Re: [Qemu-devel] [PATCH] Always load PowerPC kernel to KERNEL_LOAD_ADDR

[Aurelien Jarno <aurelien@aurel32.net>]

On Sun, Jan 25, 2009 at 03:22:25PM +0100, Alexander Graf wrote:
>
> On 25.01.2009, at 15:19, Edgar E. Iglesias wrote:
>
>> On Sun, Jan 25, 2009 at 12:54:27PM +0100, Alexander Graf wrote:
>>> Linux changed its physical address location in the elf header from
>>> 0xc0000000 to 0 on 2.6.25, causing later kernels to fail booting
>>> with the -kernel option.
>>>
>>> This patch assures that the lowest segment in the elf binary is  
>>> loaded
>>> to KERNEL_LOAD_ADDR, which is where the firmware expects it.
>>>
>>> With this patch applied, I was able to successfully boot a 2.6.18 and
>>> a 2.6.27 Linux kernel using the -kernel option.
>>>
>>> Signed-off-by: Alexander Graf <agraf@suse.de>
>>> ---
>>> hw/ppc_oldworld.c |    4 +++-
>>> 1 files changed, 3 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/hw/ppc_oldworld.c b/hw/ppc_oldworld.c
>>> index 042a40f..f64884b 100644
>>> --- a/hw/ppc_oldworld.c
>>> +++ b/hw/ppc_oldworld.c
>>> @@ -207,9 +207,11 @@ static void ppc_heathrow_init (ram_addr_t  
>>> ram_size, int vga_ram_size,
>>>     }
>>>
>>>     if (linux_boot) {
>>> +        uint64_t lowaddr = 0;
>>>         kernel_base = KERNEL_LOAD_ADDR;
>>>         /* now we can load the kernel */
>>> -        kernel_size = load_elf(kernel_filename, kernel_base -  
>>> 0xc0000000ULL,
>>> +        load_elf(kernel_filename, 0, NULL, &lowaddr, NULL);
>>> +        kernel_size = load_elf(kernel_filename, kernel_base -  
>>> lowaddr,
>>>                                NULL, NULL, NULL);
>>
>> Hello,
>>
>> Can't you speculatively load at kernel_base assuming it's a new  
>> kernel,
>> then only if lowaddr indicates it was an old kernel you do the second
>> load to fix things up?
>
> Hm - so we only call load_elf once for new kernels? Sounds like a good  
> idea :-).
>
>> Maybe also a comment or two in the code explaining the hack.. :)
>
> Right, that might be nice.
>

I have just committed a fix based on your patch and implementing that. I
also added a comment explaining the hack.

Aurelien

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