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
14 struct insn {
15 u16 opcode;
16 s32 offset;
17 } __packed;
18
19 static 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
26 static 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
33 static 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
47 static 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, &old);
55 jump_label_make_branch(entry, &new);
56 } else {
57 jump_label_make_branch(entry, &old);
58 jump_label_make_nop(entry, &new);
59 }
60 if (memcmp(code, &old, sizeof(old)))
61 jump_label_bug(entry, &old, &new);
62 s390_kernel_write(code, &new, sizeof(new));
63 }
64
65 void 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
72 bool 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
79 void arch_jump_label_transform_apply(void)
80 {
81 text_poke_sync();
82 }
83
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