Re: [PATCH] kvm tools: Sanitize output characters in serial console

[Sasha Levin <levinsasha928@gmail.com>]

On Wed, 2011-08-10 at 14:15 +0800, Asias He wrote:
> 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> wrote:
> >> 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 enabled
> >>>> �[    0.695000] serial8250: ttyS0 at I/O 0x3f8 (irq = 0) is a 16550A
> >>>> �[    0.942000] serial8250: ttyS1 at I/O 0x2f8 (irq = 0) is a 16550A
> >>>> �[    1.189000] serial8250: ttyS2 at I/O 0x3e8 (irq = 0) is a 16550A
> >>>> [    1.194000] Non-volatile memory driver v1.3
> >>>>
> >>>> After:
> >>>>
> >>>> [    0.541000] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
> >>>> [    0.788000] serial8250: ttyS0 at I/O 0x3f8 (irq = 0) is a 16550A
> >>>> [    1.041000] serial8250: ttyS1 at I/O 0x2f8 (irq = 0) is a 16550A
> >>>> [    1.294000] serial8250: ttyS2 at I/O 0x3e8 (irq = 0) is a 16550A
> >>>> [    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 != 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
> > 
> > OK, cool. Do we know what the extra characters are and why the guest
> > is sending them?
> > 
> 
> 
> 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.
> 

They are being printed when the serial device is probed. Can we
mistakenly interpret the probe as a print request?

-- 

Sasha.