1 // SPDX-License-Identifier: MIT
2 /*
3 * Copyright © 2021 Intel Corporation
4 */
5
6 #include <linux/kernel.h>
7 #include <linux/moduleparam.h>
8 #include <linux/slab.h>
9 #include <linux/string.h>
10
11 #include "i915_drv.h"
12 #include "i915_mitigations.h"
13
14 static unsigned long mitigations __read_mostly = ~0UL;
15
16 enum {
17 CLEAR_RESIDUALS = 0,
18 };
19
20 static const char * const names[] = {
21 [CLEAR_RESIDUALS] = "residuals",
22 };
23
i915_mitigate_clear_residuals(void)24 bool i915_mitigate_clear_residuals(void)
25 {
26 return READ_ONCE(mitigations) & BIT(CLEAR_RESIDUALS);
27 }
28
mitigations_set(const char * val,const struct kernel_param * kp)29 static int mitigations_set(const char *val, const struct kernel_param *kp)
30 {
31 unsigned long new = ~0UL;
32 char *str, *sep, *tok;
33 bool first = true;
34 int err = 0;
35
36 BUILD_BUG_ON(ARRAY_SIZE(names) >= BITS_PER_TYPE(mitigations));
37
38 str = kstrdup(val, GFP_KERNEL);
39 if (!str)
40 return -ENOMEM;
41
42 for (sep = str; (tok = strsep(&sep, ","));) {
43 bool enable = true;
44 int i;
45
46 /* Be tolerant of leading/trailing whitespace */
47 tok = strim(tok);
48
49 if (first) {
50 first = false;
51
52 if (!strcmp(tok, "auto"))
53 continue;
54
55 new = 0;
56 if (!strcmp(tok, "off"))
57 continue;
58 }
59
60 if (*tok == '!') {
61 enable = !enable;
62 tok++;
63 }
64
65 if (!strncmp(tok, "no", 2)) {
66 enable = !enable;
67 tok += 2;
68 }
69
70 if (*tok == '\0')
71 continue;
72
73 for (i = 0; i < ARRAY_SIZE(names); i++) {
74 if (!strcmp(tok, names[i])) {
75 if (enable)
76 new |= BIT(i);
77 else
78 new &= ~BIT(i);
79 break;
80 }
81 }
82 if (i == ARRAY_SIZE(names)) {
83 pr_err("Bad \"%s.mitigations=%s\", '%s' is unknown\n",
84 DRIVER_NAME, val, tok);
85 err = -EINVAL;
86 break;
87 }
88 }
89 kfree(str);
90 if (err)
91 return err;
92
93 WRITE_ONCE(mitigations, new);
94 return 0;
95 }
96
mitigations_get(char * buffer,const struct kernel_param * kp)97 static int mitigations_get(char *buffer, const struct kernel_param *kp)
98 {
99 unsigned long local = READ_ONCE(mitigations);
100 int count, i;
101 bool enable;
102
103 if (!local)
104 return scnprintf(buffer, PAGE_SIZE, "%s\n", "off");
105
106 if (local & BIT(BITS_PER_LONG - 1)) {
107 count = scnprintf(buffer, PAGE_SIZE, "%s,", "auto");
108 enable = false;
109 } else {
110 enable = true;
111 count = 0;
112 }
113
114 for (i = 0; i < ARRAY_SIZE(names); i++) {
115 if ((local & BIT(i)) != enable)
116 continue;
117
118 count += scnprintf(buffer + count, PAGE_SIZE - count,
119 "%s%s,", enable ? "" : "!", names[i]);
120 }
121
122 buffer[count - 1] = '\n';
123 return count;
124 }
125
126 static const struct kernel_param_ops ops = {
127 .set = mitigations_set,
128 .get = mitigations_get,
129 };
130
131 module_param_cb_unsafe(mitigations, &ops, NULL, 0600);
132 MODULE_PARM_DESC(mitigations,
133 "Selectively enable security mitigations for all Intel® GPUs in the system.\n"
134 "\n"
135 " auto -- enables all mitigations required for the platform [default]\n"
136 " off -- disables all mitigations\n"
137 "\n"
138 "Individual mitigations can be enabled by passing a comma-separated string,\n"
139 "e.g. mitigations=residuals to enable only clearing residuals or\n"
140 "mitigations=auto,noresiduals to disable only the clear residual mitigation.\n"
141 "Either '!' or 'no' may be used to switch from enabling the mitigation to\n"
142 "disabling it.\n"
143 "\n"
144 "Active mitigations for Ivybridge, Baytrail, Haswell:\n"
145 " residuals -- clear all thread-local registers between contexts"
146 );
147