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
14static unsigned long mitigations __read_mostly = ~0UL;
15
16enum {
17	CLEAR_RESIDUALS = 0,
18};
19
20static const char * const names[] = {
21	[CLEAR_RESIDUALS] = "residuals",
22};
23
24bool i915_mitigate_clear_residuals(void)
25{
26	return READ_ONCE(mitigations) & BIT(CLEAR_RESIDUALS);
27}
28
29static 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
97static 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
126static const struct kernel_param_ops ops = {
127	.set = mitigations_set,
128	.get = mitigations_get,
129};
130
131module_param_cb_unsafe(mitigations, &ops, NULL, 0600);
132MODULE_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