linux-kernel - Re: [PATCH 5/6] uaccess: add force_uaccess

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Message-ID: <CAEbi=3fk9u9n5vcENFuSMkob81+hg2r2dd0oN2FfaqLg0eosSw@mail.gmail.com>
Date:   Mon, 13 Jul 2020 18:06:42 +0800
From:   Greentime Hu <green.hu@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Nick Hu <nickhu@...estech.com>, Vincent Chen <deanbo422@...il.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-riscv@...ts.infradead.org,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/6] uaccess: add force_uaccess_{begin,end} helpers

Christoph Hellwig <hch@....de> 於 2020年7月10日 週五 下午9:57寫道：
>
> Add helpers to wraper the get_fs/set_fs magic for undoing any damange
> done by set_fs(KERNEL_DS).  There is no real functional benefit, but this
> documents the intent of these calls better, and will allow stubbing the
> functions out easily for kernels builds that do not allow address space
> overrides in the future.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  arch/arm64/kernel/sdei.c         |  2 +-
>  arch/m68k/include/asm/tlbflush.h | 12 ++++++------
>  arch/mips/kernel/unaligned.c     | 27 +++++++++++++--------------
>  arch/nds32/mm/alignment.c        |  7 +++----
>  arch/sh/kernel/traps_32.c        | 18 ++++++++----------
>  drivers/firmware/arm_sdei.c      |  5 ++---
>  include/linux/uaccess.h          | 18 ++++++++++++++++++
>  kernel/events/callchain.c        |  5 ++---
>  kernel/events/core.c             |  5 ++---
>  kernel/kthread.c                 |  5 ++---
>  kernel/stacktrace.c              |  5 ++---
>  mm/maccess.c                     | 22 ++++++++++------------
>  12 files changed, 69 insertions(+), 62 deletions(-)
>
[...]
> diff --git a/arch/nds32/mm/alignment.c b/arch/nds32/mm/alignment.c
> index c8b9061a2ee3d5..1eb7ded6992b57 100644
> --- a/arch/nds32/mm/alignment.c
> +++ b/arch/nds32/mm/alignment.c
> @@ -512,7 +512,7 @@ int do_unaligned_access(unsigned long addr, struct pt_regs *regs)
>  {
>         unsigned long inst;
>         int ret = -EFAULT;
> -       mm_segment_t seg = get_fs();
> +       mm_segment_t seg;
>
>         inst = get_inst(regs->ipc);
>
> @@ -520,13 +520,12 @@ int do_unaligned_access(unsigned long addr, struct pt_regs *regs)
>               "Faulting addr: 0x%08lx, pc: 0x%08lx [inst: 0x%08lx ]\n", addr,
>               regs->ipc, inst);
>
> -       set_fs(USER_DS);
> -
> +       seg = force_uaccess_begin();
>         if (inst & NDS32_16BIT_INSTRUCTION)
>                 ret = do_16((inst >> 16) & 0xffff, regs);
>         else
>                 ret = do_32(inst, regs);
> -       set_fs(seg);
> +       force_uaccess_end(seg);
>
>         return ret;
>  }

Hi Christoph, Thank you.
Acked-by: Greentime Hu <green.hu@...il.com>