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SubjectRe: [PATCH -v3] x86: Make sure free_init_pages() free pages in boundary
Hi,

On Fri, Mar 26, 2010 at 06:19:33PM -0700, Yinghai Lu wrote:
>
>
> When CONFIG_NO_BOOTMEM, it could use memory more effient, or more compact.
>
> Example is:
> 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 use shared with other user.
>
> When free_init_pages are called for initrd or .init, the page could be freed
> could have chance to 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.
>
> Try to make the boundaries to be page aligned.
>
> -v2: make the original initramdisk to be aligned, according to Johannes.
> otherwise we have chance to lose one page.
> we still need to keep initrd_end not aligned, otherwise it could
> confuse decompresser.
> -v3: change to WARN_ON instead according to Johannes.
>
> Reported-by: Stanislaw Gruszka <sgruszka@redhat.com>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Here is what I had in mind when I wrote what you did not read, maybe diff
works better?

Main differences:
o only fix the area allocation in relocate_initrd(), no need to do
copy the alignment bits
o keep alignment fixups in free_init_pages() out of line
o use PAGE_SIZE(); you might dislike the name, it is still the proper
operation here. if you want to fix it, please do it properly

diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
index adedeef..ec7c672 100644
--- a/arch/x86/kernel/head32.c
+++ b/arch/x86/kernel/head32.c
@@ -46,7 +46,8 @@ void __init i386_start_kernel(void)
if (boot_params.hdr.type_of_loader && boot_params.hdr.ramdisk_image) {
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
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index b5a9896..a26a8fd 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -105,7 +105,9 @@ void __init x86_64_start_reservations(char *real_mode_data)
if (boot_params.hdr.type_of_loader && boot_params.hdr.ramdisk_image) {
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
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index ca3f8fa..0594923 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -317,13 +317,14 @@ static void __init relocate_initrd(void)

u64 ramdisk_image = boot_params.hdr.ramdisk_image;
u64 ramdisk_size = boot_params.hdr.ramdisk_size;
+ u64 area_size = PAGE_ALIGN(ramdisk_size);
u64 end_of_lowmem = max_low_pfn_mapped << PAGE_SHIFT;
u64 ramdisk_here;
unsigned long slop, clen, mapaddr;
char *p, *q;

/* We need to move the initrd down into lowmem */
- ramdisk_here = find_e820_area(0, end_of_lowmem, ramdisk_size,
+ ramdisk_here = find_e820_area(0, end_of_lowmem, area_size,
PAGE_SIZE);

if (ramdisk_here == -1ULL)
@@ -332,7 +333,7 @@ static void __init relocate_initrd(void)

/* Note: this includes all the lowmem currently occupied by
the initrd, we rely on that fact to keep the data intact. */
- reserve_early(ramdisk_here, ramdisk_here + ramdisk_size,
+ reserve_early(ramdisk_here, ramdisk_here + area_size,
"NEW RAMDISK");
initrd_start = ramdisk_here + PAGE_OFFSET;
initrd_end = initrd_start + ramdisk_size;
@@ -378,7 +379,7 @@ static void __init reserve_initrd(void)
{
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);
u64 end_of_lowmem = max_low_pfn_mapped << PAGE_SHIFT;

if (!boot_params.hdr.type_of_loader ||
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index e71c5cb..018e793 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -336,6 +336,11 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
if (addr >= end)
return;

+ if (WARN_ON(addr & ~PAGE_MASK || end & ~PAGE_MASK)) {
+ addr = PAGE_ALIGN(addr);
+ end &= PAGE_MASK;
+ }
+
/*
* If debugging page accesses then do not free this memory but
* mark them not present - any buggy init-section access will
@@ -355,11 +360,10 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)

printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);

- for (; addr < end; addr += PAGE_SIZE) {
+ 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);
+ memset((void *)addr, POISON_FREE_INITMEM, PAGE_SIZE);
free_page(addr);
totalram_pages++;
}
@@ -376,6 +380,6 @@ void free_initmem(void)
#ifdef CONFIG_BLK_DEV_INITRD
void free_initrd_mem(unsigned long start, unsigned long end)
{
- free_init_pages("initrd memory", start, end);
+ free_init_pages("initrd memory", start, PAGE_ALIGN(end));
}
#endif

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