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

[Michael Jeanson]

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?

Thanks for looking into this.

> > Fixes: 68b34588e202 ("powerpc/64/sycall: Implement syscall entry/exit logic in C")
> > Cc: stable@xxxxxxxxxxxxxxx # v5.7+
> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> > Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
> > Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> > Cc: Michal Suchanek <msuchanek@xxxxxxx>
> > Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > Signed-off-by: Michael Jeanson <mjeanson@xxxxxxxxxxxx>
> > Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> > ---
> >   arch/powerpc/include/asm/ftrace.h | 12 ------------
> >   1 file changed, 12 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
> > index 3cee7115441b..e3d1f377bc5b 100644
> > --- a/arch/powerpc/include/asm/ftrace.h
> > +++ b/arch/powerpc/include/asm/ftrace.h
> > @@ -64,17 +64,6 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
> >    * those.
> >    */
> >   #define ARCH_HAS_SYSCALL_MATCH_SYM_NAME
> > -#ifdef CONFIG_PPC64_ELF_ABI_V1
> > -static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
> > -{
> > -	/* We need to skip past the initial dot, and the __se_sys alias */
> > -	return !strcmp(sym + 1, name) ||
> > -		(!strncmp(sym, ".__se_sys", 9) && !strcmp(sym + 6, name)) ||
> > -		(!strncmp(sym, ".ppc_", 5) && !strcmp(sym + 5, name + 4)) ||
> > -		(!strncmp(sym, ".ppc32_", 7) && !strcmp(sym + 7, name + 4)) ||
> > -		(!strncmp(sym, ".ppc64_", 7) && !strcmp(sym + 7, name + 4));
> > -}
> > -#else
> >   static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
> >   {
> >   	return !strcmp(sym, name) ||
> > @@ -83,7 +72,6 @@ static inline bool arch_syscall_match_sym_name(const char *sym, const char *name
> >   		(!strncmp(sym, "ppc32_", 6) && !strcmp(sym + 6, name + 4)) ||
> >   		(!strncmp(sym, "ppc64_", 6) && !strcmp(sym + 6, name + 4));
> >   }
> > -#endif /* CONFIG_PPC64_ELF_ABI_V1 */
> >   #endif /* CONFIG_FTRACE_SYSCALLS */
> >   
> >   #if defined(CONFIG_PPC64) && defined(CONFIG_FUNCTION_TRACER)
> > --
> > 2.34.1