1 files changed, 64 insertions, 0 deletions
diff --git a/libc/bionic/bionic_call_ifunc_resolver.cpp b/libc/bionic/bionic_call_ifunc_resolver.cpp
new file mode 100644
index 000000000..437de78ce
--- /dev/null
+++ b/libc/bionic/bionic_call_ifunc_resolver.cpp
@@ -0,0 +1,64 @@
+/*
+ * 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.
+ */
+
+#include "private/bionic_call_ifunc_resolver.h"
+#include <sys/auxv.h>
+#include <sys/ifunc.h>
+
+#include "private/bionic_auxv.h"
+
+// This code is called in the linker before it has been relocated, so minimize calls into other
+// parts of Bionic. In particular, we won't ever have two ifunc resolvers called concurrently, so
+// initializing the ifunc resolver argument doesn't need to be thread-safe.
+
+ElfW(Addr) __bionic_call_ifunc_resolver(ElfW(Addr) resolver_addr) {
+#if defined(__aarch64__)
+  typedef ElfW(Addr) (*ifunc_resolver_t)(uint64_t, __ifunc_arg_t*);
+  static __ifunc_arg_t arg;
+  static bool initialized = false;
+  if (!initialized) {
+    initialized = true;
+    arg._size = sizeof(__ifunc_arg_t);
+    arg._hwcap = getauxval(AT_HWCAP);
+    arg._hwcap2 = getauxval(AT_HWCAP2);
+  }
+  return reinterpret_cast<ifunc_resolver_t>(resolver_addr)(arg._hwcap | _IFUNC_ARG_HWCAP, &arg);
+#elif defined(__arm__)
+  typedef ElfW(Addr) (*ifunc_resolver_t)(unsigned long);
+  static unsigned long hwcap;
+  static bool initialized = false;
+  if (!initialized) {
+    initialized = true;
+    hwcap = getauxval(AT_HWCAP);
+  }
+  return reinterpret_cast<ifunc_resolver_t>(resolver_addr)(hwcap);
+#else
+  typedef ElfW(Addr) (*ifunc_resolver_t)(void);
+  return reinterpret_cast<ifunc_resolver_t>(resolver_addr)();
+#endif
+}