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
  18struct insn_args {
  19        struct jump_entry *entry;
  20        enum jump_label_type type;
  21};
  22
  23static 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
  30static 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
  37static 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
  51static struct insn orignop = {
  52        .opcode = 0xc004,
  53        .offset = JUMP_LABEL_NOP_OFFSET >> 1,
  54};
  55
  56static 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
  80static 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
  88void 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
  99void arch_jump_label_transform_static(struct jump_entry *entry,
 100                                      enum jump_label_type type)
 101{
 102        __jump_label_transform(entry, type, 1);
 103}
 104