linux-kernel - Re: [PATCH V4 08/17] riscv: compat: syscall: Add compat_sys_call

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Date:   Sun, 30 Jan 2022 13:54:20 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Anup Patel <anup@...infault.org>,
        gregkh <gregkh@...uxfoundation.org>,
        liush <liush@...winnertech.com>, Wei Fu <wefu@...hat.com>,
        Drew Fustini <drew@...gleboard.org>,
        Wang Junqiang <wangjunqiang@...as.ac.cn>,
        Christoph Hellwig <hch@....de>,
        Christoph Hellwig <hch@...radead.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-csky@...r.kernel.org,
        linux-s390 <linux-s390@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Parisc List <linux-parisc@...r.kernel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V4 08/17] riscv: compat: syscall: Add compat_sys_call_table
 implementation

On Sun, Jan 30, 2022 at 6:41 AM Arnd Bergmann <arnd@...db.de> wrote:
>
> > Implement compat sys_call_table and some system call functions:
> > truncate64, ftruncate64, fallocate, pread64, pwrite64,
> > sync_file_range, readahead, fadvise64_64 which need argument
> > translation.
> >
> > Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> > Signed-off-by: Guo Ren <guoren@...nel.org>
> > Cc: Arnd Bergmann <arnd@...db.de>
>
> This all looks really good, but I would change one detail:
>
> > +#ifndef compat_arg_u64
> > +#define compat_arg_u64(name)           u32  name##_lo, u32  name##_hi
> > +#define compat_arg_u64_dual(name)      u32, name##_lo, u32, name##_hi
> > +#define compat_arg_u64_glue(name)      (((u64)name##_hi << 32) | \
> > +                                        ((u64)name##_lo & 0xffffffffUL))
> > +#endif
>
> I would make these endian-specific, and reverse them on big-endian
> architectures. That way it
> should be possible to share them across all compat architectures
> without needing the override
> option.
I hope it could be another patch. Because it's not clear to
_LITTLE_ENDIAN definition in archs.

eg: Names could be __ORDER_LITTLE_ENDIAN__ CPU_LITTLE_ENDIAN
SYS_SUPPORTS_LITTLE_ENDIAN __LITTLE_ENDIAN

riscv is little-endian, but no any LITTLE_ENDIAN definition.

So let's keep them in the patch, first, Thx

>
>         Arnd



-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/