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/jump_label.h>
  10#include <linux/module.h>
  11#include <asm/text-patching.h>
  12#include <asm/ipl.h>
  13
  14struct insn {
  15        u16 opcode;
  16        s32 offset;
  17} __packed;
  18
  19static 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
  26static 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
  33static 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
  47static struct insn orignop = {
  48        .opcode = 0xc004,
  49        .offset = JUMP_LABEL_NOP_OFFSET >> 1,
  50};
  51
  52static 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
  76void 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
  83bool 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
  90void arch_jump_label_transform_apply(void)
  91{
  92        text_poke_sync();
  93}
  94
  95void __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}
 101