Livepatch uses ftrace for redirection to new patched functions. It is thus directly affected by ftrace sysctl knobs such as ftrace_enabled. Setting ftrace_enabled to 0 also disables all live patched functions. It is not a problem per se, because only administrator can set sysctl values, but it still may be surprising. Introduce PERMANENT ftrace_ops flag to amend this. If the FTRACE_OPS_FL_PERMANENT is set, the tracing of the function is not disabled. Such ftrace_ops can still be unregistered in a standard way. The patch set passes ftrace and livepatch kselftests. Miroslav Benes (3): ftrace: Make test_rec_ops_needs_regs() generic ftrace: Introduce PERMANENT ftrace_ops flag livepatch: Use FTRACE_OPS_FL_PERMANENT Documentation/trace/ftrace-uses.rst | 6 ++++ Documentation/trace/ftrace.rst | 2 ++ include/linux/ftrace.h | 8 +++-- kernel/livepatch/patch.c | 3 +- kernel/trace/ftrace.c | 47 ++++++++++++++++++++++++----- 5 files changed, 55 insertions(+), 11 deletions(-) -- 2.23.0
