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
jump_label_make_nop(struct jump_entry * entry,struct insn * insn)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
jump_label_make_branch(struct jump_entry * entry,struct insn * insn)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
jump_label_bug(struct jump_entry * entry,struct insn * expected,struct insn * new)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 struct insn orignop = {
48 .opcode = 0xc004,
49 .offset = JUMP_LABEL_NOP_OFFSET >> 1,
50 };
51
jump_label_transform(struct jump_entry * entry,enum jump_label_type type,int init)52 static 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
arch_jump_label_transform(struct jump_entry * entry,enum jump_label_type type)76 void 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
arch_jump_label_transform_queue(struct jump_entry * entry,enum jump_label_type type)83 bool 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
arch_jump_label_transform_apply(void)90 void arch_jump_label_transform_apply(void)
91 {
92 text_poke_sync();
93 }
94
arch_jump_label_transform_static(struct jump_entry * entry,enum jump_label_type type)95 void __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