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x86: put initial_pg_tables into .bss

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Impact: makes vmlinux section information more useful

Don't use ram after _end blindly for pagetables. aka init pages is before _end
put those pg table into .bss

[Adapted to use brk segment - Jeremy]

v2: keep initial page table up to 512M only.
v4: put initial page tables just before _end

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Yinghai Lu 2009-03-09 01:15:57 -07:00 committed by H. Peter Anvin
parent 796216a57f
commit 2bd2753ff4
2 changed files with 20 additions and 29 deletions
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43
arch/x86/kernel/head_32.S
View File

@ -41,41 +41,28 @@
* This is how much memory *in addition to the memory covered up to
* and including _end* we need mapped initially.
* We need:
* - one bit for each possible page, but only in low memory, which means
* 2^32/4096/8 = 128K worst case (4G/4G split.)
* - enough space to map all low memory, which means
* (2^32/4096) / 1024 pages (worst case, non PAE)
* (2^32/4096) / 512 + 4 pages (worst case for PAE)
* - a few pages for allocator use before the kernel pagetable has
* been set up
* (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE)
* (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE)
*
* Modulo rounding, each megabyte assigned here requires a kilobyte of
* memory, which is currently unreclaimed.
*
* This should be a multiple of a page.
*
* KERNEL_IMAGE_SIZE should be greater than pa(_end)
* and small than max_low_pfn, otherwise will waste some page table entries
*/
LOW_PAGES = (KERNEL_IMAGE_SIZE + PAGE_SIZE_asm - 1)>>PAGE_SHIFT
/*
* To preserve the DMA pool in PAGEALLOC kernels, we'll allocate
* pagetables from above the 16MB DMA limit, so we'll have to set
* up pagetables 16MB more (worst-case):
*/
#ifdef CONFIG_DEBUG_PAGEALLOC
LOW_PAGES = LOW_PAGES + 0x1000000
#endif
#if PTRS_PER_PMD > 1
PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PMD) + PTRS_PER_PGD
#else
PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PGD)
#endif
BOOTBITMAP_SIZE = LOW_PAGES / 8
ALLOCATOR_SLOP = 4
INIT_MAP_BEYOND_END = BOOTBITMAP_SIZE + (PAGE_TABLE_SIZE + ALLOCATOR_SLOP)*PAGE_SIZE_asm
RESERVE_BRK(pagetables, PAGE_TABLE_SIZE * PAGE_SIZE)
INIT_MAP_SIZE = (PAGE_TABLE_SIZE + ALLOCATOR_SLOP) * PAGE_SIZE_asm
RESERVE_BRK(pagetables, INIT_MAP_SIZE)
/*
* 32-bit kernel entrypoint; only used by the boot CPU. On entry,
@ -168,10 +155,10 @@ num_subarch_entries = (. - subarch_entries) / 4
/*
* Initialize page tables. This creates a PDE and a set of page
* tables, which are located immediately beyond _end. The variable
* tables, which are located immediately beyond __brk_base. The variable
* _brk_end is set up to point to the first "safe" location.
* Mappings are created both at virtual address 0 (identity mapping)
* and PAGE_OFFSET for up to _end+sizeof(page tables)+INIT_MAP_BEYOND_END.
* and PAGE_OFFSET for up to _end.
*
* Note that the stack is not yet set up!
*/
@ -210,10 +197,9 @@ default_entry:
loop 11b
/*
* End condition: we must map up to and including INIT_MAP_BEYOND_END
* bytes beyond the end of our own page tables.
* End condition: we must map up to the end.
*/
leal (INIT_MAP_BEYOND_END+PTE_IDENT_ATTR)(%edi),%ebp
movl $pa(_end) + PTE_IDENT_ATTR, %ebp
cmpl %ebp,%eax
jb 10b
1:
@ -243,11 +229,9 @@ page_pde_offset = (__PAGE_OFFSET >> 20);
addl $0x1000,%eax
loop 11b
/*
* End condition: we must map up to and including INIT_MAP_BEYOND_END
* bytes beyond the end of our own page tables; the +0x007 is
* the attribute bits
* End condition: we must map up to end
*/
leal (INIT_MAP_BEYOND_END+PTE_IDENT_ATTR)(%edi),%ebp
movl $pa(_end) + PTE_IDENT_ATTR, %ebp
cmpl %ebp,%eax
jb 10b
addl $__PAGE_OFFSET, %edi
@ -638,6 +622,7 @@ swapper_pg_fixmap:
.fill 1024,4,0
ENTRY(empty_zero_page)
.fill 4096,1,0
/*
* This starts the data section.
*/

6
arch/x86/kernel/vmlinux_32.lds.S
View File

@ -210,6 +210,12 @@ SECTIONS
DWARF_DEBUG
}
/*
* Build-time check on the image size:
*/
ASSERT((_end - LOAD_OFFSET <= KERNEL_IMAGE_SIZE),
"kernel image bigger than KERNEL_IMAGE_SIZE")
#ifdef CONFIG_KEXEC
/* Link time checks */
#include <asm/kexec.h>