c_p_a(): do a simple self test at boot

When CONFIG_DEBUG_RODATA is enabled undo the ro mapping and redo it again.
This gives some simple testing for change_page_attr().

Signed-off-by: Andi Kleen <ak@suse.de>
Acked-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 41 insertions, 0 deletions

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 9bb61e1aed69..38211ff0447f 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -204,4 +204,9 @@ config DEBUG_BOOT_PARAMS
         help
           This option will cause struct boot_params to be exported via debugfs.
 
+config CPA_DEBUG
+        bool "CPA self test code"
+        help
+          Do change_page_attr self tests at boot.
+
 endmenu
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 459b384acda9..724a5eff6f34 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -799,6 +799,20 @@ void mark_rodata_ro(void)
                 change_page_attr(virt_to_page(start),
                                  size >> PAGE_SHIFT, PAGE_KERNEL_RX);
                 printk("Write protecting the kernel text: %luk\n", size >> 10);
+
+#ifdef CONFIG_CPA_DEBUG
+                global_flush_tlb();
+
+                printk("Testing CPA: Reverting %lx-%lx\n", start, start+size);
+                change_page_attr(virt_to_page(start), size>>PAGE_SHIFT,
+                                 PAGE_KERNEL_EXEC);
+                global_flush_tlb();
+
+                printk("Testing CPA: write protecting again\n");
+                change_page_attr(virt_to_page(start), size>>PAGE_SHIFT,
+                                PAGE_KERNEL_RX);
+                global_flush_tlb();
+#endif
         }
 #endif
         start += size;
@@ -815,6 +829,18 @@ void mark_rodata_ro(void)
          * of who is the culprit.
          */
         global_flush_tlb();
+
+#ifdef CONFIG_CPA_DEBUG
+        printk("Testing CPA: undo %lx-%lx\n", start, start + size);
+        change_page_attr(virt_to_page(start), size >> PAGE_SHIFT,
+                                PAGE_KERNEL);
+        global_flush_tlb();
+
+        printk("Testing CPA: write protecting again\n");
+        change_page_attr(virt_to_page(start), size >> PAGE_SHIFT,
+                                PAGE_KERNEL_RO);
+        global_flush_tlb();
+#endif
 }
 #endif
 
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 8198840c3dcb..0fd9d7f77786 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -606,6 +606,16 @@ void mark_rodata_ro(void)
          * of who is the culprit.
          */
         global_flush_tlb();
+
+#ifdef CONFIG_CPA_DEBUG
+        printk("Testing CPA: undo %lx-%lx\n", start, end);
+        change_page_attr_addr(start, (end - start) >> PAGE_SHIFT, PAGE_KERNEL);
+        global_flush_tlb();
+
+        printk("Testing CPA: again\n");
+        change_page_attr_addr(start, (end - start) >> PAGE_SHIFT, PAGE_KERNEL_RO);
+        global_flush_tlb();
+#endif
 }
 #endif