[S390] mm: add devmem_is_allowed() for STRICT_DEVMEM checking
Provide the devmem_is_allowed() routine to restrict access to
kernel memory from userspace.
Set the CONFIG_STRICT_DEVMEM config option to switch on checking.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/Kconfig.debug b/arch/s390/Kconfig.debug
index 45e0c61..05221b1 100644
--- a/arch/s390/Kconfig.debug
+++ b/arch/s390/Kconfig.debug
@@ -6,6 +6,18 @@
source "lib/Kconfig.debug"
+config STRICT_DEVMEM
+ def_bool y
+ prompt "Filter access to /dev/mem"
+ ---help---
+ This option restricts access to /dev/mem. If this option is
+ disabled, you allow userspace access to all memory, including
+ kernel and userspace memory. Accidental memory access is likely
+ to be disastrous.
+ Memory access is required for experts who want to debug the kernel.
+
+ If you are unsure, say Y.
+
config DEBUG_STRICT_USER_COPY_CHECKS
bool "Strict user copy size checks"
---help---