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

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Message-ID: <CAMzpN2htYX7s6pmRg-c8qwZL1f1_+sB=ztDG_L=617hWsm-=8g@mail.gmail.com>
Date:   Mon, 15 Jun 2020 11:33:49 -0400
From:   Brian Gerst <brgerst@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Arnd Bergmann <arnd@...db.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 11:10 AM Christoph Hellwig <hch@....de> wrote:
>
> On Mon, Jun 15, 2020 at 04:46:15PM +0200, Arnd Bergmann wrote:
> > How about this one:
> >
> > diff --git a/arch/x86/entry/syscall_x32.c b/arch/x86/entry/syscall_x32.c
> > index 3d8d70d3896c..0ce15807cf54 100644
> > --- a/arch/x86/entry/syscall_x32.c
> > +++ b/arch/x86/entry/syscall_x32.c
> > @@ -16,6 +16,9 @@
> >  #undef __SYSCALL_X32
> >  #undef __SYSCALL_COMMON
> >
> > +#define __x32_sys_execve __x64_sys_execve
> > +#define __x32_sys_execveat __x64_sys_execveat
> > +
>
>
> arch/x86/entry/syscall_x32.c:19:26: error: ‘__x64_sys_execve’ undeclared here (not in a function); did you mean ‘__x32_sys_execve’?
>    19 | #define __x32_sys_execve __x64_sys_execve
>       |                          ^~~~~~~~~~~~~~~~
> arch/x86/entry/syscall_x32.c:22:39: note: in expansion of macro ‘__x32_sys_execve’
>    22 | #define __SYSCALL_X32(nr, sym) [nr] = __x32_##sym,
>       |                                       ^~~~~~
> ./arch/x86/include/generated/asm/syscalls_64.h:344:1: note: in expansion of macro ‘__SYSCALL_X32’
>   344 | __SYSCALL_X32(520, sys_execve)
>       | ^~~~~~~~~~~~~
> arch/x86/entry/syscall_x32.c:20:28: error: ‘__x64_sys_execveat’ undeclared here (not in a function); did you mean ‘__x32_sys_execveat’?
>    20 | #define __x32_sys_execveat __x64_sys_execveat
>       |                            ^~~~~~~~~~~~~~~~~~
> arch/x86/entry/syscall_x32.c:22:39: note: in expansion of macro ‘__x32_sys_execveat’
>    22 | #define __SYSCALL_X32(nr, sym) [nr] = __x32_##sym,
>       |                                       ^~~~~~
> ./arch/x86/include/generated/asm/syscalls_64.h:369:1: note: in expansion of macro ‘__SYSCALL_X32’
>   369 | __SYSCALL_X32(545, sys_execveat)
>       | ^~~~~~~~~~~~~
> make[2]: *** [scripts/Makefile.build:281: arch/x86/entry/syscall_x32.o] Error 1
> make[1]: *** [scripts/Makefile.build:497: arch/x86/entry] Error 2
> make[1]: *** Waiting for unfinished jobs....
> kernel/exit.o: warning: objtool: __x64_sys_exit_group()+0x14: unreachable instruction
> make: *** [Makefile:1764: arch/x86] Error 2
> make: *** Waiting for unfinished jobs....

If you move those aliases above all the __SYSCALL_* defines it will
work, since that will get the forward declaration too.  This would be
the simplest workaround.

--
Brian Gerst