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1// SPDX-License-Identifier: GPL-2.0
2#include <linux/module.h>
3#include <linux/device.h>
4#include <linux/cpu.h>
5#include <asm/nospec-branch.h>
6
7static int __init nobp_setup_early(char *str)
8{
9 bool enabled;
10 int rc;
11
12 rc = kstrtobool(str, &enabled);
13 if (rc)
14 return rc;
15 if (enabled && test_facility(82)) {
16 /*
17 * The user explicitely requested nobp=1, enable it and
18 * disable the expoline support.
19 */
20 __set_facility(82, alt_stfle_fac_list);
21 if (IS_ENABLED(CONFIG_EXPOLINE))
22 nospec_disable = 1;
23 } else {
24 __clear_facility(82, alt_stfle_fac_list);
25 }
26 return 0;
27}
28early_param("nobp", nobp_setup_early);
29
30static int __init nospec_setup_early(char *str)
31{
32 __clear_facility(82, alt_stfle_fac_list);
33 return 0;
34}
35early_param("nospec", nospec_setup_early);
36
37static int __init nospec_report(void)
38{
39 if (test_facility(156))
40 pr_info("Spectre V2 mitigation: etokens\n");
41 if (nospec_uses_trampoline())
42 pr_info("Spectre V2 mitigation: execute trampolines\n");
43 if (__test_facility(82, alt_stfle_fac_list))
44 pr_info("Spectre V2 mitigation: limited branch prediction\n");
45 return 0;
46}
47arch_initcall(nospec_report);
48
49#ifdef CONFIG_EXPOLINE
50
51int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);
52
53static int __init nospectre_v2_setup_early(char *str)
54{
55 nospec_disable = 1;
56 return 0;
57}
58early_param("nospectre_v2", nospectre_v2_setup_early);
59
60void __init nospec_auto_detect(void)
61{
62 if (test_facility(156) || cpu_mitigations_off()) {
63 /*
64 * The machine supports etokens.
65 * Disable expolines and disable nobp.
66 */
67 if (__is_defined(CC_USING_EXPOLINE))
68 nospec_disable = 1;
69 __clear_facility(82, alt_stfle_fac_list);
70 } else if (__is_defined(CC_USING_EXPOLINE)) {
71 /*
72 * The kernel has been compiled with expolines.
73 * Keep expolines enabled and disable nobp.
74 */
75 nospec_disable = 0;
76 __clear_facility(82, alt_stfle_fac_list);
77 }
78 /*
79 * If the kernel has not been compiled with expolines the
80 * nobp setting decides what is done, this depends on the
81 * CONFIG_KERNEL_NP option and the nobp/nospec parameters.
82 */
83}
84
85static int __init spectre_v2_setup_early(char *str)
86{
87 if (str && !strncmp(str, "on", 2)) {
88 nospec_disable = 0;
89 __clear_facility(82, alt_stfle_fac_list);
90 }
91 if (str && !strncmp(str, "off", 3))
92 nospec_disable = 1;
93 if (str && !strncmp(str, "auto", 4))
94 nospec_auto_detect();
95 return 0;
96}
97early_param("spectre_v2", spectre_v2_setup_early);
98
99static void __init_or_module __nospec_revert(s32 *start, s32 *end)
100{
101 enum { BRCL_EXPOLINE, BRASL_EXPOLINE } type;
102 static const u8 branch[] = { 0x47, 0x00, 0x07, 0x00 };
103 u8 *instr, *thunk, *br;
104 u8 insnbuf[6];
105 s32 *epo;
106
107 /* Second part of the instruction replace is always a nop */
108 memcpy(insnbuf + 2, branch, sizeof(branch));
109 for (epo = start; epo < end; epo++) {
110 instr = (u8 *) epo + *epo;
111 if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04)
112 type = BRCL_EXPOLINE; /* brcl instruction */
113 else if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x05)
114 type = BRASL_EXPOLINE; /* brasl instruction */
115 else
116 continue;
117 thunk = instr + (*(int *)(instr + 2)) * 2;
118 if (thunk[0] == 0xc6 && thunk[1] == 0x00)
119 /* exrl %r0,<target-br> */
120 br = thunk + (*(int *)(thunk + 2)) * 2;
121 else
122 continue;
123 if (br[0] != 0x07 || (br[1] & 0xf0) != 0xf0)
124 continue;
125 switch (type) {
126 case BRCL_EXPOLINE:
127 /* brcl to thunk, replace with br + nop */
128 insnbuf[0] = br[0];
129 insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);
130 break;
131 case BRASL_EXPOLINE:
132 /* brasl to thunk, replace with basr + nop */
133 insnbuf[0] = 0x0d;
134 insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);
135 break;
136 }
137
138 s390_kernel_write(instr, insnbuf, 6);
139 }
140}
141
142void __init_or_module nospec_revert(s32 *start, s32 *end)
143{
144 if (nospec_disable)
145 __nospec_revert(start, end);
146}
147
148extern s32 __nospec_call_start[], __nospec_call_end[];
149extern s32 __nospec_return_start[], __nospec_return_end[];
150void __init nospec_init_branches(void)
151{
152 nospec_revert(__nospec_call_start, __nospec_call_end);
153 nospec_revert(__nospec_return_start, __nospec_return_end);
154}
155
156#endif /* CONFIG_EXPOLINE */
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/module.h>
3#include <linux/device.h>
4#include <asm/nospec-branch.h>
5
6static int __init nobp_setup_early(char *str)
7{
8 bool enabled;
9 int rc;
10
11 rc = kstrtobool(str, &enabled);
12 if (rc)
13 return rc;
14 if (enabled && test_facility(82)) {
15 /*
16 * The user explicitely requested nobp=1, enable it and
17 * disable the expoline support.
18 */
19 __set_facility(82, S390_lowcore.alt_stfle_fac_list);
20 if (IS_ENABLED(CONFIG_EXPOLINE))
21 nospec_disable = 1;
22 } else {
23 __clear_facility(82, S390_lowcore.alt_stfle_fac_list);
24 }
25 return 0;
26}
27early_param("nobp", nobp_setup_early);
28
29static int __init nospec_setup_early(char *str)
30{
31 __clear_facility(82, S390_lowcore.alt_stfle_fac_list);
32 return 0;
33}
34early_param("nospec", nospec_setup_early);
35
36static int __init nospec_report(void)
37{
38 if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable)
39 pr_info("Spectre V2 mitigation: execute trampolines.\n");
40 if (__test_facility(82, S390_lowcore.alt_stfle_fac_list))
41 pr_info("Spectre V2 mitigation: limited branch prediction.\n");
42 return 0;
43}
44arch_initcall(nospec_report);
45
46#ifdef CONFIG_EXPOLINE
47
48int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);
49
50static int __init nospectre_v2_setup_early(char *str)
51{
52 nospec_disable = 1;
53 return 0;
54}
55early_param("nospectre_v2", nospectre_v2_setup_early);
56
57void __init nospec_auto_detect(void)
58{
59 if (IS_ENABLED(CC_USING_EXPOLINE)) {
60 /*
61 * The kernel has been compiled with expolines.
62 * Keep expolines enabled and disable nobp.
63 */
64 nospec_disable = 0;
65 __clear_facility(82, S390_lowcore.alt_stfle_fac_list);
66 }
67 /*
68 * If the kernel has not been compiled with expolines the
69 * nobp setting decides what is done, this depends on the
70 * CONFIG_KERNEL_NP option and the nobp/nospec parameters.
71 */
72}
73
74static int __init spectre_v2_setup_early(char *str)
75{
76 if (str && !strncmp(str, "on", 2)) {
77 nospec_disable = 0;
78 __clear_facility(82, S390_lowcore.alt_stfle_fac_list);
79 }
80 if (str && !strncmp(str, "off", 3))
81 nospec_disable = 1;
82 if (str && !strncmp(str, "auto", 4))
83 nospec_auto_detect();
84 return 0;
85}
86early_param("spectre_v2", spectre_v2_setup_early);
87
88static void __init_or_module __nospec_revert(s32 *start, s32 *end)
89{
90 enum { BRCL_EXPOLINE, BRASL_EXPOLINE } type;
91 u8 *instr, *thunk, *br;
92 u8 insnbuf[6];
93 s32 *epo;
94
95 /* Second part of the instruction replace is always a nop */
96 for (epo = start; epo < end; epo++) {
97 instr = (u8 *) epo + *epo;
98 if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04)
99 type = BRCL_EXPOLINE; /* brcl instruction */
100 else if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x05)
101 type = BRASL_EXPOLINE; /* brasl instruction */
102 else
103 continue;
104 thunk = instr + (*(int *)(instr + 2)) * 2;
105 if (thunk[0] == 0xc6 && thunk[1] == 0x00)
106 /* exrl %r0,<target-br> */
107 br = thunk + (*(int *)(thunk + 2)) * 2;
108 else if (thunk[0] == 0xc0 && (thunk[1] & 0x0f) == 0x00 &&
109 thunk[6] == 0x44 && thunk[7] == 0x00 &&
110 (thunk[8] & 0x0f) == 0x00 && thunk[9] == 0x00 &&
111 (thunk[1] & 0xf0) == (thunk[8] & 0xf0))
112 /* larl %rx,<target br> + ex %r0,0(%rx) */
113 br = thunk + (*(int *)(thunk + 2)) * 2;
114 else
115 continue;
116 /* Check for unconditional branch 0x07f? or 0x47f???? */
117 if ((br[0] & 0xbf) != 0x07 || (br[1] & 0xf0) != 0xf0)
118 continue;
119
120 memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x07, 0x00 }, 4);
121 switch (type) {
122 case BRCL_EXPOLINE:
123 insnbuf[0] = br[0];
124 insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);
125 if (br[0] == 0x47) {
126 /* brcl to b, replace with bc + nopr */
127 insnbuf[2] = br[2];
128 insnbuf[3] = br[3];
129 } else {
130 /* brcl to br, replace with bcr + nop */
131 }
132 break;
133 case BRASL_EXPOLINE:
134 insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);
135 if (br[0] == 0x47) {
136 /* brasl to b, replace with bas + nopr */
137 insnbuf[0] = 0x4d;
138 insnbuf[2] = br[2];
139 insnbuf[3] = br[3];
140 } else {
141 /* brasl to br, replace with basr + nop */
142 insnbuf[0] = 0x0d;
143 }
144 break;
145 }
146
147 s390_kernel_write(instr, insnbuf, 6);
148 }
149}
150
151void __init_or_module nospec_revert(s32 *start, s32 *end)
152{
153 if (nospec_disable)
154 __nospec_revert(start, end);
155}
156
157extern s32 __nospec_call_start[], __nospec_call_end[];
158extern s32 __nospec_return_start[], __nospec_return_end[];
159void __init nospec_init_branches(void)
160{
161 nospec_revert(__nospec_call_start, __nospec_call_end);
162 nospec_revert(__nospec_return_start, __nospec_return_end);
163}
164
165#endif /* CONFIG_EXPOLINE */