Re: [Qemu-stable] [Qemu-devel] [PATCH] multiboot: mh_load_end_addr and mh_bss_end_addr may be zero

[Göran Weinholt]

Kevin Wolf <address@hidden> writes:

> Am 23.01.2012 13:49, schrieb Göran Weinholt:
>> There are two special cases in the address fields of the multiboot
>> format. If mh_load_end_addr is zero then the whole image file should
>> be loaded and if mh_bss_end_addr is zero then there is no bss segment.
>> With this change it is again possible to boot kernels where these
>> fields are zero.
>> 
>> Signed-off-by: Göran Weinholt <address@hidden>
>> Tested-by: Alexander Graf <address@hidden>
>> ---
>>  hw/multiboot.c |   15 ++++++++++++++-
>>  1 files changed, 14 insertions(+), 1 deletions(-)
>> 
>> diff --git a/hw/multiboot.c b/hw/multiboot.c
>> index b4484a3..db28328 100644
>> --- a/hw/multiboot.c
>> +++ b/hw/multiboot.c
>> @@ -202,10 +202,23 @@ int load_multiboot(void *fw_cfg,
>>          uint32_t mh_bss_end_addr = ldl_p(header+i+24);
>>          mh_load_addr = ldl_p(header+i+16);
>>          uint32_t mb_kernel_text_offset = i - (mh_header_addr - 
>> mh_load_addr);
>> -        uint32_t mb_load_size = mh_load_end_addr - mh_load_addr;
>> +        uint32_t mb_load_size;
>> +
>> +        /* A load end address of zero indicates that the whole file
>> +         * should be loaded. */
>> +        if (!mh_load_end_addr) {
>> +            mh_load_end_addr = kernel_file_size + mh_load_addr;
>
> This is only right if the OS image starts at offset 0 in the image file.
> IIUC, in the general case it starts at byte i - (mh_header_addr -
> mh_load_addr), so you need to subtract this from kernel_file_size.

I think you're right. It would be good if someone could have a look at
fixing the patch. I will not have time to do it myself. Please Cc me so
that I can test it on my own kernel images.

Regards,

-- 
Göran Weinholt <address@hidden>
"The bus! I have missed the bus! I have become... tardy!" -- Dexter's Lab