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The archrandom interface was originally designed for x86, which supplies RDRAND/RDSEED for receiving random words into registers, resulting in one function to generate an int and another to generate a long. However, other architectures don't follow this. On arm64, the SMCCC TRNG interface can return between one and three longs. On s390, the CPACF TRNG interface can return arbitrary amounts, with four longs having the same cost as one. On UML, the os_getrandom() interface can return arbitrary amounts. So change the api signature to take a "max_longs" parameter designating the maximum number of longs requested, and then return the number of longs generated. Since callers need to check this return value and loop anyway, each arch implementation does not bother implementing its own loop to try again to fill the maximum number of longs. Additionally, all existing callers pass in a constant max_longs parameter. Taken together, these two things mean that the codegen doesn't really change much for one-word-at-a-time platforms, while performance is greatly improved on platforms such as s390. Acked-by: Heiko Carstens <hca@linux.ibm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Acked-by: Borislav Petkov <bp@suse.de> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
37 lines
902 B
C
37 lines
902 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Kernel interface for the s390 arch_random_* functions
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*
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* Copyright IBM Corp. 2017, 2020
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*
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* Author: Harald Freudenberger <freude@de.ibm.com>
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*
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*/
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#ifndef _ASM_S390_ARCHRANDOM_H
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#define _ASM_S390_ARCHRANDOM_H
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#include <linux/static_key.h>
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#include <linux/atomic.h>
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#include <asm/cpacf.h>
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DECLARE_STATIC_KEY_FALSE(s390_arch_random_available);
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extern atomic64_t s390_arch_random_counter;
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static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
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{
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return 0;
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}
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static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
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{
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if (static_branch_likely(&s390_arch_random_available)) {
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cpacf_trng(NULL, 0, (u8 *)v, max_longs * sizeof(*v));
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atomic64_add(max_longs * sizeof(*v), &s390_arch_random_counter);
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return max_longs;
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}
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return 0;
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}
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#endif /* _ASM_S390_ARCHRANDOM_H */
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