livepatch: Move tests from lib/livepatch to selftests/livepatch

The modules are being moved from lib/livepatch to
tools/testing/selftests/livepatch/test_modules.

This code moving will allow writing more complex tests, like for example an
userspace C code that will call a livepatched kernel function.

The modules are now built as out-of-tree
modules, but being part of the kernel source means they will be maintained.

Another advantage of the code moving is to be able to easily change,
debug and rebuild the tests by running make on the selftests/livepatch
directory, which is not currently possible since the modules on
lib/livepatch are build and installed using the "modules" target.

The current approach also keeps the ability to execute the tests manually
by executing the scripts inside selftests/livepatch directory, as it's
currently supported. If the modules are modified, they needed to be
rebuilt before running the scripts though.

The modules are built before running the selftests when using the
kselftest invocations:

make kselftest TARGETS=livepatch
or
make -C tools/testing/selftests/livepatch run_tests

Having the modules being built as out-of-modules requires changing the
currently used 'modprobe' by 'insmod' and adapt the test scripts that
check for the kernel message buffer.

Now it is possible to only compile the modules by running:

make -C tools/testing/selftests/livepatch/

This way the test modules and other test program can be built in order
to be packaged if so desired.

As there aren't any modules being built on lib/livepatch, remove the
TEST_LIVEPATCH Kconfig and it's references.

Note: "make gen_tar" packages the pre-built binaries into the tarball.
It means that it will store the test modules pre-built for
the kernel running on the build host.

Note that these modules need not binary compatible with
the kernel built from the same sources. But the same
is true for other packaged selftest binaries.

The entire kernel sources are needed for rebuilding
the selftests on another system.

Reviewed-by: Joe Lawrence <joe.lawrence@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

livepatch: Skip livepatch tests if ftrace cannot be configured

livepatch has a set of selftests that are used to validate the behavior of
the livepatching subsystem. One of the testcases in the livepatch
testsuite is test-ftrace.sh, which among other things, validates that
livepatching gracefully fails when ftrace is disabled. In the event that
ftrace cannot be disabled using 'sysctl kernel.ftrace_enabled=0', the test
will fail later due to it unexpectedly successfully loading the
test_klp_livepatch module.

While the livepatch selftests are careful to remove any of the livepatch
test modules between testcases to avoid this situation, ftrace may still
fail to be disabled if another trace is active on the system that was
enabled with FTRACE_OPS_FL_PERMANENT. For example, any active BPF programs
that use trampolines will cause this test to fail due to the trampoline
being implemented with register_ftrace_direct(). The following is an
example of such a trace:

tcp_drop (1) R I D tramp: ftrace_regs_caller+0x0/0x58
(call_direct_funcs+0x0/0x30)
direct-->bpf_trampoline_6442550536_0+0x0/0x1000

In order to make the test more resilient to system state that is out of its
control, this patch updates set_ftrace_enabled() to detect sysctl failures,
and skip the testrun when appropriate.

Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: David Vernet <void@manifault.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220216161100.3243100-1-void@manifault.com

selftests/livepatch: adopt to newer sysctl error format

With procfs v3.3.16, the sysctl command doesn't print the set key and
value on error. This change breaks livepatch selftest test-ftrace.sh,
that tests the interaction of sysctl ftrace_enabled:

Make it work with all sysctl versions using '-q' option.

Explicitly print the final status on success so that it can be verified
in the log. The error message is enough on failure.

Reported-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Reviewed-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/20200714091030.1611-1-pmladek@suse.com

selftests/livepatch: Don't clear dmesg when running tests

Inspired by commit f131d9edc29d ("selftests/lkdtm: Don't clear dmesg
when running tests"), keep a reference dmesg copy when beginning each
test. This way check_result() can compare against the initial copy
rather than relying upon an empty log.

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Reviewed-by: Yannick Cote <ycote@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200618181040.21132-2-joe.lawrence@redhat.com

selftests/livepatch: Test interaction with ftrace_enabled

Since livepatching depends upon ftrace handlers to implement "patched"
code functionality, verify that the ftrace_enabled sysctl value
interacts with livepatch registration as expected. At the same time,
ensure that ftrace_enabled is set and part of the test environment
configuration that is saved and restored when running the selftests.

Link: http://lkml.kernel.org/r/20191016113316.13415-4-mbenes@suse.cz

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>