linux-kernel - Re: Remaining randconfig objtool warnings, linux-next-20200428

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Message-ID: <20200430143350.qezebqmx2xwdxqxq@treble>
Date:   Thu, 30 Apr 2020 09:33:50 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: Remaining randconfig objtool warnings, linux-next-20200428

On Thu, Apr 30, 2020 at 03:41:56PM +0200, Arnd Bergmann wrote:
> On Thu, Apr 30, 2020 at 1:28 AM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> >
> > On Wed, Apr 29, 2020 at 06:11:15PM -0500, Josh Poimboeuf wrote:
> > > > We can probably move those SYS_NI() instances to kernel/sys_ni.c,
> > > > which does not include the header, but it's still a bit ugly. I'll try
> > > > that tomorrow
> > > > unless you come up with a better suggestion first.
> > >
> > > Oh I guess arm32 doesn't have SYS_NI defined.  All this syscall aliasing
> > > stuff is a total mystery to me.
> >
> > Another idea would be to split up syscalls.h into two files: one for
> > SYSCALL_* macros and one for sys_*() function prototypes.  It sounds
> > like the latter aren't needed by most header files anyway.
> >
> >  * Please note that these prototypes here are only provided for information
> >  * purposes, for static analysis, and for linking from the syscall table.
> >  * These functions should not be called elsewhere from kernel code.
> 
> To me the main purpose of the header is to ensure the calling conventions
> are sane, so I'd definitely want to see the declarations included whenever
> a syscall is defined. I would also expect to see a warnig from sparse, or
> from gcc with "make W=1" when an extern function is defined with no
> prior declaration.

Yup, makes sense.  I think I've been getting confused by the syscall
wrappers.

> How hard would it be to change objtool instead of changing the sources?

It might be a little tricky, but I can look into it.

-- 
Josh