Re: [Qemu-devel] [PATCH] Fix -kernel on target-ppc

[Aurelien Jarno <aurelien@aurel32.net>]

On Sat, Jan 24, 2009 at 10:57:19PM +0100, Alexander Graf wrote:
>
> On 24.01.2009, at 22:48, Aurelien Jarno wrote:
>
>> On Sat, Jan 24, 2009 at 09:58:35PM +0100, Alexander Graf wrote:
>>> OpenBIOS searches for the preloaded kernel at 0x1000000, so let's
>>> put it there instead of an invalid location.
>>
>> Your patch is actually wrong, the second argument of load_elf() is an
>> offset to the physical address (as found in the elf header), and not a
>> load address.
>>
>> By chance the physical address of a >= 2.6.25 kernel is 0x00000000, so
>> your patch works. But it will break supports for < 2.6.25 kernel as
>> their physical address is 0xc0000000. Not that they are only the  
>> default
>> values, they can be changed in the .config file.
>
> Aah, that explains why :-).
>
>> I have already proposed a patch to use the virtual address of the elf
>> header as done by yaboot or quik, but I have been told it is actually
>> wrong.
>>
>> We have to find another way to load the elf file at a fixed address.
>
> Hm - can't we just give load_elf an override value for the base address?
>
>             /* address_offset is hack for kernel images that are
>                linked at the wrong physical address.  */
>             addr = ph->p_paddr + address_offset;
>
>             cpu_physical_memory_write_rom(addr, data, mem_size);
>
> Just pass another variable here that overrides addr and doesn't  
> calculate it?

Except that they can be more than one segment to load, so the last one
will overwrite the previous ones. The PowerPC kernels I have seen only
have one load segment, but I am not sure it is always the case.

-- 
Aurelien Jarno	                        GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net