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Re: Apparent kernel bug with GDB on ppc405
- From: Benjamin Herrenschmidt <benh at kernel dot crashing dot org>
- To: David Daney <ddaney at avtrex dot com>
- Cc: Matt Mackall <mpm at selenic dot com>, gdb at sourceware dot org, linuxppc-embedded at ozlabs dot org
- Date: Fri, 26 Oct 2007 11:52:10 +1000
- Subject: Re: Apparent kernel bug with GDB on ppc405
- References: <20071024194640.GB19691@waste.org> <471FAC48.1070008@avtrex.com>
- Reply-to: benh at kernel dot crashing dot org
On Wed, 2007-10-24 at 13:34 -0700, David Daney wrote:
> First of all I have never used a similar configuration so this may be
> totally off base. But...
>
> If the icache is virtually indexed, then I think there are only two
> ways
> to invalidate it. The first is from the context of the debugged
> process
> where the page is mapped at the location the target program will see
> it.
> If you try to invalidate from the context of the debugger, the
> page
> will most likely not be mapped at the virtual address of the target
> program so you might have to invalidate the *entire* icache.
Yup, sounds likely. We don't handle that virtual icache well at all in
linux. Things tend to work by mere luck. I have various ideas to fix
that but haven't actually implemented them.
Ben.