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
24static u64 __boot_status __initdata;
25
26typedef bool filter_t(u64 val);
27
28struct 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
41static 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
53static 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
63static 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
82static 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
91static 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
106static 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 {}
112 },
113};
114
115static bool __init pfr1_sme_filter(u64 val)
116{
117 /*
118 * Similarly to SVE, disabling SME also means disabling all
119 * the features that are associated with it. Just set
120 * id_aa64smfr0_el1 to 0 and don't look back.
121 */
122 if (!val) {
123 id_aa64smfr0_override.val = 0;
124 id_aa64smfr0_override.mask = GENMASK(63, 0);
125 }
126
127 return true;
128}
129
130static const struct ftr_set_desc pfr1 __prel64_initconst = {
131 .name = "id_aa64pfr1",
132 .override = &id_aa64pfr1_override,
133 .fields = {
134 FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ),
135 FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL),
136 FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter),
137 {}
138 },
139};
140
141static const struct ftr_set_desc isar1 __prel64_initconst = {
142 .name = "id_aa64isar1",
143 .override = &id_aa64isar1_override,
144 .fields = {
145 FIELD("gpi", ID_AA64ISAR1_EL1_GPI_SHIFT, NULL),
146 FIELD("gpa", ID_AA64ISAR1_EL1_GPA_SHIFT, NULL),
147 FIELD("api", ID_AA64ISAR1_EL1_API_SHIFT, NULL),
148 FIELD("apa", ID_AA64ISAR1_EL1_APA_SHIFT, NULL),
149 {}
150 },
151};
152
153static const struct ftr_set_desc isar2 __prel64_initconst = {
154 .name = "id_aa64isar2",
155 .override = &id_aa64isar2_override,
156 .fields = {
157 FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL),
158 FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL),
159 FIELD("mops", ID_AA64ISAR2_EL1_MOPS_SHIFT, NULL),
160 {}
161 },
162};
163
164static const struct ftr_set_desc smfr0 __prel64_initconst = {
165 .name = "id_aa64smfr0",
166 .override = &id_aa64smfr0_override,
167 .fields = {
168 FIELD("smever", ID_AA64SMFR0_EL1_SMEver_SHIFT, NULL),
169 /* FA64 is a one bit field... :-/ */
170 { "fa64", ID_AA64SMFR0_EL1_FA64_SHIFT, 1, },
171 {}
172 },
173};
174
175static bool __init hvhe_filter(u64 val)
176{
177 u64 mmfr1 = read_sysreg(id_aa64mmfr1_el1);
178
179 return (val == 1 &&
180 lower_32_bits(__boot_status) == BOOT_CPU_MODE_EL2 &&
181 cpuid_feature_extract_unsigned_field(mmfr1,
182 ID_AA64MMFR1_EL1_VH_SHIFT));
183}
184
185static const struct ftr_set_desc sw_features __prel64_initconst = {
186 .name = "arm64_sw",
187 .override = &arm64_sw_feature_override,
188 .fields = {
189 FIELD("nokaslr", ARM64_SW_FEATURE_OVERRIDE_NOKASLR, NULL),
190 FIELD("hvhe", ARM64_SW_FEATURE_OVERRIDE_HVHE, hvhe_filter),
191 FIELD("rodataoff", ARM64_SW_FEATURE_OVERRIDE_RODATA_OFF, NULL),
192 {}
193 },
194};
195
196static const
197PREL64(const struct ftr_set_desc, reg) regs[] __prel64_initconst = {
198 { .reg: &mmfr1 },
199 { &mmfr2 },
200 { &pfr0 },
201 { &pfr1 },
202 { &isar1 },
203 { &isar2 },
204 { &smfr0 },
205 { &sw_features },
206};
207
208static const struct {
209 char alias[FTR_ALIAS_NAME_LEN];
210 char feature[FTR_ALIAS_OPTION_LEN];
211} aliases[] __initconst = {
212 { "kvm_arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
213 { "kvm_arm.mode=protected", "id_aa64mmfr1.vh=0" },
214 { "arm64.nosve", "id_aa64pfr0.sve=0" },
215 { "arm64.nosme", "id_aa64pfr1.sme=0" },
216 { "arm64.nobti", "id_aa64pfr1.bt=0" },
217 { "arm64.nopauth",
218 "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
219 "id_aa64isar1.api=0 id_aa64isar1.apa=0 "
220 "id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0" },
221 { "arm64.nomops", "id_aa64isar2.mops=0" },
222 { "arm64.nomte", "id_aa64pfr1.mte=0" },
223 { "nokaslr", "arm64_sw.nokaslr=1" },
224 { "rodata=off", "arm64_sw.rodataoff=1" },
225 { "arm64.nolva", "id_aa64mmfr2.varange=0" },
226};
227
228static int __init parse_hexdigit(const char *p, u64 *v)
229{
230 // skip "0x" if it comes next
231 if (p[0] == '0' && tolower(p[1]) == 'x')
232 p += 2;
233
234 // check whether the RHS is a single hex digit
235 if (!isxdigit(p[0]) || (p[1] && !isspace(p[1])))
236 return -EINVAL;
237
238 *v = tolower(*p) - (isdigit(c: *p) ? '0' : 'a' - 10);
239 return 0;
240}
241
242static int __init find_field(const char *cmdline, char *opt, int len,
243 const struct ftr_set_desc *reg, int f, u64 *v)
244{
245 int flen = strlen(reg->fields[f].name);
246
247 // append '<fieldname>=' to obtain '<name>.<fieldname>='
248 memcpy(opt + len, reg->fields[f].name, flen);
249 len += flen;
250 opt[len++] = '=';
251
252 if (memcmp(p: cmdline, q: opt, size: len))
253 return -1;
254
255 return parse_hexdigit(p: cmdline + len, v);
256}
257
258static void __init match_options(const char *cmdline)
259{
260 char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
261 int i;
262
263 for (i = 0; i < ARRAY_SIZE(regs); i++) {
264 const struct ftr_set_desc *reg = prel64_pointer(regs[i].reg);
265 struct arm64_ftr_override *override;
266 int len = strlen(reg->name);
267 int f;
268
269 override = prel64_pointer(reg->override);
270
271 // set opt[] to '<name>.'
272 memcpy(opt, reg->name, len);
273 opt[len++] = '.';
274
275 for (f = 0; reg->fields[f].name[0] != '\0'; f++) {
276 u64 shift = reg->fields[f].shift;
277 u64 width = reg->fields[f].width ?: 4;
278 u64 mask = GENMASK_ULL(shift + width - 1, shift);
279 bool (*filter)(u64 val);
280 u64 v;
281
282 if (find_field(cmdline, opt, len, reg, f, v: &v))
283 continue;
284
285 /*
286 * If an override gets filtered out, advertise
287 * it by setting the value to the all-ones while
288 * clearing the mask... Yes, this is fragile.
289 */
290 filter = prel64_pointer(reg->fields[f].filter);
291 if (filter && !filter(v)) {
292 override->val |= mask;
293 override->mask &= ~mask;
294 continue;
295 }
296
297 override->val &= ~mask;
298 override->val |= (v << shift) & mask;
299 override->mask |= mask;
300
301 return;
302 }
303 }
304}
305
306static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
307{
308 do {
309 char buf[256];
310 size_t len;
311 int i;
312
313 cmdline = skip_spaces(cmdline);
314
315 /* terminate on "--" appearing on the command line by itself */
316 if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
317 return;
318
319 for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++) {
320 if (len >= sizeof(buf) - 1)
321 break;
322 if (cmdline[len] == '-')
323 buf[len] = '_';
324 else
325 buf[len] = cmdline[len];
326 }
327 if (!len)
328 return;
329
330 buf[len] = 0;
331
332 cmdline += len;
333
334 match_options(cmdline: buf);
335
336 for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++)
337 if (!memcmp(p: buf, q: aliases[i].alias, size: len + 1))
338 __parse_cmdline(cmdline: aliases[i].feature, parse_aliases: false);
339 } while (1);
340}
341
342static __init const u8 *get_bootargs_cmdline(const void *fdt, int node)
343{
344 static char const bootargs[] __initconst = "bootargs";
345 const u8 *prop;
346
347 if (node < 0)
348 return NULL;
349
350 prop = fdt_getprop(fdt, nodeoffset: node, name: bootargs, NULL);
351 if (!prop)
352 return NULL;
353
354 return strlen(prop) ? prop : NULL;
355}
356
357static __init void parse_cmdline(const void *fdt, int chosen)
358{
359 static char const cmdline[] __initconst = CONFIG_CMDLINE;
360 const u8 *prop = get_bootargs_cmdline(fdt, node: chosen);
361
362 if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
363 __parse_cmdline(cmdline, parse_aliases: true);
364
365 if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
366 __parse_cmdline(cmdline: prop, parse_aliases: true);
367}
368
369void __init init_feature_override(u64 boot_status, const void *fdt,
370 int chosen)
371{
372 struct arm64_ftr_override *override;
373 const struct ftr_set_desc *reg;
374 int i;
375
376 for (i = 0; i < ARRAY_SIZE(regs); i++) {
377 reg = prel64_pointer(regs[i].reg);
378 override = prel64_pointer(reg->override);
379
380 override->val = 0;
381 override->mask = 0;
382 }
383
384 __boot_status = boot_status;
385
386 parse_cmdline(fdt, chosen);
387
388 for (i = 0; i < ARRAY_SIZE(regs); i++) {
389 reg = prel64_pointer(regs[i].reg);
390 override = prel64_pointer(reg->override);
391 dcache_clean_inval_poc((unsigned long)override,
392 (unsigned long)(override + 1));
393 }
394}
395
396char * __init skip_spaces(const char *str)
397{
398 while (isspace(*str))
399 ++str;
400 return (char *)str;
401}
402

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source code of linux/arch/arm64/kernel/pi/idreg-override.c