linux-ext4 - Re: [sparc64] sigbus in e2fsck

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Message-ID: <6a774a5e-b2e5-6276-c272-2b737bd098f0@physik.fu-berlin.de>
Date:   Tue, 30 Aug 2016 14:56:45 +0200
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Anatoly Pugachev <matorola@...il.com>, linux-ext4@...r.kernel.org
Cc:     debian-sparc <debian-sparc@...ts.debian.org>
Subject: Re: [sparc64] sigbus in e2fsck

On 08/30/2016 02:42 PM, Anatoly Pugachev wrote:
> ../../e2fsck/recovery.c:866
> 866                             blocknr = ext2fs_be64_to_cpu(* ((__u64
> *) (bh->b_data+offset)));

The reason is that this expression is casting "char * b_data" [1] into u64 [2]
which provokes unaligned access. Since such expression are often inevitable,
it's probably best to modify the conversion macros in bitops.h [3] to be
safe against unaligned accesses.

An example for that can be seen in the systemd code base [4].

Thanks,
Adrian

> [1] http://lxr.free-electrons.com/source/include/linux/buffer_head.h#L69
> [2] http://git.kernel.org/cgit/fs/ext2/e2fsprogs.git/tree/e2fsck/recovery.c#n866
> [3] http://git.kernel.org/cgit/fs/ext2/e2fsprogs.git/tree/lib/ext2fs/bitops.h
> [4] https://github.com/systemd/systemd/blob/master/src/basic/unaligned.h

-- 
 .''`.  John Paul Adrian Glaubitz
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`. `'   Freie Universitaet Berlin - glaubitz@...sik.fu-berlin.de
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