Re: [PATCH v2 2/2] selftests: livepatch: Test livepatching a heavily called syscall

[Petr Mladek <pmladek@suse.com>]

On Tue 2022-07-12 10:56:11, Joe Lawrence wrote:
> On Thu, Jun 30, 2022 at 11:12:26AM -0300, Marcos Paulo de Souza wrote:
> > Syscalls are called a tricky way. Some architectures add a prefix to the
> > syscall name (SYSCALL_WRAPPER).
> > 
> > This new test creates one userspace process per online cpu calling getpid
> > continuously and tries to livepatch the getpid function. Add the correct
> > function prefix for all archs that select HAS_SYSCALL_WRAPPER.
> > 
> > Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
> 
> Hi Marcos,
> 
> Thanks for working on this and sorry for the delayed reply.  I gave it a
> spin yesterday and have a few comments below...
> 
> > diff --git a/tools/testing/selftests/livepatch/Makefile b/tools/testing/selftests/livepatch/Makefile
> > index 5ef492b87bb1..35014197184e 100644
> > --- a/tools/testing/selftests/livepatch/Makefile
> > +++ b/tools/testing/selftests/livepatch/Makefile
> > @@ -1,10 +1,14 @@
> >  # SPDX-License-Identifier: GPL-2.0
> > +include ../../../build/Build.include
> > +include ../../../scripts/Makefile.arch
> > +include ../../../scripts/Makefile.include

This looks bad. It is outside of tools/tests/selftests/. It would
mean that the tests are not self-contained any longer.

The tests should support all scenarios described in
Documentation/dev-tools/kselftest.rst.

Note that it allows to install them and run them from
the installed copy. I guess that this is useful if you
want to package the selftests.


> Final note, kbuild is probably my weakest area, so I'm of limited help
> review-wise there.  In trying out the code, I wasn't sure exactly how to
> run things.  I did:
> 
>   $ make -C tools/testing/selftests/livepatch/ run_tests
> 
> and that built everything and ran the tests (good).  I changed a few .c
> files and tried again, but they didn't rebuild.  Then from
> tools/testing/selftests/livepatch/test_modules/ I ran `make` and it only
> ran the clean target (not good, I think).
>
> What is the typical workflow supposed to be in this combined setup?

I personally test the mainline kernels the following way:

workstation> make binrpm-pkg

test-system-qemu# sshfs workstation:/path/to/packages /mnt
test-system-qemu# rpm -ivh /mnt/RPMS/x86_64/kernel-xxxx.rpm
test-system-qemu# reboot

test-system-qemu# sshfs workstation:/path/to/sources /mnt
test-system-qemu# cd /mnt/linux/tools/tests/selftests/livepatch
test-system-qemu# make run_tests

With this patchset I get:

test-system-qemu:/mnt/kernel/linux/tools/testing/selftests/livepatch # make run_tests 
make -C test_modules test_klp_atomic_replace.ko
make[1]: Entering directory '/mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules'
make -C /lib/modules/5.19.0-rc8-default+/build M=/mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules test_klp_atomic_replace.ko
make[2]: Entering directory '/mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules'
make[2]: *** /lib/modules/5.19.0-rc8-default+/build: No such file or directory.  Stop.
make[2]: Leaving directory '/mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules'
make[1]: *** [Makefile:17: test_klp_atomic_replace.ko] Error 2
make[1]: Leaving directory '/mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules'
make: *** [Makefile:44: /mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules/test_klp_atomic_replace.ko] Error 2


I get the same when I try it from the top level directory:

test-system-qemu:/mnt/kernel/linux # make -C tools/testing/selftests TARGETS=livepatch run_tests
make: Entering directory '/mnt/kernel/linux/tools/testing/selftests'
make --no-builtin-rules ARCH=x86 -C ../../.. headers_install
make[1]: Entering directory '/mnt/kernel/linux'
  INSTALL ./usr/include
make[1]: Leaving directory '/mnt/kernel/linux'
make[1]: Entering directory '/mnt/kernel/linux/tools/testing/selftests/livepatch'
make -C test_modules test_klp_atomic_replace.ko
make[2]: Entering directory '/mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules'
make -C /lib/modules/5.19.0-rc8-default+/build M=/mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules test_klp_atomic_replace.ko
make[3]: Entering directory '/mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules'
make[3]: *** /lib/modules/5.19.0-rc8-default+/build: No such file or directory.  Stop.
make[3]: Leaving directory '/mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules'
make[2]: *** [Makefile:17: test_klp_atomic_replace.ko] Error 2
make[2]: Leaving directory '/mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules'
make[1]: *** [Makefile:44: /mnt/kernel/linux/tools/testing/selftests/livepatch/test_modules/test_klp_atomic_replace.ko] Error 2
make[1]: Leaving directory '/mnt/kernel/linux/tools/testing/selftests/livepatch'
make: *** [Makefile:178: all] Error 2
make: Leaving directory '/mnt/kernel/linux/tools/testing/selftests'


I am not sure if this is exactly the process described in
Documentation/dev-tools/kselftest.rst. But it looks to me that
it is the way how to test "any" kernel with selftests
from an up-to-date kernel sources.

Best Regards,
Petr