[OpenBIOS] [PATCH] sparc64: fix registers dealing with client

[Igor Kovalenko]

On Fri, Jul 10, 2009 at 11:20 PM, Blue Swirl<blauwirbel at gmail.com> wrote:
> On 7/6/09, Igor Kovalenko <igor.v.kovalenko at gmail.com> wrote:
>> Hi!
>>
>>  This patch improves previous proposal and adds:
>>
>>  - save/restore global registers across client interface calls.
>>  Since OS kernel generally has it's own idea of what
>>  the ABI is we have to follow this requirement.
>>
>>  - adjust stack to allow using unoptimized openbios
>>  build with linux kernel. Linux provides only 128 bytes
>>  on stack which is not enough to save arguments by
>>  code generated with gcc -O0
>>
>>  - fix switch_to so it actually could be used to switch
>>  to client image. context pointer must be volatile to
>>  prevent gcc optimizing out stores to it.
>>
>>  Signed-off-by: igor.v.kovalenko at gmail.com
>
> Thanks, but with the patch applied, SILO in most of my test images no
> longer boots. For example, HelenOS 0.2.0.5:
> OpenBIOS for Sparc64
> Configuration device id QEMU version 1 machine id 0
> CPUs: 1 x SUNW,UltraSPARC-II
> UUID: 00000000-0000-0000-0000-000000000000
> Welcome to OpenBIOS v1.0 built on Jul 10 2009 19:12
>  Type 'help' for detailed information
>
> [sparc64] Booting file 'cdrom' with parameters ''
> Not a bootable ELF image
> Not a Linux kernel image
> Loading a.out image...
> Loaded 7680 bytes
> entry point is 0x4000
> Jumping to entry point...
> switching to new context: entry point 0x4000 stack 0x00000000ffe51999
> SIUnhandled Exception 0x0000000000000068
> PC = 0x00000000ffd0ff14 NPC = 0x00000000ffd0ff18
> Stopping execution
>

I found two issues:

- block reading routines are using significant amount of stack data so
4k is not enough (8k seems OK)
- must flush windows on caller's stack before switching stack pointer,
this causes hard-to-find memory corruption

Here is updated version, now silo seems to be working here.

-- 
Kind regards,
Igor V. Kovalenko
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