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>

2 files changed, 4 insertions, 0 deletions

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