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

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Date:   Mon, 27 Apr 2020 16:16:20 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     Brian Gerst <brgerst@...il.com>, linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Andy Lutomirski <luto@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] tracing/x86: fix trace event registration for syscalls
 without arguments

Bump, bug still present in 5.7.0-rc3

root@...nel0:~# uname -r
5.7.0-rc3-test

root@...nel0:~# ls -d /sys/kernel/tracing/events/syscalls/sys_enter_{sync,fsync}
ls: cannot access '/sys/kernel/tracing/events/syscalls/sys_enter_sync': No such file or directory
/sys/kernel/tracing/events/syscalls/sys_enter_fsync

On 08/04/2020 21.13, Konstantin Khlebnikov wrote:
> Syscalls without arguments now has no ABI subs, instead of that macro
> 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
>