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From: Andreas Schwab <schwab@suse.de>
Subject: Re: [Qemu-devel] [PATCH] linux-user strace
References: <Pine.LNX.4.64.0707201501300.13035@trantor.stuart.netsweng.com>
	<jeejj2da8g.fsf@sykes.suse.de>
	<Pine.LNX.4.64.0707210907290.13035@trantor.stuart.netsweng.com>
Date: Sat, 21 Jul 2007 18:02:33 +0200
In-Reply-To: <Pine.LNX.4.64.0707210907290.13035@trantor.stuart.netsweng.com>
	(Stuart Anderson's message of "Sat\,
	21 Jul 2007 09\:10\:27 -0400 \(EDT\)")
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To: qemu-devel@nongnu.org

Stuart Anderson <anderson@netsweng.com> writes:

> On Fri, 20 Jul 2007, Andreas Schwab wrote:
>
>> Stuart Anderson <anderson@netsweng.com> writes:
>>
>>> Index: qemu/linux-user/syscall.c
>>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>>> --- qemu.orig/linux-user/syscall.c	2007-07-19 01:42:43.000000000 -040=
0
>>> +++ qemu/linux-user/syscall.c	2007-07-19 01:43:18.000000000 -0400
>>> @@ -312,6 +312,11 @@
>>>      return (unsigned long)ret >=3D (unsigned long)(-4096);
>>>  }
>>>
>>> +char *target_strerror(int err)
>>> +{
>>> +	return strerror(host_to_target_errno(err));
>>> +}
>>> +
>>
>> That looks backwards.  strerror surely expects a host errno value, but
>> host_to_target_errno returns the errno value for the target, doesn't i=
t?
>
> The function is called target_strerror() 8-).

That's the problem.  It does not return the string associated with the
target errno, but something else.

> It is used to display the errno string for the target, not the
> host.

But strerror interprets its argument as the host's errno value.  If
host_to_target_error maps ELOOP to TARGET_ELOOP, and TARGET_ELOOP
happens have be the same value as EBADFD, the function wil return
"Bad file descriptor" instead of "Too many levels of symbolic links".

Andreas.

--=20
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstra=DFe 5, 90409 N=FCrnberg, Germany
PGP key fingerprint =3D 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED=
5
"And now for something completely different."