linux-kernel - Re: [RFC PATCH -tip 1/5] kprobes: Use ENOTSUPP instead of ENOSYS

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Date:   Sat, 21 Oct 2017 00:51:55 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        Kees Cook <keescook@...omium.org>,
        Ian McDonald <ian.mcdonald@...di.co.nz>,
        Vlad Yasevich <vyasevich@...il.com>,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [RFC PATCH -tip 1/5] kprobes: Use ENOTSUPP instead of ENOSYS

On Fri, 20 Oct 2017 10:57:22 +0200
Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > Use ENOTSUPP instead of ENOSYS because ENOSYS is reserved
> > only for invalid syscall number.
> 
> Is this actually true? We use -ENOSYS in a ton of code in kernel/ already, not 
> just for non-existing syscall number.

I got a warning from checkpatches.pl, also in include/uapi/asm-generic/errno.h,

/*
 * This error code is special: arch syscall entry code will return
 * -ENOSYS if users try to call a syscall that doesn't exist.  To keep
 * failures of syscalls that really do exist distinguishable from
 * failures due to attempts to use a nonexistent syscall, syscall
 * implementations should refrain from returning -ENOSYS.
 */
#define ENOSYS          38      /* Invalid system call number */

So, I decided not to use ENOSYS for this error.

Thank you,


> 
> 	Ingo


-- 
Masami Hiramatsu <mhiramat@...nel.org>