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

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Date:   Fri, 17 Sep 2021 10:24:07 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Huacai Chen <chenhuacai@...ngson.cn>
Cc:     Arnd Bergmann <arnd@...db.de>, 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>,
        Huacai Chen <chenhuacai@...il.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: Re: [PATCH V3 13/22] LoongArch: Add system call support

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.

> +
> +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.

      Arnd