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

Cristian Marussi
2019-09-04T16:22:21Z

Hi Andrey !

On 04/09/2019 15:52, Andrey Konovalov wrote:
> 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?
>

Please feel free to post the single line patch above to quickly fix this before
release, so we don't have a broken build straight away. (our CI is already beating me...:D)

On my side (01/11) in the meantime I'll fix the top level KSFT arm64 makefile so as to calculate
and propagate once for all the headers search path down to all KSFT arm64/ in one go,
trying to guess where they are; this is needed because the above fix works fine as long
as you don't have KBUILD_OUTPUT set, once you set it, KSFT installs kheaders in a different
place and the above -I fix is fooled again....but this is a general problem also in other
KSFT tests as I can see now so I think this fix is good enough for now
(and the fix on my side, even if trivial, is not going to go into this release for sure)

Thanks !

Cheers

Cristian

> 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;
>>>>> +}
>>>>>
>>>>
>>