• David Vernet's avatar
    livepatch: Skip livepatch tests if ftrace cannot be configured · 4327b9ea
    David Vernet authored
    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: default avatarPetr Mladek <pmladek@suse.com>
    Signed-off-by: default avatarDavid Vernet <void@manifault.com>
    Acked-by: default avatarMiroslav Benes <mbenes@suse.cz>
    Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
    Tested-by: default avatarPetr Mladek <pmladek@suse.com>
    Acked-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
    Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
    Link: https://lore.kernel.org/r/20220216161100.3243100-1-void@manifault.com
    4327b9ea
functions.sh 7.34 KB