[PATCH] x86/x86_64: mark rodata section read only: x86 parts
x86 specific parts to make the .rodata section read only
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/i386/Kconfig.debug b/arch/i386/Kconfig.debug
index c48b424..bf32ecc 100644
--- a/arch/i386/Kconfig.debug
+++ b/arch/i386/Kconfig.debug
@@ -42,6 +42,16 @@
This results in a large slowdown, but helps to find certain types
of memory corruptions.
+config DEBUG_RODATA
+ bool "Write protect kernel read-only data structures"
+ depends on DEBUG_KERNEL
+ help
+ Mark the kernel read-only data as write-protected in the pagetables,
+ in order to catch accidental (and incorrect) writes to such const
+ data. This option may have a slight performance impact because a
+ portion of the kernel code won't be covered by a 2MB TLB anymore.
+ If in doubt, say "N".
+
config 4KSTACKS
bool "Use 4Kb for kernel stacks instead of 8Kb"
depends on DEBUG_KERNEL
diff --git a/arch/i386/mm/init.c b/arch/i386/mm/init.c
index 06e26f0..7df494b 100644
--- a/arch/i386/mm/init.c
+++ b/arch/i386/mm/init.c
@@ -735,6 +735,30 @@
printk (KERN_INFO "Freeing unused kernel memory: %dk freed\n", (__init_end - __init_begin) >> 10);
}
+#ifdef CONFIG_DEBUG_RODATA
+
+extern char __start_rodata, __end_rodata;
+void mark_rodata_ro(void)
+{
+ unsigned long addr = (unsigned long)&__start_rodata;
+
+ for (; addr < (unsigned long)&__end_rodata; addr += PAGE_SIZE)
+ change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RO);
+
+ printk ("Write protecting the kernel read-only data: %luk\n",
+ (unsigned long)(&__end_rodata - &__start_rodata) >> 10);
+
+ /*
+ * change_page_attr() requires a global_flush_tlb() call after it.
+ * We do this after the printk so that if something went wrong in the
+ * change, the printk gets out at least to give a better debug hint
+ * of who is the culprit.
+ */
+ global_flush_tlb();
+}
+#endif
+
+
#ifdef CONFIG_BLK_DEV_INITRD
void free_initrd_mem(unsigned long start, unsigned long end)
{
diff --git a/include/asm-i386/cacheflush.h b/include/asm-i386/cacheflush.h
index 2ea36de..7199f7b 100644
--- a/include/asm-i386/cacheflush.h
+++ b/include/asm-i386/cacheflush.h
@@ -31,4 +31,8 @@
void kernel_map_pages(struct page *page, int numpages, int enable);
#endif
+#ifdef CONFIG_DEBUG_RODATA
+void mark_rodata_ro(void);
+#endif
+
#endif /* _I386_CACHEFLUSH_H */