[PARISC] only make executable areas executable

Currently parisc has the whole kernel marked as RWX, meaning any
kernel page at all is eligible to be executed.  This can cause a
theoretical problem on systems with combined I/D TLB because the act
of referencing a page causes a TLB insertion with an executable bit.
This TLB entry may be used by the CPU as the basis for speculating the
page into the I-Cache.  If this speculated page is subsequently used
for a user process, there is the possibility we will get a stale
I-cache line picked up as the binary executes.

As a point of good practise, only mark actual kernel text pages as
executable.  The same has to be done for init_text pages, but they're
converted to data pages (and the I-Cache flushed) when the init memory
is released.

Signed-off-by: James Bottomley <James.Bottomley@suse.de>

arch/parisc/kernel/entry.S

@@ -692,6 +692,9 @@ ENTRY(fault_vector_11)
 END(fault_vector_11)
 
 #endif
+	/* Fault vector is separately protected and *must* be on its own page */
+	.align		PAGE_SIZE
+ENTRY(end_fault_vector)
 
 	.import		handle_interruption,code
 	.import		do_cpu_irq_mask,code

arch/parisc/kernel/head.S

@@ -106,8 +106,9 @@ $bss_loop:
 #endif
 
 
-	/* Now initialize the PTEs themselves */
-	ldo		0+_PAGE_KERNEL(%r0),%r3 /* Hardwired 0 phys addr start */
+	/* Now initialize the PTEs themselves.  We use RWX for
+	 * everything ... it will get remapped correctly later */
+	ldo		0+_PAGE_KERNEL_RWX(%r0),%r3 /* Hardwired 0 phys addr start */
 	ldi		(1<<(KERNEL_INITIAL_ORDER-PAGE_SHIFT)),%r11 /* PFN count */
 	load32		PA(pg0),%r1
 

arch/parisc/kernel/module.c

@@ -61,8 +61,10 @@
 #include <linux/string.h>
 #include <linux/kernel.h>
 #include <linux/bug.h>
+#include <linux/mm.h>
 #include <linux/slab.h>
 
+#include <asm/pgtable.h>
 #include <asm/unwind.h>
 
 #if 0
@@ -214,7 +216,13 @@ void *module_alloc(unsigned long size)
 {
 	if (size == 0)
 		return NULL;
-	return vmalloc(size);
+	/* using RWX means less protection for modules, but it's
+	 * easier than trying to map the text, data, init_text and
+	 * init_data correctly */
+	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
+				    GFP_KERNEL | __GFP_HIGHMEM,
+				    PAGE_KERNEL_RWX, -1,
+				    __builtin_return_address(0));
 }
 
 #ifndef CONFIG_64BIT

arch/parisc/kernel/vmlinux.lds.S

@@ -134,6 +134,7 @@ SECTIONS
 	. = ALIGN(16384);
 	__init_begin = .;
 	INIT_TEXT_SECTION(16384)
+	. = ALIGN(PAGE_SIZE);
 	INIT_DATA_SECTION(16)
 	/* we have to discard exit text and such at runtime, not link time */
 	.exit.text :