linux-kernel - Re: [PATCH] Convert filldir[64]() from __put_user() to unsafe_put

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Message-ID: <CAHk-=wgvz6k88hxY_G3=itbQ-iVz7Hc9fbF3kZ_nePA7XgvDTg@mail.gmail.com>
Date:   Mon, 7 Oct 2019 12:21:25 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Guenter Roeck <linux@...ck-us.net>,
        Michael Cree <mcree@...on.net.nz>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user()

On Sun, Oct 6, 2019 at 3:20 PM Guenter Roeck <linux@...ck-us.net> wrote:
>
> this patch causes all my sparc64 emulations to stall during boot. It causes
> all alpha emulations to crash with [1a] and [1b] when booting from a virtual
> disk, and one of the xtensa emulations to crash with [2].

So I think your alpha emulation environment may be broken, because
Michael Cree reports that it works for him on real hardware, but he
does see the kernel unaligned count being high.

But regardless, this is my current fairly minimal patch that I think
should fix the unaligned issue, while still giving the behavior we
want on x86. I hope Al can do something nicer, but I think this is
"acceptable".

I'm running this now on x86, and I verified that x86-32 code
generation looks sane too, but it woudl be good to verify that this
makes the alignment issue go away on other architectures.

                Linus

View attachment "patch.diff" of type "text/x-patch" (4604 bytes)