xref: /linux/arch/s390/kernel/jump_label.c (revision e0bf6c5ca2d3281f231c5f0c9bf145e9513644de)
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 
15 struct insn {
16 	u16 opcode;
17 	s32 offset;
18 } __packed;
19 
20 struct insn_args {
21 	struct jump_entry *entry;
22 	enum jump_label_type type;
23 };
24 
25 static 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 
32 static 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 
39 static 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 
56 static struct insn orignop = {
57 	.opcode = 0xc004,
58 	.offset = JUMP_LABEL_NOP_OFFSET >> 1,
59 };
60 
61 static 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 	probe_kernel_write((void *)entry->code, &new, sizeof(new));
82 }
83 
84 static 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 
92 void 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 
103 void 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