On Tue, Aug 04, 2026 at 07:30:11PM +0200, Christian Weisgerber wrote:
> The aarch64 runtime environment provides pre-parsed CPU feature
> capabilities for free.  We can just grab them with elf_aux_info()
> and no longer need to read the AA64ISAR0 register with sysctl or
> extract the bit fields.
> 
> OK?
> 
> Hint for -portable: This builds as-is on FreeBSD, too.

I believe the file predates the elf_aux_info work or was developed
in parallel with it.

-portable currently only uses this file for OpenBSD builds and has a
similar implementation as yours for linux (except that it calls
getauxval() once per capability, not sure if that matters much...).

Once this lands, we can look into hooking it up for freebsd.

ok tb

> 
> -----------------------------------------------
> commit fa0e19296490832c8f496272bd150d14d170fb50
> from: Christian Weisgerber <naddy@mips.inka.de>
> date: Tue Aug  4 17:10:07 2026 UTC
>  
>  switch aarch64 CPU feature detection to elf_aux_info()
>  
> diff b2b8205756684c6db49759a3153d75acd569191f fa0e19296490832c8f496272bd150d14d170fb50
> commit - b2b8205756684c6db49759a3153d75acd569191f
> commit + fa0e19296490832c8f496272bd150d14d170fb50
> blob - b31a50ef7530b47b579bcaae6b551fd22bf5a861
> blob + b9e12776a66281cc4e674de3e80f4a0c9991c89d
> --- lib/libcrypto/arch/aarch64/crypto_cpu_caps.c
> +++ lib/libcrypto/arch/aarch64/crypto_cpu_caps.c
> @@ -15,11 +15,8 @@
>   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
>   */
>  
> -#include <sys/types.h>
> -#include <sys/sysctl.h>
> +#include <sys/auxv.h>
>  
> -#include <machine/cpu.h>
> -
>  #include <stddef.h>
>  #include <stdio.h>
>  
> @@ -28,70 +25,29 @@
>  /* Machine dependent CPU capabilities. */
>  uint64_t crypto_cpu_caps_aarch64;
>  
> -static inline uint64_t
> -extract_bits(uint64_t val, int start, int end)
> -{
> -	return (val >> end) & (1ULL << (1 + start - end)) - 1;
> -}
> -
> -static uint64_t
> -parse_isar0(uint64_t isar0)
> -{
> -	uint64_t caps = 0;
> -	uint64_t feature;
> -
> -	/* AES - bits [7:4] */
> -	feature = extract_bits(isar0, 7, 4);
> -	if (feature >= 1)
> -		caps |= CRYPTO_CPU_CAPS_AARCH64_AES;
> -	if (feature >= 2)
> -		caps |= CRYPTO_CPU_CAPS_AARCH64_PMULL;
> -
> -	/* SHA1 - bits [11:8] */
> -	feature = extract_bits(isar0, 11, 8);
> -	if (feature >= 1)
> -		caps |= CRYPTO_CPU_CAPS_AARCH64_SHA1;
> -
> -	/* SHA2 - bits [15:12] */
> -	feature = extract_bits(isar0, 15, 12);
> -	if (feature >= 1)
> -		caps |= CRYPTO_CPU_CAPS_AARCH64_SHA2;
> -	if (feature >= 2)
> -		caps |= CRYPTO_CPU_CAPS_AARCH64_SHA512;
> -
> -	/* SHA3 - bits [35:32] */
> -	feature = extract_bits(isar0, 35, 32);
> -	if (feature >= 1)
> -		caps |= CRYPTO_CPU_CAPS_AARCH64_SHA3;
> -
> -	return caps;
> -}
> -
> -static int
> -read_isar0(uint64_t *isar0)
> -{
> -	uint64_t isar;
> -	int mib[2];
> -	size_t len;
> -
> -	mib[0] = CTL_MACHDEP;
> -	mib[1] = CPU_ID_AA64ISAR0;
> -	len = sizeof(isar);
> -	if (sysctl(mib, 2, &isar, &len, NULL, 0) == -1)
> -		return 0;
> -
> -	*isar0 = isar;
> -
> -	return 1;
> -}
> -
>  void
>  crypto_cpu_caps_init(void)
>  {
> -	uint64_t isar = 0;
> +	unsigned long hwcap;
>  
> -	if (!read_isar0(&isar))
> +	if (elf_aux_info(AT_HWCAP, &hwcap, sizeof(hwcap)) != 0)
>  		return;
>  
> -	crypto_cpu_caps_aarch64 = parse_isar0(isar);
> +	if (hwcap & HWCAP_AES)
> +		crypto_cpu_caps_aarch64 |= CRYPTO_CPU_CAPS_AARCH64_AES;
> +
> +	if (hwcap & HWCAP_PMULL)
> +		crypto_cpu_caps_aarch64 |= CRYPTO_CPU_CAPS_AARCH64_PMULL;
> +
> +	if (hwcap & HWCAP_SHA1)
> +		crypto_cpu_caps_aarch64 |= CRYPTO_CPU_CAPS_AARCH64_SHA1;
> +
> +	if (hwcap & HWCAP_SHA2)
> +		crypto_cpu_caps_aarch64 |= CRYPTO_CPU_CAPS_AARCH64_SHA2;
> +
> +	if (hwcap & HWCAP_SHA512)
> +		crypto_cpu_caps_aarch64 |= CRYPTO_CPU_CAPS_AARCH64_SHA512;
> +
> +	if (hwcap & HWCAP_SHA3)
> +		crypto_cpu_caps_aarch64 |= CRYPTO_CPU_CAPS_AARCH64_SHA3;
>  }
> 
> -- 
> Christian "naddy" Weisgerber                          naddy@mips.inka.de
>