Merge branch 'wip-2.6.34' into old-private-masterarchived-private-master

1 files changed, 44 insertions, 1 deletions

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index dd38bfbefd1f..28195c350b97 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -6,13 +6,13 @@
 #include <linux/bootmem.h>
 #include <linux/module.h>
 #include <linux/sched.h>
-#include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/seq_file.h>
 #include <linux/debugfs.h>
 #include <linux/pfn.h>
 #include <linux/percpu.h>
+#include <linux/gfp.h>
 
 #include <asm/e820.h>
 #include <asm/processor.h>
@@ -279,6 +279,43 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address,
                    __pa((unsigned long)__end_rodata) >> PAGE_SHIFT))
                 pgprot_val(forbidden) |= _PAGE_RW;
 
+#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
+        /*
+         * Once the kernel maps the text as RO (kernel_set_to_readonly is set),
+         * kernel text mappings for the large page aligned text, rodata sections
+         * will be always read-only. For the kernel identity mappings covering
+         * the holes caused by this alignment can be anything that user asks.
+         *
+         * This will preserve the large page mappings for kernel text/data
+         * at no extra cost.
+         */
+        if (kernel_set_to_readonly &&
+            within(address, (unsigned long)_text,
+                   (unsigned long)__end_rodata_hpage_align)) {
+                unsigned int level;
+
+                /*
+                 * Don't enforce the !RW mapping for the kernel text mapping,
+                 * if the current mapping is already using small page mapping.
+                 * No need to work hard to preserve large page mappings in this
+                 * case.
+                 *
+                 * This also fixes the Linux Xen paravirt guest boot failure
+                 * (because of unexpected read-only mappings for kernel identity
+                 * mappings). In this paravirt guest case, the kernel text
+                 * mapping and the kernel identity mapping share the same
+                 * page-table pages. Thus we can't really use different
+                 * protections for the kernel text and identity mappings. Also,
+                 * these shared mappings are made of small page mappings.
+                 * Thus this don't enforce !RW mapping for small page kernel
+                 * text mapping logic will help Linux Xen parvirt guest boot
+                 * aswell.
+                 */
+                if (lookup_address(address, &level) && (level != PG_LEVEL_4K))
+                        pgprot_val(forbidden) |= _PAGE_RW;
+        }
+#endif
+
         prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
 
         return prot;
@@ -1069,12 +1106,18 @@ EXPORT_SYMBOL(set_memory_array_wb);
 
 int set_memory_x(unsigned long addr, int numpages)
 {
+        if (!(__supported_pte_mask & _PAGE_NX))
+                return 0;
+
         return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_NX), 0);
 }
 EXPORT_SYMBOL(set_memory_x);
 
 int set_memory_nx(unsigned long addr, int numpages)
 {
+        if (!(__supported_pte_mask & _PAGE_NX))
+                return 0;
+
         return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_NX), 0);
 }
 EXPORT_SYMBOL(set_memory_nx);