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

Cristian Marussi
2019-08-23T17:49:43Z

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/
...

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;
>>> +}
>>>
>>