Re: [Xen-devel] [PATCH] xen/console: Fix build when CONFIG_DEBUG_TRACE=y

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 20/08/2019 14:12, Andrew Cooper wrote:
> On 19/08/2019 19:37, Julien Grall wrote:
> > Hi Andrew,
> >
> > On 8/19/19 7:04 PM, Andrew Cooper wrote:
> > > On 19/08/2019 19:01, Julien Grall wrote:
> > > > Commit b5e6e1ee8da "xen/console: Don't treat NUL character as the end
> > > > of the buffer" extended sercon_puts to take the number of character
> > > > to print in argument.
> > > >
> > > > Sadly, a couple of couple of the callers in debugtrace_dump_worker()
> > > > were not converted. This result to a build failure when enabling
> > > > CONFIG_DEBUG_TRACE.
> > > >
> > > > Spotted by Travis using randconfig
> > > > Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> > > > ---
> > > >    xen/drivers/char/console.c | 5 +++--
> > > >    1 file changed, 3 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
> > > > index 2c14c2ca73..924d4971ca 100644
> > > > --- a/xen/drivers/char/console.c
> > > > +++ b/xen/drivers/char/console.c
> > > > @@ -1185,11 +1185,12 @@ static void debugtrace_dump_worker(void)
> > > >          /* Print oldest portion of the ring. */
> > > >        ASSERT(debugtrace_buf[debugtrace_bytes - 1] == 0);
> > > > -    sercon_puts(&debugtrace_buf[debugtrace_prd]);
> > > > +    sercon_puts(&debugtrace_buf[debugtrace_prd],
> > > > +                strlen(&debugtrace_buf[debugtrace_prd]));
> > > Isn't this just debugtrace_bytes - debugtrace_prd - 1 ?
> > I tried and it resulted to print a lot of @^ on the console. This is
> > because the ring may not be full.
> >
> > So the portion between debugtrace_prd and debugtrace_bytes will be
> > full of zero.
> >
> > Looking at the code again, I think this portion and either be full of
> > zero character or full of non-zero character. In other word, a mix
> > would not be possible. So how about:
> >
> > if ( debugtrace_buf[debugtrace_prd] != '\0' )
> >    sercon_puts(&debugtrace_buf[debugtrace_prd],
> >                debugtrace_bytes - debugtrace_prd - 1);
> LGTM.  Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Thank you! I will update the patch and commit it.

Cheers,

--
Julien Grall

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