selftests, arm64: add a selftest for passing tagged pointers to kernel

tags_test

# 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

#!/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

// SPDX-License-Identifier: GPL-2.0

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <stdint.h>

#include <sys/prctl.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)

{

	static int tbi_enabled = 0;

	struct utsname *ptr, *tagged_ptr;

	int err;

	if (prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0) == 0)

		tbi_enabled = 1;

	ptr = (struct utsname *)malloc(sizeof(*ptr));

	if (tbi_enabled)

		tagged_ptr = (struct utsname *)SET_TAG(ptr, 0x42);

	err = uname(tagged_ptr);

	free(ptr);

	return err;

}