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

Andrey Konovalov
2019-09-04T14:52:47Z

On Fri, Aug 23, 2019 at 7:49 PM Cristian Marussi
<cristian.marussi@arm.com> wrote:
>
>
> Hi
>
> On 23/08/2019 18:16, Andrey Konovalov wrote:
> > 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).
>
> Ok. Thanks for the reply.
>
> I think I've got it in my local tree having cloned arm64/for-next-core:
>
> 18:32 $ egrep -A 10 PR_SET_TAG ./include/uapi/linux/prctl.h
> #define PR_SET_TAGGED_ADDR_CTRL 55
> #define PR_GET_TAGGED_ADDR_CTRL 56
> # define PR_TAGGED_ADDR_ENABLE (1UL << 0)
>
> #endif /* _LINUX_PRCTL_H */
>
> and Kernel header are locally installed in my kernel src dir (by KSFT indeed)
>
> 18:34 $ egrep -RA 10 PR_SET_TAG usr/include/
> usr/include/linux/prctl.h:#define PR_SET_TAGGED_ADDR_CTRL 55
> usr/include/linux/prctl.h-#define PR_GET_TAGGED_ADDR_CTRL 56
> usr/include/linux/prctl.h-# define PR_TAGGED_ADDR_ENABLE (1UL << 0)
> usr/include/linux/prctl.h-
> usr/include/linux/prctl.h-#endif /* _LINUX_PRCTL_H */
>
> but how are they supposed to be found if nor the test Makefile
> neither the KSFT Makefile who installs them pass any -I options to the
> compiler ?
> I suppose <sys/prctl.h> tries to include arch specific headers from the regular system path,
> but when you are cross-compiling ?
>
> 18:34 $ 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
> 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 -Wall -O2 -g tags_test.c -o /home/crimar01/ARM/dev/src/pdsw/out_linux/kselftest/arm64/tags/tags_test
> tags_test.c: In function ‘main’:
> tags_test.c:20:12: 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:20:12: note: each undeclared identifier is reported only once for each function it appears in
> tags_test.c:20:37: 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/tags_test' failed
> make[4]: *** [/home/crimar01/ARM/dev/src/pdsw/out_linux/kselftest/arm64/tags/tags_test] Error 1
> Makefile:19: recipe for target 'all' failed
> make[3]: *** [all] Error 2
> Makefile:137: recipe for target 'all' failed
> make[2]: *** [all] Error 2
> /home/crimar01/ARM/dev/src/pdsw/linux/Makefile:1236: 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
>
>
> In fact many KSFT testcases seems to brutally add default headers path:
>
> tools/testing/selftests/memfd/Makefile:CFLAGS += -I../../../../include/uapi/
> tools/testing/selftests/memfd/Makefile:CFLAGS += -I../../../../include/
> tools/testing/selftests/memfd/Makefile:CFLAGS += -I../../../../usr/include/
> tools/testing/selftests/net/Makefile:CFLAGS += -I../../../../usr/include/
> tools/testing/selftests/membarrier/Makefile:CFLAGS += -g -I../../../../usr/include/
> ...

Hi Cristian!

Indeed, I can reproduce the issue. I don't know what's the proper way
to resolve this. Adding "CFLAGS += -I../../../../usr/include/" looks
good to me. AFAICS your series resolves this issue in a similar way,
but I think we should fix this before the current rc is released. Do
you want to submit a patch that adds this simple fix or should I do
that?

Thanks!

>
> Cheers
>
> Cristian
> >
> >
> >
> >>
> >> 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;
> >>> +}
> >>>
> >>
>