linux-kernel - Re: [PATCH] tracing/x86: fix trace event registration for syscalls without arguments

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Message-ID: <87368pq97n.fsf@nanos.tec.linutronix.de>
Date:   Mon, 27 Apr 2020 16:44:44 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Brian Gerst <brgerst@...il.com>, linux-kernel@...r.kernel.org
Cc:     Dominik Brodowski <linux@...inikbrodowski.net>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH] tracing/x86: fix trace event registration for syscalls without arguments

Konstantin Khlebnikov <khlebnikov@...dex-team.ru> writes:

> Syscalls without arguments now has no ABI subs, instead of that macro

What is 'ABI subs'? 

> SYSCALL_DEFINE0() defines __abi_sys_name as aliase to __do_sys_name.
>
> As a result in find_syscall_meta() kallsyms_lookup() returns
> "__do_sys_name" which does not match with declared trace event.
>
> Also see commit 1c758a2202a6 ("tracing/x86: Update syscall trace events
> to handle new prefixed syscall func names")
>
> Fixes: d2b5de495ee9 ("x86/entry: Refactor SYSCALL_DEFINE0 macros")
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> ---
>  arch/x86/include/asm/ftrace.h |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
> index 85be2f506272..70b96cae5b42 100644
> --- a/arch/x86/include/asm/ftrace.h
> +++ b/arch/x86/include/asm/ftrace.h
> @@ -61,11 +61,12 @@ static inline bool arch_syscall_match_sym_name(const char *sym, const char *name
>  {
>  	/*
>  	 * Compare the symbol name with the system call name. Skip the
> -	 * "__x64_sys", "__ia32_sys" or simple "sys" prefix.
> +	 * "__x64_sys", "__ia32_sys", "__do_sys" or simple "sys" prefix.
>  	 */
>  	return !strcmp(sym + 3, name + 3) ||
>  		(!strncmp(sym, "__x64_", 6) && !strcmp(sym + 9, name + 3)) ||
> -		(!strncmp(sym, "__ia32_", 7) && !strcmp(sym + 10, name + 3));
> +		(!strncmp(sym, "__ia32_", 7) && !strcmp(sym + 10, name + 3)) ||
> +		(!strncmp(sym, "__do_sys", 8) && !strcmp(sym + 8, name + 3));
>  }
>  
>  #ifndef COMPILE_OFFSETS