Re: [PATCH v18 15/15] selftests, arm64: add a selftest for passing tagged pointers to kernel

Cristian Marussi
2019-08-23T13:56:11Z

Hi Andrey

On 24/06/2019 15:33, Andrey Konovalov wrote:
> This patch is a part of a series that extends 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.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
> tools/testing/selftests/arm64/.gitignore | 1 +
> tools/testing/selftests/arm64/Makefile | 11 +++++++
> .../testing/selftests/arm64/run_tags_test.sh | 12 ++++++++
> tools/testing/selftests/arm64/tags_test.c | 29 +++++++++++++++++++
> 4 files changed, 53 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_test.c

After building a fresh Kernel from arm64/for-next-core from scratch at:

commit 239ab658bea3b387424501e7c416640d6752dc0c
Merge: 6bfa3134bd3a 42d038c4fb00 1243cb6a676f d55c5f28afaf d06fa5a118f1 34b5560db40d
Author: Will Deacon <will@kernel.org>
Date: Thu Aug 22 18:23:53 2019 +0100

Merge branches 'for-next/error-injection', 'for-next/tbi', 'for-next/psci-cpuidle', 'for-next/cpu-topology' and 'for-next/52-bit-kva' into for-next/core

KSFT arm64 tests build is broken for me, both setting or not KBUILD_OUTPUT=

13:30 $ make TARGETS=arm64 kselftest-clean
make[1]: Entering directory '/home/crimar01/ARM/dev/src/pdsw/out_linux'
rm -f -r /home/crimar01/ARM/dev/src/pdsw/out_linux//kselftest/arm64/tags_test
make[1]: Leaving directory '/home/crimar01/ARM/dev/src/pdsw/out_linux'

✔ ~/ARM/dev/src/pdsw/linux [arm64_for_next_core|…8⚑ 23]

13:30 $ make TARGETS=arm64 kselftest
make[1]: Entering directory '/home/crimar01/ARM/dev/src/pdsw/out_linux'
arch/arm64/Makefile:56: CROSS_COMPILE_COMPAT not defined or empty, the compat vDSO will not be built
make --no-builtin-rules INSTALL_HDR_PATH=$BUILD/usr \
ARCH=arm64 -C ../../.. headers_install
HOSTCC scripts/basic/fixdep
HOSTCC scripts/unifdef
...
...
HDRINST usr/include/asm/msgbuf.h
HDRINST usr/include/asm/shmbuf.h
INSTALL /home/crimar01/ARM/dev/src/pdsw/out_linux//kselftest/usr/include
/opt/toolchains/gcc-arm-8.3-2019.03-x86_64-aarch64-linux-gnu/bin/aarch64-linux-gnu-gcc tags_test.c -o /home/crimar01/ARM/dev/src/pdsw/out_linux//kselftest/arm64/tags_test
tags_test.c: In function ‘main’:
tags_test.c:21:12: error: ‘PR_SET_TAGGED_ADDR_CTRL’ undeclared (first use in this function); did you mean ‘PR_GET_TID_ADDRESS’?
if (prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0) == 0)
^~~~~~~~~~~~~~~~~~~~~~~
PR_GET_TID_ADDRESS
tags_test.c:21:12: note: each undeclared identifier is reported only once for each function it appears in
tags_test.c:21:37: error: ‘PR_TAGGED_ADDR_ENABLE’ undeclared (first use in this function); did you mean ‘PR_GET_DUMPABLE’?
if (prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0) == 0)
^~~~~~~~~~~~~~~~~~~~~
PR_GET_DUMPABLE
../lib.mk:138: recipe for target '/home/crimar01/ARM/dev/src/pdsw/out_linux//kselftest/arm64/tags_test' failed
make[3]: *** [/home/crimar01/ARM/dev/src/pdsw/out_linux//kselftest/arm64/tags_test] Error 1
Makefile:136: recipe for target 'all' failed
make[2]: *** [all] Error 2
/home/crimar01/ARM/dev/src/pdsw/linux/Makefile:1237: recipe for target 'kselftest' failed
make[1]: *** [kselftest] Error 2
make[1]: Leaving directory '/home/crimar01/ARM/dev/src/pdsw/out_linux'
Makefile:179: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2

Despite seeing KSFT installing Kernel Headers, they cannot be found.

Fixing this patch like this make it work for me:

diff --git a/tools/testing/selftests/arm64/Makefile b/tools/testing/selftests/arm64/Makefile
index a61b2e743e99..f9f79fb272f0 100644
--- a/tools/testing/selftests/arm64/Makefile
+++ b/tools/testing/selftests/arm64/Makefile
@@ -4,6 +4,7 @@
ARCH ?= $(shell uname -m 2>/dev/null || echo not)

ifneq (,$(filter $(ARCH),aarch64 arm64))
+CFLAGS += -I../../../../usr/include/
TEST_GEN_PROGS := tags_test
TEST_PROGS := run_tags_test.sh
endif

but is not really a proper fix since it does NOT account for case in which you have
installed the Kernel Headers in a non standard location like when you use KBUILD_OUTPUT.

Am I missing something ?

Thanks

Cristian

>
> diff --git a/tools/testing/selftests/arm64/.gitignore b/tools/testing/selftests/arm64/.gitignore
> new file mode 100644
> index 000000000000..e8fae8d61ed6
> --- /dev/null
> +++ b/tools/testing/selftests/arm64/.gitignore
> @@ -0,0 +1 @@
> +tags_test
> diff --git a/tools/testing/selftests/arm64/Makefile b/tools/testing/selftests/arm64/Makefile
> new file mode 100644
> index 000000000000..a61b2e743e99
> --- /dev/null
> +++ b/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
> 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..745f11379930
> --- /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 "--------------------"
> +./tags_test
> +if [ $? -ne 0 ]; then
> + echo "[FAIL]"
> +else
> + echo "[PASS]"
> +fi
> diff --git a/tools/testing/selftests/arm64/tags_test.c b/tools/testing/selftests/arm64/tags_test.c
> new file mode 100644
> index 000000000000..22a1b266e373
> --- /dev/null
> +++ b/tools/testing/selftests/arm64/tags_test.c
> @@ -0,0 +1,29 @@
> +// 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;
> +}
>