Prev: Add MSG_WAITFORONE flag to recvmmsg
Next: [RFC] Intelligent power sharing driver
From: Yinghai Lu on 27 Mar 2010 22:10
please check.

I keep the comments about we are safe to use PAGE_ALIGN() with the initrd_end.

Thanks

Yinghai



Subject: [PATCH -v4] x86: Make sure free_init_pages() free pages in boundary

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.
-v4: use PAGE_ALIGN according to Johannes.
We may fix that MARCO 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 WARN for wrong range according Johannes.

Reported-by: Stanislaw Gruszka <sgruszka(a)redhat.com>
Signed-off-by: Yinghai Lu <yinghai(a)kernel.org>
Acked-by: Johannes Weiner <hannes(a)cmpxchg.org>
Tested-by: Stanislaw Gruszka <sgruszka(a)redhat.com>

---
arch/x86/kernel/head32.c | 3 ++-
arch/x86/kernel/head64.c | 3 ++-
arch/x86/kernel/setup.c | 19 ++++++++++---------
arch/x86/mm/init.c | 32 ++++++++++++++++++++++++++------
4 files changed, 40 insertions(+), 17 deletions(-)

Index: linux-2.6/arch/x86/mm/init.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/init.c
+++ linux-2.6/arch/x86/mm/init.c
@@ -331,11 +331,23 @@ int devmem_is_allowed(unsigned long page

void free_init_pages(char *what, unsigned long begin, unsigned long end)
{
- unsigned long addr = begin;
+ unsigned long addr;
+ unsigned long begin_aligned, end_aligned;

- if (addr >= end)
+ /* Make sure boundaries are page aligned */
+ begin_aligned = PAGE_ALIGN(begin);
+ end_aligned = end & PAGE_MASK;
+
+ if (WARN(begin_aligned >= end_aligned, "wrong range: [%#lx, %#lx]\n", begin, end))
return;

+ if (WARN_ON(begin_aligned != begin || end_aligned != end)) {
+ begin = begin_aligned;
+ end = end_aligned;
+ }
+
+ addr = begin;
+
/*
* If debugging page accesses then do not free this memory but
* mark them not present - any buggy init-section access will
@@ -343,7 +355,7 @@ void free_init_pages(char *what, unsigne
*/
#ifdef CONFIG_DEBUG_PAGEALLOC
printk(KERN_INFO "debug: unmapping init memory %08lx..%08lx\n",
- begin, PAGE_ALIGN(end));
+ begin, end);
set_memory_np(begin, (end - begin) >> PAGE_SHIFT);
#else
/*
@@ -358,8 +370,7 @@ void free_init_pages(char *what, unsigne
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 +387,15 @@ 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);
+ /*
+ * end could be not aligned, and We can not align that,
+ * decompresser could be confused by aligned initrd_end
+ * We already reserve the end partial page before in
+ * - i386_start_kernel()
+ * - x86_64_start_kernel()
+ * - relocate_initrd()
+ * So here We can do PAGE_ALIGN() safely to get partial page to be freed
+ */
+ free_init_pages("initrd memory", start, PAGE_ALIGN(end));
}
#endif
Index: linux-2.6/arch/x86/kernel/head32.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/head32.c
+++ linux-2.6/arch/x86/kernel/head32.c
@@ -44,9 +44,10 @@ 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
Index: linux-2.6/arch/x86/kernel/head64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/head64.c
+++ linux-2.6/arch/x86/kernel/head64.c
@@ -103,9 +103,10 @@ void __init x86_64_start_reservations(ch
#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
Index: linux-2.6/arch/x86/kernel/setup.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup.c
+++ linux-2.6/arch/x86/kernel/setup.c
@@ -314,16 +314,17 @@ static void __init reserve_brk(void)
#define MAX_MAP_CHUNK (NR_FIX_BTMAPS << PAGE_SHIFT)
static void __init relocate_initrd(void)
{
-
+ /* Assume only end is not page aligned */
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;
@@ -348,13 +349,13 @@ static void __init relocate_initrd(void)
memcpy(q, p, clen);
q += clen;
ramdisk_image += clen;
- ramdisk_size -= clen;
+ area_size -= clen;
}

/* Copy the highmem portion of the initrd */
- while (ramdisk_size) {
+ while (area_size) {
slop = ramdisk_image & ~PAGE_MASK;
- clen = ramdisk_size;
+ clen = area_size;
if (clen > MAX_MAP_CHUNK-slop)
clen = MAX_MAP_CHUNK-slop;
mapaddr = ramdisk_image & PAGE_MASK;
@@ -363,11 +364,10 @@ static void __init relocate_initrd(void)
early_iounmap(p, clen+slop);
q += clen;
ramdisk_image += clen;
- ramdisk_size -= clen;
+ area_size -= clen;
}
/* high pages is not converted by early_res_to_bootmem */
ramdisk_image = boot_params.hdr.ramdisk_image;
- ramdisk_size = boot_params.hdr.ramdisk_size;
printk(KERN_INFO "Move RAMDISK from %016llx - %016llx to"
" %08llx - %08llx\n",
ramdisk_image, ramdisk_image + ramdisk_size - 1,
@@ -376,9 +376,10 @@ static void __init relocate_initrd(void)

static void __init reserve_initrd(void)
{
+ /* 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);
u64 end_of_lowmem = max_low_pfn_mapped << PAGE_SHIFT;

if (!boot_params.hdr.type_of_loader ||
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
First  |  Prev  | 
Pages: 1 2
Prev: Add MSG_WAITFORONE flag to recvmmsg
Next: [RFC] Intelligent power sharing driver