Le 14/12/2021 à 15:25, Heiko Carstens a écrit :

On Mon, Dec 13, 2021 at 05:50:52PM +0000, Christophe Leroy wrote:

quoted

Le 13/12/2021 à 18:33, Steven Rostedt a écrit :

quoted

On Mon, 13 Dec 2021 17:30:48 +0000
Christophe Leroy [off-list ref] wrote:

quoted

Thanks, I will try that.

I can't find ftrace_graph_func() in s390. Does it mean that s390 doesn't
have a working function tracer anymore ?

I see your commit 0c0593b45c9b4 ("x86/ftrace: Make function graph use
ftrace directly") is dated 8 Oct 2021 while 5740a7c71ab6 ("s390/ftrace:
add HAVE_DYNAMIC_FTRACE_WITH_ARGS support") is 4 Oct 2021.

Hmm, maybe not. I can't test it.

This needs to be fixed if that's the case.

Thanks for bringing it up!

It still works, we run the full ftrace/kprobes selftests from the
kernel every day on multiple machines with several kernels (besides
other Linus' tree, but also linux-next). That said, I wanted to change
s390's code follow what x86 is currently doing anyway.

One thing to note: commit 5740a7c71ab6 ("s390/ftrace: add
HAVE_DYNAMIC_FTRACE_WITH_ARGS support") looks only that simple because
ftrace_caller _and_ ftrace_regs_caller used to save all register
contents into the pt_regs structure, which never was a requirement,
but implicitly fulfills the HAVE_DYNAMIC_FTRACE_WITH_ARGS
requirements.
Not sure if powerpc passes enough register contents via pt_regs for
HAVE_DYNAMIC_FTRACE_WITH_ARGS though. Might be something to check?

In fact there is no need to rework the function graph logic. It still 
works as is with HAVE_DYNAMIC_FTRACE_WITH_ARGS.

The problem was that the sefltests were failing with 
CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS not being selected on powerpc.

As s390 selects CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS, there is no 
problem.

Thanks
Christophe