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    SubjectJ
    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


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