0380e0a68e
rdrand64() is not clang friendly. Actually it looks like the
function is incorrect on 32bit x86 for all compilers including
gcc, but gcc won't care because the function is never called on
x86:
src/arch/x86/rdrand.c:51:15: error: invalid output size for constraint '=a'
: "=a" (*rand), "=qm" (carry));
^
1 error generated.
Guard the code correctly if ENV_X86_64 is not set.
Change-Id: Ia565897f5e4caaaccfcb02cf1245b150272dff68
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: https://review.coreboot.org/20298
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
88 lines
2.2 KiB
C
88 lines
2.2 KiB
C
/*
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* This file is part of the coreboot project.
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*
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* Copyright 2017 Intel Corporation.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; version 2 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <random.h>
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#include <rules.h>
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/*
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* Intel recommends that applications attempt 10 retries in a tight loop
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* in the unlikely event that the RDRAND instruction does not successfully
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* return a random number. The odds of ten failures in a row would in fact
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* be an indication of a larger CPU issue.
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*/
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#define RDRAND_RETRY_LOOPS 10
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/*
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* Generate a 32-bit random number through RDRAND instruction.
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* Carry flag is set on RDRAND success and 0 on failure.
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*/
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static inline uint8_t rdrand_32(uint32_t *rand)
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{
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uint8_t carry;
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__asm__ __volatile__(
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".byte 0x0f; .byte 0xc7; .byte 0xf0; setc %1"
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: "=a" (*rand), "=qm" (carry));
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return carry;
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}
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#if ENV_X86_64
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/*
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* Generate a 64-bit random number through RDRAND instruction.
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* Carry flag is set on RDRAND success and 0 on failure.
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*/
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static inline uint8_t rdrand_64(uint64_t *rand)
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{
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uint8_t carry;
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__asm__ __volatile__(
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".byte 0x48; .byte 0x0f; .byte 0xc7; .byte 0xf0; setc %1"
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: "=a" (*rand), "=qm" (carry));
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return carry;
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}
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#endif
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int get_random_number_32(uint32_t *rand)
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{
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int i;
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/* Perform a loop call until RDRAND succeeds or returns failure. */
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for (i = 0; i < RDRAND_RETRY_LOOPS; i++) {
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if (rdrand_32(rand))
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return 0;
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}
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return -1;
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}
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int get_random_number_64(uint64_t *rand)
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{
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int i;
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uint32_t rand_high, rand_low;
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/* Perform a loop call until RDRAND succeeds or returns failure. */
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for (i = 0; i < RDRAND_RETRY_LOOPS; i++) {
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#if ENV_X86_64
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if (rdrand_64(rand))
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return 0;
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else
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#endif
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if (rdrand_32(&rand_high) && rdrand_32(&rand_low)) {
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*rand = ((uint64_t)rand_high << 32) |
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(uint64_t)rand_low;
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return 0;
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}
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}
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return -1;
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}
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