xref: /openbmc/linux/arch/s390/kernel/jump_label.c (revision e7f127b2)
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 struct insn orignop = {
48 	.opcode = 0xc004,
49 	.offset = JUMP_LABEL_NOP_OFFSET >> 1,
50 };
51 
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 
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 
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 
90 void arch_jump_label_transform_apply(void)
91 {
92 	text_poke_sync();
93 }
94 
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