Re: [PATCH] powerpc/ftrace: fix syscall tracing on PPC64_ELF_ABI_V1

[Michael Jeanson]

On 2022-12-05 13:56, Christophe Leroy wrote:
> Le 05/12/2022 à 19:19, Michael Jeanson a écrit :
> > [Vous ne recevez pas souvent de courriers de mjeanson@xxxxxxxxxxxx.
> > Découvrez pourquoi ceci est important à
> > https://aka.ms/LearnAboutSenderIdentification ]
> >
> > On 2022-12-05 00:34, Michael Ellerman wrote:
> > > Michael Jeanson <mjeanson@xxxxxxxxxxxx> writes:
> > > > In v5.7 the powerpc syscall entry/exit logic was rewritten in C, on
> > > > PPC64_ELF_ABI_V1 this resulted in the symbols in the syscall table
> > > > changing from their dot prefixed variant to the non-prefixed ones.
> > > >
> > > > Since ftrace prefixes a dot to the syscall names when matching them to
> > > > build its syscall event list, this resulted in no syscall events being
> > > > available.
> > > >
> > > > Remove the PPC64_ELF_ABI_V1 specific version of
> > > > arch_syscall_match_sym_name to have the same behavior across all powerpc
> > > > variants.
> > >
> > > This doesn't seem to work for me.
> > >
> > > Event with it applied I still don't see anything in
> > > /sys/kernel/debug/tracing/events/syscalls
> > >
> > > Did we break it in some other way recently?
> > >
> > > cheers
> >
> > I've just tried this change on top of v6.1-rc8 in qemu with a base
> > config of
> > 'corenet32_smp_defconfig' and these options on top:
> >
> > CONFIG_FTRACE=y
> > CONFIG_FTRACE_SYSCALLS=y
> >
> > And I can trace syscalls with ftrace.
> >
> > What kernel tree and config are you using?
>
> If you are using a ppc32 config, CONFIG_PPC64_ELF_ABI_V1 won't be set,
> so it doesn't matter whether this change is there or not.
>
> You should try corenet64_smp_defconfig if you want
> CONFIG_PPC64_ELF_ABI_V1 to be set.
>
> You can also use ppc64_defconfig, that's a different platform but it
> also has CONFIG_PPC64_ELF_ABI_V1.

You are absolutely right, I used the wrong environment, I blame Monday 
morning. I tested again this time using 'corenet64_smp_defconfig' with the 
same options and syscall tracing with ftrace also works.

I double checked that /proc/config.gz contained CONFIG_PPC64_ELF_ABI_V1 to be 
sure.

> Christophe
>
> > Thanks for looking into this.