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];
28 bool (*filter)(u64 val);
32 static bool __init mmfr1_vh_filter(u64 val)
35 * If we ever reach this point while running VHE, we're
36 * guaranteed to be on one of these funky, VHE-stuck CPUs. If
37 * the user was trying to force nVHE on us, proceed with
38 * attitude adjustment.
40 return !(is_kernel_in_hyp_mode() && val == 0);
43 static const struct ftr_set_desc mmfr1 __initconst = {
44 .name = "id_aa64mmfr1",
45 .override = &id_aa64mmfr1_override,
47 { "vh", ID_AA64MMFR1_VHE_SHIFT, mmfr1_vh_filter },
52 static const struct ftr_set_desc pfr1 __initconst = {
53 .name = "id_aa64pfr1",
54 .override = &id_aa64pfr1_override,
56 { "bt", ID_AA64PFR1_BT_SHIFT },
61 static const struct ftr_set_desc isar1 __initconst = {
62 .name = "id_aa64isar1",
63 .override = &id_aa64isar1_override,
65 { "gpi", ID_AA64ISAR1_GPI_SHIFT },
66 { "gpa", ID_AA64ISAR1_GPA_SHIFT },
67 { "api", ID_AA64ISAR1_API_SHIFT },
68 { "apa", ID_AA64ISAR1_APA_SHIFT },
73 extern struct arm64_ftr_override kaslr_feature_override;
75 static const struct ftr_set_desc kaslr __initconst = {
77 #ifdef CONFIG_RANDOMIZE_BASE
78 .override = &kaslr_feature_override,
86 static const struct ftr_set_desc * const regs[] __initconst = {
94 char alias[FTR_ALIAS_NAME_LEN];
95 char feature[FTR_ALIAS_OPTION_LEN];
96 } aliases[] __initconst = {
97 { "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
98 { "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
99 { "arm64.nobti", "id_aa64pfr1.bt=0" },
101 "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
102 "id_aa64isar1.api=0 id_aa64isar1.apa=0" },
103 { "nokaslr", "kaslr.disabled=1" },
106 static int __init find_field(const char *cmdline,
107 const struct ftr_set_desc *reg, int f, u64 *v)
109 char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
112 len = snprintf(opt, ARRAY_SIZE(opt), "%s.%s=",
113 reg->name, reg->fields[f].name);
115 if (!parameqn(cmdline, opt, len))
118 return kstrtou64(cmdline + len, 0, v);
121 static void __init match_options(const char *cmdline)
125 for (i = 0; i < ARRAY_SIZE(regs); i++) {
128 if (!regs[i]->override)
131 for (f = 0; strlen(regs[i]->fields[f].name); f++) {
132 u64 shift = regs[i]->fields[f].shift;
133 u64 mask = 0xfUL << shift;
136 if (find_field(cmdline, regs[i], f, &v))
140 * If an override gets filtered out, advertise
141 * it by setting the value to 0xf, but
142 * clearing the mask... Yes, this is fragile.
144 if (regs[i]->fields[f].filter &&
145 !regs[i]->fields[f].filter(v)) {
146 regs[i]->override->val |= mask;
147 regs[i]->override->mask &= ~mask;
151 regs[i]->override->val &= ~mask;
152 regs[i]->override->val |= (v << shift) & mask;
153 regs[i]->override->mask |= mask;
160 static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
167 cmdline = skip_spaces(cmdline);
169 for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++);
173 len = min(len, ARRAY_SIZE(buf) - 1);
174 strncpy(buf, cmdline, len);
177 if (strcmp(buf, "--") == 0)
184 for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++)
185 if (parameq(buf, aliases[i].alias))
186 __parse_cmdline(aliases[i].feature, false);
190 static __init const u8 *get_bootargs_cmdline(void)
196 fdt = get_early_fdt_ptr();
200 node = fdt_path_offset(fdt, "/chosen");
204 prop = fdt_getprop(fdt, node, "bootargs", NULL);
208 return strlen(prop) ? prop : NULL;
211 static __init void parse_cmdline(void)
213 const u8 *prop = get_bootargs_cmdline();
215 if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
216 __parse_cmdline(CONFIG_CMDLINE, true);
218 if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
219 __parse_cmdline(prop, true);
222 /* Keep checkers quiet */
223 void init_feature_override(void);
225 asmlinkage void __init init_feature_override(void)
229 for (i = 0; i < ARRAY_SIZE(regs); i++) {
230 if (regs[i]->override) {
231 regs[i]->override->val = 0;
232 regs[i]->override->mask = 0;
238 for (i = 0; i < ARRAY_SIZE(regs); i++) {
239 if (regs[i]->override)
240 dcache_clean_inval_poc((unsigned long)regs[i]->override,
241 (unsigned long)regs[i]->override +
242 sizeof(*regs[i]->override));