arch/s390/kernel/jump_label.c

   1 /*
   2  * Jump label s390 support
   3  *
   4  * Copyright IBM Corp. 2011
   5  * Author(s): Jan Glauber <[email protected]>
   6  */
   7 #include <linux/uaccess.h>
   8 #include <linux/stop_machine.h>
   9 #include <linux/jump_label.h>
  10 #include <asm/ipl.h>
  11
  12 #ifdef HAVE_JUMP_LABEL
  13
  14 struct insn {
  15         u16 opcode;
  16         s32 offset;
  17 } __packed;
  18
  19 struct insn_args {
  20         struct jump_entry *entry;
  21         enum jump_label_type type;
  22 };
  23
  24 static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn)
  25 {
  26         /* brcl 0,0 */
  27         insn->opcode = 0xc004;
  28         insn->offset = 0;
  29 }
  30
  31 static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
  32 {
  33         /* brcl 15,offset */
  34         insn->opcode = 0xc0f4;
  35         insn->offset = (entry->target - entry->code) >> 1;
  36 }
  37
  38 static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
  39                            struct insn *new)
  40 {
  41         unsigned char *ipc = (unsigned char *)entry->code;
  42         unsigned char *ipe = (unsigned char *)expected;
  43         unsigned char *ipn = (unsigned char *)new;
  44
  45         pr_emerg("Jump label code mismatch at %pS [%p]\n", ipc, ipc);
  46         pr_emerg("Found:    %6ph\n", ipc);
  47         pr_emerg("Expected: %6ph\n", ipe);
  48         pr_emerg("New:      %6ph\n", ipn);
  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_JMP) {
  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, &orignop, &new);
  73         } else {
  74                 if (memcmp((void *)entry->code, &old, sizeof(old)))
  75                         jump_label_bug(entry, &old, &new);
  76         }
  77         s390_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_cpuslocked(__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