Provide devmem_is_allowed() routine to restrict access to kernel
memory from userspace.
Set CONFIG_STRICT_DEVMEM config option to switch on checking.
Signed-off-by: Steve Best <sfb...@us.ibm.com>
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 2d38a50..6805d5d 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -299,4 +299,16 @@ config PPC_EARLY_DEBUG_CPM_ADDR
platform probing is done, all platforms selected must
share the same address.
+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.
+
endmenu
diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index 53b64be..f225032 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -262,6 +262,11 @@ extern void copy_user_page(void *to, void *from, unsigned
long vaddr,
struct page *p);
extern int page_is_ram(unsigned long pfn);
+static inline int devmem_is_allowed(unsigned long pfn)
+{
+ return 0;
+}
+
#ifdef CONFIG_PPC_SMLPAR
void arch_free_page(struct page *page, int order);
#define HAVE_ARCH_FREE_PAGE
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