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_make_nop(struct jump_entry *entry, struct insn *insn)
  26 {
  27         /* brcl 0,0 */
  28         insn->opcode = 0xc004;
  29         insn->offset = 0;
  30 }
  31
  32 static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
  33 {
  34         /* brcl 15,offset */
  35         insn->opcode = 0xc0f4;
  36         insn->offset = (entry->target - entry->code) >> 1;
  37 }
  38
  39 static void jump_label_bug(struct jump_entry *entry, struct insn *insn)
  40 {
  41         unsigned char *ipc = (unsigned char *)entry->code;
  42         unsigned char *ipe = (unsigned char *)insn;
  43
  44         pr_emerg("Jump label code mismatch at %pS [%p]\n", ipc, ipc);
  45         pr_emerg("Found:    %02x %02x %02x %02x %02x %02x\n",
  46                  ipc[0], ipc[1], ipc[2], ipc[3], ipc[4], ipc[5]);
  47         pr_emerg("Expected: %02x %02x %02x %02x %02x %02x\n",
  48                  ipe[0], ipe[1], ipe[2], ipe[3], ipe[4], ipe[5]);
  49         panic("Corrupted kernel text");
  50 }
  51
  52 static struct insn orignop = {
  53         .opcode = 0xc004,
  54         .offset = JUMP_LABEL_NOP_OFFSET >> 1,
  55 };
  56
  57 static void __jump_label_transform(struct jump_entry *entry,
  58                                    enum jump_label_type type,
  59                                    int init)
  60 {
  61         struct insn old, new;
  62
  63         if (type == JUMP_LABEL_ENABLE) {
  64                 jump_label_make_nop(entry, &old);
  65                 jump_label_make_branch(entry, &new);
  66         } else {
  67                 jump_label_make_branch(entry, &old);
  68                 jump_label_make_nop(entry, &new);
  69         }
  70         if (init) {
  71                 if (memcmp((void *)entry->code, &orignop, sizeof(orignop)))
  72                         jump_label_bug(entry, &old);
  73         } else {
  74                 if (memcmp((void *)entry->code, &old, sizeof(old)))
  75                         jump_label_bug(entry, &old);
  76         }
  77         probe_kernel_write((void *)entry->code, &new, sizeof(new));
  78 }
  79
  80 static int __sm_arch_jump_label_transform(void *data)
  81 {
  82         struct insn_args *args = data;
  83
  84         __jump_label_transform(args->entry, args->type, 0);
  85         return 0;
  86 }
  87
  88 void arch_jump_label_transform(struct jump_entry *entry,
  89                                enum jump_label_type type)
  90 {
  91         struct insn_args args;
  92
  93         args.entry = entry;
  94         args.type = type;
  95
  96         stop_machine(__sm_arch_jump_label_transform, &args, NULL);
  97 }
  98
  99 void arch_jump_label_transform_static(struct jump_entry *entry,
 100                                       enum jump_label_type type)
 101 {
 102         __jump_label_transform(entry, type, 1);
 103 }
 104
 105 #endif