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/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