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 17:51:15 +0530
From:	"Abhishek Sagar" <sagar.abhishek@...il.com>
To:	jmerkey@...fmountaingroup.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.27-rc1-git5 2/26] mdb: correct kprobes int3 trap

On Tue, Aug 5, 2008 at 11:56 AM,  <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)
> @@ -865,6 +890,16 @@
>  }
>  #endif

If the mdb() call modifies the IF flag in regs, then it should
probably be called after trace_hardirqs_fixup. Best to keep it behind
notify_die() ensuring that kprobes handles all breakpoints first.
Otherwise at least the mdb function (and others in its call chain)
should be marked as __kprobes.

-- Abhishek Sagar
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