From: Marc Zyngier Date: Mon, 8 Feb 2021 09:57:22 +0000 (+0000) Subject: arm64: cpufeature: Add an early command-line cpufeature override facility X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=33200303553d;p=uclinux-h8%2Flinux.git arm64: cpufeature: Add an early command-line cpufeature override facility In order to be able to override CPU features at boot time, let's add a command line parser that matches options of the form "cpureg.feature=value", and store the corresponding value into the override val/mask pair. No features are currently defined, so no expected change in functionality. Signed-off-by: Marc Zyngier Acked-by: David Brazdil Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20210208095732.3267263-14-maz@kernel.org Signed-off-by: Will Deacon --- diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 86364ab6f13f..2262f0392857 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -17,7 +17,7 @@ obj-y := debug-monitors.o entry.o irq.o fpsimd.o \ return_address.o cpuinfo.o cpu_errata.o \ cpufeature.o alternative.o cacheinfo.o \ smp.o smp_spin_table.o topology.o smccc-call.o \ - syscall.o proton-pack.o + syscall.o proton-pack.o idreg-override.o targets += efi-entry.o diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 070d1c6ec9eb..e7f12bf49730 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -438,6 +438,7 @@ SYM_FUNC_START_LOCAL(__primary_switched) #endif mov x0, x21 // pass FDT address in x0 bl early_fdt_map // Try mapping the FDT early + bl init_feature_override // Parse cpu feature overrides #ifdef CONFIG_RANDOMIZE_BASE tst x23, ~(MIN_KIMG_ALIGN - 1) // already running randomized? b.ne 0f diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c new file mode 100644 index 000000000000..3a347b42d07e --- /dev/null +++ b/arch/arm64/kernel/idreg-override.c @@ -0,0 +1,150 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Early cpufeature override framework + * + * Copyright (C) 2020 Google LLC + * Author: Marc Zyngier + */ + +#include +#include +#include + +#include +#include + +#define FTR_DESC_NAME_LEN 20 +#define FTR_DESC_FIELD_LEN 10 + +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 * const regs[] __initconst = { +}; + +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) +{ + 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); + + } 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); + + if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND)) + return; + } + +out: + __parse_cmdline(CONFIG_CMDLINE); +} + +/* 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)); + } +}