Implement ifunc support for static executables.
A static executable is almost entirely statically relocated by the
linker, with the exception of IRELATIVE relocations, which must be
resolved by libc by enumerating the relocations using the special
linker-defined symbols __rela?_iplt_{start,end}. This patch implements
ifunc support by enumerating the relocations in this way.
Bug: 112482891
Test: /data/nativetest{,64}/bionic-unit-tests-static/bionic-unit-tests-static on walleye_hwasan-userdebug
Change-Id: Ia5522a190da0b86e095b141d5d4e68dd7dd4b695
diff --git a/libc/bionic/libc_init_static.cpp b/libc/bionic/libc_init_static.cpp
index 8fbc20e..83f2e23 100644
--- a/libc/bionic/libc_init_static.cpp
+++ b/libc/bionic/libc_init_static.cpp
@@ -66,6 +66,30 @@
}
}
+#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);
@@ -134,6 +158,7 @@
__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
diff --git a/tests/Android.bp b/tests/Android.bp
index 8ac0531..a409b2a 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -95,6 +95,7 @@
"grp_pwd_file_test.cpp",
"iconv_test.cpp",
"ifaddrs_test.cpp",
+ "ifunc_test.cpp",
"inttypes_test.cpp",
"iso646_test.c",
"langinfo_test.cpp",
diff --git a/tests/ifunc_test.cpp b/tests/ifunc_test.cpp
new file mode 100644
index 0000000..7ab5899
--- /dev/null
+++ b/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());
+}