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Re: execution failing

To: <linux-mips@fnet.fr>
Subject: Re: execution failing
From: Elias Kesh <elias@scruznet.com>
Date: Thu, 15 May 97 01:20:40 +0100
 
Here is some more information. If we try and execute pad zero the machine 
locks up and we are not sure where yet. If we comment that out we then 
get a page fault when it tries to execute the code at 0x400000. The 5230 
has 96 tlbs set up as two pairs of 48 (odd/even). Currently I have the 
tags set up for 32 tbl entries since we were using a 4300 before this. I 
have not verified that the tbls are in fact working but I imaging that 
that are in order to get this far. We turned on the code to dump the tlbs 
in the exception routine but we must not be getting there since they 
never get displayed. I'm not expert on virtual menory management so I am 
now reading up on how it is implemented on linux. We did try and write a 
very small binary which turns on the LEDs on the board and it behave 
exactly the same way as trying to execute sh. Any comments would be 
greatly appreciated.

Thank,

Elias



Hi Elias,

> Question. I am trying to load and elf file (sh, the first file the kernel 
> tries to execute) and it's failing. It seems as if it's trying to load it 
> at 0x400000 which is a physical address. The function do_load_elf_binary 
> in fs/binfmt_elf.c returns no error, but when it tries to pad zeros or 
> execute it starting at 0x400000 logical it dies. Is there some mapping 
> that has to go on that I have failed to set up ? I am using version 
> 2.0.21 of the kernel on the Algorithmics P4032 board with a 5230 
> processor from QED.

That function tries to access the userspace using clear_user().  Doing
so it will also load TLB entries into the TLB.  It might be that the
pipeline of the 5230 is a bit different such that this fails.

What exactly does happen?  If you can catch the error - what's the TLB's
contents after your problem happend?

For testing purposes it is probably helpfull if you use a very small
program like the assembler written hello world program available on
FNet.

   Ralf




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