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

Andrey Konovalov
2019-08-23T17:16:33Z

On Fri, Aug 23, 2019 at 3:56 PM Cristian Marussi
<cristian.marussi@arm.com> wrote:
>
> 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 ?

Hm, PR_SET_TAGGED_ADDR_CTRL is defined in include/uapi/linux/prctl.h,
and the test has #include <sys/prctl.h> so as long as you've updated
your kernel headers this should work.

(I'm OOO next week, I'll see if I can reproduce this once I'm back).

>
> 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;
> > +}
> >
>