From: Al Viro <viro@ZenIV.linux.org.uk>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-kernel@vger.kernel.org,
Yoshinori Sato <ysato@users.sourceforge.jp>,
linux-sh@vger.kernel.org, Rich Felker <dalias@libc.org>
Subject: Re: Runtime failure running sh:qemu in -next due to 'sh: fix copy_from_user()'
Date: Fri, 16 Sep 2016 23:00:08 +0000 [thread overview]
Message-ID: <20160916230008.GC2356@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20160916224704.GA21916@roeck-us.net>
On Fri, Sep 16, 2016 at 03:47:04PM -0700, Guenter Roeck wrote:
> Adding pr_info() just before the "if (unlikely..." fixes the problem.
>
> Commenting out the "if (unlikely())" code fixes the problem.
>
> Using a new variable "unsigned long x" for the return code instead of
> re-using __copy_size fixes the problem.
>
> Replacing "return __copy_size;" with "return __copy_size & 0xffffffff;"
> fixes the problem.
>
> The problem only seems to be seen if the copy size length is odd (more
> specifically, the failing copy always has a length of 25 bytes).
>
> No idea what is going on. Bug in __copy_user() ? Compiler bug ?
Definitely a compiler bug. __kernel_size_t is 32 bits on sh; that & 0xffffffff
should've been optimized away, for crying out loud!
WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-kernel@vger.kernel.org,
Yoshinori Sato <ysato@users.sourceforge.jp>,
linux-sh@vger.kernel.org, Rich Felker <dalias@libc.org>
Subject: Re: Runtime failure running sh:qemu in -next due to 'sh: fix copy_from_user()'
Date: Sat, 17 Sep 2016 00:00:08 +0100 [thread overview]
Message-ID: <20160916230008.GC2356@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20160916224704.GA21916@roeck-us.net>
On Fri, Sep 16, 2016 at 03:47:04PM -0700, Guenter Roeck wrote:
> Adding pr_info() just before the "if (unlikely..." fixes the problem.
>
> Commenting out the "if (unlikely())" code fixes the problem.
>
> Using a new variable "unsigned long x" for the return code instead of
> re-using __copy_size fixes the problem.
>
> Replacing "return __copy_size;" with "return __copy_size & 0xffffffff;"
> fixes the problem.
>
> The problem only seems to be seen if the copy size length is odd (more
> specifically, the failing copy always has a length of 25 bytes).
>
> No idea what is going on. Bug in __copy_user() ? Compiler bug ?
Definitely a compiler bug. __kernel_size_t is 32 bits on sh; that & 0xffffffff
should've been optimized away, for crying out loud!
next prev parent reply other threads:[~2016-09-16 23:00 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-16 19:12 Runtime failure running sh:qemu in -next due to 'sh: fix copy_from_user()' Guenter Roeck
2016-09-16 19:12 ` Guenter Roeck
2016-09-16 19:45 ` Al Viro
2016-09-16 19:45 ` Al Viro
2016-09-16 20:59 ` Guenter Roeck
2016-09-16 20:59 ` Guenter Roeck
2016-09-16 21:31 ` Al Viro
2016-09-16 21:31 ` Al Viro
2016-09-16 21:39 ` Rich Felker
2016-09-16 21:39 ` Rich Felker
2016-09-16 22:47 ` Guenter Roeck
2016-09-16 22:47 ` Guenter Roeck
2016-09-16 23:32 ` Rich Felker
2016-09-16 23:32 ` Rich Felker
2016-09-17 2:23 ` Guenter Roeck
2016-09-17 2:23 ` Guenter Roeck
2016-09-18 4:40 ` Rob Landley
2016-09-18 4:40 ` Rob Landley
2016-09-18 15:17 ` Rich Felker
2016-09-18 15:17 ` Rich Felker
2016-09-29 2:36 ` Rob Landley
2016-09-29 2:36 ` Rob Landley
2016-09-17 2:28 ` Guenter Roeck
2016-09-17 2:28 ` Guenter Roeck
2016-09-16 22:47 ` Guenter Roeck
2016-09-16 22:47 ` Guenter Roeck
2016-09-16 23:00 ` Al Viro [this message]
2016-09-16 23:00 ` Al Viro
2016-09-16 20:03 ` Al Viro
2016-09-16 20:03 ` Al Viro
2016-09-16 20:32 ` Guenter Roeck
2016-09-16 20:32 ` Guenter Roeck
2016-09-16 20:43 ` Lennart Sorensen
2016-09-16 20:43 ` Lennart Sorensen
2016-09-16 21:20 ` Al Viro
2016-09-16 21:20 ` Al Viro
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