linux-kernel - Re: [RFC Patch 0/9] Hardware Breakpoint interfaces

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Date:	Thu, 22 Jan 2009 10:42:48 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Roland McGrath <roland@...hat.com>,
	<akpm@...ux-foundation.org>, <mingo@...e.hu>,
	<richardj_moore@...ibm.com>, <naren@...ux.vnet.ibm.com>
Subject: Re: [RFC Patch 0/9] Hardware Breakpoint interfaces - v4

On Thu, 22 Jan 2009, K.Prasad wrote:

> Hi All,
> 	Please find the new set of patches that introduce kernel
> interfaces to use Hardware Breakpoint registers and an implementation
> for x86 (and x86_64) architecture, now labelled as Version IV.
> 
> The patches are based on 2.6.29-rc2 and have been tested to work fine on
> x86 architecture. Some of the major changes over the previous version of
> patches include:
> i) A sample kernel module that uses Data Hardware breakpoint over a
> kernel variable to monitor write operations. See
> samples/hw_breakpoint/data_breakpoint.c.
> ii) Changes in the register_kernel_hw_breakpoint() interface to accept
> only one parameter - pointer to a 'hw_breakpoint' structure which will
> contain all relevant data members.

I see some problems with this immediately.  Firstly, as a result of
this change the sample code in include/asm-generic/hw_breakpoint.h is
now incorrect.  You need to change the comments when you change the
code.

Second, your arch_store_info() routine is broken.  It checks for a
kernel symbol name even if when a userspace breakpoint is being
registered.  You should move that check up into validate_settings().

As a related matter, why did you put the "name" field into the
arch-dependent part?  Clearly it should be arch-independent.

Alan Stern

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