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

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hi,

On 27.08.25 17:53, chalianis1@gmail.com wrote:
> From: Chali Anis <chalianis1@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

Thanks for your patch. It's good to have the check, but are you sure
you don't have the ARMv8.0 Crypto Extensions?

arm_cpu_lowlevel_init() enables SIMD, so maybe not calling that
is the reason you got the crash?

For EFI payloads in particular, I don't think we should call
the whole arm_cpu_lowlevel_init(), but maybe there is an argument to be made
that FP/SIMD at least should be enabled. I am not sure if that alone
could lead to issues affecting the EFI loader though.

Cheers,
Ahmad

> 
> Signed-off-by: Chali Anis <chalianis1@gmail.com>
> ---
>  arch/arm/crypto/sha1-ce-glue.c | 7 +++++++
>  arch/arm/crypto/sha2-ce-glue.c | 9 +++++++--
>  arch/arm/include/asm/sysreg.h  | 6 ++++++
>  3 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/crypto/sha1-ce-glue.c b/arch/arm/crypto/sha1-ce-glue.c
> index 5b49237573fa..fea15f295a00 100644
> --- a/arch/arm/crypto/sha1-ce-glue.c
> +++ b/arch/arm/crypto/sha1-ce-glue.c
> @@ -14,6 +14,7 @@
>  #include <linux/linkage.h>
>  #include <asm/byteorder.h>
>  #include <asm/neon.h>
> +#include <asm/sysreg.h>
>  
>  MODULE_DESCRIPTION("SHA1 secure hash using ARMv8 Crypto Extensions");
>  MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
> @@ -88,6 +89,12 @@ static struct digest_algo m = {
>  
>  static int sha1_ce_mod_init(void)
>  {
> +	uint64_t isar0;
> +
> +	isar0 = read_sysreg(ID_AA64ISAR0_EL1);
> +	if (!(isar0 & ID_AA64ISAR0_EL1_SHA1_MASK))
> +		return -EOPNOTSUPP;
> +
>  	return digest_algo_register(&m);
>  }
>  coredevice_initcall(sha1_ce_mod_init);
> diff --git a/arch/arm/crypto/sha2-ce-glue.c b/arch/arm/crypto/sha2-ce-glue.c
> index 88cbc7993dac..8479b3c60cb3 100644
> --- a/arch/arm/crypto/sha2-ce-glue.c
> +++ b/arch/arm/crypto/sha2-ce-glue.c
> @@ -14,8 +14,7 @@
>  #include <linux/linkage.h>
>  #include <asm/byteorder.h>
>  #include <asm/neon.h>
> -
> -#include <asm/neon.h>
> +#include <asm/sysreg.h>
>  
>  MODULE_DESCRIPTION("SHA-224/SHA-256 secure hash using ARMv8 Crypto Extensions");
>  MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
> @@ -116,6 +115,12 @@ static struct digest_algo sha256 = {
>  
>  static int sha256_ce_digest_register(void)
>  {
> +	uint64_t isar0;
> +
> +	isar0 = read_sysreg(ID_AA64ISAR0_EL1);
> +	if (!(isar0 & ID_AA64ISAR0_EL1_SHA2_MASK))
> +		return -EOPNOTSUPP;
> +
>  	return digest_algo_register(&sha256);
>  }
>  coredevice_initcall(sha256_ce_digest_register);
> diff --git a/arch/arm/include/asm/sysreg.h b/arch/arm/include/asm/sysreg.h
> index 7d567e08d8b7..6f47016e54e8 100644
> --- a/arch/arm/include/asm/sysreg.h
> +++ b/arch/arm/include/asm/sysreg.h
> @@ -12,6 +12,12 @@
>  #include <asm/system.h>
>  #include <linux/stringify.h>
>  
> +/*
> + *	ARM64 registers
> + */
> +#define ID_AA64ISAR0_EL1_SHA1_MASK      0xF00UL
> +#define ID_AA64ISAR0_EL1_SHA2_MASK      0xF000UL
> +
>  /*
>   * Unlike read_cpuid, calls to read_sysreg are never expected to be
>   * optimized away or replaced with synthetic values.


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