Hi, On Mon, 30 Sep 2024, Michael Vetter wrote: > The test proves that a function that is being kprobed and uses a > post_handler cannot be livepatched. > > Only one ftrace_ops with FTRACE_OPS_FL_IPMODIFY set may be registered > to any given function at a time. > > Signed-off-by: Michael Vetter <mvetter@xxxxxxxx> since my memory is short, I wondered why you need a separate module to register a kprobe for cmdline_proc_show() in vmlinux and why it cannot be achieved through tracefs. So... the test ensures that FTRACE_OPS_FL_IPMODIFY is exclusive. A kprobe sets FTRACE_OPS_FL_IPMODIFY flag if and only if post_handler is not NULL which also indicates a situation when regs->ip may be changed in that kprobe. This is something which cannot be done in tracefs and hence the module. It was not clear to me from the changelog. Miroslav
