| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Early cpufeature override framework |
| * |
| * Copyright (C) 2020 Google LLC |
| * Author: Marc Zyngier <maz@kernel.org> |
| */ |
| |
| #include <linux/ctype.h> |
| #include <linux/kernel.h> |
| #include <linux/libfdt.h> |
| |
| #include <asm/cacheflush.h> |
| #include <asm/cpufeature.h> |
| #include <asm/setup.h> |
| |
| #define FTR_DESC_NAME_LEN 20 |
| #define FTR_DESC_FIELD_LEN 10 |
| #define FTR_ALIAS_NAME_LEN 30 |
| #define FTR_ALIAS_OPTION_LEN 80 |
| |
| struct ftr_set_desc { |
| char name[FTR_DESC_NAME_LEN]; |
| struct arm64_ftr_override *override; |
| struct { |
| char name[FTR_DESC_FIELD_LEN]; |
| u8 shift; |
| bool (*filter)(u64 val); |
| } fields[]; |
| }; |
| |
| static bool __init mmfr1_vh_filter(u64 val) |
| { |
| /* |
| * If we ever reach this point while running VHE, we're |
| * guaranteed to be on one of these funky, VHE-stuck CPUs. If |
| * the user was trying to force nVHE on us, proceed with |
| * attitude adjustment. |
| */ |
| return !(is_kernel_in_hyp_mode() && val == 0); |
| } |
| |
| static const struct ftr_set_desc mmfr1 __initconst = { |
| .name = "id_aa64mmfr1", |
| .override = &id_aa64mmfr1_override, |
| .fields = { |
| { "vh", ID_AA64MMFR1_VHE_SHIFT, mmfr1_vh_filter }, |
| {} |
| }, |
| }; |
| |
| static const struct ftr_set_desc pfr1 __initconst = { |
| .name = "id_aa64pfr1", |
| .override = &id_aa64pfr1_override, |
| .fields = { |
| { "bt", ID_AA64PFR1_BT_SHIFT }, |
| {} |
| }, |
| }; |
| |
| static const struct ftr_set_desc isar1 __initconst = { |
| .name = "id_aa64isar1", |
| .override = &id_aa64isar1_override, |
| .fields = { |
| { "gpi", ID_AA64ISAR1_GPI_SHIFT }, |
| { "gpa", ID_AA64ISAR1_GPA_SHIFT }, |
| { "api", ID_AA64ISAR1_API_SHIFT }, |
| { "apa", ID_AA64ISAR1_APA_SHIFT }, |
| {} |
| }, |
| }; |
| |
| extern struct arm64_ftr_override kaslr_feature_override; |
| |
| static const struct ftr_set_desc kaslr __initconst = { |
| .name = "kaslr", |
| #ifdef CONFIG_RANDOMIZE_BASE |
| .override = &kaslr_feature_override, |
| #endif |
| .fields = { |
| { "disabled", 0 }, |
| {} |
| }, |
| }; |
| |
| static const struct ftr_set_desc * const regs[] __initconst = { |
| &mmfr1, |
| &pfr1, |
| &isar1, |
| &kaslr, |
| }; |
| |
| static const struct { |
| char alias[FTR_ALIAS_NAME_LEN]; |
| char feature[FTR_ALIAS_OPTION_LEN]; |
| } aliases[] __initconst = { |
| { "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" }, |
| { "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" }, |
| { "arm64.nobti", "id_aa64pfr1.bt=0" }, |
| { "arm64.nopauth", |
| "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 " |
| "id_aa64isar1.api=0 id_aa64isar1.apa=0" }, |
| { "nokaslr", "kaslr.disabled=1" }, |
| }; |
| |
| static int __init find_field(const char *cmdline, |
| const struct ftr_set_desc *reg, int f, u64 *v) |
| { |
| char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2]; |
| int len; |
| |
| len = snprintf(opt, ARRAY_SIZE(opt), "%s.%s=", |
| reg->name, reg->fields[f].name); |
| |
| if (!parameqn(cmdline, opt, len)) |
| return -1; |
| |
| return kstrtou64(cmdline + len, 0, v); |
| } |
| |
| static void __init match_options(const char *cmdline) |
| { |
| int i; |
| |
| for (i = 0; i < ARRAY_SIZE(regs); i++) { |
| int f; |
| |
| if (!regs[i]->override) |
| continue; |
| |
| for (f = 0; strlen(regs[i]->fields[f].name); f++) { |
| u64 shift = regs[i]->fields[f].shift; |
| u64 mask = 0xfUL << shift; |
| u64 v; |
| |
| if (find_field(cmdline, regs[i], f, &v)) |
| continue; |
| |
| /* |
| * If an override gets filtered out, advertise |
| * it by setting the value to 0xf, but |
| * clearing the mask... Yes, this is fragile. |
| */ |
| if (regs[i]->fields[f].filter && |
| !regs[i]->fields[f].filter(v)) { |
| regs[i]->override->val |= mask; |
| regs[i]->override->mask &= ~mask; |
| continue; |
| } |
| |
| regs[i]->override->val &= ~mask; |
| regs[i]->override->val |= (v << shift) & mask; |
| regs[i]->override->mask |= mask; |
| |
| return; |
| } |
| } |
| } |
| |
| static __init void __parse_cmdline(const char *cmdline, bool parse_aliases) |
| { |
| do { |
| char buf[256]; |
| size_t len; |
| int i; |
| |
| cmdline = skip_spaces(cmdline); |
| |
| for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++); |
| if (!len) |
| return; |
| |
| len = min(len, ARRAY_SIZE(buf) - 1); |
| strncpy(buf, cmdline, len); |
| buf[len] = 0; |
| |
| if (strcmp(buf, "--") == 0) |
| return; |
| |
| cmdline += len; |
| |
| match_options(buf); |
| |
| for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++) |
| if (parameq(buf, aliases[i].alias)) |
| __parse_cmdline(aliases[i].feature, false); |
| } while (1); |
| } |
| |
| static __init const u8 *get_bootargs_cmdline(void) |
| { |
| const u8 *prop; |
| void *fdt; |
| int node; |
| |
| fdt = get_early_fdt_ptr(); |
| if (!fdt) |
| return NULL; |
| |
| node = fdt_path_offset(fdt, "/chosen"); |
| if (node < 0) |
| return NULL; |
| |
| prop = fdt_getprop(fdt, node, "bootargs", NULL); |
| if (!prop) |
| return NULL; |
| |
| return strlen(prop) ? prop : NULL; |
| } |
| |
| static __init void parse_cmdline(void) |
| { |
| const u8 *prop = get_bootargs_cmdline(); |
| |
| if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop) |
| __parse_cmdline(CONFIG_CMDLINE, true); |
| |
| if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop) |
| __parse_cmdline(prop, true); |
| } |
| |
| /* Keep checkers quiet */ |
| void init_feature_override(void); |
| |
| asmlinkage void __init init_feature_override(void) |
| { |
| int i; |
| |
| for (i = 0; i < ARRAY_SIZE(regs); i++) { |
| if (regs[i]->override) { |
| regs[i]->override->val = 0; |
| regs[i]->override->mask = 0; |
| } |
| } |
| |
| parse_cmdline(); |
| |
| for (i = 0; i < ARRAY_SIZE(regs); i++) { |
| if (regs[i]->override) |
| dcache_clean_inval_poc((unsigned long)regs[i]->override, |
| (unsigned long)regs[i]->override + |
| sizeof(*regs[i]->override)); |
| } |
| } |