Re: Patch to detect on CPU capabilities on Apple Silicon

[Niels Möller]

Tim Kosse  writes:

> Whoops, I made a typo in the constant for SHA256, please use this
> revised patch instead.

Thanks, applied and pushed to the master-updates branch for testing.

Regards,
/Niels

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Re: Patch to detect on CPU capabilities on Apple Silicon

[Tim Kosse]

Whoops, I made a typo in the constant for SHA256, please use this 
revised patch instead.


Regards,
Tim--- nettle-3.9.1_orig/fat-arm64.c   2023-12-05 02:16:50
+++ nettle-3.9.1/fat-arm64.c2023-12-05 02:15:23
@@ -50,6 +50,8 @@
 # include 
 # include 
 # include 
+#elif defined(__APPLE__)
+# include 
 #endif
 
 #include "nettle-types.h"
@@ -85,6 +87,16 @@
 
 #define MATCH(s, slen, literal, llen) \
   ((slen) == (llen) && memcmp ((s), (literal), llen) == 0)
+
+#if defined(__APPLE__)
+static int
+check_sysctlbyname(const char* name)
+{
+  int val;
+  size_t s = sizeof(val);
+  return sysctlbyname(name, &val, &s, NULL, 0) ? 0 : val;
+}
+#endif
 
 static void
 get_arm64_features (struct arm64_features *features)
@@ -141,6 +153,12 @@
 = (ID_AA64ISAR0_SHA1(isar0) >= ID_AA64ISAR0_SHA1_BASE);
   features->have_sha2
 = (ID_AA64ISAR0_SHA2(isar0) >= ID_AA64ISAR0_SHA2_BASE);
+#elif defined(__APPLE__)
+  /* See 
https://developer.apple.com/documentation/kernel/1387446-sysctlbyname/determining_instruction_set_characteristics
 */
+  features->have_aes = check_sysctlbyname("hw.optional.arm.FEAT_AES");
+  features->have_pmull = check_sysctlbyname("hw.optional.arm.FEAT_PMULL");
+  features->have_sha1 = check_sysctlbyname("hw.optional.arm.FEAT_SHA1");
+  features->have_sha2 = check_sysctlbyname("hw.optional.arm.FEAT_SHA256");
 #endif
 }
 }
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Patch to detect on CPU capabilities on Apple Silicon

[Tim Kosse]

Hi,

after building Nettle natively for Apple devices running Apple Silicon, 
I noticed a drastic performance different between the native build, and 
an x86_64 build emulated via Apple's Rosetta. The latter, despite 
emulation, was over 10 times faster in some algorithms, e.g. AES-128-GCM.


I found out that get_arm64_features did not at all detect the CPU 
capabilities on Apple devices.


The attached patch fixes the issue for me, with it in place the CPU 
features are correctly detected.


AES-128-GCM benchmark results:
   Native (pre-patch): 200MB/s
   Emulated: 3.2GB/s
   Native (patched): 5.2GB/s

Regards,
Tim Kosse--- nettle-3.9.1_orig/fat-arm64.c   2023-12-05 02:16:50
+++ nettle-3.9.1/fat-arm64.c2023-12-05 02:15:23
@@ -50,6 +50,8 @@
 # include 
 # include 
 # include 
+#elif defined(__APPLE__)
+# include 
 #endif
 
 #include "nettle-types.h"
@@ -85,6 +87,16 @@
 
 #define MATCH(s, slen, literal, llen) \
   ((slen) == (llen) && memcmp ((s), (literal), llen) == 0)
+
+#if defined(__APPLE__)
+static int
+check_sysctlbyname(const char* name)
+{
+  int val;
+  size_t s = sizeof(val);
+  return sysctlbyname(name, &val, &s, NULL, 0) ? 0 : val;
+}
+#endif
 
 static void
 get_arm64_features (struct arm64_features *features)
@@ -141,6 +153,12 @@
 = (ID_AA64ISAR0_SHA1(isar0) >= ID_AA64ISAR0_SHA1_BASE);
   features->have_sha2
 = (ID_AA64ISAR0_SHA2(isar0) >= ID_AA64ISAR0_SHA2_BASE);
+#elif defined(__APPLE__)
+  /* See 
https://developer.apple.com/documentation/kernel/1387446-sysctlbyname/determining_instruction_set_characteristics
 */
+  features->have_aes = check_sysctlbyname("hw.optional.arm.FEAT_AES");
+  features->have_pmull = check_sysctlbyname("hw.optional.arm.FEAT_PMULL");
+  features->have_sha1 = check_sysctlbyname("hw.optional.arm.FEAT_SHA1");
+  features->have_sha2 = check_sysctlbyname("hw.optional.arm.FEAT_SHA2");
 #endif
 }
 }
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