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 #include "pi.h"
18
19 #define FTR_DESC_NAME_LEN 20
20 #define FTR_DESC_FIELD_LEN 10
21 #define FTR_ALIAS_NAME_LEN 30
22 #define FTR_ALIAS_OPTION_LEN 116
23
24 static u64 __boot_status __initdata;
25
26 typedef bool filter_t(u64 val);
27
28 struct ftr_set_desc {
29 char name[FTR_DESC_NAME_LEN];
30 PREL64(struct arm64_ftr_override, override);
31 struct {
32 char name[FTR_DESC_FIELD_LEN];
33 u8 shift;
34 u8 width;
35 PREL64(filter_t, filter);
36 } fields[];
37 };
38
39 #define FIELD(n, s, f) { .name = n, .shift = s, .width = 4, .filter = f }
40
41 static bool __init mmfr1_vh_filter(u64 val)
42 {
43 /*
44 * If we ever reach this point while running VHE, we're
45 * guaranteed to be on one of these funky, VHE-stuck CPUs. If
46 * the user was trying to force nVHE on us, proceed with
47 * attitude adjustment.
48 */
49 return !(__boot_status == (BOOT_CPU_FLAG_E2H | BOOT_CPU_MODE_EL2) &&
50 val == 0);
51 }
52
53 static const struct ftr_set_desc mmfr1 __prel64_initconst = {
54 .name = "id_aa64mmfr1",
55 .override = &id_aa64mmfr1_override,
56 .fields = {
57 FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT, mmfr1_vh_filter),
58 {}
59 },
60 };
61
62
63 static bool __init mmfr2_varange_filter(u64 val)
64 {
65 int __maybe_unused feat;
66
67 if (val)
68 return false;
69
70 #ifdef CONFIG_ARM64_LPA2
71 feat = cpuid_feature_extract_signed_field(read_sysreg(id_aa64mmfr0_el1),
72 ID_AA64MMFR0_EL1_TGRAN_SHIFT);
73 if (feat >= ID_AA64MMFR0_EL1_TGRAN_LPA2) {
74 id_aa64mmfr0_override.val |=
75 (ID_AA64MMFR0_EL1_TGRAN_LPA2 - 1) << ID_AA64MMFR0_EL1_TGRAN_SHIFT;
76 id_aa64mmfr0_override.mask |= 0xfU << ID_AA64MMFR0_EL1_TGRAN_SHIFT;
77 }
78 #endif
79 return true;
80 }
81
82 static const struct ftr_set_desc mmfr2 __prel64_initconst = {
83 .name = "id_aa64mmfr2",
84 .override = &id_aa64mmfr2_override,
85 .fields = {
86 FIELD("varange", ID_AA64MMFR2_EL1_VARange_SHIFT, mmfr2_varange_filter),
87 {}
88 },
89 };
90
91 static bool __init pfr0_sve_filter(u64 val)
92 {
93 /*
94 * Disabling SVE also means disabling all the features that
95 * are associated with it. The easiest way to do it is just to
96 * override id_aa64zfr0_el1 to be 0.
97 */
98 if (!val) {
99 id_aa64zfr0_override.val = 0;
100 id_aa64zfr0_override.mask = GENMASK(63, 0);
101 }
102
103 return true;
104 }
105
106 static const struct ftr_set_desc pfr0 __prel64_initconst = {
107 .name = "id_aa64pfr0",
108 .override = &id_aa64pfr0_override,
109 .fields = {
110 FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter),
111 FIELD("el0", ID_AA64PFR0_EL1_EL0_SHIFT, NULL),
112 {}
113 },
114 };
115
116 static bool __init pfr1_sme_filter(u64 val)
117 {
118 /*
119 * Similarly to SVE, disabling SME also means disabling all
120 * the features that are associated with it. Just set
121 * id_aa64smfr0_el1 to 0 and don't look back.
122 */
123 if (!val) {
124 id_aa64smfr0_override.val = 0;
125 id_aa64smfr0_override.mask = GENMASK(63, 0);
126 }
127
128 return true;
129 }
130
131 static const struct ftr_set_desc pfr1 __prel64_initconst = {
132 .name = "id_aa64pfr1",
133 .override = &id_aa64pfr1_override,
134 .fields = {
135 FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ),
136 FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL),
137 FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter),
138 {}
139 },
140 };
141
142 static const struct ftr_set_desc isar1 __prel64_initconst = {
143 .name = "id_aa64isar1",
144 .override = &id_aa64isar1_override,
145 .fields = {
146 FIELD("gpi", ID_AA64ISAR1_EL1_GPI_SHIFT, NULL),
147 FIELD("gpa", ID_AA64ISAR1_EL1_GPA_SHIFT, NULL),
148 FIELD("api", ID_AA64ISAR1_EL1_API_SHIFT, NULL),
149 FIELD("apa", ID_AA64ISAR1_EL1_APA_SHIFT, NULL),
150 {}
151 },
152 };
153
154 static const struct ftr_set_desc isar2 __prel64_initconst = {
155 .name = "id_aa64isar2",
156 .override = &id_aa64isar2_override,
157 .fields = {
158 FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL),
159 FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL),
160 FIELD("mops", ID_AA64ISAR2_EL1_MOPS_SHIFT, NULL),
161 {}
162 },
163 };
164
165 static const struct ftr_set_desc smfr0 __prel64_initconst = {
166 .name = "id_aa64smfr0",
167 .override = &id_aa64smfr0_override,
168 .fields = {
169 FIELD("smever", ID_AA64SMFR0_EL1_SMEver_SHIFT, NULL),
170 /* FA64 is a one bit field... :-/ */
171 { "fa64", ID_AA64SMFR0_EL1_FA64_SHIFT, 1, },
172 {}
173 },
174 };
175
176 static bool __init hvhe_filter(u64 val)
177 {
178 u64 mmfr1 = read_sysreg(id_aa64mmfr1_el1);
179
180 return (val == 1 &&
181 lower_32_bits(__boot_status) == BOOT_CPU_MODE_EL2 &&
182 cpuid_feature_extract_unsigned_field(mmfr1,
183 ID_AA64MMFR1_EL1_VH_SHIFT));
184 }
185
186 static const struct ftr_set_desc sw_features __prel64_initconst = {
187 .name = "arm64_sw",
188 .override = &arm64_sw_feature_override,
189 .fields = {
190 FIELD("nokaslr", ARM64_SW_FEATURE_OVERRIDE_NOKASLR, NULL),
191 FIELD("hvhe", ARM64_SW_FEATURE_OVERRIDE_HVHE, hvhe_filter),
192 FIELD("rodataoff", ARM64_SW_FEATURE_OVERRIDE_RODATA_OFF, NULL),
193 {}
194 },
195 };
196
197 static const
198 PREL64(const struct ftr_set_desc, reg) regs[] __prel64_initconst = {
199 { &mmfr1 },
200 { &mmfr2 },
201 { &pfr0 },
202 { &pfr1 },
203 { &isar1 },
204 { &isar2 },
205 { &smfr0 },
206 { &sw_features },
207 };
208
209 static const struct {
210 char alias[FTR_ALIAS_NAME_LEN];
211 char feature[FTR_ALIAS_OPTION_LEN];
212 } aliases[] __initconst = {
213 { "kvm_arm.mode=nvhe", "arm64_sw.hvhe=0 id_aa64mmfr1.vh=0" },
214 { "kvm_arm.mode=protected", "arm64_sw.hvhe=1" },
215 { "arm64.nosve", "id_aa64pfr0.sve=0" },
216 { "arm64.nosme", "id_aa64pfr1.sme=0" },
217 { "arm64.nobti", "id_aa64pfr1.bt=0" },
218 { "arm64.nopauth",
219 "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
220 "id_aa64isar1.api=0 id_aa64isar1.apa=0 "
221 "id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0" },
222 { "arm64.nomops", "id_aa64isar2.mops=0" },
223 { "arm64.nomte", "id_aa64pfr1.mte=0" },
224 { "nokaslr", "arm64_sw.nokaslr=1" },
225 { "rodata=off", "arm64_sw.rodataoff=1" },
226 { "arm64.nolva", "id_aa64mmfr2.varange=0" },
227 { "arm64.no32bit_el0", "id_aa64pfr0.el0=1" },
228 };
229
230 static int __init parse_hexdigit(const char *p, u64 *v)
231 {
232 // skip "0x" if it comes next
233 if (p[0] == '' && tolower(p[1]) == 'x')
234 p += 2;
235
236 // check whether the RHS is a single hex digit
237 if (!isxdigit(p[0]) || (p[1] && !isspace(p[1])))
238 return -EINVAL;
239
240 *v = tolower(*p) - (isdigit(*p) ? '' : 'a' - 10);
241 return 0;
242 }
243
244 static int __init find_field(const char *cmdline, char *opt, int len,
245 const struct ftr_set_desc *reg, int f, u64 *v)
246 {
247 int flen = strlen(reg->fields[f].name);
248
249 // append '<fieldname>=' to obtain '<name>.<fieldname>='
250 memcpy(opt + len, reg->fields[f].name, flen);
251 len += flen;
252 opt[len++] = '=';
253
254 if (memcmp(cmdline, opt, len))
255 return -1;
256
257 return parse_hexdigit(cmdline + len, v);
258 }
259
260 static void __init match_options(const char *cmdline)
261 {
262 char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
263 int i;
264
265 for (i = 0; i < ARRAY_SIZE(regs); i++) {
266 const struct ftr_set_desc *reg = prel64_pointer(regs[i].reg);
267 struct arm64_ftr_override *override;
268 int len = strlen(reg->name);
269 int f;
270
271 override = prel64_pointer(reg->override);
272
273 // set opt[] to '<name>.'
274 memcpy(opt, reg->name, len);
275 opt[len++] = '.';
276
277 for (f = 0; reg->fields[f].name[0] != '\0'; f++) {
278 u64 shift = reg->fields[f].shift;
279 u64 width = reg->fields[f].width ?: 4;
280 u64 mask = GENMASK_ULL(shift + width - 1, shift);
281 bool (*filter)(u64 val);
282 u64 v;
283
284 if (find_field(cmdline, opt, len, reg, f, &v))
285 continue;
286
287 /*
288 * If an override gets filtered out, advertise
289 * it by setting the value to the all-ones while
290 * clearing the mask... Yes, this is fragile.
291 */
292 filter = prel64_pointer(reg->fields[f].filter);
293 if (filter && !filter(v)) {
294 override->val |= mask;
295 override->mask &= ~mask;
296 continue;
297 }
298
299 override->val &= ~mask;
300 override->val |= (v << shift) & mask;
301 override->mask |= mask;
302
303 return;
304 }
305 }
306 }
307
308 static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
309 {
310 do {
311 char buf[256];
312 size_t len;
313 int i;
314
315 cmdline = skip_spaces(cmdline);
316
317 /* terminate on "--" appearing on the command line by itself */
318 if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
319 return;
320
321 for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++) {
322 if (len >= sizeof(buf) - 1)
323 break;
324 if (cmdline[len] == '-')
325 buf[len] = '_';
326 else
327 buf[len] = cmdline[len];
328 }
329 if (!len)
330 return;
331
332 buf[len] = 0;
333
334 cmdline += len;
335
336 match_options(buf);
337
338 for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++)
339 if (!memcmp(buf, aliases[i].alias, len + 1))
340 __parse_cmdline(aliases[i].feature, false);
341 } while (1);
342 }
343
344 static __init const u8 *get_bootargs_cmdline(const void *fdt, int node)
345 {
346 static char const bootargs[] __initconst = "bootargs";
347 const u8 *prop;
348
349 if (node < 0)
350 return NULL;
351
352 prop = fdt_getprop(fdt, node, bootargs, NULL);
353 if (!prop)
354 return NULL;
355
356 return strlen(prop) ? prop : NULL;
357 }
358
359 static __init void parse_cmdline(const void *fdt, int chosen)
360 {
361 static char const cmdline[] __initconst = CONFIG_CMDLINE;
362 const u8 *prop = get_bootargs_cmdline(fdt, chosen);
363
364 if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
365 __parse_cmdline(cmdline, true);
366
367 if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
368 __parse_cmdline(prop, true);
369 }
370
371 void __init init_feature_override(u64 boot_status, const void *fdt,
372 int chosen)
373 {
374 struct arm64_ftr_override *override;
375 const struct ftr_set_desc *reg;
376 int i;
377
378 for (i = 0; i < ARRAY_SIZE(regs); i++) {
379 reg = prel64_pointer(regs[i].reg);
380 override = prel64_pointer(reg->override);
381
382 override->val = 0;
383 override->mask = 0;
384 }
385
386 __boot_status = boot_status;
387
388 parse_cmdline(fdt, chosen);
389
390 for (i = 0; i < ARRAY_SIZE(regs); i++) {
391 reg = prel64_pointer(regs[i].reg);
392 override = prel64_pointer(reg->override);
393 dcache_clean_inval_poc((unsigned long)override,
394 (unsigned long)(override + 1));
395 }
396 }
397
398 char * __init skip_spaces(const char *str)
399 {
400 while (isspace(*str))
401 ++str;
402 return (char *)str;
403 }
404
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