[PATCH v17 15/15] selftests, arm64: add a selftest for passing tagged pointers to kernel

[Andrey Konovalov]

This patch is a part of a series that extends arm64 kernel ABI to allow to
pass tagged user pointers (with the top byte set to something else other
than 0x00) as syscall arguments.

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.

Co-developed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
---
 tools/testing/selftests/arm64/.gitignore      |  2 +
 tools/testing/selftests/arm64/Makefile        | 22 +++++++
 .../testing/selftests/arm64/run_tags_test.sh  | 12 ++++
 tools/testing/selftests/arm64/tags_lib.c      | 62 +++++++++++++++++++
 tools/testing/selftests/arm64/tags_test.c     | 18 ++++++
 5 files changed, 116 insertions(+)
 create mode 100644 tools/testing/selftests/arm64/.gitignore
 create mode 100644 tools/testing/selftests/arm64/Makefile
 create mode 100755 tools/testing/selftests/arm64/run_tags_test.sh
 create mode 100644 tools/testing/selftests/arm64/tags_lib.c
 create mode 100644 tools/testing/selftests/arm64/tags_test.c

diff --git a/tools/testing/selftests/arm64/.gitignore b/tools/testing/selftests/arm64/.gitignore
new file mode 100644
index 000000000000..9b6a568de17f
--- /dev/null
+++ b/tools/testing/selftests/arm64/.gitignore
@@ -0,0 +1,2 @@
+tags_test
+tags_lib.so
diff --git a/tools/testing/selftests/arm64/Makefile b/tools/testing/selftests/arm64/Makefile
new file mode 100644
index 000000000000..9dee18727923
--- /dev/null
+++ b/tools/testing/selftests/arm64/Makefile
@@ -0,0 +1,22 @@
+# SPDX-License-Identifier: GPL-2.0
+
+include ../lib.mk
+
+# 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_CUSTOM_PROGS := $(OUTPUT)/tags_test
+
+$(OUTPUT)/tags_test: tags_test.c $(OUTPUT)/tags_lib.so
+	$(CC) -o $@ $(CFLAGS) $(LDFLAGS) $<
+
+$(OUTPUT)/tags_lib.so: tags_lib.c
+	$(CC) -o $@ -shared $(CFLAGS) $(LDFLAGS) $^
+
+TEST_PROGS := run_tags_test.sh
+
+all: $(TEST_CUSTOM_PROGS)
+
+endif
diff --git a/tools/testing/selftests/arm64/run_tags_test.sh b/tools/testing/selftests/arm64/run_tags_test.sh
new file mode 100755
index 000000000000..2bbe0cd4220b
--- /dev/null
+++ b/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 "--------------------"
+LD_PRELOAD=./tags_lib.so ./tags_test
+if [ $? -ne 0 ]; then
+	echo "[FAIL]"
+else
+	echo "[PASS]"
+fi
diff --git a/tools/testing/selftests/arm64/tags_lib.c b/tools/testing/selftests/arm64/tags_lib.c
new file mode 100644
index 000000000000..55f64fc1aae6
--- /dev/null
+++ b/tools/testing/selftests/arm64/tags_lib.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <stdlib.h>
+#include <sys/prctl.h>
+
+#define TAG_SHIFT	(56)
+#define TAG_MASK	(0xffUL << TAG_SHIFT)
+
+#define PR_SET_TAGGED_ADDR_CTRL	55
+#define PR_GET_TAGGED_ADDR_CTRL	56
+#define PR_TAGGED_ADDR_ENABLE	(1UL << 0)
+
+void *__libc_malloc(size_t size);
+void __libc_free(void *ptr);
+void *__libc_realloc(void *ptr, size_t size);
+void *__libc_calloc(size_t nmemb, size_t size);
+
+static void *tag_ptr(void *ptr)
+{
+	static int tagged_addr_err = 1;
+	unsigned long tag = 0;
+
+	/*
+	 * Note that this code is racy. We only use it as a part of a single
+	 * threaded test application. Beware of using in multithreaded ones.
+	 */
+	if (tagged_addr_err == 1)
+		tagged_addr_err = prctl(PR_SET_TAGGED_ADDR_CTRL,
+				PR_TAGGED_ADDR_ENABLE, 0, 0, 0);
+
+	if (!ptr)
+		return ptr;
+	if (!tagged_addr_err)
+		tag = rand() & 0xff;
+
+	return (void *)((unsigned long)ptr | (tag << TAG_SHIFT));
+}
+
+static void *untag_ptr(void *ptr)
+{
+	return (void *)((unsigned long)ptr & ~TAG_MASK);
+}
+
+void *malloc(size_t size)
+{
+	return tag_ptr(__libc_malloc(size));
+}
+
+void free(void *ptr)
+{
+	__libc_free(untag_ptr(ptr));
+}
+
+void *realloc(void *ptr, size_t size)
+{
+	return tag_ptr(__libc_realloc(untag_ptr(ptr), size));
+}
+
+void *calloc(size_t nmemb, size_t size)
+{
+	return tag_ptr(__libc_calloc(nmemb, size));
+}
diff --git a/tools/testing/selftests/arm64/tags_test.c b/tools/testing/selftests/arm64/tags_test.c
new file mode 100644
index 000000000000..263b302874ed
--- /dev/null
+++ b/tools/testing/selftests/arm64/tags_test.c
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <sys/utsname.h>
+
+int main(void)
+{
+	struct utsname *ptr;
+	int err;
+
+	ptr = (struct utsname *)malloc(sizeof(*ptr));
+	err = uname(ptr);
+	free(ptr);
+	return err;
+}
-- 
2.22.0.rc2.383.gf4fbbf30c2-goog