From c967da6a0ba837f762042e931d4afcf72045547c Mon Sep 17 00:00:00 2001 From: Yinghai Lu Date: Sun, 28 Mar 2010 19:42:55 -0700 Subject: 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 Tested-by: Stanislaw Gruszka Signed-off-by: Yinghai Lu Acked-by: Johannes Weiner Cc: David Miller Cc: Benjamin Herrenschmidt Cc: Linus Torvalds LKML-Reference: <1269830604-26214-3-git-send-email-yinghai@kernel.org> Signed-off-by: Ingo Molnar --- arch/x86/kernel/head32.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'arch/x86/kernel/head32.c') diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c index adedeef1dedc..b2e246037392 100644 --- a/arch/x86/kernel/head32.c +++ b/arch/x86/kernel/head32.c @@ -7,6 +7,7 @@ #include #include +#include #include #include @@ -44,9 +45,10 @@ void __init i386_start_kernel(void) #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 = ramdisk_image + ramdisk_size; + u64 ramdisk_end = PAGE_ALIGN(ramdisk_image + ramdisk_size); reserve_early(ramdisk_image, ramdisk_end, "RAMDISK"); } #endif -- cgit