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Re: Weird characters in virtual terminal consoles from (CTRL-ALT) F2 to F6 and over F7

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Hello, all.
Just wanted to report on the status so far.  The patch did not work,
it printed a different weird (mess?) on the screen.  It was not a
recognizable character.  Trying 0x20 resulted in a mostly blank
screen.  The first column had characters in it, sometimes.
.
Next test was to add a printk() to the routines in question.  It was
noted that the charcnt was zero in some (most) cases.  To start were
some characters, ch, between 0x20 and 0x79 inclusive (on my machine).
Then a long list of ch == 0x20 and the charcnt == 0.  Not sure if this
is expected or if it indicates a bug somewhere else.
.
The charcnt variable was added by Junjie Cao in the patch that caused
the problem.  The patch looks like a good idea to avoid a buffer
overrun.  Maybe if charcnt is zero, the routine should just return
early?
.
Let me know and I will test it out.
.
William Burrow.
.

On Mon, Dec 22, 2025 at 11:09 AM Camaleón <noelamac@gmail.com> wrote:
>
> El 2025-12-22 a las 11:59 +0100, Gianluca Renzi escribió:
> > On 12/22/25 11:13, Helge Deller wrote:
> > > On 12/22/25 11:09, Gianluca Renzi wrote:
> > > > Wow! So you found the culprit.
>
> My deepest congrats (and a bunch of thanks) to William Burrow and
> Gianluca Renzi for their finding, testing, reporting (finally, «time
> spent») and the overall well job done! :-)
>
> > > Well, it seems pretty likely that you get the "copyright symbol",
> > > because ch gets assigned "0".  The question is: Why does this happen?
> > > It shouldn't.
> > >
> > > Does it only happens with old kernels (5.x), or does it happen with
> > > latest
> > > Linux kernels (>= 6.8) too?
> > >
> > The issue is not present with the kernel 5.10.0-36-amd64, only in kernel
> > 5.10.0-37-amd64 (5.10.247-1)
> >
> > I have a couple of Debian 12 machines laying around, and this bug is not
> > present for sure.
> >
> > I do not remember which kernel they can have, but it's the stable Debian 12
> > version.
>
> (...)
>
> Well, I do confirm I CANNOT reproduce the «©©©©©©©©©©©©©©©©©©©©©©©©©©©©»
> copyright issue neither on my Debian testing (kernel image
> 6.17.9+deb14) nor Debian stable (kernel image 6.1.0-41).
>
> Cheers,
>
> --
> Camaleón

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Re: Weird characters in virtual terminal consoles from (CTRL-ALT) F2  to F6 and over F7 William Burrow <wbkernel@gmail.com> - 2025-12-22 03:20 +0100
  Re: Weird characters in virtual terminal consoles from (CTRL-ALT) F2  to F6 and over F7 Helge Deller <deller@kernel.org> - 2025-12-22 11:10 +0100
    Re: Weird characters in virtual terminal consoles from (CTRL-ALT) F2  to F6 and over F7 Gianluca Renzi <icjtqr@gmail.com> - 2025-12-22 11:10 +0100
      Re: Weird characters in virtual terminal consoles from (CTRL-ALT) F2  to F6 and over F7 Gianluca Renzi <gianlucarenzi@eurek.it> - 2025-12-22 12:20 +0100
        Re: Weird characters in virtual terminal consoles from (CTRL-ALT) F2  to F6 and over F7 Camaleón <noelamac@gmail.com> - 2025-12-22 16:30 +0100
          Re: Weird characters in virtual terminal consoles from (CTRL-ALT) F2  to F6 and over F7 William Burrow <wbkernel@gmail.com> - 2025-12-23 19:00 +0100

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