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 *expected,
  40                            struct insn *new)
  41 {
  42         unsigned char *ipc = (unsigned char *)entry->code;
  43         unsigned char *ipe = (unsigned char *)expected;
  44         unsigned char *ipn = (unsigned char *)new;
  45
  46         pr_emerg("Jump label code mismatch at %pS [%px]\n", ipc, ipc);
  47         pr_emerg("Found:    %6ph\n", ipc);
  48         pr_emerg("Expected: %6ph\n", ipe);
  49         pr_emerg("New:      %6ph\n", ipn);
  50         panic("Corrupted kernel text");
  51 }
  52
  53 static struct insn orignop = {
  54         .opcode = 0xc004,
  55         .offset = JUMP_LABEL_NOP_OFFSET >> 1,
  56 };
  57
  58 static void __jump_label_transform(struct jump_entry *entry,
  59                                    enum jump_label_type type,
  60                                    int init)
  61 {
  62         struct insn old, new;
  63
  64         if (type == JUMP_LABEL_JMP) {
  65                 jump_label_make_nop(entry, &old);
  66                 jump_label_make_branch(entry, &new);
  67         } else {
  68                 jump_label_make_branch(entry, &old);
  69                 jump_label_make_nop(entry, &new);
  70         }
  71         if (init) {
  72                 if (memcmp((void *)entry->code, &orignop, sizeof(orignop)))
  73                         jump_label_bug(entry, &orignop, &new);
  74         } else {
  75                 if (memcmp((void *)entry->code, &old, sizeof(old)))
  76                         jump_label_bug(entry, &old, &new);
  77         }
  78         s390_kernel_write((void *)entry->code, &new, sizeof(new));
  79 }
  80
  81 static int __sm_arch_jump_label_transform(void *data)
  82 {
  83         struct insn_args *args = data;
  84
  85         __jump_label_transform(args->entry, args->type, 0);
  86         return 0;
  87 }
  88
  89 void arch_jump_label_transform(struct jump_entry *entry,
  90                                enum jump_label_type type)
  91 {
  92         struct insn_args args;
  93
  94         args.entry = entry;
  95         args.type = type;
  96
  97         stop_machine(__sm_arch_jump_label_transform, &args, NULL);
  98 }
  99
 100 void arch_jump_label_transform_static(struct jump_entry *entry,
 101                                       enum jump_label_type type)
 102 {
 103         __jump_label_transform(entry, type, 1);
 104 }
 105
 106 #endif