From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.xen@gmail.com>
Subject: Re: [PATCH] xen/x86: Introduce early_invalid_op()
	handler.
Date: Mon, 09 Sep 2013 07:37:03 -0700
Message-ID: <CE532B1F.5D232%keir.xen@gmail.com>
References: <522DF7B302000078000F1942@nat28.tlf.novell.com>
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To: Jan Beulich <JBeulich@suse.com>, Andrew Cooper <andrew.cooper3@citrix.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>
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On 09/09/2013 07:30, "Jan Beulich" <JBeulich@suse.com> wrote:

>>>> On 09.09.13 at 16:17, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>> +void __init  __attribute__((noreturn))
>> +do_early_invalid_op(struct cpu_user_regs *regs)
>> +{
>> +    if ( *(u16 *)regs->eip == 0x0b0f )
> 
> Without even a range check on regs->eip? I don't think we want to
> needlessly risk #PF or #GP here...
> 
>> +        printk("Early ud2 at %p - BUG/WARN/ASSERT perhaps?\n",
>> _p(regs->eip));
>> +    else
>> +        printk("Unidentified early #UD at %p\n", _p(regs->eip));
>> +
> 
> You probably also meant to at least print the same raw stack
> dump that do_early_page_fault() produces?

I suggest less cleverness in this printk and indeed dump regs and error
code. More useful, potentially. Also then the handler will not be
UD-specific and could be called for all early exceptions (except those with
a more specific handler such as #PG).

All that would be needed in asm is a per-exception push/mov and jmp to
common asm which does the SAVE_ALL stuff and jmp to C.

 -- Keir

> Jan
> 
>> +    for ( ; ; )
>> +        halt();
>> +}
> 
>