From: Franz Sirl <Franz.Sirl-kernel@lauterbach.com>
To: Jim Chapman <jim.chapman@iname.com>
Cc: linuxppc-dev@lists.linuxppc.org
Subject: Re: Q: Register usage in mpc860 ports
Date: Fri, 21 May 1999 18:36:16 +0200 [thread overview]
Message-ID: <4.2.0.37.19990521183415.04a02b30@mail.lauterbach.com> (raw)
In-Reply-To: <37457D27.DA34E026@iname.com>
At 17:35 21.05.99 , Jim Chapman wrote:
>I am porting LinuxPPC to a custom embedded mpc860 board. I am starting
>with the mbx port and using home-built egcs-1.1.2 tools on a Linux
>host, using the instructions in
>http://members.home.com/mmporter/cross.html
>
>There seem to be register usage conflicts in the MMU TLB handlers. The
>code tries to use location 0 (according to the comment) to store a
>couple of register values, e.g. in arch/ppc/kernel/head.S
>
>InstructionTLBMiss:
> mtspr M_TW, r20 /* Save a couple of working registers */
> mfcr r20
> stw r20, 0(r0)
> stw r21, 4(r0)
>
>However, I am finding that r0 isn't zero when the MMU exceptions are
>taken. Instead, it points to somewhere in the text or data segment. I
>hacked the code to save r20 & r21 to a specific memory location and that
>fixed that particular problem.
r0 represents 0 in a number of PPC instructions, lookup stw in your PPC
assembler book.
Franz.
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prev parent reply other threads:[~1999-05-21 16:36 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-05-21 15:35 Q: Register usage in mpc860 ports Jim Chapman
1999-05-21 16:36 ` Franz Sirl [this message]
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