Hi Jackie, That is actiall what I'm working on now :) Here is my previous implementation (but not applicable because now we need to remove kretprobe trampoline with it.) https://lore.kernel.org/all/164735287344.1084943.9787335632585653418.stgit@devnote2/ Let me explain my idea. I would like to replace the kretprobe with fprobe exit handler so that we can intgrate the function return hook with fgraph tracer. Currently fprobe entry/exit handler uses pt_regs, but I will replace it with ftrace_regs. And this means rethook has to work with ftrace_regs and it can not support kretprobes anymore on some arch (HAVE_RETHOOK but !HAVE_DYNAMIC_FTRACE_WITH_REGS). There are many good reasons, like; - On some arch (e.g. arm64) can not emulate full pt_regs. - Saving full register on function entry/exit is not efficient. - Enabling both fgraph tracer and rethook are redundant. This requires some changes on kprobe users like BPF and SystemTap, so I need to talk with them about - Moving onto the fprobe to trace function entry/exit. - Using ftrace_regs API to access function argument and return value. Anyway, I'll add CONFIG_DYNAMIC_FTRACE_WITH_REGS dependency to them until in-kernel stuffs are ready. It ensures ftrace_regs can be converted to pt_regs. I also introduced fprobe events, so I will send a series of patches how to do that (fprobe entry side has been done, working on rethook side). Thank you, On Sun, 25 Jun 2023 16:27:44 +0800 Jackie Liu <liu.yun@xxxxxxxxx> wrote: > Hi, Mark Rutland and other developers. > > I am trying to implement the rethook of the arm64 platform, referring to > the code of other architectures, it can already run normally on the v6.1 > branch, but after commit 26299b3f6ba2 ("ftrace: arm64: move from REGS to > ARGS"), regs is no longer supported, resulting in CONFIG_FPROBE is also > not supported (although RETHOOK is implemented). I try to revert the > patch, and kprobe.multi can be run correctly. Now, what should I do? > Should I roll back this patch or find a way to run fprobe without regs? > > Any help is welcome. > > -- > Jackie Liu -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
