2019年5月7日(火) 21:54 Steven Rostedt rostedt@goodmis.org:
On Tue, 7 May 2019 14:41:31 +0200 Peter Zijlstra peterz@infradead.org wrote:
Kprobes sets the FTRACE_OPS_FL_IPMODIFY flag, thus they can never be put at the same location that is being live patched.
OK, so do we want to allow kprobes that also modify regs->sp ? Because then we need to change these trampolines a bit.
I'd prefer not to allow kprobes this.
I believe no kprobe changes sp, because it would have had the same issues we are trying to solve now. And even though we are changing things to allow it, it's not a regression to keep kprobes from doing it.
No, kprobes doesn't allow to change sp. At this moment we can't change "®s->sp" since it is just a value :) kprobes user (e.g. function fault-injection) will change regs->ip, that is why kprobes sets IPMODIFY flag.
Thank you,