1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Early cpufeature override framework
4 *
5 * Copyright (C) 2020 Google LLC
6 * Author: Marc Zyngier <maz@kernel.org>
7 */
8
9 #include <linux/ctype.h>
10 #include <linux/kernel.h>
11 #include <linux/libfdt.h>
12
13 #include <asm/cacheflush.h>
14 #include <asm/cpufeature.h>
15 #include <asm/setup.h>
16
17 #define FTR_DESC_NAME_LEN 20
18 #define FTR_DESC_FIELD_LEN 10
19 #define FTR_ALIAS_NAME_LEN 30
20 #define FTR_ALIAS_OPTION_LEN 80
21
22 struct ftr_set_desc {
23 char name[FTR_DESC_NAME_LEN];
24 struct arm64_ftr_override *override;
25 struct {
26 char name[FTR_DESC_FIELD_LEN];
27 u8 shift;
28 } fields[];
29 };
30
31 static const struct ftr_set_desc mmfr1 __initconst = {
32 .name = "id_aa64mmfr1",
33 .override = &id_aa64mmfr1_override,
34 .fields = {
35 { "vh", ID_AA64MMFR1_VHE_SHIFT },
36 {}
37 },
38 };
39
40 static const struct ftr_set_desc pfr1 __initconst = {
41 .name = "id_aa64pfr1",
42 .override = &id_aa64pfr1_override,
43 .fields = {
44 { "bt", ID_AA64PFR1_BT_SHIFT },
45 { "mte", ID_AA64PFR1_MTE_SHIFT},
46 {}
47 },
48 };
49
50 static const struct ftr_set_desc isar1 __initconst = {
51 .name = "id_aa64isar1",
52 .override = &id_aa64isar1_override,
53 .fields = {
54 { "gpi", ID_AA64ISAR1_GPI_SHIFT },
55 { "gpa", ID_AA64ISAR1_GPA_SHIFT },
56 { "api", ID_AA64ISAR1_API_SHIFT },
57 { "apa", ID_AA64ISAR1_APA_SHIFT },
58 {}
59 },
60 };
61
62 extern struct arm64_ftr_override kaslr_feature_override;
63
64 static const struct ftr_set_desc kaslr __initconst = {
65 .name = "kaslr",
66 #ifdef CONFIG_RANDOMIZE_BASE
67 .override = &kaslr_feature_override,
68 #endif
69 .fields = {
70 { "disabled", 0 },
71 {}
72 },
73 };
74
75 static const struct ftr_set_desc * const regs[] __initconst = {
76 &mmfr1,
77 &pfr1,
78 &isar1,
79 &kaslr,
80 };
81
82 static const struct {
83 char alias[FTR_ALIAS_NAME_LEN];
84 char feature[FTR_ALIAS_OPTION_LEN];
85 } aliases[] __initconst = {
86 { "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
87 { "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
88 { "arm64.nobti", "id_aa64pfr1.bt=0" },
89 { "arm64.nopauth",
90 "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
91 "id_aa64isar1.api=0 id_aa64isar1.apa=0" },
92 { "arm64.nomte", "id_aa64pfr1.mte=0" },
93 { "nokaslr", "kaslr.disabled=1" },
94 };
95
find_field(const char * cmdline,const struct ftr_set_desc * reg,int f,u64 * v)96 static int __init find_field(const char *cmdline,
97 const struct ftr_set_desc *reg, int f, u64 *v)
98 {
99 char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
100 int len;
101
102 len = snprintf(opt, ARRAY_SIZE(opt), "%s.%s=",
103 reg->name, reg->fields[f].name);
104
105 if (!parameqn(cmdline, opt, len))
106 return -1;
107
108 return kstrtou64(cmdline + len, 0, v);
109 }
110
match_options(const char * cmdline)111 static void __init match_options(const char *cmdline)
112 {
113 int i;
114
115 for (i = 0; i < ARRAY_SIZE(regs); i++) {
116 int f;
117
118 if (!regs[i]->override)
119 continue;
120
121 for (f = 0; strlen(regs[i]->fields[f].name); f++) {
122 u64 shift = regs[i]->fields[f].shift;
123 u64 mask = 0xfUL << shift;
124 u64 v;
125
126 if (find_field(cmdline, regs[i], f, &v))
127 continue;
128
129 regs[i]->override->val &= ~mask;
130 regs[i]->override->val |= (v << shift) & mask;
131 regs[i]->override->mask |= mask;
132
133 return;
134 }
135 }
136 }
137
__parse_cmdline(const char * cmdline,bool parse_aliases)138 static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
139 {
140 do {
141 char buf[256];
142 size_t len;
143 int i;
144
145 cmdline = skip_spaces(cmdline);
146
147 for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++);
148 if (!len)
149 return;
150
151 len = min(len, ARRAY_SIZE(buf) - 1);
152 strncpy(buf, cmdline, len);
153 buf[len] = 0;
154
155 if (strcmp(buf, "--") == 0)
156 return;
157
158 cmdline += len;
159
160 match_options(buf);
161
162 for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++)
163 if (parameq(buf, aliases[i].alias))
164 __parse_cmdline(aliases[i].feature, false);
165 } while (1);
166 }
167
get_bootargs_cmdline(void)168 static __init const u8 *get_bootargs_cmdline(void)
169 {
170 const u8 *prop;
171 void *fdt;
172 int node;
173
174 fdt = get_early_fdt_ptr();
175 if (!fdt)
176 return NULL;
177
178 node = fdt_path_offset(fdt, "/chosen");
179 if (node < 0)
180 return NULL;
181
182 prop = fdt_getprop(fdt, node, "bootargs", NULL);
183 if (!prop)
184 return NULL;
185
186 return strlen(prop) ? prop : NULL;
187 }
188
parse_cmdline(void)189 static __init void parse_cmdline(void)
190 {
191 const u8 *prop = get_bootargs_cmdline();
192
193 if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
194 IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
195 !prop) {
196 __parse_cmdline(CONFIG_CMDLINE, true);
197 }
198
199 if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
200 __parse_cmdline(prop, true);
201 }
202
203 /* Keep checkers quiet */
204 void init_feature_override(void);
205
init_feature_override(void)206 asmlinkage void __init init_feature_override(void)
207 {
208 int i;
209
210 for (i = 0; i < ARRAY_SIZE(regs); i++) {
211 if (regs[i]->override) {
212 regs[i]->override->val = 0;
213 regs[i]->override->mask = 0;
214 }
215 }
216
217 parse_cmdline();
218
219 for (i = 0; i < ARRAY_SIZE(regs); i++) {
220 if (regs[i]->override)
221 __flush_dcache_area(regs[i]->override,
222 sizeof(*regs[i]->override));
223 }
224 }
225