x86: teach the static_protection function about high mappings

Right now, enforcing that the high mapping of the kernel text doesn't
get the NX bit is done deep in the guts of CPA, rather than in the
static_protection() function that enforces all other per-arch sanity
checks.

This patch moves this sanity check into the central static_protection()
function instead, and makes it apply ONLY to the kernel text, not to all
other areas in the high mapping.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/mm/pageattr.c

@@ -106,6 +106,22 @@ static void cpa_flush_range(unsigned long start, int numpages)
 	}
 }
 
+#define HIGH_MAP_START	__START_KERNEL_map
+#define HIGH_MAP_END	(__START_KERNEL_map + KERNEL_TEXT_SIZE)
+
+
+/*
+ * Converts a virtual address to a X86-64 highmap address
+ */
+static unsigned long virt_to_highmap(void *address)
+{
+#ifdef CONFIG_X86_64
+	return __pa((unsigned long)address) + HIGH_MAP_START - phys_base;
+#else
+	return (unsigned long)address;
+#endif
+}
+
 /*
  * Certain areas of memory on x86 require very specific protection flags,
  * for example the BIOS area or kernel text. Callers don't always get this
@@ -129,12 +145,24 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address)
 	 */
 	if (within(address, (unsigned long)_text, (unsigned long)_etext))
 		pgprot_val(forbidden) |= _PAGE_NX;
+	/*
+	 * Do the same for the x86-64 high kernel mapping
+	 */
+	if (within(address, virt_to_highmap(_text), virt_to_highmap(_etext)))
+		pgprot_val(forbidden) |= _PAGE_NX;
+
 
 #ifdef CONFIG_DEBUG_RODATA
 	/* The .rodata section needs to be read-only */
 	if (within(address, (unsigned long)__start_rodata,
 				(unsigned long)__end_rodata))
 		pgprot_val(forbidden) |= _PAGE_RW;
+	/*
+	 * Do the same for the x86-64 high kernel mapping
+	 */
+	if (within(address, virt_to_highmap(__start_rodata),
+				virt_to_highmap(__end_rodata)))
+		pgprot_val(forbidden) |= _PAGE_RW;
 #endif
 
 	prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
@@ -304,8 +332,6 @@ repeat:
  * Modules and drivers should use the set_memory_* APIs instead.
  */
 
-#define HIGH_MAP_START	__START_KERNEL_map
-#define HIGH_MAP_END	(__START_KERNEL_map + KERNEL_TEXT_SIZE)
 
 static int
 change_page_attr_addr(unsigned long address, pgprot_t mask_set,
@@ -338,10 +364,11 @@ change_page_attr_addr(unsigned long address, pgprot_t mask_set,
 		/*
 		 * Calc the high mapping address. See __phys_addr()
 		 * for the non obvious details.
+		 *
+		 * Note that NX and other required permissions are
+		 * checked in static_protections().
 		 */
 		address = phys_addr + HIGH_MAP_START - phys_base;
-		/* Make sure the kernel mappings stay executable */
-		pgprot_val(mask_clr) |= _PAGE_NX;
 
 		/*
 		 * Our high aliases are imprecise, because we check