Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=9ce8c2ed12550f90fd6e902990652b13df647793
Commit: 9ce8c2ed12550f90fd6e902990652b13df647793
Parent: c5413fbe894924ddb8aa474a4d4da52e7a6c7e0b
Author: Jeremy Fitzhardinge <[EMAIL PROTECTED]>
AuthorDate: Wed May 2 19:27:16 2007 +0200
Committer: Andi Kleen <[EMAIL PROTECTED]>
CommitDate: Wed May 2 19:27:16 2007 +0200
[PATCH] i386: map enough initial memory to create lowmem mappings
head.S creates the very initial pagetable for the kernel. This just
maps enough space for the kernel itself, and an allocation bitmap.
The amount of mapped memory is rounded up to 4Mbytes, and so this
typically ends up mapping 8Mbytes of memory.
When booting, pagetable_init() needs to create mappings for all
lowmem, and the pagetables for these mappings are allocated from the
free pages around the kernel in low memory. If the number of
pagetable pages + kernel size exceeds head.S's initial mapping, it
will end up faulting on an unmapped page. This will only happen with
specific combinations of kernel size and memory size.
This patch makes sure that head.S also maps enough space to fit the
kernel pagetables as well as the kernel itself. It ends up using an
additional two pages of unreclaimable memory.
Signed-off-by: Jeremy Fitzhardinge <[EMAIL PROTECTED]>
Signed-off-by: Andi Kleen <[EMAIL PROTECTED]>
Acked-by: "H. Peter Anvin" <[EMAIL PROTECTED]>
Cc: Andi Kleen <[EMAIL PROTECTED]>
Cc: Zachary Amsden <[EMAIL PROTECTED]>
Cc: Chris Wright <[EMAIL PROTECTED]>
Cc: "Eric W. Biederman" <[EMAIL PROTECTED]>
Cc: Linus Torvalds <[EMAIL PROTECTED]>,
---
arch/i386/kernel/asm-offsets.c | 6 ++++++
arch/i386/kernel/head.S | 23 +++++++++++++++++++----
2 files changed, 25 insertions(+), 4 deletions(-)
diff --git a/arch/i386/kernel/asm-offsets.c b/arch/i386/kernel/asm-offsets.c
index b05e85f..27a776c 100644
--- a/arch/i386/kernel/asm-offsets.c
+++ b/arch/i386/kernel/asm-offsets.c
@@ -11,6 +11,7 @@
#include <linux/suspend.h>
#include <asm/ucontext.h>
#include "sigframe.h"
+#include <asm/pgtable.h>
#include <asm/fixmap.h>
#include <asm/processor.h>
#include <asm/thread_info.h>
@@ -96,6 +97,11 @@ void foo(void)
sizeof(struct tss_struct));
DEFINE(PAGE_SIZE_asm, PAGE_SIZE);
+ DEFINE(PAGE_SHIFT_asm, PAGE_SHIFT);
+ DEFINE(PTRS_PER_PTE, PTRS_PER_PTE);
+ DEFINE(PTRS_PER_PMD, PTRS_PER_PMD);
+ DEFINE(PTRS_PER_PGD, PTRS_PER_PGD);
+
DEFINE(VDSO_PRELINK_asm, VDSO_PRELINK);
OFFSET(crypto_tfm_ctx_offset, crypto_tfm, __crt_ctx);
diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
index 12277d8..9b10af6 100644
--- a/arch/i386/kernel/head.S
+++ b/arch/i386/kernel/head.S
@@ -34,17 +34,32 @@
/*
* 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.)
+ * 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
*
* Modulo rounding, each megabyte assigned here requires a kilobyte of
* memory, which is currently unreclaimed.
*
* This should be a multiple of a page.
*/
-#define INIT_MAP_BEYOND_END (128*1024)
+LOW_PAGES = 1<<(32-PAGE_SHIFT_asm)
+#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
/*
* 32-bit kernel entrypoint; only used by the boot CPU. On entry,
-
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