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 116
21
22 static u64 __boot_status __initdata;
23
24 struct ftr_set_desc {
25 char name[FTR_DESC_NAME_LEN];
26 struct arm64_ftr_override *override;
27 struct {
28 char name[FTR_DESC_FIELD_LEN];
29 u8 shift;
30 u8 width;
31 bool (*filter)(u64 val);
32 } fields[];
33 };
34
35 #define FIELD(n, s, f) { .name = n, .shift = s, .width = 4, .filter = f }
36
mmfr1_vh_filter(u64 val)37 static bool __init mmfr1_vh_filter(u64 val)
38 {
39 /*
40 * If we ever reach this point while running VHE, we're
41 * guaranteed to be on one of these funky, VHE-stuck CPUs. If
42 * the user was trying to force nVHE on us, proceed with
43 * attitude adjustment.
44 */
45 return !(__boot_status == (BOOT_CPU_FLAG_E2H | BOOT_CPU_MODE_EL2) &&
46 val == 0);
47 }
48
49 static const struct ftr_set_desc mmfr1 __initconst = {
50 .name = "id_aa64mmfr1",
51 .override = &id_aa64mmfr1_override,
52 .fields = {
53 FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT, mmfr1_vh_filter),
54 {}
55 },
56 };
57
pfr0_sve_filter(u64 val)58 static bool __init pfr0_sve_filter(u64 val)
59 {
60 /*
61 * Disabling SVE also means disabling all the features that
62 * are associated with it. The easiest way to do it is just to
63 * override id_aa64zfr0_el1 to be 0.
64 */
65 if (!val) {
66 id_aa64zfr0_override.val = 0;
67 id_aa64zfr0_override.mask = GENMASK(63, 0);
68 }
69
70 return true;
71 }
72
73 static const struct ftr_set_desc pfr0 __initconst = {
74 .name = "id_aa64pfr0",
75 .override = &id_aa64pfr0_override,
76 .fields = {
77 FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter),
78 {}
79 },
80 };
81
pfr1_sme_filter(u64 val)82 static bool __init pfr1_sme_filter(u64 val)
83 {
84 /*
85 * Similarly to SVE, disabling SME also means disabling all
86 * the features that are associated with it. Just set
87 * id_aa64smfr0_el1 to 0 and don't look back.
88 */
89 if (!val) {
90 id_aa64smfr0_override.val = 0;
91 id_aa64smfr0_override.mask = GENMASK(63, 0);
92 }
93
94 return true;
95 }
96
97 static const struct ftr_set_desc pfr1 __initconst = {
98 .name = "id_aa64pfr1",
99 .override = &id_aa64pfr1_override,
100 .fields = {
101 FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ),
102 FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL),
103 FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter),
104 {}
105 },
106 };
107
108 static const struct ftr_set_desc isar1 __initconst = {
109 .name = "id_aa64isar1",
110 .override = &id_aa64isar1_override,
111 .fields = {
112 FIELD("gpi", ID_AA64ISAR1_EL1_GPI_SHIFT, NULL),
113 FIELD("gpa", ID_AA64ISAR1_EL1_GPA_SHIFT, NULL),
114 FIELD("api", ID_AA64ISAR1_EL1_API_SHIFT, NULL),
115 FIELD("apa", ID_AA64ISAR1_EL1_APA_SHIFT, NULL),
116 {}
117 },
118 };
119
120 static const struct ftr_set_desc isar2 __initconst = {
121 .name = "id_aa64isar2",
122 .override = &id_aa64isar2_override,
123 .fields = {
124 FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL),
125 FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL),
126 {}
127 },
128 };
129
130 static const struct ftr_set_desc smfr0 __initconst = {
131 .name = "id_aa64smfr0",
132 .override = &id_aa64smfr0_override,
133 .fields = {
134 /* FA64 is a one bit field... :-/ */
135 { "fa64", ID_AA64SMFR0_EL1_FA64_SHIFT, 1, },
136 {}
137 },
138 };
139
140 extern struct arm64_ftr_override kaslr_feature_override;
141
142 static const struct ftr_set_desc kaslr __initconst = {
143 .name = "kaslr",
144 #ifdef CONFIG_RANDOMIZE_BASE
145 .override = &kaslr_feature_override,
146 #endif
147 .fields = {
148 FIELD("disabled", 0, NULL),
149 {}
150 },
151 };
152
153 static const struct ftr_set_desc * const regs[] __initconst = {
154 &mmfr1,
155 &pfr0,
156 &pfr1,
157 &isar1,
158 &isar2,
159 &smfr0,
160 &kaslr,
161 };
162
163 static const struct {
164 char alias[FTR_ALIAS_NAME_LEN];
165 char feature[FTR_ALIAS_OPTION_LEN];
166 } aliases[] __initconst = {
167 { "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
168 { "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
169 { "arm64.nosve", "id_aa64pfr0.sve=0 id_aa64pfr1.sme=0" },
170 { "arm64.nosme", "id_aa64pfr1.sme=0" },
171 { "arm64.nobti", "id_aa64pfr1.bt=0" },
172 { "arm64.nopauth",
173 "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
174 "id_aa64isar1.api=0 id_aa64isar1.apa=0 "
175 "id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0" },
176 { "arm64.nomte", "id_aa64pfr1.mte=0" },
177 { "nokaslr", "kaslr.disabled=1" },
178 };
179
find_field(const char * cmdline,const struct ftr_set_desc * reg,int f,u64 * v)180 static int __init find_field(const char *cmdline,
181 const struct ftr_set_desc *reg, int f, u64 *v)
182 {
183 char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
184 int len;
185
186 len = snprintf(opt, ARRAY_SIZE(opt), "%s.%s=",
187 reg->name, reg->fields[f].name);
188
189 if (!parameqn(cmdline, opt, len))
190 return -1;
191
192 return kstrtou64(cmdline + len, 0, v);
193 }
194
match_options(const char * cmdline)195 static void __init match_options(const char *cmdline)
196 {
197 int i;
198
199 for (i = 0; i < ARRAY_SIZE(regs); i++) {
200 int f;
201
202 if (!regs[i]->override)
203 continue;
204
205 for (f = 0; strlen(regs[i]->fields[f].name); f++) {
206 u64 shift = regs[i]->fields[f].shift;
207 u64 width = regs[i]->fields[f].width ?: 4;
208 u64 mask = GENMASK_ULL(shift + width - 1, shift);
209 u64 v;
210
211 if (find_field(cmdline, regs[i], f, &v))
212 continue;
213
214 /*
215 * If an override gets filtered out, advertise
216 * it by setting the value to the all-ones while
217 * clearing the mask... Yes, this is fragile.
218 */
219 if (regs[i]->fields[f].filter &&
220 !regs[i]->fields[f].filter(v)) {
221 regs[i]->override->val |= mask;
222 regs[i]->override->mask &= ~mask;
223 continue;
224 }
225
226 regs[i]->override->val &= ~mask;
227 regs[i]->override->val |= (v << shift) & mask;
228 regs[i]->override->mask |= mask;
229
230 return;
231 }
232 }
233 }
234
__parse_cmdline(const char * cmdline,bool parse_aliases)235 static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
236 {
237 do {
238 char buf[256];
239 size_t len;
240 int i;
241
242 cmdline = skip_spaces(cmdline);
243
244 for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++);
245 if (!len)
246 return;
247
248 len = min(len, ARRAY_SIZE(buf) - 1);
249 strncpy(buf, cmdline, len);
250 buf[len] = 0;
251
252 if (strcmp(buf, "--") == 0)
253 return;
254
255 cmdline += len;
256
257 match_options(buf);
258
259 for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++)
260 if (parameq(buf, aliases[i].alias))
261 __parse_cmdline(aliases[i].feature, false);
262 } while (1);
263 }
264
get_bootargs_cmdline(void)265 static __init const u8 *get_bootargs_cmdline(void)
266 {
267 const u8 *prop;
268 void *fdt;
269 int node;
270
271 fdt = get_early_fdt_ptr();
272 if (!fdt)
273 return NULL;
274
275 node = fdt_path_offset(fdt, "/chosen");
276 if (node < 0)
277 return NULL;
278
279 prop = fdt_getprop(fdt, node, "bootargs", NULL);
280 if (!prop)
281 return NULL;
282
283 return strlen(prop) ? prop : NULL;
284 }
285
parse_cmdline(void)286 static __init void parse_cmdline(void)
287 {
288 const u8 *prop = get_bootargs_cmdline();
289
290 if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
291 __parse_cmdline(CONFIG_CMDLINE, true);
292
293 if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
294 __parse_cmdline(prop, true);
295 }
296
297 /* Keep checkers quiet */
298 void init_feature_override(u64 boot_status);
299
init_feature_override(u64 boot_status)300 asmlinkage void __init init_feature_override(u64 boot_status)
301 {
302 int i;
303
304 for (i = 0; i < ARRAY_SIZE(regs); i++) {
305 if (regs[i]->override) {
306 regs[i]->override->val = 0;
307 regs[i]->override->mask = 0;
308 }
309 }
310
311 __boot_status = boot_status;
312
313 parse_cmdline();
314
315 for (i = 0; i < ARRAY_SIZE(regs); i++) {
316 if (regs[i]->override)
317 dcache_clean_inval_poc((unsigned long)regs[i]->override,
318 (unsigned long)regs[i]->override +
319 sizeof(*regs[i]->override));
320 }
321 }
322
