The patch titled
i386: for debugging, make the initial page table setup less forgiving.
has been added to the -mm tree. Its filename is
mm-only-i386-for-debugging-make-the-initial-page-table-setup-less-forgiving.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: i386: for debugging, make the initial page table setup less forgiving.
From: "H. Peter Anvin" <hpa@xxxxxxxxx>
We just discovered that the accounting for initial memory usage (head.S:
INIT_MAP_BEYOND_END) has been way, way off for a very long time. This
patch makes the initial page table not round up to the nearest 4M boundary,
but instead stop dead (and zero the rest of the final page table) as soon
as it hits the configured limit.
This patch is intended as a debugging aid. If it goes into the kernel, it
should go in at the very beginning of a review cycle, as it may very well
expose real failures (without Jeremy's patch to fix the accounting, it
*will* crash.)
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/i386/kernel/head.S | 22 +++++++++++++++++-----
1 files changed, 17 insertions(+), 5 deletions(-)
diff -puN arch/i386/kernel/head.S~mm-only-i386-for-debugging-make-the-initial-page-table-setup-less-forgiving arch/i386/kernel/head.S
--- a/arch/i386/kernel/head.S~mm-only-i386-for-debugging-make-the-initial-page-table-setup-less-forgiving
+++ a/arch/i386/kernel/head.S
@@ -146,15 +146,27 @@ page_pde_offset = (__PAGE_OFFSET >> 20);
movl %ecx,page_pde_offset(%edx) /* Store kernel PDE entry */
addl $4,%edx
movl $1024, %ecx
+ /*
+ * End condition: we must map up to and including
+ * INIT_MAP_BEYOND_END bytes beyond the end of our
+ * own page tables; 0x1000 is the size of the page
+ * table were about to write, and +0x007 is the
+ * attribute bits.
+ */
+ leal (INIT_MAP_BEYOND_END+0x1000+0x007)(%edi),%ebp
11:
stosl
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 */
- leal (INIT_MAP_BEYOND_END+0x007)(%edi),%ebp
cmpl %ebp,%eax
- jb 10b
+ jae 12f
+ loop 11b
+ jmp 10b
+12:
+ /* Clear the remainder of the last page table */
+ decl %ecx
+ xorl %eax,%eax
+ rep; stosl
+
movl %edi,(init_pg_tables_end - __PAGE_OFFSET)
xorl %ebx,%ebx /* This is the boot CPU (BSP) */
_
Patches currently in -mm which might be from hpa@xxxxxxxxx are
git-kbuild.patch
i386-map-enough-initial-memory-to-create-lowmem-mappings.patch
mm-only-i386-for-debugging-make-the-initial-page-table-setup-less-forgiving.patch
devpts-add-fsnotify-create-event.patch
vt-expose-system-wide-utf-8-default-setting-via-sysfs.patch
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