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Date: Fri, 27 Feb 2009 17:51:20 -0800
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: the arch/x86 maintainers <x86@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: [PATCH] x86-32: use brk segment for allocating initial kernel pagetable
From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.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.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
arch/x86/include/asm/pgtable_32.h | 3 ---
arch/x86/include/asm/setup.h | 3 ---
arch/x86/kernel/head32.c | 5 -----
arch/x86/kernel/head_32.S | 14 +++++++-------
arch/x86/kernel/setup.c | 12 ++++--------
arch/x86/kernel/vmlinux_32.lds.S | 3 +--
arch/x86/kernel/vmlinux_64.lds.S | 2 ++
arch/x86/lguest/boot.c | 8 --------
arch/x86/xen/mmu.c | 8 +++++---
9 files changed, 19 insertions(+), 39 deletions(-)
diff --git a/arch/x86/include/asm/pgtable_32.h b/arch/x86/include/asm/pgtable_32.h
index 97612fc..31bd120 100644
--- a/arch/x86/include/asm/pgtable_32.h
+++ b/arch/x86/include/asm/pgtable_32.h
@@ -42,9 +42,6 @@ extern void set_pmd_pfn(unsigned long, unsigned long, pgprot_t);
*/
#undef TEST_ACCESS_OK
-/* The boot page tables (all created as a single array) */
-extern unsigned long pg0[];
-
#ifdef CONFIG_X86_PAE
# include <asm/pgtable-3level.h>
#else
diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index fd9b420..2ca00a9 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -110,9 +110,6 @@ void *extend_brk(size_t size, size_t align);
void __init i386_start_kernel(void);
extern void probe_roms(void);
-extern unsigned long init_pg_tables_start;
-extern unsigned long init_pg_tables_end;
-
#else
void __init x86_64_start_kernel(char *real_mode);
void __init x86_64_start_reservations(char *real_mode_data);
diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
index fa9ae31..b6caa9e 100644
--- a/arch/x86/kernel/head32.c
+++ b/arch/x86/kernel/head32.c
@@ -29,13 +29,8 @@ void __init i386_start_kernel(void)
reserve_early(ramdisk_image, ramdisk_end, "RAMDISK");
}
#endif
- reserve_early(init_pg_tables_start, init_pg_tables_end,
- "INIT_PG_TABLE");
-
reserve_ebda_region();
- init_brk((unsigned long)__va(init_pg_tables_end));
-
/*
* At this point everything still needed from the boot loader
* or BIOS or kernel text should be early reserved or marked not
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 6219259..d243437 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -167,7 +167,7 @@ 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
- * init_pg_tables_end is set up to point to the first "safe" location.
+ * _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.
*
@@ -190,8 +190,7 @@ default_entry:
xorl %ebx,%ebx /* %ebx is kept at zero */
- movl $pa(pg0), %edi
- movl %edi, pa(init_pg_tables_start)
+ movl $pa(__brk_base), %edi
movl $pa(swapper_pg_pmd), %edx
movl $PTE_IDENT_ATTR, %eax
10:
@@ -216,7 +215,8 @@ default_entry:
cmpl %ebp,%eax
jb 10b
1:
- movl %edi,pa(init_pg_tables_end)
+ addl $__PAGE_OFFSET, %edi
+ movl %edi, pa(_brk_end)
shrl $12, %eax
movl %eax, pa(max_pfn_mapped)
@@ -227,8 +227,7 @@ default_entry:
page_pde_offset = (__PAGE_OFFSET >> 20);
- movl $pa(pg0), %edi
- movl %edi, pa(init_pg_tables_start)
+ movl $pa(__brk_base), %edi
movl $pa(swapper_pg_dir), %edx
movl $PTE_IDENT_ATTR, %eax
10:
@@ -249,7 +248,8 @@ page_pde_offset = (__PAGE_OFFSET >> 20);
leal (INIT_MAP_BEYOND_END+PTE_IDENT_ATTR)(%edi),%ebp
cmpl %ebp,%eax
jb 10b
- movl %edi,pa(init_pg_tables_end)
+ addl $__PAGE_OFFSET, %edi
+ movl %edi, pa(_brk_end)
shrl $12, %eax
movl %eax, pa(max_pfn_mapped)
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;
#ifdef CONFIG_X86_64
int default_cpu_present_to_apicid(int mps_cpu)
@@ -160,12 +162,6 @@ static struct resource bss_resource = {
#ifdef CONFIG_X86_32
-/* This value is set up by the early boot code to point to the value
- immediately after the boot time page tables. It contains a *physical*
- address, and must not be in the .bss segment! */
-unsigned long init_pg_tables_start __initdata = ~0UL;
-unsigned long init_pg_tables_end __initdata = ~0UL;
-
static struct resource video_ram_resource = {
.name = "Video RAM area",
.start = 0xa0000,
diff --git a/arch/x86/kernel/vmlinux_32.lds.S b/arch/x86/kernel/vmlinux_32.lds.S
index 0d86096..2f772dc 100644
--- a/arch/x86/kernel/vmlinux_32.lds.S
+++ b/arch/x86/kernel/vmlinux_32.lds.S
@@ -190,9 +190,8 @@ SECTIONS
. = ALIGN(4);
__bss_stop = .;
_end = . ;
- /* This is where the kernel creates the early boot page tables */
. = ALIGN(PAGE_SIZE);
- pg0 = . ;
+ __brk_base = . ;
}
/* Sections to be discarded */
diff --git a/arch/x86/kernel/vmlinux_64.lds.S b/arch/x86/kernel/vmlinux_64.lds.S
index fbfced6..4878198 100644
--- a/arch/x86/kernel/vmlinux_64.lds.S
+++ b/arch/x86/kernel/vmlinux_64.lds.S
@@ -245,6 +245,8 @@ SECTIONS
__bss_stop = .;
_end = . ;
+ . = ALIGN(PAGE_SIZE);
+ __brk_base = . ;
/* Sections to be discarded */
/DISCARD/ : {
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index f3a5305..ba2c2da 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1051,14 +1051,6 @@ __init void lguest_init(void)
* lguest_init() where the rest of the fairly chaotic boot setup
* occurs. */
- /* The native boot code sets up initial page tables immediately after
- * the kernel itself, and sets init_pg_tables_end so they're not
- * clobbered. The Launcher places our initial pagetables somewhere at
- * the top of our physical memory, so we don't need extra space: set
- * init_pg_tables_end to the end of the kernel. */
- init_pg_tables_start = __pa(pg0);
- init_pg_tables_end = __pa(pg0);
-
/* As described in head_32.S, we map the first 128M of memory. */
max_pfn_mapped = (128*1024*1024) >> PAGE_SHIFT;
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 319bd40..cf16959 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1716,9 +1716,11 @@ __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
{
pmd_t *kernel_pmd;
- init_pg_tables_start = __pa(pgd);
- init_pg_tables_end = __pa(pgd) + xen_start_info->nr_pt_frames*PAGE_SIZE;
- max_pfn_mapped = PFN_DOWN(init_pg_tables_end + 512*1024);
+ /*
+ * We already set _brk_start to point to the end of the
+ * Xen-provided pagetables.
+ */
+ max_pfn_mapped = PFN_DOWN(_brk_start + 512*1024);
kernel_pmd = m2v(pgd[KERNEL_PGD_BOUNDARY].pgd);
memcpy(level2_kernel_pgt, kernel_pmd, sizeof(pmd_t) * PTRS_PER_PMD);
--
1.6.0.6
--
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