On Mon, 11 Sep 2023 09:55:09 +0200 Sven Schnelle <svens@xxxxxxxxxxxxx> wrote: > Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> writes: > > >> > IOW, it is ftrace save regs/restore regs code issue. I need to check how the > >> > function_graph implements it. > >> > >> gpr2-gpr14 are always saved in ftrace_caller/ftrace_regs_caller(), > >> regardless of the FTRACE_WITH_REGS flags. The only difference is that > >> without the FTRACE_WITH_REGS flag the program status word (psw) is not > >> saved because collecting that is a rather expensive operation. > > > > Thanks for checking that! So s390 will recover those saved registers > > even if FTRACE_WITH_REGS flag is not set? (I wonder what is the requirement > > of the ftrace_regs when returning from ftrace_call() without > > FTRACE_WITH_REGS?) > > Yes, it will recover these in all cases. Thanks for the confirmation! > > >> > >> I used the following commands to test rethook (is that the correct > >> testcase?) > >> > >> #!/bin/bash > >> cd /sys/kernel/tracing > >> > >> echo 'r:icmp_rcv icmp_rcv' >kprobe_events > >> echo 1 >events/kprobes/icmp_rcv/enable > >> ping -c 1 127.0.0.1 > >> cat trace > > > > No, the kprobe will path pt_regs to rethook. > > Cna you run > > > > echo "f:icmp_rcv%return icmp_rcv" >> dynamic_events > > Ah, ok. Seems to work as well: > > ping-481 [001] ..s2. 53.918480: icmp_rcv: (ip_protocol_deliver_rcu+0x42/0x218 <- icmp_rcv) > ping-481 [001] ..s2. 53.918491: icmp_rcv: (ip_protocol_deliver_rcu+0x42/0x218 <- icmp_rcv) Nice! OK, then s390 is safe to use ftrace_regs :) Thanks! -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
