1/*
2 * Jump label s390 support
3 *
4 * Copyright IBM Corp. 2011
5 * Author(s): Jan Glauber <jang@linux.vnet.ibm.com>
6 */
7#include <linux/module.h>
8#include <linux/uaccess.h>
9#include <linux/stop_machine.h>
10#include <linux/jump_label.h>
11#include <asm/ipl.h>
12
13#ifdef HAVE_JUMP_LABEL
14
15struct insn {
16	u16 opcode;
17	s32 offset;
18} __packed;
19
20struct insn_args {
21	struct jump_entry *entry;
22	enum jump_label_type type;
23};
24
25static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn)
26{
27	/* brcl 0,0 */
28	insn->opcode = 0xc004;
29	insn->offset = 0;
30}
31
32static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
33{
34	/* brcl 15,offset */
35	insn->opcode = 0xc0f4;
36	insn->offset = (entry->target - entry->code) >> 1;
37}
38
39static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
40			   struct insn *new)
41{
42	unsigned char *ipc = (unsigned char *)entry->code;
43	unsigned char *ipe = (unsigned char *)expected;
44	unsigned char *ipn = (unsigned char *)new;
45
46	pr_emerg("Jump label code mismatch at %pS [%p]\n", ipc, ipc);
47	pr_emerg("Found:    %02x %02x %02x %02x %02x %02x\n",
48		 ipc[0], ipc[1], ipc[2], ipc[3], ipc[4], ipc[5]);
49	pr_emerg("Expected: %02x %02x %02x %02x %02x %02x\n",
50		 ipe[0], ipe[1], ipe[2], ipe[3], ipe[4], ipe[5]);
51	pr_emerg("New:      %02x %02x %02x %02x %02x %02x\n",
52		 ipn[0], ipn[1], ipn[2], ipn[3], ipn[4], ipn[5]);
53	panic("Corrupted kernel text");
54}
55
56static struct insn orignop = {
57	.opcode = 0xc004,
58	.offset = JUMP_LABEL_NOP_OFFSET >> 1,
59};
60
61static void __jump_label_transform(struct jump_entry *entry,
62				   enum jump_label_type type,
63				   int init)
64{
65	struct insn old, new;
66
67	if (type == JUMP_LABEL_ENABLE) {
68		jump_label_make_nop(entry, &old);
69		jump_label_make_branch(entry, &new);
70	} else {
71		jump_label_make_branch(entry, &old);
72		jump_label_make_nop(entry, &new);
73	}
74	if (init) {
75		if (memcmp((void *)entry->code, &orignop, sizeof(orignop)))
76			jump_label_bug(entry, &orignop, &new);
77	} else {
78		if (memcmp((void *)entry->code, &old, sizeof(old)))
79			jump_label_bug(entry, &old, &new);
80	}
81	s390_kernel_write((void *)entry->code, &new, sizeof(new));
82}
83
84static int __sm_arch_jump_label_transform(void *data)
85{
86	struct insn_args *args = data;
87
88	__jump_label_transform(args->entry, args->type, 0);
89	return 0;
90}
91
92void arch_jump_label_transform(struct jump_entry *entry,
93			       enum jump_label_type type)
94{
95	struct insn_args args;
96
97	args.entry = entry;
98	args.type = type;
99
100	stop_machine(__sm_arch_jump_label_transform, &args, NULL);
101}
102
103void arch_jump_label_transform_static(struct jump_entry *entry,
104				      enum jump_label_type type)
105{
106	__jump_label_transform(entry, type, 1);
107}
108
109#endif
110