Messages in this thread | | | Date | Mon, 23 Oct 2017 19:28:19 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH] Revert "kprobes: Warn if optprobe handler tries to change execution path" |
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On 2017/10/19 09:38PM, Masami Hiramatsu wrote: > On Tue, 17 Oct 2017 13:48:34 +0530 > "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote: > > > This reverts commit e863d539614641 ("kprobes: Warn if optprobe handler > > tries to change execution path"). > > > > On powerpc, we place a probe at kretprobe_trampoline to catch function > > returns and with CONFIG_OPTPROBES, this probe gets optimized. This > > works for us due to the way we handle the optprobe as described in > > commit 762df10bad6954 ("powerpc/kprobes: Optimize kprobe > > in kretprobe_trampoline()"). With the above commit, we end up with a > > warning. As such, revert this change. > > OK, so for ppc, optprobe can handle nip change. > > Acked-by: Masami Hiramatsu <mhiramat@kernel.org> > > I'll update the document too.
Thanks. We don't quite handle the nip change (yet), but just work around it for kretprobe trampoline by using the link register, and issuing a 'blr' after the trampoline code.
Regards, Naveen
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