xref: /openbmc/linux/arch/s390/kernel/jump_label.c (revision 7e6b9db2)
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 
jump_label_transform(struct jump_entry * entry,enum jump_label_type type)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 
arch_jump_label_transform(struct jump_entry * entry,enum jump_label_type type)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 
arch_jump_label_transform_queue(struct jump_entry * entry,enum jump_label_type type)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 
arch_jump_label_transform_apply(void)79 void arch_jump_label_transform_apply(void)
80 {
81 	text_poke_sync();
82 }
83