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 struct insn {
  14         u16 opcode;
  15         s32 offset;
  16 } __packed;
  17
  18 struct insn_args {
  19         struct jump_entry *entry;
  20         enum jump_label_type type;
  21 };
  22
  23 static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn)
  24 {
  25         /* brcl 0,0 */
  26         insn->opcode = 0xc004;
  27         insn->offset = 0;
  28 }
  29
  30 static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
  31 {
  32         /* brcl 15,offset */
  33         insn->opcode = 0xc0f4;
  34         insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
  35 }
  36
  37 static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
  38                            struct insn *new)
  39 {
  40         unsigned char *ipc = (unsigned char *)jump_entry_code(entry);
  41         unsigned char *ipe = (unsigned char *)expected;
  42         unsigned char *ipn = (unsigned char *)new;
  43
  44         pr_emerg("Jump label code mismatch at %pS [%p]\n", ipc, ipc);
  45         pr_emerg("Found:    %6ph\n", ipc);
  46         pr_emerg("Expected: %6ph\n", ipe);
  47         pr_emerg("New:      %6ph\n", ipn);
  48         panic("Corrupted kernel text");
  49 }
  50
  51 static struct insn orignop = {
  52         .opcode = 0xc004,
  53         .offset = JUMP_LABEL_NOP_OFFSET >> 1,
  54 };
  55
  56 static void __jump_label_transform(struct jump_entry *entry,
  57                                    enum jump_label_type type,
  58                                    int init)
  59 {
  60         void *code = (void *)jump_entry_code(entry);
  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(code, &orignop, sizeof(orignop)))
  72                         jump_label_bug(entry, &orignop, &new);
  73         } else {
  74                 if (memcmp(code, &old, sizeof(old)))
  75                         jump_label_bug(entry, &old, &new);
  76         }
  77         s390_kernel_write(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 }