Hi Horseriver,
On Sun, Feb 24, 2013 at 7:26 AM, horseriver <horserivers@xxxxxxxxx> wrote:
> On Sun, Feb 24, 2013 at 04:00:37PM +0700, Mulyadi Santosa wrote:
>> On Sat, Feb 23, 2013 at 6:45 AM, horseriver <horserivers@xxxxxxxxx> wrote:
>> > hi:
>> >
>> > I have built vmlinux at the top dir of kernel source ,then I use objdump to look into
>> > its section information.I find the statup_32 which is the start routine of kernel ,
>> > locats at 0xc0100000. I know the 0x100000 is the defined address for locating
>> > protect-mode code .But which I can not understand is the 0xc prefix .where does it come from?
>>
>> If my guess is right, that's because kernel mode code start at
>> 0xc000000 a.k.a a bit above 3 GiB on x86 32 bit machine
>
> I have find this answer .
> It is defined in lds script file .
>
> here is the code :
> SECTIONS
> {
> . = 0xC0000000 + 0x100000;
> /* read-only */
> _text = .; /* Text and read-only data */
>
>
> why use 0xC0000000 as its start ? why not just use 0x100000 only ?
> if use 0xC0000000,every linked symbole will be prefixed by 0xc , what is the purpose ?
Usually, user kernel space split is 3G:1G.
ie 1G for kernel space. And this starts from 0xC000_0000 till 0xFFFF_FFFF
All the address below 0xC000_0000(ie 3G from 0x0 to 0xBFFF_FFFF) is
used for user space.
Thanks,
Arun
>
> thanks!
>
>
>
> --
>> regards,
>>
>> Mulyadi Santosa
>> Freelance Linux trainer and consultant
>>
>> blog: the-hydra.blogspot.com
>> training: mulyaditraining.blogspot.com
>
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