linux-kernel - Re: [PATCH] ANDROID: binder: remove 32-bit binder interface.

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Message-ID: <CAMuHMdW0nxOmq7gjJiySg0fho2XDYkyrCgp88OOuULRLH+jt6w@mail.gmail.com>
Date:   Mon, 14 May 2018 16:00:19 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Martijn Coenen <maco@...roid.com>,
        kbuild test robot <lkp@...el.com>,
        Greg KH <gregkh@...uxfoundation.org>, kbuild-all@...org,
        John Stultz <john.stultz@...aro.org>,
        Todd Kjos <tkjos@...gle.com>,
        Arve Hjønnevåg <arve@...roid.com>,
        Amit Pundir <amit.pundir@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        Martijn Coenen <maco@...gle.com>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] ANDROID: binder: remove 32-bit binder interface.

Hi Christoph,

On Mon, May 14, 2018 at 2:03 PM, Christoph Hellwig <hch@...radead.org> wrote:
> On Fri, May 11, 2018 at 09:57:52AM +0200, Martijn Coenen wrote:
>> On Sat, May 5, 2018 at 2:10 PM, kbuild test robot <lkp@...el.com> wrote:
>> >    drivers/android/binder.o: In function `binder_thread_write':
>> >>> binder.c:(.text+0x6a16): undefined reference to `__get_user_bad'
>>
>> Looks like m68k doesn't support 64-bit get_user(). I could just have
>> binder depend on !CONFIG_M68K, but there may be other architectures
>> still that don't support this. Another alternative would be to
>> whitelist the architectures Android supports - eg arm, arm64, x86,
>> x86_64. But I'm not sure if arch-limited drivers are considered bad
>> form. Does anybody have suggestions for how to deal with this?
>
> The proper fix is to just support 640bit get/put_user on m68k instead

I hope we'll never need 640bit support in {get,put}_user() ;-)

> of working around this.

Patch sent.

BTW, sh also doesn't seem to have 64-bit get_user().
There may be others.

BTW2, does the Android Binder need to care about endianness when talking
to userspace?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds