diff options
Diffstat (limited to 'arch/arm64/kernel/idreg-override.c')
| -rw-r--r-- | arch/arm64/kernel/idreg-override.c | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c new file mode 100644 index 000000000000..dffb16682330 --- /dev/null +++ b/arch/arm64/kernel/idreg-override.c @@ -0,0 +1,216 @@ +// 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; + } fields[]; +}; + +static const struct ftr_set_desc mmfr1 __initconst = { + .name = "id_aa64mmfr1", + .override = &id_aa64mmfr1_override, + .fields = { + { "vh", ID_AA64MMFR1_VHE_SHIFT }, + {} + }, +}; + +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; + + 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 void parse_cmdline(void) +{ + if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) { + const u8 *prop; + void *fdt; + int node; + + fdt = get_early_fdt_ptr(); + if (!fdt) + goto out; + + node = fdt_path_offset(fdt, "/chosen"); + if (node < 0) + goto out; + + prop = fdt_getprop(fdt, node, "bootargs", NULL); + if (!prop) + goto out; + + __parse_cmdline(prop, true); + + if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND)) + return; + } + +out: + __parse_cmdline(CONFIG_CMDLINE, 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) + __flush_dcache_area(regs[i]->override, + sizeof(*regs[i]->override)); + } +} |