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/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 = (jump_entry_target(entry) - jump_entry_code(entry)) >> 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 *)jump_entry_code(entry);
  43         unsigned char *ipe = (unsigned char *)expected;
  44         unsigned char *ipn = (unsigned char *)new;
  45
  46         pr_emerg("Jump label code mismatch at %pS [%p]\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         void *code = (void *)jump_entry_code(entry);
  63         struct insn old, new;
  64
  65         if (type == JUMP_LABEL_JMP) {
  66                 jump_label_make_nop(entry, &old);
  67                 jump_label_make_branch(entry, &new);
  68         } else {
  69                 jump_label_make_branch(entry, &old);
  70                 jump_label_make_nop(entry, &new);
  71         }
  72         if (init) {
  73                 if (memcmp(code, &orignop, sizeof(orignop)))
  74                         jump_label_bug(entry, &orignop, &new);
  75         } else {
  76                 if (memcmp(code, &old, sizeof(old)))
  77                         jump_label_bug(entry, &old, &new);
  78         }
  79         s390_kernel_write(code, &new, sizeof(new));
  80 }
  81
  82 static int __sm_arch_jump_label_transform(void *data)
  83 {
  84         struct insn_args *args = data;
  85
  86         __jump_label_transform(args->entry, args->type, 0);
  87         return 0;
  88 }
  89
  90 void arch_jump_label_transform(struct jump_entry *entry,
  91                                enum jump_label_type type)
  92 {
  93         struct insn_args args;
  94
  95         args.entry = entry;
  96         args.type = type;
  97
  98         stop_machine_cpuslocked(__sm_arch_jump_label_transform, &args, NULL);
  99 }
 100
 101 void arch_jump_label_transform_static(struct jump_entry *entry,
 102                                       enum jump_label_type type)
 103 {
 104         __jump_label_transform(entry, type, 1);
 105 }
 106
 107 #endif