s390/kernel/jump_label.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Jump label s390 support
   4  *
   5  * Copyright IBM Corp. 2011
   6  * Author(s): Jan Glauber <jang@linux.vnet.ibm.com>
   7  */
   8 #include <linux/uaccess.h>
   9 #include <linux/jump_label.h>
  10 #include <linux/module.h>
  11 #include <asm/text-patching.h>
  12 #include <asm/ipl.h>
  13
  14 struct insn {
  15         u16 opcode;
  16         s32 offset;
  17 } __packed;
  18
  19 static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn)
  20 {
  21         /* brcl 0,offset */
  22         insn->opcode = 0xc004;
  23         insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
  24 }
  25
  26 static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
  27 {
  28         /* brcl 15,offset */
  29         insn->opcode = 0xc0f4;
  30         insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
  31 }
  32
  33 static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
  34                            struct insn *new)
  35 {
  36         unsigned char *ipc = (unsigned char *)jump_entry_code(entry);
  37         unsigned char *ipe = (unsigned char *)expected;
  38         unsigned char *ipn = (unsigned char *)new;
  39
  40         pr_emerg("Jump label code mismatch at %pS [%px]\n", ipc, ipc);
  41         pr_emerg("Found:    %6ph\n", ipc);
  42         pr_emerg("Expected: %6ph\n", ipe);
  43         pr_emerg("New:      %6ph\n", ipn);
  44         panic("Corrupted kernel text");
  45 }
  46
  47 static void jump_label_transform(struct jump_entry *entry,
  48                                  enum jump_label_type type)
  49 {
  50         void *code = (void *)jump_entry_code(entry);
  51         struct insn old, new;
  52
  53         if (type == JUMP_LABEL_JMP) {
  54                 jump_label_make_nop(entry, &old);
  55                 jump_label_make_branch(entry, &new);
  56         } else {
  57                 jump_label_make_branch(entry, &old);
  58                 jump_label_make_nop(entry, &new);
  59         }
  60         if (memcmp(code, &old, sizeof(old)))
  61                 jump_label_bug(entry, &old, &new);
  62         s390_kernel_write(code, &new, sizeof(new));
  63 }
  64
  65 void arch_jump_label_transform(struct jump_entry *entry,
  66                                enum jump_label_type type)
  67 {
  68         jump_label_transform(entry, type);
  69         text_poke_sync();
  70 }
  71
  72 bool arch_jump_label_transform_queue(struct jump_entry *entry,
  73                                      enum jump_label_type type)
  74 {
  75         jump_label_transform(entry, type);
  76         return true;
  77 }
  78
  79 void arch_jump_label_transform_apply(void)
  80 {
  81         text_poke_sync();
  82 }