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linux/arch/x86/kernel/head32.c
Yinghai Lu c967da6a0b x86: Make sure free_init_pages() frees pages on page boundary
When CONFIG_NO_BOOTMEM=y, it could use memory more effiently, or
in a more compact fashion.

Example:

 Allocated new RAMDISK: 00ec2000 - 0248ce57
 Move RAMDISK from 000000002ea04000 - 000000002ffcee56 to 00ec2000 - 0248ce56

The new RAMDISK's end is not page aligned.
Last page could be shared with other users.

When free_init_pages are called for initrd or .init, the page
could be freed and we could corrupt other data.

code segment in free_init_pages():

 |        for (; addr < end; addr += PAGE_SIZE) {
 |                ClearPageReserved(virt_to_page(addr));
 |                init_page_count(virt_to_page(addr));
 |                memset((void *)(addr & ~(PAGE_SIZE-1)),
 |                        POISON_FREE_INITMEM, PAGE_SIZE);
 |                free_page(addr);
 |                totalram_pages++;
 |        }

last half page could be used as one whole free page.

So page align the boundaries.

-v2: make the original initramdisk to be aligned, according to
     Johannes, otherwise we have the chance to lose one page.
     we still need to keep initrd_end not aligned, otherwise it could
     confuse decompressor.
-v3: change to WARN_ON instead, suggested by Johannes.
-v4: use PAGE_ALIGN, suggested by Johannes.
     We may fix that macro name later to PAGE_ALIGN_UP, and PAGE_ALIGN_DOWN
     Add comments about assuming ramdisk start is aligned
     in relocate_initrd(), change to re get ramdisk_image instead of save it
     to make diff smaller. Add warning for wrong range, suggested by Johannes.
-v6: remove one WARN()
     We need to align beginning in free_init_pages()
     do not copy more than ramdisk_size, noticed by Johannes

Reported-by: Stanislaw Gruszka <sgruszka@redhat.com>
Tested-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Miller <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1269830604-26214-3-git-send-email-yinghai@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-29 18:55:33 +02:00

74 lines
2.0 KiB
C

/*
* linux/arch/i386/kernel/head32.c -- prepare to run common code
*
* Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
* Copyright (C) 2007 Eric Biederman <ebiederm@xmission.com>
*/
#include <linux/init.h>
#include <linux/start_kernel.h>
#include <linux/mm.h>
#include <asm/setup.h>
#include <asm/sections.h>
#include <asm/e820.h>
#include <asm/page.h>
#include <asm/trampoline.h>
#include <asm/apic.h>
#include <asm/io_apic.h>
#include <asm/bios_ebda.h>
static void __init i386_default_early_setup(void)
{
/* Initilize 32bit specific setup functions */
x86_init.resources.probe_roms = probe_roms;
x86_init.resources.reserve_resources = i386_reserve_resources;
x86_init.mpparse.setup_ioapic_ids = setup_ioapic_ids_from_mpc;
reserve_ebda_region();
}
void __init i386_start_kernel(void)
{
#ifdef CONFIG_X86_TRAMPOLINE
/*
* But first pinch a few for the stack/trampoline stuff
* FIXME: Don't need the extra page at 4K, but need to fix
* trampoline before removing it. (see the GDT stuff)
*/
reserve_early_overlap_ok(PAGE_SIZE, PAGE_SIZE + PAGE_SIZE,
"EX TRAMPOLINE");
#endif
reserve_early(__pa_symbol(&_text), __pa_symbol(&__bss_stop), "TEXT DATA BSS");
#ifdef CONFIG_BLK_DEV_INITRD
/* Reserve INITRD */
if (boot_params.hdr.type_of_loader && boot_params.hdr.ramdisk_image) {
/* Assume only end is not page aligned */
u64 ramdisk_image = boot_params.hdr.ramdisk_image;
u64 ramdisk_size = boot_params.hdr.ramdisk_size;
u64 ramdisk_end = PAGE_ALIGN(ramdisk_image + ramdisk_size);
reserve_early(ramdisk_image, ramdisk_end, "RAMDISK");
}
#endif
/* Call the subarch specific early setup function */
switch (boot_params.hdr.hardware_subarch) {
case X86_SUBARCH_MRST:
x86_mrst_early_setup();
break;
default:
i386_default_early_setup();
break;
}
/*
* At this point everything still needed from the boot loader
* or BIOS or kernel text should be early reserved or marked not
* RAM in e820. All other memory is free game.
*/
start_kernel();
}