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
  13struct insn {
  14        u16 opcode;
  15        s32 offset;
  16} __packed;
  17
  18static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn)
  19{
  20        /* brcl 0,offset */
  21        insn->opcode = 0xc004;
  22        insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
  23}
  24
  25static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
  26{
  27        /* brcl 15,offset */
  28        insn->opcode = 0xc0f4;
  29        insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
  30}
  31
  32static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
  33                           struct insn *new)
  34{
  35        unsigned char *ipc = (unsigned char *)jump_entry_code(entry);
  36        unsigned char *ipe = (unsigned char *)expected;
  37        unsigned char *ipn = (unsigned char *)new;
  38
  39        pr_emerg("Jump label code mismatch at %pS [%p]\n", ipc, ipc);
  40        pr_emerg("Found:    %6ph\n", ipc);
  41        pr_emerg("Expected: %6ph\n", ipe);
  42        pr_emerg("New:      %6ph\n", ipn);
  43        panic("Corrupted kernel text");
  44}
  45
  46static struct insn orignop = {
  47        .opcode = 0xc004,
  48        .offset = JUMP_LABEL_NOP_OFFSET >> 1,
  49};
  50
  51static void __jump_label_transform(struct jump_entry *entry,
  52                                   enum jump_label_type type,
  53                                   int init)
  54{
  55        void *code = (void *)jump_entry_code(entry);
  56        struct insn old, new;
  57
  58        if (type == JUMP_LABEL_JMP) {
  59                jump_label_make_nop(entry, &old);
  60                jump_label_make_branch(entry, &new);
  61        } else {
  62                jump_label_make_branch(entry, &old);
  63                jump_label_make_nop(entry, &new);
  64        }
  65        if (init) {
  66                if (memcmp(code, &orignop, sizeof(orignop)))
  67                        jump_label_bug(entry, &orignop, &new);
  68        } else {
  69                if (memcmp(code, &old, sizeof(old)))
  70                        jump_label_bug(entry, &old, &new);
  71        }
  72        s390_kernel_write(code, &new, sizeof(new));
  73}
  74
  75static void __jump_label_sync(void *dummy)
  76{
  77}
  78
  79void arch_jump_label_transform(struct jump_entry *entry,
  80                               enum jump_label_type type)
  81{
  82        __jump_label_transform(entry, type, 0);
  83        smp_call_function(__jump_label_sync, NULL, 1);
  84}
  85
  86void arch_jump_label_transform_static(struct jump_entry *entry,
  87                                      enum jump_label_type type)
  88{
  89        __jump_label_transform(entry, type, 1);
  90}
  91