Add arm64 string.h function implementations for use with hardware supporting MTE.
As it turns out, our "generic" arm64 implementations of certain string.h
functions are not actually generic, since they will eagerly read memory
possibly outside of the bounds of an MTE granule, which may lead to a segfault
on MTE-enabled hardware. Therefore, move the implementations into a "default"
directory and use ifuncs to select between them and a new set of "mte"
implementations, conditional on whether the hardware and kernel support MTE.
The MTE implementations are currently naive implementations written in C
but will later be replaced with a set of optimized assembly implementations.
Bug: 135772972
Change-Id: Ife37c4e0e6fd60ff20a34594cc09c541af4d1dd7
diff --git a/libc/arch-arm64/dynamic_function_dispatch.cpp b/libc/arch-arm64/dynamic_function_dispatch.cpp
new file mode 100644
index 0000000..37abea4
--- /dev/null
+++ b/libc/arch-arm64/dynamic_function_dispatch.cpp
@@ -0,0 +1,99 @@
+/*
+ * 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 <platform/bionic/mte_kernel.h>
+#include <private/bionic_ifuncs.h>
+#include <stddef.h>
+#include <sys/auxv.h>
+
+extern "C" {
+
+static bool supports_mte(unsigned long hwcap2) {
+#ifdef ANDROID_EXPERIMENTAL_MTE
+ return hwcap2 & HWCAP2_MTE;
+#else
+ (void)hwcap2;
+ return false;
+#endif
+}
+
+typedef void* memchr_func(const void*, int, size_t);
+DEFINE_IFUNC_FOR(memchr) {
+ if (supports_mte(arg->_hwcap2)) {
+ RETURN_FUNC(memchr_func, memchr_mte);
+ } else {
+ RETURN_FUNC(memchr_func, memchr_default);
+ }
+}
+
+typedef char* strchr_func(const char*, int);
+DEFINE_IFUNC_FOR(strchr) {
+ if (supports_mte(arg->_hwcap2)) {
+ RETURN_FUNC(strchr_func, strchr_mte);
+ } else {
+ RETURN_FUNC(strchr_func, strchr_default);
+ }
+}
+
+typedef int strcmp_func(const char*, const char*);
+DEFINE_IFUNC_FOR(strcmp) {
+ if (supports_mte(arg->_hwcap2)) {
+ RETURN_FUNC(strcmp_func, strcmp_mte);
+ } else {
+ RETURN_FUNC(strcmp_func, strcmp_default);
+ }
+}
+
+typedef size_t strlen_func(const char*);
+DEFINE_IFUNC_FOR(strlen) {
+ if (supports_mte(arg->_hwcap2)) {
+ RETURN_FUNC(strlen_func, strlen_mte);
+ } else {
+ RETURN_FUNC(strlen_func, strlen_default);
+ }
+}
+
+typedef int strncmp_func(const char*, const char*, int);
+DEFINE_IFUNC_FOR(strncmp) {
+ if (supports_mte(arg->_hwcap2)) {
+ RETURN_FUNC(strncmp_func, strncmp_mte);
+ } else {
+ RETURN_FUNC(strncmp_func, strncmp_default);
+ }
+}
+
+typedef size_t strnlen_func(const char*, int);
+DEFINE_IFUNC_FOR(strnlen) {
+ if (supports_mte(arg->_hwcap2)) {
+ RETURN_FUNC(strnlen_func, strnlen_mte);
+ } else {
+ RETURN_FUNC(strnlen_func, strnlen_default);
+ }
+}
+
+} // extern "C"