[PATCH] arm: crypto: add a check for crypto extensions support.

[Sascha Hauer]

Hi,

On Wed, Aug 27, 2025 at 02:06:06AM -0400, chalianis1 at gmail.com wrote:
> From: Chali Anis <chalianis1 at gmail.com>
> 
> In some configuration the CPU may raise an exception bacause of an
> unknown instruction if it does not support Crypto Extensions for
> example in some BCM281X (RPi3B in my case) when running barebox
> as an EFI Payload, where the EFI stops with a synchronous execption
> See bellow:
> Synchronous Exception at 0x0000000037BFF548
> SP 0x0000000037F798C0 ELR 0x0000000037BFF548
> SPSR 0x20000209 FPSR 0x00000000
> ESR 0x02000000 FAR 0x14F64325185430BF
> ESR : EC 0x00 IL 0x1 ISS 0x00000000
> 
> Signed-off-by: Chali Anis <chalianis1 at gmail.com>
> ---
>  arch/arm/crypto/sha1-ce-glue.c | 6 ++++++
>  arch/arm/crypto/sha2-ce-glue.c | 6 ++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/arch/arm/crypto/sha1-ce-glue.c b/arch/arm/crypto/sha1-ce-glue.c
> index 5b49237573fa..3c5213774429 100644
> --- a/arch/arm/crypto/sha1-ce-glue.c
> +++ b/arch/arm/crypto/sha1-ce-glue.c
> @@ -88,6 +88,12 @@ static struct digest_algo m = {
>  
>  static int sha1_ce_mod_init(void)
>  {
> +	uint64_t isar0;
> +
> +	asm volatile("mrs %0, ID_AA64ISAR0_EL1" : "=r"(isar0));

You could use read_sysreg():

#include <asm/sysreg.h>

	isar0 = read_sysreg(ID_AA64ISAR0_EL1);

> +	if (!(isar0 & 0xF00))
> +		return -EOPNOTSUPP;

defines for this bitmask would be cool. I just looked at the kernel and
it seems a bit overkill for barebox, but maybe something like

#define ID_AA64ISAR0_EL1_SHA1_MASK	GENMASK(11, 8)
#define ID_AA64ISAR0_EL1_SHA2_MASK	GENMASK(15, 12)

in asm/sysreg.h would do it as a start.

Sascha

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