From d349ab99eec7ab0f977fc4aac27aa476907acf90 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Sun, 17 Jul 2022 12:35:24 +0200 Subject: random: handle archrandom with multiple longs 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 Acked-by: Catalin Marinas Acked-by: Mark Rutland Acked-by: Michael Ellerman Acked-by: Borislav Petkov Signed-off-by: Jason A. Donenfeld --- arch/x86/kernel/espfix_64.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/kernel/espfix_64.c') diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c index 4fe7af58cfe1..9417d5aa7305 100644 --- a/arch/x86/kernel/espfix_64.c +++ b/arch/x86/kernel/espfix_64.c @@ -100,7 +100,7 @@ static void init_espfix_random(void) * This is run before the entropy pools are initialized, * but this is hopefully better than nothing. */ - if (!arch_get_random_long(&rand)) { + if (!arch_get_random_longs(&rand, 1)) { /* The constant is an arbitrary large prime */ rand = rdtsc(); rand *= 0xc345c6b72fd16123UL; -- cgit v1.2.3