Adding ARM AT_HWCAP support for FreeBSD (#7750)

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/7750

Reviewed By: ltamasi

Differential Revision: D25400609

Pulled By: pdillinger

fbshipit-source-id: 13b15e2f490acc011b648fbd9615ea8e580cccc7

util/crc32c_arm64.cc

@@ -43,21 +43,23 @@
 extern bool pmull_runtime_flag;
 
 uint32_t crc32c_runtime_check(void) {
-#ifdef ROCKSDB_AUXV_GETAUXVAL_PRESENT
-  uint64_t auxv = getauxval(AT_HWCAP);
-  return (auxv & HWCAP_CRC32) != 0;
-#else
-  return 0;
+  uint64_t auxv = 0;
+#if defined(ROCKSDB_AUXV_GETAUXVAL_PRESENT)
+  auxv = getauxval(AT_HWCAP);
+#elif defined(__FreeBSD__)
+  elf_aux_info(AT_HWCAP, &auxv, sizeof(auxv));
 #endif
+  return (auxv & HWCAP_CRC32) != 0;
 }
 
 bool crc32c_pmull_runtime_check(void) {
-#ifdef ROCKSDB_AUXV_GETAUXVAL_PRESENT
-  uint64_t auxv = getauxval(AT_HWCAP);
-  return (auxv & HWCAP_PMULL) != 0;
-#else
-  return false;
+  uint64_t auxv = 0;
+#if defined(ROCKSDB_AUXV_GETAUXVAL_PRESENT)
+  auxv = getauxval(AT_HWCAP);
+#elif defined(__FreeBSD__)
+  elf_aux_info(AT_HWCAP, &auxv, sizeof(auxv));
 #endif
+  return (auxv & HWCAP_PMULL) != 0;
 }
 
 #ifdef ROCKSDB_UBSAN_RUN