generic debug pagealloc

CONFIG_DEBUG_PAGEALLOC is now supported by x86, powerpc, sparc64, and
s390.  This patch implements it for the rest of the architectures by
filling the pages with poison byte patterns after free_pages() and
verifying the poison patterns before alloc_pages().

This generic one cannot detect invalid page accesses immediately but
invalid read access may cause invalid dereference by poisoned memory and
invalid write access can be detected after a long delay.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

16 files changed, 202 insertions, 19 deletions

diff --git a/arch/avr32/mm/fault.c b/arch/avr32/mm/fault.c
index ce4e4296b954..62d4abbaa654 100644
--- a/arch/avr32/mm/fault.c
+++ b/arch/avr32/mm/fault.c
@@ -250,21 +250,3 @@ asmlinkage void do_bus_error(unsigned long addr, int write_access,
         dump_dtlb();
         die("Bus Error", regs, SIGKILL);
 }
-
-/*
- * This functionality is currently not possible to implement because
- * we're using segmentation to ensure a fixed mapping of the kernel
- * virtual address space.
- *
- * It would be possible to implement this, but it would require us to
- * disable segmentation at startup and load the kernel mappings into
- * the TLB like any other pages. There will be lots of trickery to
- * avoid recursive invocation of the TLB miss handler, though...
- */
-#ifdef CONFIG_DEBUG_PAGEALLOC
-void kernel_map_pages(struct page *page, int numpages, int enable)
-{
-
-}
-EXPORT_SYMBOL(kernel_map_pages);
-#endif
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index ad6b1c084fe3..45192dce65c4 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -228,6 +228,9 @@ config PPC_OF_PLATFORM_PCI
         depends on PPC64 # not supported on 32 bits yet
         default n
 
+config ARCH_SUPPORTS_DEBUG_PAGEALLOC
+        def_bool y
+
 source "init/Kconfig"
 
 source "kernel/Kconfig.freezer"
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 22091bbfdc9b..6aa0b5e087cd 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -30,6 +30,7 @@ config DEBUG_STACK_USAGE
 config DEBUG_PAGEALLOC
         bool "Debug page memory allocations"
         depends on DEBUG_KERNEL && !HIBERNATION
+        depends on ARCH_SUPPORTS_DEBUG_PAGEALLOC
         help
           Unmap pages from the kernel linear mapping after free_pages().
           This results in a large slowdown, but helps to find certain types
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 2a8af5e16345..dcb667c4375a 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -72,6 +72,9 @@ config PGSTE
 config VIRT_CPU_ACCOUNTING
         def_bool y
 
+config ARCH_SUPPORTS_DEBUG_PAGEALLOC
+        def_bool y
+
 mainmenu "Linux Kernel Configuration"
 
 config S390
diff --git a/arch/s390/Kconfig.debug b/arch/s390/Kconfig.debug
index 4599fa06bd82..7e297a3cde34 100644
--- a/arch/s390/Kconfig.debug
+++ b/arch/s390/Kconfig.debug
@@ -9,6 +9,7 @@ source "lib/Kconfig.debug"
 config DEBUG_PAGEALLOC
         bool "Debug page memory allocations"
         depends on DEBUG_KERNEL
+        depends on ARCH_SUPPORTS_DEBUG_PAGEALLOC
         help
           Unmap pages from the kernel linear mapping after free_pages().
           This results in a slowdown, but helps to find certain types of
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index c3ea215334f6..cc12cd48bbc5 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -124,6 +124,9 @@ config ARCH_NO_VIRT_TO_BUS
 config OF
         def_bool y
 
+config ARCH_SUPPORTS_DEBUG_PAGEALLOC
+        def_bool y if SPARC64
+
 source "init/Kconfig"
 
 source "kernel/Kconfig.freezer"
diff --git a/arch/sparc/Kconfig.debug b/arch/sparc/Kconfig.debug
index b8a15e271bfa..d001b42041a5 100644
--- a/arch/sparc/Kconfig.debug
+++ b/arch/sparc/Kconfig.debug
@@ -24,7 +24,8 @@ config STACK_DEBUG
 
 config DEBUG_PAGEALLOC
         bool "Debug page memory allocations"
-        depends on SPARC64 && DEBUG_KERNEL && !HIBERNATION
+        depends on DEBUG_KERNEL && !HIBERNATION
+        depends on ARCH_SUPPORTS_DEBUG_PAGEALLOC
         help
           Unmap pages from the kernel linear mapping after free_pages().
           This results in a large slowdown, but helps to find certain types
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 45161b816313..748e50a1a152 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -165,6 +165,9 @@ config AUDIT_ARCH
 config ARCH_SUPPORTS_OPTIMIZED_INLINING
         def_bool y
 
+config ARCH_SUPPORTS_DEBUG_PAGEALLOC
+        def_bool y
+
 # Use the generic interrupt handling code in kernel/irq/:
 config GENERIC_HARDIRQS
         bool
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index fdb45df608b6..a345cb5447a8 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -75,6 +75,7 @@ config DEBUG_STACK_USAGE
 config DEBUG_PAGEALLOC
         bool "Debug page memory allocations"
         depends on DEBUG_KERNEL
+        depends on ARCH_SUPPORTS_DEBUG_PAGEALLOC
         ---help---
           Unmap pages from the kernel linear mapping after free_pages().
           This results in a large slowdown, but helps to find certain types
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index d84feb7bdbf0..ddadb4defe00 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -11,6 +11,7 @@
 #include <linux/rwsem.h>
 #include <linux/completion.h>
 #include <linux/cpumask.h>
+#include <linux/page-debug-flags.h>
 #include <asm/page.h>
 #include <asm/mmu.h>
 
@@ -174,6 +175,9 @@ struct vm_area_struct {
 #ifdef CONFIG_NUMA
         struct mempolicy *vm_policy;    /* NUMA policy for the VMA */
 #endif
+#ifdef CONFIG_WANT_PAGE_DEBUG_FLAGS
+        unsigned long debug_flags;      /* Use atomic bitops on this */
+#endif
 };
 
 struct core_thread {
diff --git a/include/linux/page-debug-flags.h b/include/linux/page-debug-flags.h
new file mode 100644
index 000000000000..b0638fd91e92
--- /dev/null
+++ b/include/linux/page-debug-flags.h
@@ -0,0 +1,30 @@
+#ifndef LINUX_PAGE_DEBUG_FLAGS_H
+#define  LINUX_PAGE_DEBUG_FLAGS_H
+
+/*
+ * page->debug_flags bits:
+ *
+ * PAGE_DEBUG_FLAG_POISON is set for poisoned pages. This is used to
+ * implement generic debug pagealloc feature. The pages are filled with
+ * poison patterns and set this flag after free_pages(). The poisoned
+ * pages are verified whether the patterns are not corrupted and clear
+ * the flag before alloc_pages().
+ */
+
+enum page_debug_flags {
+        PAGE_DEBUG_FLAG_POISON,         /* Page is poisoned */
+};
+
+/*
+ * Ensure that CONFIG_WANT_PAGE_DEBUG_FLAGS reliably
+ * gets turned off when no debug features are enabling it!
+ */
+
+#ifdef CONFIG_WANT_PAGE_DEBUG_FLAGS
+#if !defined(CONFIG_PAGE_POISONING) \
+/* && !defined(CONFIG_PAGE_DEBUG_SOMETHING_ELSE) && ... */
+#error WANT_PAGE_DEBUG_FLAGS is turned on with no debug features!
+#endif
+#endif /* CONFIG_WANT_PAGE_DEBUG_FLAGS */
+
+#endif /* LINUX_PAGE_DEBUG_FLAGS_H */
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 9f31683728fd..6729f7dcd60e 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -17,6 +17,9 @@
  */
 #define TIMER_ENTRY_STATIC      ((void *) 0x74737461)
 
+/********** mm/debug-pagealloc.c **********/
+#define PAGE_POISON 0xaa
+
 /********** mm/slab.c **********/
 /*
  * Magic nums for obj red zoning.
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 58bfe7e8faba..9638d99644af 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -796,6 +796,7 @@ config SYSCTL_SYSCALL_CHECK
           to properly maintain and use. This enables checks that help
           you to keep things correct.
 
+source mm/Kconfig.debug
 source kernel/trace/Kconfig
 
 config PROVIDE_OHCI1394_DMA_INIT
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
new file mode 100644
index 000000000000..c8d62d49a44e
--- /dev/null
+++ b/mm/Kconfig.debug
@@ -0,0 +1,17 @@
+config WANT_PAGE_DEBUG_FLAGS
+        bool
+
+config PAGE_POISONING
+        bool "Debug page memory allocations"
+        depends on DEBUG_KERNEL && !ARCH_SUPPORTS_DEBUG_PAGEALLOC
+        depends on !HIBERNATION
+        select DEBUG_PAGEALLOC
+        select WANT_PAGE_DEBUG_FLAGS
+        help
+           Fill the pages with poison patterns after free_pages() and verify
+           the patterns before alloc_pages(). This results in a large slowdown,
+           but helps to find certain types of memory corruptions.
+
+           This option cannot enalbe with hibernation. Otherwise, it will get
+           wrong messages for memory corruption because the free pages are not
+           saved to the suspend image.
diff --git a/mm/Makefile b/mm/Makefile
index 818569b68f46..ec73c68b6015 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_SPARSEMEM_VMEMMAP) += sparse-vmemmap.o
 obj-$(CONFIG_TMPFS_POSIX_ACL) += shmem_acl.o
 obj-$(CONFIG_SLOB) += slob.o
 obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o
+obj-$(CONFIG_PAGE_POISONING) += debug-pagealloc.o
 obj-$(CONFIG_SLAB) += slab.o
 obj-$(CONFIG_SLUB) += slub.o
 obj-$(CONFIG_FAILSLAB) += failslab.o
diff --git a/mm/debug-pagealloc.c b/mm/debug-pagealloc.c
new file mode 100644
index 000000000000..a1e3324de2b5
--- /dev/null
+++ b/mm/debug-pagealloc.c
@@ -0,0 +1,129 @@
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/page-debug-flags.h>
+#include <linux/poison.h>
+
+static inline void set_page_poison(struct page *page)
+{
+        __set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
+}
+
+static inline void clear_page_poison(struct page *page)
+{
+        __clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
+}
+
+static inline bool page_poison(struct page *page)
+{
+        return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
+}
+
+static void poison_highpage(struct page *page)
+{
+        /*
+         * Page poisoning for highmem pages is not implemented.
+         *
+         * This can be called from interrupt contexts.
+         * So we need to create a new kmap_atomic slot for this
+         * application and it will need interrupt protection.
+         */
+}
+
+static void poison_page(struct page *page)
+{
+        void *addr;
+
+        if (PageHighMem(page)) {
+                poison_highpage(page);
+                return;
+        }
+        set_page_poison(page);
+        addr = page_address(page);
+        memset(addr, PAGE_POISON, PAGE_SIZE);
+}
+
+static void poison_pages(struct page *page, int n)
+{
+        int i;
+
+        for (i = 0; i < n; i++)
+                poison_page(page + i);
+}
+
+static bool single_bit_flip(unsigned char a, unsigned char b)
+{
+        unsigned char error = a ^ b;
+
+        return error && !(error & (error - 1));
+}
+
+static void check_poison_mem(unsigned char *mem, size_t bytes)
+{
+        unsigned char *start;
+        unsigned char *end;
+
+        for (start = mem; start < mem + bytes; start++) {
+                if (*start != PAGE_POISON)
+                        break;
+        }
+        if (start == mem + bytes)
+                return;
+
+        for (end = mem + bytes - 1; end > start; end--) {
+                if (*end != PAGE_POISON)
+                        break;
+        }
+
+        if (!printk_ratelimit())
+                return;
+        else if (start == end && single_bit_flip(*start, PAGE_POISON))
+                printk(KERN_ERR "pagealloc: single bit error\n");
+        else
+                printk(KERN_ERR "pagealloc: memory corruption\n");
+
+        print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
+                        end - start + 1, 1);
+        dump_stack();
+}
+
+static void unpoison_highpage(struct page *page)
+{
+        /*
+         * See comment in poison_highpage().
+         * Highmem pages should not be poisoned for now
+         */
+        BUG_ON(page_poison(page));
+}
+
+static void unpoison_page(struct page *page)
+{
+        if (PageHighMem(page)) {
+                unpoison_highpage(page);
+                return;
+        }
+        if (page_poison(page)) {
+                void *addr = page_address(page);
+
+                check_poison_mem(addr, PAGE_SIZE);
+                clear_page_poison(page);
+        }
+}
+
+static void unpoison_pages(struct page *page, int n)
+{
+        int i;
+
+        for (i = 0; i < n; i++)
+                unpoison_page(page + i);
+}
+
+void kernel_map_pages(struct page *page, int numpages, int enable)
+{
+        if (!debug_pagealloc_enabled)
+                return;
+
+        if (enable)
+                unpoison_pages(page, numpages);
+        else
+                poison_pages(page, numpages);
+}