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Subject[PATCH v17 15/15] selftests, arm64: add a selftest for passing tagged pointers to kernel
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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@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
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
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