s390/kprobes: make insn pages read-only

Make sure that kprobe insn pages are not writable anymore.
Tested-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/kernel/kprobes.c

@@ -7,6 +7,7 @@
  * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
  */
 
+#include <linux/moduleloader.h>
 #include <linux/kprobes.h>
 #include <linux/ptrace.h>
 #include <linux/preempt.h>
@@ -32,17 +33,33 @@ DEFINE_INSN_CACHE_OPS(s390_insn);
 static int insn_page_in_use;
 static char insn_page[PAGE_SIZE] __aligned(PAGE_SIZE);
 
+void *alloc_insn_page(void)
+{
+	void *page;
+
+	page = module_alloc(PAGE_SIZE);
+	if (!page)
+		return NULL;
+	__set_memory((unsigned long) page, 1, SET_MEMORY_RO | SET_MEMORY_X);
+	return page;
+}
+
+void free_insn_page(void *page)
+{
+	module_memfree(page);
+}
+
 static void *alloc_s390_insn_page(void)
 {
 	if (xchg(&insn_page_in_use, 1) == 1)
 		return NULL;
-	set_memory_x((unsigned long) &insn_page, 1);
+	__set_memory((unsigned long) &insn_page, 1, SET_MEMORY_RO | SET_MEMORY_X);
 	return &insn_page;
 }
 
 static void free_s390_insn_page(void *page)
 {
-	set_memory_nx((unsigned long) page, 1);
+	__set_memory((unsigned long) page, 1, SET_MEMORY_RW | SET_MEMORY_NX);
 	xchg(&insn_page_in_use, 0);
 }
 
@@ -56,25 +73,29 @@ struct kprobe_insn_cache kprobe_s390_insn_slots = {
 
 static void copy_instruction(struct kprobe *p)
 {
+	kprobe_opcode_t insn[MAX_INSN_SIZE];
 	s64 disp, new_disp;
 	u64 addr, new_addr;
+	unsigned int len;
 
-	memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
-	p->opcode = p->ainsn.insn[0];
-	if (!probe_is_insn_relative_long(p->ainsn.insn))
-		return;
-	/*
-	 * For pc-relative instructions in RIL-b or RIL-c format patch the
-	 * RI2 displacement field. We have already made sure that the insn
-	 * slot for the patched instruction is within the same 2GB area
-	 * as the original instruction (either kernel image or module area).
-	 * Therefore the new displacement will always fit.
-	 */
-	disp = *(s32 *)&p->ainsn.insn[1];
-	addr = (u64)(unsigned long)p->addr;
-	new_addr = (u64)(unsigned long)p->ainsn.insn;
-	new_disp = ((addr + (disp * 2)) - new_addr) / 2;
-	*(s32 *)&p->ainsn.insn[1] = new_disp;
+	len = insn_length(*p->addr >> 8);
+	memcpy(&insn, p->addr, len);
+	p->opcode = insn[0];
+	if (probe_is_insn_relative_long(&insn[0])) {
+		/*
+		 * For pc-relative instructions in RIL-b or RIL-c format patch
+		 * the RI2 displacement field. We have already made sure that
+		 * the insn slot for the patched instruction is within the same
+		 * 2GB area as the original instruction (either kernel image or
+		 * module area). Therefore the new displacement will always fit.
+		 */
+		disp = *(s32 *)&insn[1];
+		addr = (u64)(unsigned long)p->addr;
+		new_addr = (u64)(unsigned long)p->ainsn.insn;
+		new_disp = ((addr + (disp * 2)) - new_addr) / 2;
+		*(s32 *)&insn[1] = new_disp;
+	}
+	s390_kernel_write(p->ainsn.insn, &insn, len);
 }
 NOKPROBE_SYMBOL(copy_instruction);