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Re: [Qemu-devel] Porting QEMU to Minix - op_goto_tb1 segfaults because t


From: Ulrich Hecht
Subject: Re: [Qemu-devel] Porting QEMU to Minix - op_goto_tb1 segfaults because tb_next[1] is NULL
Date: Thu, 23 Aug 2007 11:37:27 +0200
User-agent: KMail/1.9.6 (enterprise 20070731.694771)

On Wednesday 22 August 2007, Erik van der Kouwe wrote:
> My problem is the following: quickly after starting I get a
> segmentation fault while the generated code is running.
>
> This happens in the code generated from op_goto_tb1 and is caused by
> jumping to a NULL pointer. This NULL pointer originates from the
> tb_next[1] field of the translation block data structure passed as a
> parameter. I have verified in the disassembler that the parameter in
> the generated code is processed correctly and the field is indeed
> tb_next[1].

I had a similar problem when fixing S/390 hosts. IIRC it was caused by 
the "portable" GOTO_TB macro. On translation the goto is patched to jump 
out of the block, which is something the compiler does not reckon with. 
You may want to disassemble it and check if registers are overwritten 
before the jump takes place.

CU
Uli

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