>  #ifdef CONFIG_SMP
> -		if (!nl)
> -			printk(KERN_EMERG);
>  		printk("SMP ");
> -		nl = 1;
>  #endif
>  #ifdef CONFIG_DEBUG_PAGEALLOC
> -		if (!nl)
> -			printk(KERN_EMERG);
>  		printk("DEBUG_PAGEALLOC");
> -		nl = 1;
>  #endif
> -		if (nl)
> -			printk("\n");
> +		printk("\n");
> +
>  		if (notify_die(DIE_OOPS, str, regs, err,
>  					current->thread.trap_no, SIGSEGV) !=
>  				NOTIFY_STOP) {
> Index: linux/arch/i386/mm/fault.c
> ===================================================================
> --- linux.orig/arch/i386/mm/fault.c
> +++ linux/arch/i386/mm/fault.c
> @@ -544,23 +544,22 @@ no_context:
>  			printk(KERN_ALERT "BUG: unable to handle kernel paging"
>  					" request");
>  		printk(" at virtual address %08lx\n",address);
> -		printk(KERN_ALERT " printing eip:\n");
> -		printk("%08lx\n", regs->eip);
> +		printk(KERN_ALERT "printing eip: %08lx ", regs->eip);
>  
>  		page = read_cr3();
>  		page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT];
>  #ifdef CONFIG_X86_PAE
> -		printk(KERN_ALERT "*pdpt = %016Lx\n", page);
> +		printk("*pdpt = %016Lx ", page);
>  		if ((page >> PAGE_SHIFT) < max_low_pfn
>  		    && page & _PAGE_PRESENT) {
>  			page &= PAGE_MASK;
>  			page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT)
>  			                                         & (PTRS_PER_PMD - 1)];
> -			printk(KERN_ALERT "*pde = %016Lx\n", page);
> +			printk(KERN_ALERT "*pde = %016Lx ", page);
>  			page &= ~_PAGE_NX;
>  		}
>  #else
> -		printk(KERN_ALERT "*pde = %08lx\n", page);
> +		printk("*pde = %08lx ", page);
>  #endif
>  
>  		/*
> @@ -574,8 +573,10 @@ no_context:
>  			page &= PAGE_MASK;
>  			page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT)
>  			                                         & (PTRS_PER_PTE - 1)];
> -			printk(KERN_ALERT "*pte = %0*Lx\n", sizeof(page)*2, (u64)page);
> +			printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page);
>  		}
> +
> +		printk("\n");
>  	}
>  
>  	tsk->thread.cr2 = address;
-
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