Re: git: 9eecef052155 - main - Add an Armv8 rndr random number provider

> On 22 Nov 2023, at 18:14, John Baldwin <jhb@FreeBSD.org> wrote:
> 
> On 11/15/23 4:29 PM, Jessica Clarke wrote:
>> 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.
> 
> The aarch64 GitHub build is still broken and has been broken now for a
> week.  Can this be fixed to work with that version or should we deprecated
> support for LLVM 12 for aarch64?  Morello LLVM is at LLVM 13 currently.

I think depicting LLVM 12 is best. There is https://apt.llvm.org/ that may be usable to get a toolchain to build FreeBSD on older Ubuntu and Debian installs.

I’m happy to keep 13 as the baseline for now, but expect we will find it’s too old as I work through adding support for newer Architecture features.

Andrew