J

[Jeremy Fitzhardinge <jeremy@goop.org>]

Yinghai Lu wrote:
> On Fri, Feb 27, 2009 at 5:51 PM, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>   
>> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
>>
>> Rather than having special purpose init_pg_table_start/end variables
>> to delimit the kernel pagetable built by head_32.S, just use the brk
>> mechanism to extend the bss for the new pagetable.
>>
>> This patch removes init_pg_table_start/end and pg0, defines __brk_base
>> (which is page-aligned and immediately follows _end), initializes
>> the brk region to start there, and uses it for the 32-bit pagetable.
>>     
> ...
>
>   
>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>> index c246dc4..ed02176 100644
>> --- a/arch/x86/kernel/setup.c
>> +++ b/arch/x86/kernel/setup.c
>> @@ -113,8 +113,10 @@
>>  #endif
>>
>>  unsigned int boot_cpu_id __read_mostly;
>> -__initdata unsigned long _brk_start = (unsigned long)&_end;
>> -__initdata unsigned long _brk_end = (unsigned long)&_end;
>> +
>> +extern char __brk_base[];
>> +__initdata unsigned long _brk_start = (unsigned long)__brk_base;
>> +__initdata unsigned long _brk_end = (unsigned long)&__brk_base;
>>     
>
> ?
>   

What are you asking?  __brk_base is _end rounded up to a page boundary, 
so head_32.S can use it directly for pagetable allocation.  Are you 
flagging the '&' typo?  Something else?

    J