1 files changed, 26 insertions, 6 deletions

diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index 576368c4f605..a466bab6677e 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -155,15 +155,34 @@ void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
 static int __kprobes swap_instruction(void *aref)
 {
         struct ins_replace_args *args = aref;
+        u32 *addr;
+        u32 instr;
         int err = -EFAULT;
 
+        /*
+         * Text segment is read-only, hence we use stura to bypass dynamic
+         * address translation to exchange the instruction. Since stura
+         * always operates on four bytes, but we only want to exchange two
+         * bytes do some calculations to get things right. In addition we
+         * shall not cross any page boundaries (vmalloc area!) when writing
+         * the new instruction.
+         */
+        addr = (u32 *)ALIGN((unsigned long)args->ptr, 4);
+        if ((unsigned long)args->ptr & 2)
+                instr = ((*addr) & 0xffff0000) | args->new;
+        else
+                instr = ((*addr) & 0x0000ffff) | args->new << 16;
+
         asm volatile(
-                "0: mvc  0(2,%2),0(%3)\n"
-                "1: la   %0,0\n"
+                "       lra     %1,0(%1)\n"
+                "0:     stura   %2,%1\n"
+                "1:     la      %0,0\n"
                 "2:\n"
                 EX_TABLE(0b,2b)
-                : "+d" (err), "=m" (*args->ptr)
-                : "a" (args->ptr), "a" (&args->new), "m" (args->new));
+                : "+d" (err)
+                : "a" (addr), "d" (instr)
+                : "memory", "cc");
+
         return err;
 }
 
@@ -356,7 +375,7 @@ no_kprobe:
  *      - When the probed function returns, this probe
  *              causes the handlers to fire
  */
-void __kprobes kretprobe_trampoline_holder(void)
+void kretprobe_trampoline_holder(void)
 {
         asm volatile(".global kretprobe_trampoline\n"
                      "kretprobe_trampoline: bcr 0,0\n");
@@ -365,7 +384,8 @@ void __kprobes kretprobe_trampoline_holder(void)
 /*
  * Called when the probe at kretprobe trampoline is hit
  */
-int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+static int __kprobes trampoline_probe_handler(struct kprobe *p,
+                                              struct pt_regs *regs)
 {
         struct kretprobe_instance *ri = NULL;
         struct hlist_head *head, empty_rp;