linux-kernel - Re: [PATCH] powerpc/ftrace: fix syscall tracing on PPC64_ELF_ABI

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Date:   Mon, 05 Dec 2022 16:34:49 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Michael Jeanson <mjeanson@...icios.com>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     Michael Jeanson <mjeanson@...icios.com>, stable@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Michal Suchanek <msuchanek@...e.de>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH] powerpc/ftrace: fix syscall tracing on PPC64_ELF_ABI_V1

Michael Jeanson <mjeanson@...icios.com> 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


> Fixes: 68b34588e202 ("powerpc/64/sycall: Implement syscall entry/exit logic in C")
> Cc: stable@...r.kernel.org # v5.7+
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> Cc: Michal Suchanek <msuchanek@...e.de>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Michael Jeanson <mjeanson@...icios.com>
> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> ---
>  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