[PATCH man 0/1] TIOCLINUX.2const: Document TIOCL_SETSEL selection modes

[PATCH man 0/1] TIOCLINUX.2const: Document TIOCL_SETSEL selection modes

[Günther Noack]

Hi!

For context:

TIOCLINUX's TIOCL_SETSEL sub-code has another layer of sub-operations,
called "selection modes" (even though not all of them actually deal
with the mouse selection).

Going forward, the CAP_SYS_ADMIN requirement will be different for
some of these selection modes, which promted me to at least list the
different selection modes with a short description.  I am leaving
CAP_SYS_ADMIN documentation as it is for now and will send another
patch once these semantics are finalized [1].

Thanks,
–Günther

[1] https://lore.kernel.org/all/20250221.0a947528d8f3@gnoack.org/

Günther Noack (1):
  TIOCLINUX.2const: Document TIOCL_SETSEL selection modes

 man/man2const/TIOCLINUX.2const | 48 ++++++++++++++++++++++++++++++----
 1 file changed, 43 insertions(+), 5 deletions(-)

-- 
2.48.1

[PATCH man 1/1] TIOCLINUX.2const: Document TIOCL_SETSEL selection modes

[Günther Noack]

These previously undocumented selection modes for the Linux console
are implemented in drivers/tty/vt/selection.c.

Cc: Jared Finder <jared@finder.org>
Cc: Hanno Böck <hanno@hboeck.de>
Cc: Jann Horn <jannh@google.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: jwilk@jwilk.net
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
---
 man/man2const/TIOCLINUX.2const | 48 ++++++++++++++++++++++++++++++----
 1 file changed, 43 insertions(+), 5 deletions(-)

diff --git a/man/man2const/TIOCLINUX.2const b/man/man2const/TIOCLINUX.2const
index c0acdd0ea..27758584e 100644
--- a/man/man2const/TIOCLINUX.2const
+++ b/man/man2const/TIOCLINUX.2const
@@ -65,11 +65,49 @@ are the ending
 column and row.
 (Upper left corner is row=column=1.)
 .I sel_mode
-is 0 for character-by-character selection,
-1 for word-by-word selection,
-or 2 for line-by-line selection.
-The indicated screen characters are highlighted and saved
-in a kernel buffer.
+may be one of the following operations:
+.RS
+.TP
+.B TIOCL_SELCHAR
+Select character-by-character.
+The indicated screen characters are highlighted
+and saved in a kernel buffer.
+.TP
+.B TIOCL_SELWORD
+Select word-by-word.
+The indicated screen characters are highlighted
+and saved in a kernel buffer.
+.TP
+.B TIOCL_SELLINE
+Select line-by-line.
+The indicated screen characters are highlighted
+and saved in a kernel buffer.
+.TP
+.B TIOCL_SELPOINTER
+Show the pointer at position
+.RI ( xe ", " ye ).
+.TP
+.B TIOCL_SELCLEAR
+Remove the current selection highlight, if any,
+from the console holding the selection.
+.TP
+.B TIOCL_SELMOUSEREPORT
+Report
+.RI ( xs ", " ys )
+as the current mouse location.
+In this selection mode,
+the lower 4 bits of
+.I sel_mode
+.RB ( TIOCL_SELBUTTONMASK )
+may additionally be set to indicate the desired button press and
+modifier key information for the mouse event.
+.\" https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-Normal-tracking-mode
+.IP
+If mouse reporting is not enabled for the terminal,
+this operation yields an
+.B EINVAL
+error.
+.RE
 .IP
 Since Linux 6.7, using this subcode requires the
 .B CAP_SYS_ADMIN
-- 
2.48.1

Re: [PATCH man 1/1] TIOCLINUX.2const: Document TIOCL_SETSEL selection modes

[Jared Finder]

On 2025-02-23 01:13, Günther Noack wrote:
> These previously undocumented selection modes for the Linux console
> are implemented in drivers/tty/vt/selection.c.
> 
> Cc: Jared Finder <jared@finder.org>
> Cc: Hanno Böck <hanno@hboeck.de>
> Cc: Jann Horn <jannh@google.com>
> Cc: Jiri Slaby <jirislaby@kernel.org>
> Cc: jwilk@jwilk.net
> Signed-off-by: Günther Noack <gnoack3000@gmail.com>
> ---
>  man/man2const/TIOCLINUX.2const | 48 ++++++++++++++++++++++++++++++----
>  1 file changed, 43 insertions(+), 5 deletions(-)
> 
> diff --git a/man/man2const/TIOCLINUX.2const 
> b/man/man2const/TIOCLINUX.2const
> index c0acdd0ea..27758584e 100644
> --- a/man/man2const/TIOCLINUX.2const
> +++ b/man/man2const/TIOCLINUX.2const
> @@ -65,11 +65,49 @@ are the ending
>  column and row.
>  (Upper left corner is row=column=1.)
>  .I sel_mode
> -is 0 for character-by-character selection,
> -1 for word-by-word selection,
> -or 2 for line-by-line selection.
> -The indicated screen characters are highlighted and saved
> -in a kernel buffer.
> +may be one of the following operations:
> +.RS
> +.TP
> +.B TIOCL_SELCHAR
> +Select character-by-character.
> +The indicated screen characters are highlighted
> +and saved in a kernel buffer.
> +.TP
> +.B TIOCL_SELWORD
> +Select word-by-word.
> +The indicated screen characters are highlighted
> +and saved in a kernel buffer.
> +.TP
> +.B TIOCL_SELLINE
> +Select line-by-line.
> +The indicated screen characters are highlighted
> +and saved in a kernel buffer.
> +.TP
> +.B TIOCL_SELPOINTER
> +Show the pointer at position
> +.RI ( xe ", " ye ).
> +.TP

Wouldn't it be appropriate to call out here that this specific code is 
not intended to be protected by CAP_SYS_ADMIN?

> +.B TIOCL_SELCLEAR
> +Remove the current selection highlight, if any,
> +from the console holding the selection.
> +.TP

And this one too?

> +.B TIOCL_SELMOUSEREPORT
> +Report
> +.RI ( xs ", " ys )
> +as the current mouse location.
> +In this selection mode,
> +the lower 4 bits of
> +.I sel_mode
> +.RB ( TIOCL_SELBUTTONMASK )
> +may additionally be set to indicate the desired button press and
> +modifier key information for the mouse event.
> +.\" 
> https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-Normal-tracking-mode
> +.IP
> +If mouse reporting is not enabled for the terminal,
> +this operation yields an
> +.B EINVAL
> +error.
> +.RE
>  .IP
>  Since Linux 6.7, using this subcode requires the
>  .B CAP_SYS_ADMIN

   -- MJF

Re: [PATCH man 1/1] TIOCLINUX.2const: Document TIOCL_SETSEL selection modes

[Günther Noack]

Hi!

Thanks for the review!

On Sun, Feb 23, 2025 at 08:35:16AM -0800, Jared Finder wrote:
> On 2025-02-23 01:13, Günther Noack wrote:
> > diff --git a/man/man2const/TIOCLINUX.2const
> > b/man/man2const/TIOCLINUX.2const
> > index c0acdd0ea..27758584e 100644
> > --- a/man/man2const/TIOCLINUX.2const
> > +++ b/man/man2const/TIOCLINUX.2const
> > @@ -65,11 +65,49 @@ are the ending
> >  column and row.
> >  (Upper left corner is row=column=1.)
> >  .I sel_mode
> > -is 0 for character-by-character selection,
> > -1 for word-by-word selection,
> > -or 2 for line-by-line selection.
> > -The indicated screen characters are highlighted and saved
> > -in a kernel buffer.
> > +may be one of the following operations:
> > +.RS
> > +.TP
> > +.B TIOCL_SELCHAR
> > +Select character-by-character.
> > +The indicated screen characters are highlighted
> > +and saved in a kernel buffer.
> > +.TP
> > +.B TIOCL_SELWORD
> > +Select word-by-word.
> > +The indicated screen characters are highlighted
> > +and saved in a kernel buffer.
> > +.TP
> > +.B TIOCL_SELLINE
> > +Select line-by-line.
> > +The indicated screen characters are highlighted
> > +and saved in a kernel buffer.
> > +.TP
> > +.B TIOCL_SELPOINTER
> > +Show the pointer at position
> > +.RI ( xe ", " ye ).
> > +.TP
> 
> Wouldn't it be appropriate to call out here that this specific code is not
> intended to be protected by CAP_SYS_ADMIN?

Yes, it would, and that's the intention and what this change is
preparing for.  This commit describes the "selection modes" (without
touching on the CAP_SYS_ADMIN topic) and a follow-up commit should
move the CAP_SYS_ADMIN remark into the sections for the individual
selection modes.

I intentionally postponed the CAP_SYS_ADMIN part of the change until
the time when the semantics are finalized in the kernel, because I did
not want to risk calling the slightly broken intermediate logic to
anyone's attention (where TIOCL_SELMOUSEREPORT requires CAP_SYS_ADMIN,
but only as long as one of the lower four bits of the sel_mode are
set) - that behavior was unintentional and I don't want to promote
that further than necessary. ;-)

So yes, I'll send another small patch once we have a fix on the kernel
side which is merged.

–Günther

Re: [PATCH man 1/1] TIOCLINUX.2const: Document TIOCL_SETSEL selection modes

[Alejandro Colomar]

[-- Attachment #1: Type: text/plain, Size: 2893 bytes --]

Hi!

On Sun, Feb 23, 2025 at 10:13:42AM +0100, Günther Noack wrote:
> These previously undocumented selection modes for the Linux console
> are implemented in drivers/tty/vt/selection.c.
> 
> Cc: Jared Finder <jared@finder.org>
> Cc: Hanno Böck <hanno@hboeck.de>
> Cc: Jann Horn <jannh@google.com>
> Cc: Jiri Slaby <jirislaby@kernel.org>
> Cc: jwilk@jwilk.net
> Signed-off-by: Günther Noack <gnoack3000@gmail.com>
> ---
>  man/man2const/TIOCLINUX.2const | 48 ++++++++++++++++++++++++++++++----
>  1 file changed, 43 insertions(+), 5 deletions(-)
> 
> diff --git a/man/man2const/TIOCLINUX.2const b/man/man2const/TIOCLINUX.2const
> index c0acdd0ea..27758584e 100644
> --- a/man/man2const/TIOCLINUX.2const
> +++ b/man/man2const/TIOCLINUX.2const
> @@ -65,11 +65,49 @@ are the ending
>  column and row.
>  (Upper left corner is row=column=1.)
>  .I sel_mode
> -is 0 for character-by-character selection,
> -1 for word-by-word selection,
> -or 2 for line-by-line selection.
> -The indicated screen characters are highlighted and saved
> -in a kernel buffer.
> +may be one of the following operations:
> +.RS
> +.TP
> +.B TIOCL_SELCHAR
> +Select character-by-character.
> +The indicated screen characters are highlighted
> +and saved in a kernel buffer.
> +.TP
> +.B TIOCL_SELWORD
> +Select word-by-word.
> +The indicated screen characters are highlighted
> +and saved in a kernel buffer.
> +.TP
> +.B TIOCL_SELLINE
> +Select line-by-line.
> +The indicated screen characters are highlighted
> +and saved in a kernel buffer.

It might be interesting to split this into two patches:

1)  A first one that fixes existing wording, line breaks, etc, and gives
    names to the values 0,1,2.

2)  And a second one that adds new documentation.

> +.TP
> +.B TIOCL_SELPOINTER
> +Show the pointer at position
> +.RI ( xe ", " ye ).

I'd use a non-breaking space \~, which also has the benefit of not
needing quotes:

	.RI ( xe ,\~ ye ).

> +.TP
> +.B TIOCL_SELCLEAR
> +Remove the current selection highlight, if any,
> +from the console holding the selection.
> +.TP
> +.B TIOCL_SELMOUSEREPORT
> +Report
> +.RI ( xs ", " ys )

.

> +as the current mouse location.
> +In this selection mode,
> +the lower 4 bits of
> +.I sel_mode
> +.RB ( TIOCL_SELBUTTONMASK )
> +may additionally be set to indicate the desired button press and
> +modifier key information for the mouse event.
> +.\" https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-Normal-tracking-mode

Please always enclose URIs in <>.  (See uri(7).)

> +.IP
> +If mouse reporting is not enabled for the terminal,
> +this operation yields an
> +.B EINVAL
> +error.
> +.RE

Have a lovely night!
Alex

>  .IP
>  Since Linux 6.7, using this subcode requires the
>  .B CAP_SYS_ADMIN
> -- 
> 2.48.1
> 

-- 
<https://www.alejandro-colomar.es/>

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