LXR linux/arch/s390/kernel/jump

   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
  15struct insn {
  16        u16 opcode;
  17        s32 offset;
  18} __packed;
  19
  20struct insn_args {
  21        struct jump_entry *entry;
  22        enum jump_label_type type;
  23};
  24
  25static 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
  32static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
  33{
  34        /* brcl 15,offset */
  35        insn->opcode = 0xc0f4;
  36        insn->offset = (entry->target - entry->code) >> 1;
  37}
  38
  39static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
  40                           struct insn *new)
  41{
  42        unsigned char *ipc = (unsigned char *)entry->code;
  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
  53static struct insn orignop = {
  54        .opcode = 0xc004,
  55        .offset = JUMP_LABEL_NOP_OFFSET >> 1,
  56};
  57
  58static void __jump_label_transform(struct jump_entry *entry,
  59                                   enum jump_label_type type,
  60                                   int init)
  61{
  62        struct insn old, new;
  63
  64        if (type == JUMP_LABEL_JMP) {
  65                jump_label_make_nop(entry, &old);
  66                jump_label_make_branch(entry, &new);
  67        } else {
  68                jump_label_make_branch(entry, &old);
  69                jump_label_make_nop(entry, &new);
  70        }
  71        if (init) {
  72                if (memcmp((void *)entry->code, &orignop, sizeof(orignop)))
  73                        jump_label_bug(entry, &orignop, &new);
  74        } else {
  75                if (memcmp((void *)entry->code, &old, sizeof(old)))
  76                        jump_label_bug(entry, &old, &new);
  77        }
  78        s390_kernel_write((void *)entry->code, &new, sizeof(new));
  79}
  80
  81static int __sm_arch_jump_label_transform(void *data)
  82{
  83        struct insn_args *args = data;
  84
  85        __jump_label_transform(args->entry, args->type, 0);
  86        return 0;
  87}
  88
  89void arch_jump_label_transform(struct jump_entry *entry,
  90                               enum jump_label_type type)
  91{
  92        struct insn_args args;
  93
  94        args.entry = entry;
  95        args.type = type;
  96
  97        stop_machine_cpuslocked(__sm_arch_jump_label_transform, &args, NULL);
  98}
  99
 100void arch_jump_label_transform_static(struct jump_entry *entry,
 101                                      enum jump_label_type type)
 102{
 103        __jump_label_transform(entry, type, 1);
 104}
 105
 106#endif
 107