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>

1 files changed, 26 insertions, 6 deletions

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index e71c5cbc8f35..452ee5b8f309 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -331,11 +331,23 @@ int devmem_is_allowed(unsigned long pagenr)
 
 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_ON(begin_aligned != begin || end_aligned != end)) {
+                begin = begin_aligned;
+                end   = end_aligned;
+        }
+
+        if (begin >= end)
                 return;
 
+        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, unsigned long begin, unsigned long end)
          */
 #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, unsigned long begin, unsigned long end)
         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