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         struct jump_entry *entry;
  22         enum jump_label_type type;
  23 };
  24
  25 static void __jump_label_transform(struct jump_entry *entry,
  26                                    enum jump_label_type type)
  27 {
  28         struct insn insn;
  29         int rc;
  30
  31         if (type == JUMP_LABEL_ENABLE) {
  32                 /* brcl 15,offset */
  33                 insn.opcode = 0xc0f4;
  34                 insn.offset = (entry->target - entry->code) >> 1;
  35         } else {
  36                 /* brcl 0,0 */
  37                 insn.opcode = 0xc004;
  38                 insn.offset = 0;
  39         }
  40
  41         rc = probe_kernel_write((void *)entry->code, &insn, JUMP_LABEL_NOP_SIZE);
  42         WARN_ON_ONCE(rc < 0);
  43 }
  44
  45 static int __sm_arch_jump_label_transform(void *data)
  46 {
  47         struct insn_args *args = data;
  48
  49         __jump_label_transform(args->entry, args->type);
  50         return 0;
  51 }
  52
  53 void arch_jump_label_transform(struct jump_entry *entry,
  54                                enum jump_label_type type)
  55 {
  56         struct insn_args args;
  57
  58         args.entry = entry;
  59         args.type = type;
  60
  61         stop_machine(__sm_arch_jump_label_transform, &args, NULL);
  62 }
  63
  64 void arch_jump_label_transform_static(struct jump_entry *entry,
  65                                       enum jump_label_type type)
  66 {
  67         __jump_label_transform(entry, type);
  68 }
  69
  70 #endif