On Sat, Mar 30, 2024 at 10:52 AM Jiri Olsa olsajiri@gmail.com wrote:
On Sat, Mar 30, 2024 at 08:27:55AM -0400, Steven Rostedt wrote:
On Fri, 29 Mar 2024 16:28:33 -0700 Andrii Nakryiko andrii.nakryiko@gmail.com wrote:
I thought I'll just ask instead of digging through code, sorry for being lazy :) Is there any way to pass pt_regs/ftrace_regs captured before function execution to a return probe (fexit/kretprobe)? I.e., how hard is it to pass input function arguments to a kretprobe? That's the biggest advantage of fexit over kretprobe, and if we can make these original pt_regs/ftrace_regs available to kretprobe, then multi-kretprobe will effectively be this multi-fexit.
This should be possible with the updates that Masami is doing with the fgraph code.
yes, I have bpf kprobe-multi link support for that [0] (it's on top of Masami's fprobe-over-fgraph changes) we discussed that in [1]
Sorry, I forgot the regs/args part, mostly remembering we discussed session cookie ideas. Thanks for reminder!
jirka
[0] https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git/log/?h=bpf/se... [1] https://lore.kernel.org/bpf/20240228090242.4040210-1-jolsa@kernel.org/