linux-kernel - Re: [PATCH 2.6.27-rc1-git5 2/26] mdb: correct kprobes int3 trap

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Date:	Wed, 6 Aug 2008 07:36:40 -0600 (MDT)
From:	jmerkey@...fmountaingroup.com
To:	ananth@...ibm.com
Cc:	jmerkey@...fmountaingroup.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.27-rc1-git5 2/26] mdb: correct kprobes int3 trap

> On Tue, Aug 05, 2008 at 12:26:35AM -0600, jmerkey@...fmountaingroup.com
> wrote:
> ...
>
>> @@ -850,6 +871,10 @@
>>  #ifdef CONFIG_KPROBES
>>  void __kprobes do_int3(struct pt_regs *regs, long error_code)
>>  {
>> +#ifdef	CONFIG_MDB
>> +        if (mdb(BREAKPOINT_EXCEPTION, error_code, regs))
>> +           return;
>> +#endif // CONFIG_MDB
>>  	trace_hardirqs_fixup();
>>
>>  	if (notify_die(DIE_INT3, "int3", regs, error_code, 3, SIGTRAP)
>
> Kprobes needs to be the first consumer of these exceptions (via
> notify_die); if the exception was due to a kprobe, it does its thing
> without requiring any user intervention. Here, for example, you can get
> into mdb for a kprobe breakpoint hit.
>
> Please move the mdb hooks to after kprobes has been notified. Better
> still, integrate mdb to use the notify_die infrastructure and use a
> lower priority than what kprobes does for it.
>
> Ananth
>

I have removed these hooks already and converted to debugger to use
notify_die -- finished it last night as per Andi's suggestions.  This code
section has already been removed from reboot.c and traps_XX.c.

I'll post the new patch with the module based debugger later today.

Jeff

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