Merge "Implement ifunc support for static executables."

libc/bionic/libc_init_static.cpp

@@ -66,6 +66,30 @@ static void call_array(void(**list)()) {
   }
 }
 
+#if defined(__aarch64__) || defined(__x86_64__)
+extern __LIBC_HIDDEN__ ElfW(Rela) __rela_iplt_start[], __rela_iplt_end[];
+
+static void call_ifunc_resolvers() {
+  typedef ElfW(Addr) (*ifunc_resolver_t)(void);
+  for (ElfW(Rela) *r = __rela_iplt_start; r != __rela_iplt_end; ++r) {
+    ElfW(Addr)* offset = reinterpret_cast<ElfW(Addr)*>(r->r_offset);
+    ElfW(Addr) resolver = r->r_addend;
+    *offset = reinterpret_cast<ifunc_resolver_t>(resolver)();
+  }
+}
+#else
+extern __LIBC_HIDDEN__ ElfW(Rel) __rel_iplt_start[], __rel_iplt_end[];
+
+static void call_ifunc_resolvers() {
+  typedef ElfW(Addr) (*ifunc_resolver_t)(void);
+  for (ElfW(Rel) *r = __rel_iplt_start; r != __rel_iplt_end; ++r) {
+    ElfW(Addr)* offset = reinterpret_cast<ElfW(Addr)*>(r->r_offset);
+    ElfW(Addr) resolver = *offset;
+    *offset = reinterpret_cast<ifunc_resolver_t>(resolver)();
+  }
+}
+#endif
+
 static void apply_gnu_relro() {
   ElfW(Phdr)* phdr_start = reinterpret_cast<ElfW(Phdr)*>(getauxval(AT_PHDR));
   unsigned long int phdr_ct = getauxval(AT_PHNUM);
@@ -137,6 +161,7 @@ __noreturn static void __real_libc_init(void *raw_args,
   __libc_init_main_thread_final();
   __libc_init_common();
 
+  call_ifunc_resolvers();
   apply_gnu_relro();
 
   // Several Linux ABIs don't pass the onexit pointer, and the ones that

tests/Android.bp

@@ -95,6 +95,7 @@ cc_test_library {
         "grp_pwd_file_test.cpp",
         "iconv_test.cpp",
         "ifaddrs_test.cpp",
+        "ifunc_test.cpp",
         "inttypes_test.cpp",
         "iso646_test.c",
         "langinfo_test.cpp",

tests/ifunc_test.cpp

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gtest/gtest.h>
+
+int ret42() {
+  return 42;
+}
+
+extern "C" void* resolver() {
+  return (void*)ret42;
+}
+
+int ifunc() __attribute__((ifunc("resolver")));
+
+TEST(ifunc, function) {
+  ASSERT_EQ(42, ifunc());
+}