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Message-ID: <4D4760E1.9000400@caviumnetworks.com>
Date:   Mon, 31 Jan 2011 17:24:49 -0800
From:   David Daney <ddaney@caviumnetworks.com>
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To:     Earl Chew <echew@ixiacom.com>
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Subject: Re: Filling in struct mips64_watch_regs from a 32 bit process
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On 01/31/2011 05:12 PM, Earl Chew wrote:
>>> I notice that a 32 bit process running on a 64 bit kernel is expected to
>>> know that it should fill in mips64_watch_regs --- even though it is running
>>> against a 32 bit ABI.
>>>
>>> Is this an oversight, or am I missing something ?
>>
>> It is intentional.
>
> Oh I see ... I have to call PTRACE_SET_WATCH_REGS first in order to figure
> out whether the kernel is expecting me to use pt_watch_style_mips32 or
> pt_watch_style_mips64.
>

That would be PTRACE_GET_WATCH_REGS.  It will tell you the width of the 
registers as well as how many are available (in the num_valid field) and 
the properties of each (in the watch_masks[] fields).

Fill in watchlo[] and watchhi[], write them back with 
PTRACE_SET_WATCH_REGS, then sit back and wait for SIGTRAP.

David Daney