From: Richard Henderson <richard.henderson@xxxxxxxxxx> Expose the ID_AA64ISAR0.RNDR field to userspace, as the RNG system registers are always available at EL0. Signed-off-by: Richard Henderson <richard.henderson@xxxxxxxxxx> --- v2: Use __mrs_s and fix missing cc clobber (Mark), Log rng failures with pr_warn (Mark), Use __must_check; put RNDR in arch_get_random_long and RNDRRS in arch_get_random_seed_long (Ard), Use ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE, and check this_cpu_has_cap when reading random data. Move everything out of line, now that there are 5 other function calls involved, and to unify the rate limiting on the pr_warn. v3: Keep arch_get_random{,_seed}_long in sync. v4: Use __cpus_have_const_cap before falling back to this_cpu_has_cap. v5: Improve commentary; fix some checkpatch warnings. v6: Drop arch_get_random_long, use RNDR in arch_get_random_seed_long, do not use RNDRRS at all (Ard). Drop the pr_warn mis-communication (Mark). Use ARM64_CPUCAP_SYSTEM_FEATURE for feature detection (Mark). Move arch_get_random_seed_long back inline using ALTERNATIVE_CB. --- Documentation/arm64/cpu-feature-registers.rst | 2 + arch/arm64/include/asm/archrandom.h | 55 +++++++++++++++ arch/arm64/include/asm/cpucaps.h | 3 +- arch/arm64/include/asm/sysreg.h | 4 ++ arch/arm64/kernel/cpufeature.c | 13 ++++ arch/arm64/kernel/random.c | 67 +++++++++++++++++++ arch/arm64/Kconfig | 12 ++++ arch/arm64/kernel/Makefile | 1 + drivers/char/Kconfig | 4 +- 9 files changed, 158 insertions(+), 3 deletions(-) create mode 100644 arch/arm64/include/asm/archrandom.h create mode 100644 arch/arm64/kernel/random.c diff --git a/Documentation/arm64/cpu-feature-registers.rst b/Documentation/arm64/cpu-feature-registers.rst index 2955287e9acc..78d6f5c6e824 100644 --- a/Documentation/arm64/cpu-feature-registers.rst +++ b/Documentation/arm64/cpu-feature-registers.rst @@ -117,6 +117,8 @@ infrastructure: +------------------------------+---------+---------+ | Name | bits | visible | +------------------------------+---------+---------+ + | RNDR | [63-60] | y | + +------------------------------+---------+---------+ | TS | [55-52] | y | +------------------------------+---------+---------+ | FHM | [51-48] | y | diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h new file mode 100644 index 000000000000..7b9f397d2a54 --- /dev/null +++ b/arch/arm64/include/asm/archrandom.h @@ -0,0 +1,55 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_ARCHRANDOM_H +#define _ASM_ARCHRANDOM_H + +#ifdef CONFIG_ARCH_RANDOM + +#include <asm/alternative.h> + +void arm64_update_get_random_seed_long(struct alt_instr *alt, + __le32 *origptr, __le32 *updptr, + int nr_inst); + +static inline bool __must_check arch_get_random_long(unsigned long *v) +{ + return false; +} + +static inline bool __must_check arch_get_random_int(unsigned int *v) +{ + return false; +} + +/* + * The ALTERNATIVE infrastructure leads GCC to believe that the + * inline assembly is quite large, rather than two insns, which + * leads to the function being considered not profitable to inline. + * Override this decision with __always_inline. + */ +static __always_inline __must_check +bool arch_get_random_seed_long(unsigned long *v) +{ + register unsigned long x0 __asm__("x0"); + unsigned long ok; + + asm volatile(ALTERNATIVE_CB("bl boot_get_random_seed_long\n", + arm64_update_get_random_seed_long) + "cset %1, ne\n" + : "=r" (x0), "=r" (ok) : : "cc"); + + *v = x0; + return ok; +} + +static __always_inline __must_check +bool arch_get_random_seed_int(unsigned int *v) +{ + unsigned long val; + bool ok = arch_get_random_seed_long(&val); + + *v = val; + return ok; +} + +#endif /* CONFIG_ARCH_RANDOM */ +#endif /* _ASM_ARCHRANDOM_H */ diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h index ac1dbca3d0cd..1dd7644bc59a 100644 --- a/arch/arm64/include/asm/cpucaps.h +++ b/arch/arm64/include/asm/cpucaps.h @@ -54,7 +54,8 @@ #define ARM64_WORKAROUND_1463225 44 #define ARM64_WORKAROUND_CAVIUM_TX2_219_TVM 45 #define ARM64_WORKAROUND_CAVIUM_TX2_219_PRFM 46 +#define ARM64_HAS_RNG 47 -#define ARM64_NCAPS 47 +#define ARM64_NCAPS 48 #endif /* __ASM_CPUCAPS_H */ diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index 6e919fafb43d..5e718f279469 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -365,6 +365,9 @@ #define SYS_CTR_EL0 sys_reg(3, 3, 0, 0, 1) #define SYS_DCZID_EL0 sys_reg(3, 3, 0, 0, 7) +#define SYS_RNDR_EL0 sys_reg(3, 3, 2, 4, 0) +#define SYS_RNDRRS_EL0 sys_reg(3, 3, 2, 4, 1) + #define SYS_PMCR_EL0 sys_reg(3, 3, 9, 12, 0) #define SYS_PMCNTENSET_EL0 sys_reg(3, 3, 9, 12, 1) #define SYS_PMCNTENCLR_EL0 sys_reg(3, 3, 9, 12, 2) @@ -539,6 +542,7 @@ ENDIAN_SET_EL1 | SCTLR_EL1_UCI | SCTLR_EL1_RES1) /* id_aa64isar0 */ +#define ID_AA64ISAR0_RNDR_SHIFT 60 #define ID_AA64ISAR0_TS_SHIFT 52 #define ID_AA64ISAR0_FHM_SHIFT 48 #define ID_AA64ISAR0_DP_SHIFT 44 diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 80f459ad0190..8c3be148c3a2 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -119,6 +119,7 @@ static void cpu_enable_cnp(struct arm64_cpu_capabilities const *cap); * sync with the documentation of the CPU feature register ABI. */ static const struct arm64_ftr_bits ftr_id_aa64isar0[] = { + ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_RNDR_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_TS_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_FHM_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_DP_SHIFT, 4, 0), @@ -1565,6 +1566,18 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .sign = FTR_UNSIGNED, .min_field_value = 1, }, +#endif +#ifdef CONFIG_ARCH_RANDOM + { + .desc = "Random Number Generator", + .capability = ARM64_HAS_RNG, + .type = ARM64_CPUCAP_SYSTEM_FEATURE, + .matches = has_cpuid_feature, + .sys_reg = SYS_ID_AA64ISAR0_EL1, + .field_pos = ID_AA64ISAR0_RNDR_SHIFT, + .sign = FTR_UNSIGNED, + .min_field_value = 1, + }, #endif {}, }; diff --git a/arch/arm64/kernel/random.c b/arch/arm64/kernel/random.c new file mode 100644 index 000000000000..04c65445c43f --- /dev/null +++ b/arch/arm64/kernel/random.c @@ -0,0 +1,67 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Random number generation using ARMv8.5-RNG. + */ + +#include <linux/random.h> +#include <linux/ratelimit.h> +#include <linux/printk.h> +#include <linux/preempt.h> +#include <asm/cpufeature.h> + +/* + * Before alternatives are finalized, arch_get_random_seed_long calls + * this function. The abi is as if + * + * msr x0, rndr + * + * Preserve all other call-clobbered regs. + */ + +asm(".globl boot_get_random_seed_long\n" +".type boot_get_random_seed_long, @function\n" +"boot_get_random_seed_long:\n" +" stp x29, x30, [sp, -160]!\n" +" stp x1, x2, [sp, 16]\n" +" stp x3, x4, [sp, 32]\n" +" stp x5, x6, [sp, 48]\n" +" stp x7, x8, [sp, 64]\n" +" stp x9, x10, [sp, 80]\n" +" stp x11, x12, [sp, 96]\n" +" stp x13, x14, [sp, 112]\n" +" stp x15, x16, [sp, 128]\n" +" stp x17, x18, [sp, 144]\n" +" mov x0, " __stringify(ARM64_HAS_RNG) "\n" +" bl this_cpu_has_cap\n" +" ldp x1, x2, [sp, 16]\n" +" ldp x3, x4, [sp, 32]\n" +" ldp x5, x6, [sp, 48]\n" +" ldp x7, x8, [sp, 64]\n" +" ldp x9, x10, [sp, 80]\n" +" ldp x11, x12, [sp, 96]\n" +" ldp x13, x14, [sp, 112]\n" +" ldp x15, x16, [sp, 128]\n" +" ldp x17, x18, [sp, 144]\n" +" ldp x29, x30, [sp], 160\n" +/* Test this_cpu_has_cap result, clearing x0 and setting Z if false. */ +" ands w0, w0, #0xff\n" +" beq 1f\n" + __mrs_s("x0", SYS_RNDR_EL0) "\n" +"1: ret\n" +".size boot_get_random_seed_long, . - boot_get_random_seed_long\n"); + + +void arm64_update_get_random_seed_long(struct alt_instr *alt, + __le32 *origptr, __le32 *updptr, + int nr_inst) +{ + u32 insn; + + BUG_ON(nr_inst != 1); + + if (cpus_have_cap(ARM64_HAS_RNG)) + insn = 0xd53b2400; /* mrs x0, rndr */ + else + insn = 0xea1f03e0; /* ands x0, xzr, xzr */ + updptr[0] = cpu_to_le32(insn); +} diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 3f047afb982c..5bc88601f07b 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1438,6 +1438,18 @@ config ARM64_PTR_AUTH endmenu +menu "ARMv8.5 architectural features" + +config ARCH_RANDOM + bool "Enable support for random number generation" + default y + help + Random number generation (part of the ARMv8.5 Extensions) + provides a high bandwidth, cryptographically secure + hardware random number generator. + +endmenu + config ARM64_SVE bool "ARM Scalable Vector Extension support" default y diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 478491f07b4f..a47c2b984da7 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -63,6 +63,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o obj-$(CONFIG_ARM64_SSBD) += ssbd.o obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o +obj-$(CONFIG_ARCH_RANDOM) += random.o obj-y += vdso/ probes/ obj-$(CONFIG_COMPAT_VDSO) += vdso32/ diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig index df0fc997dc3e..f26a0a8cc0d0 100644 --- a/drivers/char/Kconfig +++ b/drivers/char/Kconfig @@ -539,7 +539,7 @@ endmenu config RANDOM_TRUST_CPU bool "Trust the CPU manufacturer to initialize Linux's CRNG" - depends on X86 || S390 || PPC + depends on X86 || S390 || PPC || ARM64 default n help Assume that CPU manufacturer (e.g., Intel or AMD for RDSEED or @@ -559,4 +559,4 @@ config RANDOM_TRUST_BOOTLOADER device randomness. Say Y here to assume the entropy provided by the booloader is trustworthy so it will be added to the kernel's entropy pool. Otherwise, say N here so it will be regarded as device input that - only mixes the entropy pool. \ No newline at end of file + only mixes the entropy pool. -- 2.17.1