Bug 1575843 - Detect AArch64 CPU features on FreeBSD r=jcj

Environment checks are reogranized to be separate from platform code
    to make it impossible to forget to check disable_FEATURE on one platform
    but not the other.

Differential Revision: https://phabricator.services.mozilla.com/D55386

--HG--
extra : moz-landing-system : lando

lib/freebl/blinit.c

@@ -133,6 +133,8 @@ static unsigned long (*getauxval)(unsigned long) = NULL;
 /* clang-format on */
 
 #if defined(__aarch64__)
+
+#if defined(__linux__)
 // Defines from hwcap.h in Linux kernel - ARM64
 #ifndef HWCAP_AES
 #define HWCAP_AES (1 << 3)
@@ -146,30 +148,54 @@ static unsigned long (*getauxval)(unsigned long) = NULL;
 #ifndef HWCAP_SHA2
 #define HWCAP_SHA2 (1 << 6)
 #endif
+#endif /* defined(__linux__) */
+
+#if defined(__FreeBSD__)
+#include <stdint.h>
+#include <machine/armreg.h>
+// Support for older version of armreg.h
+#ifndef ID_AA64ISAR0_AES_VAL
+#define ID_AA64ISAR0_AES_VAL ID_AA64ISAR0_AES
+#endif
+#ifndef ID_AA64ISAR0_SHA1_VAL
+#define ID_AA64ISAR0_SHA1_VAL ID_AA64ISAR0_SHA1
+#endif
+#ifndef ID_AA64ISAR0_SHA2_VAL
+#define ID_AA64ISAR0_SHA2_VAL ID_AA64ISAR0_SHA2
+#endif
+#endif /* defined(__FreeBSD__) */
 
 void
 CheckARMSupport()
 {
-    char *disable_arm_neon = PR_GetEnvSecure("NSS_DISABLE_ARM_NEON");
-    char *disable_hw_aes = PR_GetEnvSecure("NSS_DISABLE_HW_AES");
-    char *disable_pmull = PR_GetEnvSecure("NSS_DISABLE_PMULL");
 #if defined(_WIN64)
     BOOL arm_crypto_support = IsProcessorFeaturePresent(PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE);
-    arm_aes_support_ = arm_crypto_support && disable_hw_aes == NULL;
-    arm_pmull_support_ = arm_crypto_support && disable_pmull == NULL;
+    arm_aes_support_ = arm_crypto_support;
+    arm_pmull_support_ = arm_crypto_support;
     arm_sha1_support_ = arm_crypto_support;
     arm_sha2_support_ = arm_crypto_support;
-#else
+#elif defined(__linux__)
     if (getauxval) {
         long hwcaps = getauxval(AT_HWCAP);
-        arm_aes_support_ = hwcaps & HWCAP_AES && disable_hw_aes == NULL;
-        arm_pmull_support_ = hwcaps & HWCAP_PMULL && disable_pmull == NULL;
-        arm_sha1_support_ = hwcaps & HWCAP_SHA1;
-        arm_sha2_support_ = hwcaps & HWCAP_SHA2;
+        arm_aes_support_ = (hwcaps & HWCAP_AES) == HWCAP_AES;
+        arm_pmull_support_ = (hwcaps & HWCAP_PMULL) == HWCAP_PMULL;
+        arm_sha1_support_ = (hwcaps & HWCAP_SHA1) == HWCAP_SHA1;
+        arm_sha2_support_ = (hwcaps & HWCAP_SHA2) == HWCAP_SHA2;
+    }
+#elif defined(__FreeBSD__)
+    /* qemu-user does not support register access from userspace */
+    if (PR_GetEnvSecure("QEMU_EMULATING") == NULL) {
+        uint64_t isar0 = READ_SPECIALREG(id_aa64isar0_el1);
+        arm_aes_support_ = ID_AA64ISAR0_AES_VAL(isar0) >= ID_AA64ISAR0_AES_BASE;
+        arm_pmull_support_ = ID_AA64ISAR0_AES_VAL(isar0) >= ID_AA64ISAR0_AES_PMULL;
+        arm_sha1_support_ = ID_AA64ISAR0_SHA1_VAL(isar0) >= ID_AA64ISAR0_SHA1_BASE;
+        arm_sha2_support_ = ID_AA64ISAR0_SHA2_VAL(isar0) >= ID_AA64ISAR0_SHA2_BASE;
     }
 #endif
     /* aarch64 must support NEON. */
-    arm_neon_support_ = disable_arm_neon == NULL;
+    arm_neon_support_ = PR_GetEnvSecure("NSS_DISABLE_ARM_NEON") == NULL;
+    arm_aes_support_ &= PR_GetEnvSecure("NSS_DISABLE_HW_AES") == NULL;
+    arm_pmull_support_ &= PR_GetEnvSecure("NSS_DISABLE_PMULL") == NULL;
 }
 #endif /* defined(__aarch64__) */