Allow DEBUG_RODATA and KPROBES to co-exist

Do not mark the kernel text read only if KPROBES is in the kernel;
kprobes needs to hot-patch the kernel text to insert it's
instrumentation.

In this case, only mark the .rodata segment as read only.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Tested-by: S. P. Prasanna <prasanna@in.ibm.com>
Cc: Andi Kleen <ak@suse.de>
Cc: William Cohen <wcohen@redhat.com>
Cc: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/i386/Kconfig.debug

@@ -49,7 +49,6 @@ config DEBUG_PAGEALLOC
 config DEBUG_RODATA
 	bool "Write protect kernel read-only data structures"
 	depends on DEBUG_KERNEL
-	depends on !KPROBES # temporary for 2.6.22
 	help
 	  Mark the kernel read-only data as write-protected in the pagetables,
 	  in order to catch accidental (and incorrect) writes to such const

arch/i386/mm/init.c

@@ -799,6 +799,7 @@ void mark_rodata_ro(void)
 	unsigned long start = PFN_ALIGN(_text);
 	unsigned long size = PFN_ALIGN(_etext) - start;
 
+#ifndef CONFIG_KPROBES
 #ifdef CONFIG_HOTPLUG_CPU
 	/* It must still be possible to apply SMP alternatives. */
 	if (num_possible_cpus() <= 1)
@@ -808,7 +809,7 @@ void mark_rodata_ro(void)
 		                 size >> PAGE_SHIFT, PAGE_KERNEL_RX);
 		printk("Write protecting the kernel text: %luk\n", size >> 10);
 	}
-
+#endif
 	start += size;
 	size = (unsigned long)__end_rodata - start;
 	change_page_attr(virt_to_page(start),

arch/x86_64/Kconfig.debug

@@ -9,7 +9,6 @@ source "lib/Kconfig.debug"
 config DEBUG_RODATA
        bool "Write protect kernel read-only data structures"
        depends on DEBUG_KERNEL
-       depends on !KPROBES # temporary for 2.6.22
        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.

arch/x86_64/mm/init.c

@@ -605,6 +605,11 @@ void mark_rodata_ro(void)
 	if (num_possible_cpus() > 1)
 		start = (unsigned long)_etext;
 #endif
+
+#ifdef CONFIG_KPROBES
+	start = (unsigned long)__start_rodata;
+#endif
+
 	end = (unsigned long)__end_rodata;
 	start = (start + PAGE_SIZE - 1) & PAGE_MASK;
 	end &= PAGE_MASK;