Re: git: 9eecef052155 - main - Add an Armv8 rndr random number provider
Date: Thu, 16 Nov 2023 00:29:41 UTC
On 15 Nov 2023, at 18:27, Jessica Clarke <jrtc27@FreeBSD.org> wrote:
>
> On 15 Nov 2023, at 18:12, Andrew Turner <andrew@FreeBSD.org> wrote:
>>
>> The branch main has been updated by andrew:
>>
>> URL: https://cgit.FreeBSD.org/src/commit/?id=9eecef052155646fbc5f8f533b952b372572d06a
>>
>> commit 9eecef052155646fbc5f8f533b952b372572d06a
>> Author: Andrew Turner <andrew@FreeBSD.org>
>> AuthorDate: 2023-11-15 17:42:02 +0000
>> Commit: Andrew Turner <andrew@FreeBSD.org>
>> CommitDate: 2023-11-15 18:05:08 +0000
>>
>> Add an Armv8 rndr random number provider
>>
>> Armv8.5 adds an optional random number generator. This is implemented
>> as two special registers one to read a random number, the other to
>> re-seed the entropy pool before reading a random number. Both registers
>> will set the condition flags to tell the caller they can't produce a
>> random number in a reasonable amount of time.
>>
>> Without a signal to reseed the entropy pool use the latter register
>> to provide random numbers to the kernel pool. If at a later time we
>> had a way to tell the provider if it needs to reseed or not we could
>> use the former.
>>
>> On an Amazon AWS Graviton3 VM this never failed, however this may not
>> be the case on low end CPUs so retry reading the random number 10 times
>> before returning an error.
>>
>> Reviewed by: imp, delphij (csprng)
>> Sponsored by: The FreeBSD Foundation
>> Sponsored by: Arm Ltd
>> Differential Revision: https://reviews.freebsd.org/D35411
>> ---
>> sys/arm64/conf/std.dev | 1 +
>> sys/conf/files.arm64 | 2 +
>> sys/dev/random/armv8rng.c | 135 +++++++++++++++++++++++++++++++++++++++
>> sys/dev/random/random_harvestq.c | 1 +
>> sys/modules/Makefile | 2 +
>> sys/modules/armv8_rng/Makefile | 11 ++++
>> sys/sys/random.h | 1 +
>> 7 files changed, 153 insertions(+)
>>
>> diff --git a/sys/arm64/conf/std.dev b/sys/arm64/conf/std.dev
>> index 74d2407e0aec..0ebf2e775b11 100644
>> --- a/sys/arm64/conf/std.dev
>> +++ b/sys/arm64/conf/std.dev
>> @@ -53,6 +53,7 @@ device vt_simplefb
>>
>> # Pseudo devices.
>> device crypto # core crypto support
>> +device armv8_rng # Armv8.5 rndr RNG
>> device loop # Network loopback
>> device ether # Ethernet support
>> device vlan # 802.1Q VLAN support
>> diff --git a/sys/conf/files.arm64 b/sys/conf/files.arm64
>> index 38b9e40463eb..9ccead6a98e1 100644
>> --- a/sys/conf/files.arm64
>> +++ b/sys/conf/files.arm64
>> @@ -379,6 +379,8 @@ dev/psci/psci.c standard
>> dev/psci/smccc_arm64.S standard
>> dev/psci/smccc.c standard
>>
>> +dev/random/armv8rng.c optional armv8_rng !random_loadable
>> +
>> dev/safexcel/safexcel.c optional safexcel fdt
>>
>> dev/sdhci/sdhci_xenon.c optional sdhci_xenon sdhci
>> diff --git a/sys/dev/random/armv8rng.c b/sys/dev/random/armv8rng.c
>> new file mode 100644
>> index 000000000000..3cca42a5bbf3
>> --- /dev/null
>> +++ b/sys/dev/random/armv8rng.c
>> @@ -0,0 +1,135 @@
>> +/*-
>> + * Copyright (c) 2022 The FreeBSD Foundation
>> + *
>> + * This software was developed by Andrew Turner under sponsorship from
>> + * the FreeBSD Foundation.
>> + *
>> + * Redistribution and use in source and binary forms, with or without
>> + * modification, are permitted provided that the following conditions
>> + * are met:
>> + * 1. Redistributions of source code must retain the above copyright
>> + * notice, this list of conditions and the following disclaimer.
>> + * 2. Redistributions in binary form must reproduce the above copyright
>> + * notice, this list of conditions and the following disclaimer in the
>> + * documentation and/or other materials provided with the distribution.
>> + *
>> + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
>> + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
>> + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
>> + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
>> + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
>> + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
>> + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
>> + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
>> + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
>> + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
>> + * SUCH DAMAGE.
>> + */
>> +
>> +#include <sys/cdefs.h>
>> +
>> +#include <sys/param.h>
>> +#include <sys/systm.h>
>> +#include <sys/conf.h>
>> +#include <sys/kernel.h>
>> +#include <sys/lock.h>
>> +#include <sys/malloc.h>
>> +#include <sys/module.h>
>> +#include <sys/random.h>
>> +
>> +#include <machine/armreg.h>
>> +
>> +#include <dev/random/randomdev.h>
>> +
>> +static u_int random_rndr_read(void *, u_int);
>> +
>> +static bool has_rndr;
>> +static struct random_source random_armv8_rndr = {
>> + .rs_ident = "Armv8 rndr RNG",
>> + .rs_source = RANDOM_PURE_ARMV8,
>> + .rs_read = random_rndr_read,
>> +};
>> +
>> +static inline int
>> +random_rndr_read_one(u_long *buf)
>> +{
>> + u_long val;
>> + int loop, ret;
>> +
>> + loop = 10;
>> + do {
>> + __asm __volatile(
>> + ".arch_extension rng \n"
>> + "mrs %0, rndrrs \n" /* Read the random number */
>> + "cset %w1, ne \n" /* 1 on success, 0 on failure */
>> + ".arch_extension norng \n"
>> + : "=&r" (val), "=&r"(ret) :: "cc");
>
> Early clobber doesn’t make sense with no inputs.
This also breaks the aarch64 ubuntu-20.04 GitHub build, as its LLVM
doesn’t know about the RNG extension. Can you please stop breaking the
arm64 kernel build with older LLVM, this is far from the first time
it’s happened, and some of those never got fixed upstream, we just had
to hack around them downstream.
Jess