1. should use _brk_end instead of &end, as we only use partial of
   brk.
2. [_brk_end, pm_end) page range is already converted. aka
   is not wasted.

---
 arch/x86/mm/init_64.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Index: linux-2.6/arch/x86/mm/init_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/init_64.c
+++ linux-2.6/arch/x86/mm/init_64.c
@@ -1124,7 +1124,8 @@ void mark_rodata_ro(void)
 	unsigned long end = (unsigned long) &__end_rodata_hpage_align;
 	unsigned long text_end = PFN_ALIGN(&__stop___ex_table);
 	unsigned long rodata_end = PFN_ALIGN(&__end_rodata);
-	unsigned long all_end = PFN_ALIGN(&_end);
+	unsigned long all_end = PFN_ALIGN(_brk_end);
+	unsigned long pmd_end = roundup(all_end, PMD_SIZE);
 
 	printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
 	       (end - start) >> 10);
@@ -1136,7 +1137,7 @@ void mark_rodata_ro(void)
 	 * The rodata/data/bss/brk section (but not the kernel text!)
 	 * should also be not-executable.
 	 */
-	set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT);
+	set_memory_nx(rodata_start, (pmd_end - rodata_start) >> PAGE_SHIFT);
 
 	rodata_test();
 
@@ -1148,6 +1149,7 @@ void mark_rodata_ro(void)
 	set_memory_ro(start, (end-start) >> PAGE_SHIFT);
 #endif
 
+	/* all_end to pmd_end is handled via free_all_bootmem() */
 	free_init_pages("unused kernel",
 			(unsigned long) __va(__pa_symbol(text_end)),
 			(unsigned long) __va(__pa_symbol(rodata_start)));