arch/s390/kernel/jump_label.c

   1 /*
   2  * Jump label s390 support
   3  *
   4  * Copyright IBM Corp. 2011
   5  * Author(s): Jan Glauber <jang@linux.vnet.ibm.com>
   6  */
   7 #include <linux/module.h>
   8 #include <linux/uaccess.h>
   9 #include <linux/stop_machine.h>
  10 #include <linux/jump_label.h>
  11 #include <asm/ipl.h>
  12
  13 #ifdef HAVE_JUMP_LABEL
  14
  15 struct insn {
  16         u16 opcode;
  17         s32 offset;
  18 } __packed;
  19
  20 struct insn_args {
  21         unsigned long *target;
  22         struct insn *insn;
  23         ssize_t size;
  24 };
  25
  26 static int __arch_jump_label_transform(void *data)
  27 {
  28         struct insn_args *args = data;
  29         int rc;
  30
  31         rc = probe_kernel_write(args->target, args->insn, args->size);
  32         WARN_ON_ONCE(rc < 0);
  33         return 0;
  34 }
  35
  36 void arch_jump_label_transform(struct jump_entry *entry,
  37                                enum jump_label_type type)
  38 {
  39         struct insn_args args;
  40         struct insn insn;
  41
  42         if (type == JUMP_LABEL_ENABLE) {
  43                 /* brcl 15,offset */
  44                 insn.opcode = 0xc0f4;
  45                 insn.offset = (entry->target - entry->code) >> 1;
  46         } else {
  47                 /* brcl 0,0 */
  48                 insn.opcode = 0xc004;
  49                 insn.offset = 0;
  50         }
  51
  52         args.target = (void *) entry->code;
  53         args.insn = &insn;
  54         args.size = JUMP_LABEL_NOP_SIZE;
  55
  56         stop_machine(__arch_jump_label_transform, &args, NULL);
  57 }
  58
  59 #endif