linux-kernel - Re: [PATCH 2/6] exec: simplify the compat syscall handling

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Message-ID: <CAMzpN2iDPKatOqs+Uuw70ACbnB-D__dgSRZU0wBjOUBwTGOJ-A@mail.gmail.com>
Date:   Mon, 15 Jun 2020 15:45:24 -0400
From:   Brian Gerst <brgerst@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Christoph Hellwig <hch@....de>, Al Viro <viro@...iv.linux.org.uk>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        Parisc List <linux-parisc@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] exec: simplify the compat syscall handling

On Mon, Jun 15, 2020 at 2:47 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Mon, Jun 15, 2020 at 4:48 PM Brian Gerst <brgerst@...il.com> wrote:
> > On Mon, Jun 15, 2020 at 10:13 AM Christoph Hellwig <hch@....de> wrote:
> > > On Mon, Jun 15, 2020 at 03:31:35PM +0200, Arnd Bergmann wrote:
>
> > >
> > > I'd rather keep it in common code as that allows all the low-level
> > > exec stuff to be marked static, and avoid us growing new pointless
> > > compat variants through copy and paste.
> > > smart compiler to d
> > >
> > > > I don't really understand
> > > > the comment, why can't this just use this?
> > >
> > > That errors out with:
> > >
> > > ld: arch/x86/entry/syscall_x32.o:(.rodata+0x1040): undefined reference to
> > > `__x32_sys_execve'
> > > ld: arch/x86/entry/syscall_x32.o:(.rodata+0x1108): undefined reference to
> > > `__x32_sys_execveat'
> > > make: *** [Makefile:1139: vmlinux] Error 1
> >
> > I think I have a fix for this, by modifying the syscall wrappers to
> > add an alias for the __x32 variant to the native __x64_sys_foo().
> > I'll get back to you with a patch.
>
> Do we actually need the __x32 prefix any more, or could we just
> change all x32 specific calls to use __x64_compat_sys_foo()?

I suppose that would work too.  The prefix really describes the
register mapping.

--
Brian Gerst