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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
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| .. | ||
| config | ||
| functions.sh | ||
| Makefile | ||
| README | ||
| settings | ||
| test-callbacks.sh | ||
| test-ftrace.sh | ||
| test-livepatch.sh | ||
| test-shadow-vars.sh | ||
| test-state.sh | ||
==================== Livepatch Self Tests ==================== This is a small set of sanity tests for the kernel livepatching. The test suite loads and unloads several test kernel modules to verify livepatch behavior. Debug information is logged to the kernel's message buffer and parsed for expected messages. (Note: the tests will compare the message buffer for only the duration of each individual test.) Config ------ Set these config options and their prerequisites: CONFIG_LIVEPATCH=y CONFIG_TEST_LIVEPATCH=m Running the tests ----------------- Test kernel modules are built as part of lib/ (make modules) and need to be installed (make modules_install) as the test scripts will modprobe them. To run the livepatch selftests, from the top of the kernel source tree: % make -C tools/testing/selftests TARGETS=livepatch run_tests Adding tests ------------ See the common functions.sh file for the existing collection of utility functions, most importantly setup_config(), start_test() and check_result(). The latter function greps the kernel's ring buffer for "livepatch:" and "test_klp" strings, so tests be sure to include one of those strings for result comparison. Other utility functions include general module loading and livepatch loading helpers (waiting for patch transitions, sysfs entries, etc.)