arch/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 struct insn orignop = {
  48         .opcode = 0xc004,
  49         .offset = JUMP_LABEL_NOP_OFFSET >> 1,
  50 };
  51
  52 static void jump_label_transform(struct jump_entry *entry,
  53                                  enum jump_label_type type,
  54                                  int init)
  55 {
  56         void *code = (void *)jump_entry_code(entry);
  57         struct insn old, new;
  58
  59         if (type == JUMP_LABEL_JMP) {
  60                 jump_label_make_nop(entry, &old);
  61                 jump_label_make_branch(entry, &new);
  62         } else {
  63                 jump_label_make_branch(entry, &old);
  64                 jump_label_make_nop(entry, &new);
  65         }
  66         if (init) {
  67                 if (memcmp(code, &orignop, sizeof(orignop)))
  68                         jump_label_bug(entry, &orignop, &new);
  69         } else {
  70                 if (memcmp(code, &old, sizeof(old)))
  71                         jump_label_bug(entry, &old, &new);
  72         }
  73         s390_kernel_write(code, &new, sizeof(new));
  74 }
  75
  76 void arch_jump_label_transform(struct jump_entry *entry,
  77                                enum jump_label_type type)
  78 {
  79         jump_label_transform(entry, type, 0);
  80         text_poke_sync();
  81 }
  82
  83 bool arch_jump_label_transform_queue(struct jump_entry *entry,
  84                                      enum jump_label_type type)
  85 {
  86         jump_label_transform(entry, type, 0);
  87         return true;
  88 }
  89
  90 void arch_jump_label_transform_apply(void)
  91 {
  92         text_poke_sync();
  93 }
  94
  95 void __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
  96                                                        enum jump_label_type type)
  97 {
  98         jump_label_transform(entry, type, 1);
  99         text_poke_sync();
 100 }