[PATCH] x86/x86_64: mark rodata section read-only: x86-64 support
x86-64 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>
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/x86_64/Kconfig.debug b/arch/x86_64/Kconfig.debug
index e2c6e64a..fcb06a5 100644
--- a/arch/x86_64/Kconfig.debug
+++ b/arch/x86_64/Kconfig.debug
@@ -9,6 +9,16 @@
Fill __init and __initdata at the end of boot. This helps debugging
illegal uses of __init and __initdata after initialization.
+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 IOMMU_DEBUG
depends on GART_IOMMU && DEBUG_KERNEL
bool "Enable IOMMU debugging"
diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index c016dfe..1faae5f 100644
--- a/arch/x86_64/mm/init.c
+++ b/arch/x86_64/mm/init.c
@@ -498,6 +498,29 @@
printk ("Freeing unused kernel memory: %luk 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_addr(addr, 1, PAGE_KERNEL_RO);
+
+ printk ("Write protecting the kernel read-only data: %luk\n",
+ (&__end_rodata - &__start_rodata) >> 10);
+
+ /*
+ * change_page_attr_addr() 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)
{