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x86: Make sure free_init_pages() frees pages on page boundary

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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>
This commit is contained in:
Yinghai Lu 2010-03-28 19:42:55 -07:00 • committed by Ingo Molnar
parent 596b711ed6
commit c967da6a0b
4 changed files with 37 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

3
arch/x86/kernel/head64.c
View file

@ -103,9 +103,10 @@ void __init x86_64_start_reservations(char *real_mode_data)
#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 */
unsigned long ramdisk_image = boot_params.hdr.ramdisk_image;
unsigned long ramdisk_size = boot_params.hdr.ramdisk_size;
unsigned long ramdisk_end = ramdisk_image + ramdisk_size;
unsigned long ramdisk_end = PAGE_ALIGN(ramdisk_image + ramdisk_size);
reserve_early(ramdisk_image, ramdisk_end, "RAMDISK");
}
#endif