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_driver.h"
12#include "i915_drv.h"
13#include "i915_mitigations.h"
14
15static unsigned long mitigations __read_mostly = ~0UL;
16
17enum {
18 CLEAR_RESIDUALS = 0,
19};
20
21static const char * const names[] = {
22 [CLEAR_RESIDUALS] = "residuals",
23};
24
25bool i915_mitigate_clear_residuals(void)
26{
27 return READ_ONCE(mitigations) & BIT(CLEAR_RESIDUALS);
28}
29
30static int mitigations_set(const char *val, const struct kernel_param *kp)
31{
32 unsigned long new = ~0UL;
33 char *str, *sep, *tok;
34 bool first = true;
35 int err = 0;
36
37 BUILD_BUG_ON(ARRAY_SIZE(names) >= BITS_PER_TYPE(mitigations));
38
39 str = kstrdup(s: val, GFP_KERNEL);
40 if (!str)
41 return -ENOMEM;
42
43 for (sep = str; (tok = strsep(&sep, ","));) {
44 bool enable = true;
45 int i;
46
47 /* Be tolerant of leading/trailing whitespace */
48 tok = strim(tok);
49
50 if (first) {
51 first = false;
52
53 if (!strcmp(tok, "auto"))
54 continue;
55
56 new = 0;
57 if (!strcmp(tok, "off"))
58 continue;
59 }
60
61 if (*tok == '!') {
62 enable = !enable;
63 tok++;
64 }
65
66 if (!strncmp(tok, "no", 2)) {
67 enable = !enable;
68 tok += 2;
69 }
70
71 if (*tok == '\0')
72 continue;
73
74 for (i = 0; i < ARRAY_SIZE(names); i++) {
75 if (!strcmp(tok, names[i])) {
76 if (enable)
77 new |= BIT(i);
78 else
79 new &= ~BIT(i);
80 break;
81 }
82 }
83 if (i == ARRAY_SIZE(names)) {
84 pr_err("Bad \"%s.mitigations=%s\", '%s' is unknown\n",
85 DRIVER_NAME, val, tok);
86 err = -EINVAL;
87 break;
88 }
89 }
90 kfree(objp: str);
91 if (err)
92 return err;
93
94 WRITE_ONCE(mitigations, new);
95 return 0;
96}
97
98static int mitigations_get(char *buffer, const struct kernel_param *kp)
99{
100 unsigned long local = READ_ONCE(mitigations);
101 int count, i;
102 bool enable;
103
104 if (!local)
105 return scnprintf(buf: buffer, PAGE_SIZE, fmt: "%s\n", "off");
106
107 if (local & BIT(BITS_PER_LONG - 1)) {
108 count = scnprintf(buf: buffer, PAGE_SIZE, fmt: "%s,", "auto");
109 enable = false;
110 } else {
111 enable = true;
112 count = 0;
113 }
114
115 for (i = 0; i < ARRAY_SIZE(names); i++) {
116 if ((local & BIT(i)) != enable)
117 continue;
118
119 count += scnprintf(buf: buffer + count, PAGE_SIZE - count,
120 fmt: "%s%s,", enable ? "" : "!", names[i]);
121 }
122
123 buffer[count - 1] = '\n';
124 return count;
125}
126
127static const struct kernel_param_ops ops = {
128 .set = mitigations_set,
129 .get = mitigations_get,
130};
131
132module_param_cb_unsafe(mitigations, &ops, NULL, 0600);
133MODULE_PARM_DESC(mitigations,
134"Selectively enable security mitigations for all Intel® GPUs in the system.\n"
135"\n"
136" auto -- enables all mitigations required for the platform [default]\n"
137" off -- disables all mitigations\n"
138"\n"
139"Individual mitigations can be enabled by passing a comma-separated string,\n"
140"e.g. mitigations=residuals to enable only clearing residuals or\n"
141"mitigations=auto,noresiduals to disable only the clear residual mitigation.\n"
142"Either '!' or 'no' may be used to switch from enabling the mitigation to\n"
143"disabling it.\n"
144"\n"
145"Active mitigations for Ivybridge, Baytrail, Haswell:\n"
146" residuals -- clear all thread-local registers between contexts"
147);
148