s390/kprobes: add support for compare and branch instructions

The compare and branch instructions (not relative) all need special
handling when kprobed:
- if a branch was taken, the instruction pointer should be left alone
- if a branch was not taken, the instruction pointer must be adjusted

The compare and branch instructions family was introduced with the general
instruction extension facility (z10).

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 19 insertions, 2 deletions

diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index 3388b2b2a07d..adbbe7f1cb0d 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -105,14 +105,31 @@ static int __kprobes get_fixup_type(kprobe_opcode_t *insn)
                 fixup |= FIXUP_RETURN_REGISTER;
                 break;
         case 0xeb:
-                if ((insn[2] & 0xff) == 0x44 || /* bxhg  */
-                    (insn[2] & 0xff) == 0x45)   /* bxleg */
+                switch (insn[2] & 0xff) {
+                case 0x44: /* bxhg  */
+                case 0x45: /* bxleg */
                         fixup = FIXUP_BRANCH_NOT_TAKEN;
+                        break;
+                }
                 break;
         case 0xe3:      /* bctg */
                 if ((insn[2] & 0xff) == 0x46)
                         fixup = FIXUP_BRANCH_NOT_TAKEN;
                 break;
+        case 0xec:
+                switch (insn[2] & 0xff) {
+                case 0xe5: /* clgrb */
+                case 0xe6: /* cgrb  */
+                case 0xf6: /* crb   */
+                case 0xf7: /* clrb  */
+                case 0xfc: /* cgib  */
+                case 0xfd: /* cglib */
+                case 0xfe: /* cib   */
+                case 0xff: /* clib  */
+                        fixup = FIXUP_BRANCH_NOT_TAKEN;
+                        break;
+                }
+                break;
         }
         return fixup;
 }