linux-kernel - Re: [PATCH 9/9] ARM: add uprobes support

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Date:	Sun, 21 Oct 2012 20:27:56 +0200
From:	Rabin Vincent <rabin@....in>
To:	Dave Martin <dave.martin@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, oleg@...hat.com
Subject: Re: [PATCH 9/9] ARM: add uprobes support

On Mon, Oct 15, 2012 at 06:31:47PM +0100, Dave Martin wrote:
> On Sun, Oct 14, 2012 at 09:23:13PM +0200, Rabin Vincent wrote:
> > +static int uprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
> > +{
> > +	unsigned long flags;
> > +
> > +	local_irq_save(flags);
> > +	if ((instr & 0x0fffffff) == UPROBE_SWBP_INSN)
> 
> Is the check unnecessary here?  I think the same comparison will
> happen as a result of evaluating the associated undef_hook.

The check is there because this uprobe_trap_handler() is registered for
two different undefined instructions: UPROBE_SWBP_INSN (the one which is
used to insert the probe) and UPROBE_SS_INSN (the one placed in the XOL
area for simulating single-stepping).
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