GNU Linux-libre 4.9.288-gnu1
[releases.git] / arch / s390 / kernel / jump_label.c
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 [%px]\n", ipc, ipc);
47         pr_emerg("Found:    %6ph\n", ipc);
48         pr_emerg("Expected: %6ph\n", ipe);
49         pr_emerg("New:      %6ph\n", ipn);
50         panic("Corrupted kernel text");
51 }
52
53 static struct insn orignop = {
54         .opcode = 0xc004,
55         .offset = JUMP_LABEL_NOP_OFFSET >> 1,
56 };
57
58 static void __jump_label_transform(struct jump_entry *entry,
59                                    enum jump_label_type type,
60                                    int init)
61 {
62         struct insn old, new;
63
64         if (type == JUMP_LABEL_JMP) {
65                 jump_label_make_nop(entry, &old);
66                 jump_label_make_branch(entry, &new);
67         } else {
68                 jump_label_make_branch(entry, &old);
69                 jump_label_make_nop(entry, &new);
70         }
71         if (init) {
72                 if (memcmp((void *)entry->code, &orignop, sizeof(orignop)))
73                         jump_label_bug(entry, &orignop, &new);
74         } else {
75                 if (memcmp((void *)entry->code, &old, sizeof(old)))
76                         jump_label_bug(entry, &old, &new);
77         }
78         s390_kernel_write((void *)entry->code, &new, sizeof(new));
79 }
80
81 static int __sm_arch_jump_label_transform(void *data)
82 {
83         struct insn_args *args = data;
84
85         __jump_label_transform(args->entry, args->type, 0);
86         return 0;
87 }
88
89 void arch_jump_label_transform(struct jump_entry *entry,
90                                enum jump_label_type type)
91 {
92         struct insn_args args;
93
94         args.entry = entry;
95         args.type = type;
96
97         stop_machine(__sm_arch_jump_label_transform, &args, NULL);
98 }
99
100 void arch_jump_label_transform_static(struct jump_entry *entry,
101                                       enum jump_label_type type)
102 {
103         __jump_label_transform(entry, type, 1);
104 }
105
106 #endif