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

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Date:   Mon, 15 Jun 2020 16:40:28 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Christoph Hellwig <hch@....de>
Cc:     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 4:12 PM Christoph Hellwig <hch@....de> wrote:
> On Mon, Jun 15, 2020 at 03:31:35PM +0200, Arnd Bergmann wrote:

>
> > 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

Ah, I see: it's marked x32-only, so arch/x86/entry/syscall_x32.c
uses the __x32 prefix instead of the __x64 one. Marking it 'common'
instead would make it work, but also create an extra entry point
for native processes, something that commit
6365b842aae4 ("x86/syscalls: Split the x32 syscalls into their own table")
was trying to avoid.

      Arnd