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Add CPU feature checks on M1 macOS.

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I booted my M1 Mac into macOS rather than Asahi for the first time in
a while, and discovered that an OS update seems to have added some
sysctl flags indicating the presence of the CPU extensions that I
previously knew of no way to check for! Added them checks to
arm_arch_queries.c, though I've also retained backwards compat with
the previous OS version which didn't have them at all.
This commit is contained in:
Simon Tatham 2022-08-16 18:39:12 +01:00
parent 840043f06e
commit fd840f0dfe
2 changed files with 27 additions and 13 deletions
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28
unix/utils/arm_arch_queries.c
View File

@ -17,10 +17,11 @@ bool platform_aes_neon_available(void)
#elif defined HWCAP2_AES
return getauxval(AT_HWCAP2) & HWCAP2_AES;
#elif defined __APPLE__
/* M1 macOS defines no optional sysctl flag indicating presence of
* the AES extension, which I assume to be because it's always
* present */
return true;
SysctlResult res = test_sysctl_flag("hw.optional.arm.FEAT_AES");
/* Older M1 macOS didn't provide this flag, but as far as I know
* implemented the crypto extension anyway, so treat 'feature
* missing' as 'implemented' */
return res != SYSCTL_OFF;
#else
return false;
#endif
@ -33,8 +34,9 @@ bool platform_sha256_neon_available(void)
#elif defined HWCAP2_SHA2
return getauxval(AT_HWCAP2) & HWCAP2_SHA2;
#elif defined __APPLE__
/* Assume always present on M1 macOS, similarly to AES */
return true;
SysctlResult res = test_sysctl_flag("hw.optional.arm.FEAT_SHA256");
/* As above, treat 'missing' as enabled */
return res != SYSCTL_OFF;
#else
return false;
#endif
@ -47,8 +49,9 @@ bool platform_sha1_neon_available(void)
#elif defined HWCAP2_SHA1
return getauxval(AT_HWCAP2) & HWCAP2_SHA1;
#elif defined __APPLE__
/* Assume always present on M1 macOS, similarly to AES */
return true;
SysctlResult res = test_sysctl_flag("hw.optional.arm.FEAT_SHA1");
/* As above, treat 'missing' as enabled */
return res != SYSCTL_OFF;
#else
return false;
#endif
@ -61,7 +64,14 @@ bool platform_sha512_neon_available(void)
#elif defined HWCAP2_SHA512
return getauxval(AT_HWCAP2) & HWCAP2_SHA512;
#elif defined __APPLE__
return test_sysctl_flag("hw.optional.armv8_2_sha512");
/* There are two sysctl flags for this, apparently invented at
* different times. Try both, falling back to the older one. */
SysctlResult res = test_sysctl_flag("hw.optional.arm.FEAT_SHA512");
if (res != SYSCTL_MISSING)
return res == SYSCTL_ON;
res = test_sysctl_flag("hw.optional.armv8_2_sha512");
return res == SYSCTL_ON;
#else
return false;
#endif

12
unix/utils/arm_arch_queries.h
View File

@ -49,15 +49,19 @@ static inline u_long getauxval(int which) { return 0; }
#endif /* defined __arm__ || defined __aarch64__ */
#if defined __APPLE__
static inline bool test_sysctl_flag(const char *flagname)
typedef enum { SYSCTL_MISSING, SYSCTL_OFF, SYSCTL_ON } SysctlResult;
static inline SysctlResult test_sysctl_flag(const char *flagname)
{
#if HAVE_SYSCTLBYNAME
int value;
size_t size = sizeof(value);
return (sysctlbyname(flagname, &value, &size, NULL, 0) == 0 &&
size == sizeof(value) && value != 0);
if (sysctlbyname(flagname, &value, &size, NULL, 0) == 0 &&
size == sizeof(value)) {
return value != 0 ? SYSCTL_ON : SYSCTL_OFF;
}
#else /* HAVE_SYSCTLBYNAME */
return false;
return SYSCTL_MISSING;
#endif /* HAVE_SYSCTLBYNAME */
}
#endif /* defined __APPLE__ */