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x86-32: use brk segment for allocating initial kernel pagetable

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Impact: use new interface instead of previous ad hoc implementation

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@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Jeremy Fitzhardinge 2009-02-27 13:27:38 -08:00 committed by H. Peter Anvin
parent 5368a2be34
commit ccf3fe02e3
7 changed files with 7 additions and 34 deletions
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3
arch/x86/include/asm/pgtable_32.h
View File

@ -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

3
arch/x86/include/asm/setup.h
View File

@ -109,9 +109,6 @@ 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);

3
arch/x86/kernel/head32.c
View File

@ -29,9 +29,6 @@ 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();
/*

14
arch/x86/kernel/head_32.S
View File

@ -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)

6
arch/x86/kernel/setup.c
View File

@ -161,12 +161,6 @@ 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,

4
arch/x86/kernel/vmlinux_32.lds.S
View File

@ -196,10 +196,6 @@ SECTIONS
__brk_limit = . ;
_end = . ;
/* This is where the kernel creates the early boot page tables */
. = ALIGN(PAGE_SIZE);
pg0 = . ;
}
/* Sections to be discarded */

8
arch/x86/lguest/boot.c
View File

@ -1058,14 +1058,6 @@ __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;