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(fmt: "Corrupted kernel text");
45}
46
47static void jump_label_transform(struct jump_entry *entry,
48 enum jump_label_type type)
49{
50 void *code = (void *)jump_entry_code(entry);
51 struct insn old, new;
52
53 if (type == JUMP_LABEL_JMP) {
54 jump_label_make_nop(entry, insn: &old);
55 jump_label_make_branch(entry, insn: &new);
56 } else {
57 jump_label_make_branch(entry, insn: &old);
58 jump_label_make_nop(entry, insn: &new);
59 }
60 if (memcmp(p: code, q: &old, size: sizeof(old)))
61 jump_label_bug(entry, expected: &old, new: &new);
62 s390_kernel_write(code, &new, sizeof(new));
63}
64
65void arch_jump_label_transform(struct jump_entry *entry,
66 enum jump_label_type type)
67{
68 jump_label_transform(entry, type);
69 text_poke_sync();
70}
71
72bool arch_jump_label_transform_queue(struct jump_entry *entry,
73 enum jump_label_type type)
74{
75 jump_label_transform(entry, type);
76 return true;
77}
78
79void arch_jump_label_transform_apply(void)
80{
81 text_poke_sync();
82}
83

source code of linux/arch/s390/kernel/jump_label.c