Detect ARM CPU features on FreeBSD.

elf_aux_info is similar to getauxval but is nop on aarch64.

--- lib/freebl/blinit.c.orig	2019-08-30 15:46:32 UTC
+++ lib/freebl/blinit.c
@@ -96,8 +96,8 @@ CheckX86CPUSupport()
 #ifndef __has_include
 #define __has_include(x) 0
 #endif
-#if (__has_include(<sys/auxv.h>) || defined(__linux__)) && \
-    defined(__GNUC__) && __GNUC__ >= 2 && defined(__ELF__)
+#if defined(__linux__)
+#if defined(__GNUC__) && __GNUC__ >= 2 && defined(__ELF__)
 /* This might be conflict with host compiler */
 #if !defined(__ANDROID__)
 #include <sys/auxv.h>
@@ -106,6 +106,10 @@ extern unsigned long getauxval(unsigned long type) __a
 #else
 static unsigned long (*getauxval)(unsigned long) = NULL;
 #endif /* defined(__GNUC__) && __GNUC__ >= 2 && defined(__ELF__)*/
+#elif defined(__FreeBSD__) && __has_include(<sys/auxv.h>)
+#include <sys/auxv.h>
+#define HAVE_ELF_AUX_INFO
+#endif /* defined(__linux__) */
 
 #ifndef AT_HWCAP2
 #define AT_HWCAP2 26
@@ -118,6 +122,9 @@ static unsigned long (*getauxval)(unsigned long) = NUL
 /* clang-format on */
 
 #if defined(__aarch64__)
+#if defined(__FreeBSD__)
+#include <machine/armreg.h>
+#endif
 // Defines from hwcap.h in Linux kernel - ARM64
 #ifndef HWCAP_AES
 #define HWCAP_AES (1 << 3)
@@ -138,6 +145,7 @@ 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(__linux__)
     if (getauxval) {
         long hwcaps = getauxval(AT_HWCAP);
         arm_aes_support_ = hwcaps & HWCAP_AES && disable_hw_aes == NULL;
@@ -145,6 +153,14 @@ CheckARMSupport()
         arm_sha1_support_ = hwcaps & HWCAP_SHA1;
         arm_sha2_support_ = hwcaps & HWCAP_SHA2;
     }
+#elif defined(__FreeBSD__)
+    uint64_t id_aa64isar0;
+    id_aa64isar0 = READ_SPECIALREG(ID_AA64ISAR0_EL1);
+    arm_aes_support_ = ID_AA64ISAR0_AES(id_aa64isar0) >= ID_AA64ISAR0_AES_BASE && disable_hw_aes == NULL;
+    arm_pmull_support_ = ID_AA64ISAR0_AES(id_aa64isar0) == ID_AA64ISAR0_AES_PMULL && disable_pmull == NULL;
+    arm_sha1_support_ = ID_AA64ISAR0_SHA1(id_aa64isar0) == ID_AA64ISAR0_SHA1_BASE;
+    arm_sha2_support_ = ID_AA64ISAR0_SHA2(id_aa64isar0) >= ID_AA64ISAR0_SHA2_BASE;
+#endif /* defined(__linux__) */
     /* aarch64 must support NEON. */
     arm_neon_support_ = disable_arm_neon == NULL;
 }
@@ -187,7 +203,7 @@ GetNeonSupport()
     // If no getauxval, compiler generate NEON instruction by default,
     // we should allow NOEN support.
     return PR_TRUE;
-#elif !defined(__ANDROID__)
+#elif defined(__linux__) && !defined(__ANDROID__)
     // Android's cpu-features.c detects features by the following logic
     //
     // - Call getauxval(AT_HWCAP)
@@ -201,6 +217,10 @@ GetNeonSupport()
     if (getauxval) {
         return (getauxval(AT_HWCAP) & HWCAP_NEON);
     }
+#elif defined(__FreeBSD__) && defined(HAVE_ELF_AUX_INFO)
+    unsigned long hwcap = 0;
+    elf_aux_info(AT_HWCAP, &hwcap, sizeof(hwcap));
+    return (hwcap & HWCAP_NEON);
 #endif /* defined(__ARM_NEON) || defined(__ARM_NEON__) */
     return PR_FALSE;
 }
@@ -249,6 +269,7 @@ void
 CheckARMSupport()
 {
     char *disable_hw_aes = PR_GetEnvSecure("NSS_DISABLE_HW_AES");
+#if defined(__linux__)
     if (getauxval) {
         // Android's cpu-features.c uses AT_HWCAP2 for newer features.
         // AT_HWCAP2 is implemented on newer devices / kernel, so we can trust
@@ -257,13 +278,19 @@ CheckARMSupport()
         // AT_HWCAP2 isn't supported by glibc or Linux kernel, getauxval will
         // returns 0.
         long hwcaps = getauxval(AT_HWCAP2);
-#ifdef __linux__
         if (!hwcaps) {
             // Some ARMv8 devices may not implement AT_HWCAP2. So we also
             // read /proc/cpuinfo if AT_HWCAP2 is 0.
             hwcaps = ReadCPUInfoForHWCAP2();
         }
-#endif
+#elif defined(__FreeBSD__) && defined(HAVE_ELF_AUX_INFO)
+    unsigned long hwcaps = 0;
+    elf_aux_info(AT_HWCAP2, &hwcaps, sizeof(hwcaps));
+    {
+#else
+    if (0) {
+        unsigned long hwcaps = 0;
+#endif /* defined(__linux__) */
         arm_aes_support_ = hwcaps & HWCAP2_AES && disable_hw_aes == NULL;
         arm_pmull_support_ = hwcaps & HWCAP2_PMULL;
         arm_sha1_support_ = hwcaps & HWCAP2_SHA1;