linux-kernel - Re: [PATCH v5] Fix INT1 Recursion with unregistered breakpoints

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Message-ID: <CAO6TR8W7cchQtmK-5kt3zHbrXVrAockfm+TyHhpxzN5G51r7VQ@mail.gmail.com>
Date:	Sat, 19 Dec 2015 20:15:52 -0700
From:	Jeff Merkey <linux.mdb@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, peterz@...radead.org, luto@...nel.org
Subject: Re: [PATCH v5] Fix INT1 Recursion with unregistered breakpoints

>  		/*
> +		 * Check if we got an execute breakpoint, if so
> +		 * set the resume flag to avoid int1 recursion.
> +		 */
> +		if ((dr7 & (DR_RW_MASK << ((i * DR_CONTROL_SIZE) +
> +			DR_CONTROL_SHIFT))) == DR_RW_EXECUTE)
> +			args->regs->flags |= X86_EFLAGS_RF;
> +
> +		/*

This patch is functionaly correct but I still need to make it perfect.
I more try and test run.
I tested this and it works, but I need to shift it the other way
(right) rather than (left) since DR_RW_EXECUTE is always 0 this will
always work but to be perfect I need to do:

if (((dr7 >> ((i * DR_CONTROL_SIZE) + DR_CONTROL_SHIFT)) & DR_RW_MASK)
== DR_RW_EXECUTE)

and that is perfect syntax.

Jeff
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