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

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Date:   Mon, 27 Apr 2020 15:13:48 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     Brian Gerst <brgerst@...il.com>, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] tracing/x86: fix trace event registration for syscalls
 without arguments

On Mon, 27 Apr 2020 16:16:20 +0300
Konstantin Khlebnikov <khlebnikov@...dex-team.ru> wrote:

> 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")

This is the first I've seen of this patch.

> > 
> > 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));
> >   }

Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> >   
> >   #ifndef COMPILE_OFFSETS
> >