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

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Message-ID: <CAK8P3a3JGP6fLVOyLgdNw2YpRSmArbEX8orUhRrN=GHmcdk=1g@mail.gmail.com>
Date:   Sat, 29 Jan 2022 23:12:53 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Guo Ren <guoren@...nel.org>
Cc:     Palmer Dabbelt <palmer@...belt.com>, Arnd Bergmann <arnd@...db.de>,
        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

> 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.

        Arnd