diff --git a/libc/include/sys/ifunc.h b/libc/include/sys/ifunc.h
new file mode 100644
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+++ b/libc/include/sys/ifunc.h
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+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <sys/cdefs.h>
+
+/**
+ * @file sys/ifunc.h
+ * @brief Declarations used for ifunc resolvers. Currently only meaningful for arm64.
+ */
+
+__BEGIN_DECLS
+
+#if defined(__aarch64__)
+
+/**
+ * Provides information about hardware capabilities to ifunc resolvers.
+ *
+ * Starting with API level 30, ifunc resolvers on arm64 are passed two arguments. The first is a
+ * uint64_t whose value is equal to getauxval(AT_HWCAP) | _IFUNC_ARG_HWCAP. The second is a pointer
+ * to a data structure of this type. Prior to API level 30, no arguments are passed to ifunc
+ * resolvers. Code that wishes to be compatible with prior API levels should not accept any
+ * arguments in the resolver.
+ */
+typedef struct __ifunc_arg_t {
+  /** Set to sizeof(__ifunc_arg_t). */
+  unsigned long _size;
+
+  /** Set to getauxval(AT_HWCAP). */
+  unsigned long _hwcap;
+
+  /** Set to getauxval(AT_HWCAP2). */
+  unsigned long _hwcap2;
+} __ifunc_arg_t;
+
+/**
+ * If this bit is set in the first argument to an ifunc resolver, indicates that the second argument
+ * is a pointer to a data structure of type __ifunc_arg_t. This bit is always set on Android
+ * starting with API level 30.
+ */
+#define _IFUNC_ARG_HWCAP (1ULL << 62)
+
+#endif
+
+__END_DECLS