From mboxrd@z Thu Jan  1 00:00:00 1970
From: Asias He <asias.hejun@gmail.com>
Subject: Re: [PATCH] kvm tools: Sanitize output characters in serial console
Date: Wed, 10 Aug 2011 14:15:45 +0800
Message-ID: <4E422211.9000704@gmail.com>
References: <1312934218-32666-1-git-send-email-asias.hejun@gmail.com> <4E421784.2020703@kernel.org> <4E421A72.9080203@gmail.com> <CAOJsxLEXRwRT8cWZZf921qLuqUtxP3nSVXp9q58466858Xp3DA@mail.gmail.com>
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Cc: Cyrill Gorcunov <gorcunov@gmail.com>, Ingo Molnar <mingo@elte.hu>,
	Sasha Levin <levinsasha928@gmail.com>,
	Prasad Joshi <prasadjoshi124@gmail.com>, kvm@vger.kernel.org
To: Pekka Enberg <penberg@kernel.org>
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On 08/10/2011 01:55 PM, Pekka Enberg wrote:
> On Wed, Aug 10, 2011 at 8:43 AM, Asias He <asias.hejun@gmail.com> wro=
te:
>> On 08/10/2011 01:30 PM, Pekka Enberg wrote:
>>> On 8/10/11 2:56 AM, Asias He wrote:
>>>> This patch fixes strange characters in serial console.
>>>>
>>>> Before:
>>>>
>>>> [    0.448000] Serial: 8250/16550 driver, 4 ports, IRQ sharing ena=
bled
>>>> =EF=BF=BD[    0.695000] serial8250: ttyS0 at I/O 0x3f8 (irq =3D 0)=
 is a 16550A
>>>> =EF=BF=BD[    0.942000] serial8250: ttyS1 at I/O 0x2f8 (irq =3D 0)=
 is a 16550A
>>>> =EF=BF=BD[    1.189000] serial8250: ttyS2 at I/O 0x3e8 (irq =3D 0)=
 is a 16550A
>>>> [    1.194000] Non-volatile memory driver v1.3
>>>>
>>>> After:
>>>>
>>>> [    0.541000] Serial: 8250/16550 driver, 4 ports, IRQ sharing ena=
bled
>>>> [    0.788000] serial8250: ttyS0 at I/O 0x3f8 (irq =3D 0) is a 165=
50A
>>>> [    1.041000] serial8250: ttyS1 at I/O 0x2f8 (irq =3D 0) is a 165=
50A
>>>> [    1.294000] serial8250: ttyS2 at I/O 0x3e8 (irq =3D 0) is a 165=
50A
>>>> [    1.309000] Non-volatile memory driver v1.3
>>>>
>>>> Signed-off-by: Asias He<asias.hejun@gmail.com>
>>>> ---
>>>>   tools/kvm/term.c |    7 +++++--
>>>>   1 files changed, 5 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/tools/kvm/term.c b/tools/kvm/term.c
>>>> index 2a3e1f0..85b41e7 100644
>>>> --- a/tools/kvm/term.c
>>>> +++ b/tools/kvm/term.c
>>>> @@ -5,6 +5,7 @@
>>>>   #include<unistd.h>
>>>>   #include<sys/uio.h>
>>>>   #include<signal.h>
>>>> +#include<ctype.h>
>>>>
>>>>   #include "kvm/read-write.h"
>>>>   #include "kvm/term.h"
>>>> @@ -57,8 +58,10 @@ int term_putc(int who, char *addr, int cnt)
>>>>       if (who !=3D active_console)
>>>>           return -1;
>>>>
>>>> -    while (cnt--)
>>>> -        fprintf(stdout, "%c", *addr++);
>>>> +    while (cnt--) {
>>>> +        if (isascii(*addr))
>>>
>>> Do things like backspace still work with this?
>>
>> Sure. Have a try ;-)
>>
>> http://en.wikipedia.org/wiki/ASCII
>=20
> OK, cool. Do we know what the extra characters are and why the guest
> is sending them?
>=20


This tells us

        while (cnt--) {
               if (isascii(*addr))
                       fprintf(stdout, "%c", *addr++);
               else
                       fprintf(stdout, "\n---%x---\n", *addr++);
        }

the extra chars is 0xff.

The reason is not understood.

--=20
Best Regards,
Asias He