diff options
| -rw-r--r-- | arch/arm64/include/asm/archrandom.h | 45 |
1 files changed, 39 insertions, 6 deletions
diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h index 09e43272ccb0..d1bb5e71df25 100644 --- a/arch/arm64/include/asm/archrandom.h +++ b/arch/arm64/include/asm/archrandom.h @@ -42,13 +42,47 @@ static inline bool __arm64_rndr(unsigned long *v) return ok; } +static inline bool __arm64_rndrrs(unsigned long *v) +{ + bool ok; + + /* + * Reads of RNDRRS set PSTATE.NZCV to 0b0000 on success, + * and set PSTATE.NZCV to 0b0100 otherwise. + */ + asm volatile( + __mrs_s("%0", SYS_RNDRRS_EL0) "\n" + " cset %w1, ne\n" + : "=r" (*v), "=r" (ok) + : + : "cc"); + + return ok; +} + static inline bool __must_check arch_get_random_long(unsigned long *v) { + /* + * Only support the generic interface after we have detected + * the system wide capability, avoiding complexity with the + * cpufeature code and with potential scheduling between CPUs + * with and without the feature. + */ + if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v)) + return true; return false; } static inline bool __must_check arch_get_random_int(unsigned int *v) { + if (cpus_have_const_cap(ARM64_HAS_RNG)) { + unsigned long val; + + if (__arm64_rndr(&val)) { + *v = val; + return true; + } + } return false; } @@ -71,12 +105,11 @@ static inline bool __must_check arch_get_random_seed_long(unsigned long *v) } /* - * Only support the generic interface after we have detected - * the system wide capability, avoiding complexity with the - * cpufeature code and with potential scheduling between CPUs - * with and without the feature. + * RNDRRS is not backed by an entropy source but by a DRBG that is + * reseeded after each invocation. This is not a 100% fit but good + * enough to implement this API if no other entropy source exists. */ - if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v)) + if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndrrs(v)) return true; return false; @@ -96,7 +129,7 @@ static inline bool __must_check arch_get_random_seed_int(unsigned int *v) } if (cpus_have_const_cap(ARM64_HAS_RNG)) { - if (__arm64_rndr(&val)) { + if (__arm64_rndrrs(&val)) { *v = val; return true; } |