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Re: Using hardware watchpoint for applications debugging

To: Nigel Stephens <nigel@mips.com>
Subject: Re: Using hardware watchpoint for applications debugging
From: Daniel Jacobowitz <dan@debian.org>
Date: Thu, 30 Mar 2006 13:57:04 -0500
Cc: colin <colin@realtek.com.tw>, linux-mips@linux-mips.org
In-reply-to: <442BB7B2.1010204@mips.com>
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References: <024c01c65337$63931c90$106215ac@realtek.com.tw> <442A94D0.1020106@mips.com> <002d01c6539f$d040a200$106215ac@realtek.com.tw> <442BB7B2.1010204@mips.com>
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On Thu, Mar 30, 2006 at 11:49:22AM +0100, Nigel Stephens wrote:
> They're variable, but not very variable: the PID->ASID mapping will only
> change when the ASIDs roll over and the ASID gets reallocated to a
> different process, which will only happen after another 256 processes
> have been created. But in that case your watched process will have to be
> allocated a new ASID before it can run again. So you could, perhaps,
> modify the TLB management code to clear the Watch registers whenever an
> ASID belong to a process with watchpoints is recycled, and then
> reprogram the Watch registers when such a process is allocated a new
> ASID. Alternatively you could maintain pre-process copies of the Watch
> registers, and context switch them along with other per-process register
> state -- though that is adding context switch overhead to processes
> which don't use watchpoints, and might not be popular with the maintainer.

If you want GDB to use them, you almost certainly want them to be
per-process.  You can context switch them lazily, though.  We've solved
this problem before plenty of times...

-- 
Daniel Jacobowitz
CodeSourcery

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