linux-kernel - Re: [PATCH] [20/20] x86: Print which shared library/executable faulted in segfault etc. messages

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Date:	Thu, 3 Jan 2008 12:00:34 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <ak@...e.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [20/20] x86: Print which shared library/executable
	faulted in segfault etc. messages


* Andi Kleen <ak@...e.de> wrote:

> They now look like
> 
> hal-resmgr[13791]: segfault at 3c rip 2b9c8caec182 rsp 7fff1e825d30 
> error 4 in libacl.so.1.1.0[2b9c8caea000+6000]
> 
> This makes it easier to pinpoint bugs to specific libraries.

yep, that's really useful.

I think the patch needs one more iteration though:

> And printing the offset into a mapping also always allows to find the 
> correct fault point in a library even with randomized mappings. Previously
> there was no way to actually find the correct code address inside
> the randomized mapping.
> 
> Relies on earlier patch to shorten the printk formats.
> 
> They are often now longer than 80 characters, but I think that's worth 
> it.

why not make it multi-line? that way the %lx hack wouldnt be needed 
either.

> +void print_vma_addr(char *prefix, unsigned long ip)
> +{
> +	struct mm_struct *mm = current->mm;
> +	struct vm_area_struct *vma;
> +	down_read(&mm->mmap_sem);
> +	vma = find_vma(mm, ip);

grumble. Proper CodingStyle please.

> +		if (buf) {
> +			char *p, *s;
> +			p = d_path(f->f_dentry, f->f_vfsmnt, buf, PAGE_SIZE);

this one too.

> +	if (show_unhandled_signals && printk_ratelimit()) {
> +		printk("%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
>  	       me->comm,me->pid,where,frame,regs->ip,regs->sp,regs->orig_ax);

and this.

	Ingo
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