1 // SPDX-License-Identifier: GPL-2.0
3 * Early cpufeature override framework
5 * Copyright (C) 2020 Google LLC
6 * Author: Marc Zyngier <maz@kernel.org>
9 #include <linux/ctype.h>
10 #include <linux/kernel.h>
11 #include <linux/libfdt.h>
13 #include <asm/cacheflush.h>
14 #include <asm/cpufeature.h>
15 #include <asm/setup.h>
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
23 char name[FTR_DESC_NAME_LEN];
24 struct arm64_ftr_override *override;
26 char name[FTR_DESC_FIELD_LEN];
31 static const struct ftr_set_desc mmfr1 __initconst = {
32 .name = "id_aa64mmfr1",
33 .override = &id_aa64mmfr1_override,
35 { "vh", ID_AA64MMFR1_VHE_SHIFT },
40 static const struct ftr_set_desc pfr1 __initconst = {
41 .name = "id_aa64pfr1",
42 .override = &id_aa64pfr1_override,
44 { "bt", ID_AA64PFR1_BT_SHIFT },
49 static const struct ftr_set_desc isar1 __initconst = {
50 .name = "id_aa64isar1",
51 .override = &id_aa64isar1_override,
53 { "gpi", ID_AA64ISAR1_GPI_SHIFT },
54 { "gpa", ID_AA64ISAR1_GPA_SHIFT },
55 { "api", ID_AA64ISAR1_API_SHIFT },
56 { "apa", ID_AA64ISAR1_APA_SHIFT },
61 extern struct arm64_ftr_override kaslr_feature_override;
63 static const struct ftr_set_desc kaslr __initconst = {
65 #ifdef CONFIG_RANDOMIZE_BASE
66 .override = &kaslr_feature_override,
74 static const struct ftr_set_desc * const regs[] __initconst = {
82 char alias[FTR_ALIAS_NAME_LEN];
83 char feature[FTR_ALIAS_OPTION_LEN];
84 } aliases[] __initconst = {
85 { "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
86 { "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
87 { "arm64.nobti", "id_aa64pfr1.bt=0" },
89 "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
90 "id_aa64isar1.api=0 id_aa64isar1.apa=0" },
91 { "nokaslr", "kaslr.disabled=1" },
94 static int __init find_field(const char *cmdline,
95 const struct ftr_set_desc *reg, int f, u64 *v)
97 char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
100 len = snprintf(opt, ARRAY_SIZE(opt), "%s.%s=",
101 reg->name, reg->fields[f].name);
103 if (!parameqn(cmdline, opt, len))
106 return kstrtou64(cmdline + len, 0, v);
109 static void __init match_options(const char *cmdline)
113 for (i = 0; i < ARRAY_SIZE(regs); i++) {
116 if (!regs[i]->override)
119 for (f = 0; strlen(regs[i]->fields[f].name); f++) {
120 u64 shift = regs[i]->fields[f].shift;
121 u64 mask = 0xfUL << shift;
124 if (find_field(cmdline, regs[i], f, &v))
127 regs[i]->override->val &= ~mask;
128 regs[i]->override->val |= (v << shift) & mask;
129 regs[i]->override->mask |= mask;
136 static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
143 cmdline = skip_spaces(cmdline);
145 for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++);
149 len = min(len, ARRAY_SIZE(buf) - 1);
150 strncpy(buf, cmdline, len);
153 if (strcmp(buf, "--") == 0)
160 for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++)
161 if (parameq(buf, aliases[i].alias))
162 __parse_cmdline(aliases[i].feature, false);
166 static __init const u8 *get_bootargs_cmdline(void)
172 fdt = get_early_fdt_ptr();
176 node = fdt_path_offset(fdt, "/chosen");
180 prop = fdt_getprop(fdt, node, "bootargs", NULL);
184 return strlen(prop) ? prop : NULL;
187 static __init void parse_cmdline(void)
189 const u8 *prop = get_bootargs_cmdline();
191 if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
192 __parse_cmdline(CONFIG_CMDLINE, true);
194 if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
195 __parse_cmdline(prop, true);
198 /* Keep checkers quiet */
199 void init_feature_override(void);
201 asmlinkage void __init init_feature_override(void)
205 for (i = 0; i < ARRAY_SIZE(regs); i++) {
206 if (regs[i]->override) {
207 regs[i]->override->val = 0;
208 regs[i]->override->mask = 0;
214 for (i = 0; i < ARRAY_SIZE(regs); i++) {
215 if (regs[i]->override)
216 __flush_dcache_area(regs[i]->override,
217 sizeof(*regs[i]->override));