FROMLIST: selftests, arm64: add a selftest for passing tagged pointer…

…s to kernel

(from https://lore.kernel.org/patchwork/patch/994348)

This patch adds a simple test, that calls the uname syscall with a
tagged user pointer as an argument. Without the kernel accepting tagged
user pointers the test fails with EFAULT.

Bug: 112461694
Change-Id: Id23d66680a6bb55a098ef69bfa8af90c096fe53b
Signed-off-by: Andrey Konovalov <[email protected]>
Signed-off-by: Chenyang Zhong <[email protected]>

tools/testing/selftests/arm64/.gitignore

@@ -0,0 +1 @@
+tags_test

tools/testing/selftests/arm64/Makefile

@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# ARCH can be overridden by the user for cross compiling
+ARCH ?= $(shell uname -m 2>/dev/null || echo not)
+
+ifneq (,$(filter $(ARCH),aarch64 arm64))
+TEST_GEN_PROGS := tags_test
+TEST_PROGS := run_tags_test.sh
+endif
+
+include ../lib.mk

tools/testing/selftests/arm64/run_tags_test.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+echo "--------------------"
+echo "running tags test"
+echo "--------------------"
+./tags_test
+if [ $? -ne 0 ]; then
+	echo "[FAIL]"
+else
+	echo "[PASS]"
+fi

tools/testing/selftests/arm64/tags_test.c

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <sys/utsname.h>
+
+#define SHIFT_TAG(tag)		((uint64_t)(tag) << 56)
+#define SET_TAG(ptr, tag)	(((uint64_t)(ptr) & ~SHIFT_TAG(0xff)) | \
+					SHIFT_TAG(tag))
+
+int main(void)
+{
+	struct utsname utsname;
+	void *ptr = &utsname;
+	void *tagged_ptr = (void *)SET_TAG(ptr, 0x42);
+	int err = uname(tagged_ptr);
+	return err;
+}