linux-kernel - Re: [PATCH V3 13/22] LoongArch: Add system call support

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Date:   Sat, 18 Sep 2021 14:55:02 +0800
From:   Huacai Chen <chenhuacai@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Huacai Chen <chenhuacai@...ngson.cn>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Airlie <airlied@...ux.ie>,
        Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Yanteng Si <siyanteng@...ngson.cn>,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: Re: [PATCH V3 13/22] LoongArch: Add system call support

Hi, Arnd,

On Fri, Sep 17, 2021 at 4:24 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Fri, Sep 17, 2021 at 5:57 AM Huacai Chen <chenhuacai@...ngson.cn> wrote:
> > +#define NR_syscalls (__NR_syscalls)
> > diff --git a/arch/loongarch/include/uapi/asm/unistd.h b/arch/loongarch/include/uapi/asm/unistd.h
> > new file mode 100644
> > index 000000000000..b344b1f91715
> > --- /dev/null
> > +++ b/arch/loongarch/include/uapi/asm/unistd.h
> > @@ -0,0 +1,6 @@
> > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > +#define __ARCH_WANT_NEW_STAT
> > +#define __ARCH_WANT_SYS_CLONE
> > +#define __ARCH_WANT_SYS_CLONE3
>
> I still think you need to remove __ARCH_WANT_NEW_STAT and
> __ARCH_WANT_SYS_CLONE here.
>
> I understand that those are needed for the transitional period when you
> still need to support your existing glibc library files, but you likely still
> have other kernel patches that are not part of this series, so I suggest
> you add those two lines as a custom patch there until you are ready to
> drop support for old libc.
The clone story:
When I sent V1 of this series, the upstream glibc (2.33) hadn't merge
the clone3 support. Now glibc 2.34 has merged clone3, so
__ARCH_WANT_SYS_CLONE seems can be removed. But I think there is
someone just download this series and suppose it can work with current
userspace. So I want to keep it for a while, until this series can be
merged.

The statx story:
The latest upstream glibc (2.34) is still like this
(sysdeps/unix/sysv/linux/fstatat64.c):
#if (__WORDSIZE == 32 \
     && (!defined __SYSCALL_WORDSIZE || __SYSCALL_WORDSIZE == 32)) \
     || defined STAT_HAS_TIME32
# define FSTATAT_USE_STATX 1
#else
# define FSTATAT_USE_STATX 0
#endif

This means statx is supposed to use in 32bit systems, or 64bit systems
with 32bit timestamp (e.g. MIPS64). So I think __ARCH_WANT_NEW_STAT is
still needed.


>
> > +
> > +SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
> > +       unsigned long, prot, unsigned long, flags, unsigned long,
> > +       fd, off_t, offset)
> > +{
> > +       if (offset & ~PAGE_MASK)
> > +               return -EINVAL;
> > +       return ksys_mmap_pgoff(addr, len, prot, flags, fd,
> > +                              offset >> PAGE_SHIFT);
> > +}
> > +
> > +SYSCALL_DEFINE6(mmap2, unsigned long, addr, unsigned long, len,
> > +       unsigned long, prot, unsigned long, flags, unsigned long, fd,
> > +       unsigned long, pgoff)
> > +{
> > +       if (pgoff & (~PAGE_MASK >> 12))
> > +               return -EINVAL;
> > +
> > +       return ksys_mmap_pgoff(addr, len, prot, flags, fd,
> > +                              pgoff >> (PAGE_SHIFT - 12));
> > +}
>
> sys_mmap2() is only used on 32-bit architectures, you only need
> sys_mmap() here.
>
> Ideally we'd just move those two definitions you have here into
> mm/mmap.c and remove all the duplicate definitions. Maybe
> you can come up with a patch to do this?
>
> Note that some architectures use either nonstandard names,
> or shift value other than 12, so those need to keep their own
> versions.
OK, sys_mmap2() will be removed. But can "move sys_mmap() to
mm/mmap.c" be done by others? (I think my credit is not enough to do
this, at least now).

Huacai
>
>       Arnd