Re: [Xen-devel] [PATCH] xenconsole: add option to avoid escape sequences in log

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Jul 25, 2018 at 09:49:39AM +0100, Wei Liu wrote:
> On Sat, Jul 21, 2018 at 02:14:12AM +0200, Marek Marczykowski-Górecki wrote:
> > Add --replace-escape, -e option to xenconsoled, which replaces ESC with
> > '.' in console output written to log file. This makes it slightly safer
> > to do tail -f on a console output of untrusted guest.
> > The pty output is unaffected by this option.
> 
> I would rather only have the long option, not the short one.
> 
> > 
> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> > ---
> > Is there any more documentation to be updated? I didn't found
> > xenconsoled man page or such.
> 
> No. But you're welcome to expand the help string in usage() to be more
> verbose. :-)
> 
> > ---
> >  tools/console/daemon/io.c   | 18 ++++++++++++++++++
> >  tools/console/daemon/main.c |  9 +++++++--
> >  2 files changed, 25 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/console/daemon/io.c b/tools/console/daemon/io.c
> > index e22009aa39..c8280e0b7c 100644
> > --- a/tools/console/daemon/io.c
> > +++ b/tools/console/daemon/io.c
> > @@ -68,6 +68,7 @@ extern int log_time_hv;
> >  extern int log_time_guest;
> >  extern char *log_dir;
> >  extern int discard_overflowed_data;
> > +extern int replace_escape;
> >  
> >  static int log_time_hv_needts = 1;
> >  static int log_time_guest_needts = 1;
> > @@ -227,8 +228,25 @@ static inline int console_iter_int_arg3(struct domain 
> > *d,
> >     return ret;
> >  }
> >  
> > +static void do_replace_escape(const char *buf, char *dest, int len) {
> 
> Coding style - { should be on a new line.
> 
> > +   int i;
> > +
> > +   memcpy(dest, buf, len);
> > +   for (i = 0; i < len; i++) {
> > +           if (dest[i] == '\033')
> > +                   dest[i] = '.';
> > +   }
> 
> This could be made more efficient by using:
> 
>         for (i = 0; i < len; i++) {
>              if (src[i] == '\033')
>                  dst[i] = '.';
>              else
>                  dst[i] = src[i];

Oh this can even be written in a shorter form:

  dst[i] = src[i] != '\033' ?: '.';

Wei.

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