1 // SPDX-License-Identifier: GPL-2.0 1
2 #include <linux/module.h>
3 #include <linux/device.h>
4 #include <linux/cpu.h>
5 #include <asm/nospec-branch.h>
6
7 int nobp = IS_ENABLED(CONFIG_KERNEL_NOBP);
8
9 static int __init nobp_setup_early(char *str)
10 {
11 bool enabled;
12 int rc;
13
14 rc = kstrtobool(str, &enabled);
15 if (rc)
16 return rc;
17 if (enabled && test_facility(82)) {
18 /*
19 * The user explicitly request
20 * disable the expoline suppor
21 */
22 nobp = 1;
23 if (IS_ENABLED(CONFIG_EXPOLINE
24 nospec_disable = 1;
25 } else {
26 nobp = 0;
27 }
28 return 0;
29 }
30 early_param("nobp", nobp_setup_early);
31
32 static int __init nospec_setup_early(char *str
33 {
34 nobp = 0;
35 return 0;
36 }
37 early_param("nospec", nospec_setup_early);
38
39 static int __init nospec_report(void)
40 {
41 if (test_facility(156))
42 pr_info("Spectre V2 mitigation
43 if (nospec_uses_trampoline())
44 pr_info("Spectre V2 mitigation
45 if (nobp_enabled())
46 pr_info("Spectre V2 mitigation
47 return 0;
48 }
49 arch_initcall(nospec_report);
50
51 #ifdef CONFIG_EXPOLINE
52
53 int nospec_disable = IS_ENABLED(CONFIG_EXPOLIN
54
55 static int __init nospectre_v2_setup_early(cha
56 {
57 nospec_disable = 1;
58 return 0;
59 }
60 early_param("nospectre_v2", nospectre_v2_setup
61
62 void __init nospec_auto_detect(void)
63 {
64 if (test_facility(156) || cpu_mitigati
65 /*
66 * The machine supports etoken
67 * Disable expolines and disab
68 */
69 if (__is_defined(CC_USING_EXPO
70 nospec_disable = 1;
71 nobp = 0;
72 } else if (__is_defined(CC_USING_EXPOL
73 /*
74 * The kernel has been compile
75 * Keep expolines enabled and
76 */
77 nospec_disable = 0;
78 nobp = 0;
79 }
80 /*
81 * If the kernel has not been compiled
82 * nobp setting decides what is done,
83 * CONFIG_KERNEL_NP option and the nob
84 */
85 }
86
87 static int __init spectre_v2_setup_early(char
88 {
89 if (str && !strncmp(str, "on", 2)) {
90 nospec_disable = 0;
91 nobp = 0;
92 }
93 if (str && !strncmp(str, "off", 3))
94 nospec_disable = 1;
95 if (str && !strncmp(str, "auto", 4))
96 nospec_auto_detect();
97 return 0;
98 }
99 early_param("spectre_v2", spectre_v2_setup_ear
100
101 static void __init_or_module __nospec_revert(s
102 {
103 enum { BRCL_EXPOLINE, BRASL_EXPOLINE }
104 static const u8 branch[] = { 0x47, 0x0
105 u8 *instr, *thunk, *br;
106 u8 insnbuf[6];
107 s32 *epo;
108
109 /* Second part of the instruction repl
110 memcpy(insnbuf + 2, branch, sizeof(bra
111 for (epo = start; epo < end; epo++) {
112 instr = (u8 *) epo + *epo;
113 if (instr[0] == 0xc0 && (instr
114 type = BRCL_EXPOLINE;
115 else if (instr[0] == 0xc0 && (
116 type = BRASL_EXPOLINE;
117 else
118 continue;
119 thunk = instr + (long)(*(int *
120 if (thunk[0] == 0xc6 && thunk[
121 /* exrl %r0,<target-br
122 br = thunk + (long)(*(
123 else
124 continue;
125 if (br[0] != 0x07 || (br[1] &
126 continue;
127 switch (type) {
128 case BRCL_EXPOLINE:
129 /* brcl to thunk, repl
130 insnbuf[0] = br[0];
131 insnbuf[1] = (instr[1]
132 break;
133 case BRASL_EXPOLINE:
134 /* brasl to thunk, rep
135 insnbuf[0] = 0x0d;
136 insnbuf[1] = (instr[1]
137 break;
138 }
139
140 s390_kernel_write(instr, insnb
141 }
142 }
143
144 void __init_or_module nospec_revert(s32 *start
145 {
146 if (nospec_disable)
147 __nospec_revert(start, end);
148 }
149
150 extern s32 __nospec_call_start[], __nospec_cal
151 extern s32 __nospec_return_start[], __nospec_r
152 void __init nospec_init_branches(void)
153 {
154 nospec_revert(__nospec_call_start, __n
155 nospec_revert(__nospec_return_start, _
156 }
157
158 #endif /* CONFIG_EXPOLINE */
159
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