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Message-ID: <20230726121301.kbkskd23mwoptvvx@viti.kaiser.cx>
Date: Wed, 26 Jul 2023 14:13:01 +0200
From: Martin Kaiser <lists@...ser.cx>
To: LeoLiu-oc <LeoLiu-oc@...oxin.com>
Cc: olivia@...enic.com, herbert@...dor.apana.org.au,
jiajie.ho@...rfivetech.com, conor.dooley@...rochip.com,
mmyangfl@...il.com, jenny.zhang@...rfivetech.com,
linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
leoliu@...oxin.com, CobeChen@...oxin.com, YunShen@...oxin.com,
TonyWWang@...oxin.com
Subject: Re: [PATCH] hwrng: add Zhaoxin HW RNG driver
Hi,
some quick remarks. Feel free to correct me if I misunderstood
something.
LeoLiu-oc (LeoLiu-oc@...oxin.com) wrote:
> From: leoliu-oc <leoliu-oc@...oxin.com>
> Add support for Zhaoxin HW RNG.
> Signed-off-by: leoliu-oc <leoliu-oc@...oxin.com>
> ---
> drivers/char/hw_random/Kconfig | 13 +++
> drivers/char/hw_random/Makefile | 1 +
> drivers/char/hw_random/via-rng.c | 17 ++--
> drivers/char/hw_random/zhaoxin-rng.c | 116 +++++++++++++++++++++++++++
> 4 files changed, 139 insertions(+), 8 deletions(-)
> create mode 100644 drivers/char/hw_random/zhaoxin-rng.c
> diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
> index e0b3786ca51b..3b3c00e87b7b 100644
> --- a/drivers/char/hw_random/Kconfig
> +++ b/drivers/char/hw_random/Kconfig
> @@ -150,6 +150,19 @@ config HW_RANDOM_VIA
> If unsure, say Y.
> +config HW_RANDOM_ZHAOXIN
> + tristate "Zhaoxin HW Random Number Generator support"
> + depends on X86
depends on X86 || COMPILE_TEST
> + default HW_RANDOM
> + help
> + This driver provides kernel-side support for the Random Number
> + Generator hardware found on Zhaoxin based motherboards.
> +
> + To compile this driver as a module, choose M here: the
> + module will be called zhaoxin-rng.
> +
> + If unsure, say Y.
> +
> config HW_RANDOM_IXP4XX
> tristate "Intel IXP4xx NPU HW Pseudo-Random Number Generator support"
> depends on ARCH_IXP4XX || COMPILE_TEST
> diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
> index 32549a1186dc..ef5b3ae0794d 100644
> --- a/drivers/char/hw_random/Makefile
> +++ b/drivers/char/hw_random/Makefile
> @@ -14,6 +14,7 @@ obj-$(CONFIG_HW_RANDOM_GEODE) += geode-rng.o
> obj-$(CONFIG_HW_RANDOM_N2RNG) += n2-rng.o
> n2-rng-y := n2-drv.o n2-asm.o
> obj-$(CONFIG_HW_RANDOM_VIA) += via-rng.o
> +obj-$(CONFIG_HW_RANDOM_ZHAOXIN) += zhaoxin-rng.o
> obj-$(CONFIG_HW_RANDOM_EXYNOS) += exynos-trng.o
> obj-$(CONFIG_HW_RANDOM_IXP4XX) += ixp4xx-rng.o
> obj-$(CONFIG_HW_RANDOM_OMAP) += omap-rng.o
> diff --git a/drivers/char/hw_random/via-rng.c b/drivers/char/hw_random/via-rng.c
> index a9a0a3b09c8b..33a6e2fdacd1 100644
> --- a/drivers/char/hw_random/via-rng.c
> +++ b/drivers/char/hw_random/via-rng.c
> @@ -135,7 +135,7 @@ static int via_rng_init(struct hwrng *rng)
> * is always enabled if CPUID rng_en is set. There is no
> * RNG configuration like it used to be the case in this
> * register */
> - if (((c->x86 == 6) && (c->x86_model >= 0x0f)) || (c->x86 > 6)){
> + if ((c->x86 == 6) && (c->x86_model >= 0x0f)) {
> if (!boot_cpu_has(X86_FEATURE_XSTORE_EN)) {
> pr_err(PFX "can't enable hardware RNG "
> "if XSTORE is not enabled\n");
> @@ -191,13 +191,20 @@ static struct hwrng via_rng = {
> .data_read = via_rng_data_read,
> };
> +static const struct x86_cpu_id via_rng_cpu_ids[] = {
> + X86_MATCH_VENDOR_FAM_FEATURE(CENTAUR, 6, X86_FEATURE_XSTORE, NULL),
> + {}
> +};
> +MODULE_DEVICE_TABLE(x86cpu, via_rng_cpu_ids);
> static int __init via_rng_mod_init(void)
> {
> int err;
> - if (!boot_cpu_has(X86_FEATURE_XSTORE))
> + if (!x86_match_cpu(via_rng_cpu_ids)) {
> + pr_err(PFX "The CPU isn't support XSTORE.\n");
doesn't support
Generally: Should we print an error message if our driver doesn't
support this cpu? It seems that most other callers of x86_match_cpu
simply return without an error message.
> return -ENODEV;
> + }
> pr_info("VIA RNG detected\n");
> err = hwrng_register(&via_rng);
> @@ -217,11 +224,5 @@ static void __exit via_rng_mod_exit(void)
> }
> module_exit(via_rng_mod_exit);
> -static struct x86_cpu_id __maybe_unused via_rng_cpu_id[] = {
> - X86_MATCH_FEATURE(X86_FEATURE_XSTORE, NULL),
> - {}
> -};
> -MODULE_DEVICE_TABLE(x86cpu, via_rng_cpu_id);
> -
> MODULE_DESCRIPTION("H/W RNG driver for VIA CPU with PadLock");
> MODULE_LICENSE("GPL");
> diff --git a/drivers/char/hw_random/zhaoxin-rng.c b/drivers/char/hw_random/zhaoxin-rng.c
> new file mode 100644
> index 000000000000..2e657b227c5b
> --- /dev/null
> +++ b/drivers/char/hw_random/zhaoxin-rng.c
> @@ -0,0 +1,116 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * RNG driver for Zhaoxin RNGs
> + *
> + * Copyright 2005 (c) MontaVista Software, Inc.
Should this be Copyright 2023 by you?
> + *
> + * with the majority of the code coming from:
> + *
> + * Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
> + * (c) Copyright 2003 Red Hat Inc <jgarzik@...hat.com>
> + *
> + * derived from
> + *
> + * Hardware driver for the AMD 768 Random Number Generator (RNG)
> + * (c) Copyright 2001 Red Hat Inc
> + *
> + * derived from
> + *
> + * Hardware driver for Intel i810 Random Number Generator (RNG)
> + * Copyright 2000,2001 Jeff Garzik <jgarzik@...ox.com>
> + * Copyright 2000,2001 Philipp Rumpf <prumpf@...drakesoft.com>
> + *
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2. This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +
> +#include <crypto/padlock.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/hw_random.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/cpufeature.h>
> +#include <asm/cpu_device_id.h>
> +#include <asm/fpu/api.h>
> +
> +enum {
> + ZHAOXIN_RNG_CHUNK_8 = 0x00, /* 64 rand bits, 64 stored bits*/
> + ZHAOXIN_RNG_CHUNK_4 = 0x01, /* 32 rand bits, 32 stored bits */
> + ZHAOXIN_RNG_CHUNK_2 = 0x02, /* 16 rand bits, 32 stored bits */
> + ZHAOXIN_RNG_CHUNK_1 = 0x03, /* 8 rand bits, 32 stored bits */
> + ZHAOXIN_RNG_MAX_SIZE = (128*1024),
> +};
> +
> +static int zhaoxin_rng_init(struct hwrng *rng)
> +{
> + if (!boot_cpu_has(X86_FEATURE_XSTORE_EN)) {
> + pr_err(PFX "can't enable hardware RNG if XSTORE is not enabled\n");
> + return -ENODEV;
> + }
Can't we check this when the driver is loaded? (This init function here
is called when the rng becomes active.)
> + return 0;
> +}
> +
> +static inline int rep_xstore(size_t size, size_t factor, void *result)
> +{
> + __asm__ __volatile__ (
> + "movq %0, %%rcx\n"
> + "movq %1, %%rdx\n"
> + "movq %2, %%rdi\n"
> + ".byte 0xf3, 0x0f, 0xa7, 0xc0"
> + :
> + : "r"(size), "r"(factor), "r"(result)
> + : "%rcx", "%rdx", "%rdi", "memory");
> +
> + return 0;
> +}
> +
> +static int zhaoxin_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
> +{
> + if (max > ZHAOXIN_RNG_MAX_SIZE)
> + max = ZHAOXIN_RNG_MAX_SIZE;
> + rep_xstore(max, ZHAOXIN_RNG_CHUNK_1, data);
> + return max;
> +}
> +
> +static struct hwrng zhaoxin_rng = {
> + .name = "zhaoxin",
> + .init = zhaoxin_rng_init,
> + .read = zhaoxin_rng_read,
> +};
> +
> +static const struct x86_cpu_id zhaoxin_rng_cpu_ids[] = {
> + X86_MATCH_VENDOR_FAM_FEATURE(ZHAOXIN, 6, X86_FEATURE_XSTORE, NULL),
> + X86_MATCH_VENDOR_FAM_FEATURE(ZHAOXIN, 7, X86_FEATURE_XSTORE, NULL),
> + X86_MATCH_VENDOR_FAM_FEATURE(CENTAUR, 7, X86_FEATURE_XSTORE, NULL),
> + {}
> +};
> +MODULE_DEVICE_TABLE(x86cpu, zhaoxin_rng_cpu_ids);
> +
> +static int __init zhaoxin_rng_mod_init(void)
> +{
> + int err;
> +
> + if (!x86_match_cpu(zhaoxin_rng_cpu_ids)) {
> + pr_err(PFX "The CPU isn't support XSTORE.\n");
Yet again, is this really an error?
> + return -ENODEV;
> + }
> +
> + pr_info("Zhaoxin RNG detected\n");
> + err = hwrng_register(&zhaoxin_rng);
> + if (err)
> + pr_err(PFX "RNG registering failed (%d)\n", err);
> +
> + return err;
> +}
> +module_init(zhaoxin_rng_mod_init);
> +
> +static void __exit zhaoxin_rng_mod_exit(void)
> +{
> + hwrng_unregister(&zhaoxin_rng);
> +}
> +module_exit(zhaoxin_rng_mod_exit);
> +MODULE_DESCRIPTION("H/W RNG driver for Zhaoxin CPU");
> +MODULE_AUTHOR("YunShen@...oxin.com");
> +MODULE_LICENSE("GPL");
> --
> 2.34.1
Best regards,
Martin
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