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authorYinghai Lu <yinghai@kernel.org>2009-03-09 01:15:57 -0700
committerH. Peter Anvin <hpa@zytor.com>2009-03-14 17:23:47 -0700
commit2bd2753ff46346543ab92e80df9d96366e21baa5 (patch)
tree4a83c0b4012abe33a95715d9890bf07f81a3d547 /arch/x86/kernel/head_32.S
parent796216a57fe45c04adc35bda1f0782efec78a713 (diff)
x86: put initial_pg_tables into .bss
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>
Diffstat (limited to 'arch/x86/kernel/head_32.S')
-rw-r--r--arch/x86/kernel/head_32.S43
1 files changed, 14 insertions, 29 deletions
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 9e89f2a14b9..c79741cfb07 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -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.
*/