From: nick black dankamongmen@gmail.com
commit 3a2b2eb55681158d3e3ef464fbf47574cf0c517c upstream.
The Linux console's VT102 implementation already consumes OSC ("Operating System Command") sequences, probably because that's how palette changes are transmitted.
In addition to OSC, there are three other major clases of ANSI control strings: APC ("Application Program Command"), PM ("Privacy Message"), and DCS ("Device Control String"). They are handled similarly to OSC in terms of termination.
Source: vt100.net
Add three new enumerated states, one for each of these types. All three are handled the same way right now--they simply consume input until terminated. I hope to expand upon this firmament in the future. Add new predicate ansi_control_string(), returning true for any of these states. Replace explicit checks against ESosc with calls to this function. Transition to these states appropriately from the escape initiation (ESesc) state.
This was motivated by the following Notcurses bugs:
https://github.com/dankamongmen/notcurses/issues/2050 https://github.com/dankamongmen/notcurses/issues/1828 https://github.com/dankamongmen/notcurses/issues/2069
where standard VT sequences are not consumed by the Linux console. It's not necessary that the Linux console *support* these sequences, but it ought *consume* these well-specified classes of sequences.
Tested by sending a variety of escape sequences to the console, and verifying that they still worked, or were now properly consumed. Verified that the escapes were properly terminated at a generic level. Verified that the Notcurses tools continued to show expected output on the Linux console, except now without escape bleedthrough.
Link: https://lore.kernel.org/lkml/YSydL0q8iaUfkphg@schwarzgerat.orthanc/ Signed-off-by: nick black dankamongmen@gmail.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Jiri Slaby jirislaby@kernel.org Cc: Tetsuo Handa penguin-kernel@i-love.sakura.ne.jp Cc: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/vt/vt.c | 31 +++++++++++++++++++++++++++---- 1 file changed, 27 insertions(+), 4 deletions(-)
--- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -2059,7 +2059,7 @@ static void restore_cur(struct vc_data *
enum { ESnormal, ESesc, ESsquare, ESgetpars, ESfunckey, EShash, ESsetG0, ESsetG1, ESpercent, EScsiignore, ESnonstd, - ESpalette, ESosc }; + ESpalette, ESosc, ESapc, ESpm, ESdcs };
/* console_lock is held (except via vc_init()) */ static void reset_terminal(struct vc_data *vc, int do_clear) @@ -2133,20 +2133,28 @@ static void vc_setGx(struct vc_data *vc, vc->vc_translate = set_translate(*charset, vc); }
+/* is this state an ANSI control string? */ +static bool ansi_control_string(unsigned int state) +{ + if (state == ESosc || state == ESapc || state == ESpm || state == ESdcs) + return true; + return false; +} + /* console_lock is held */ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c) { /* * Control characters can be used in the _middle_ - * of an escape sequence. + * of an escape sequence, aside from ANSI control strings. */ - if (vc->vc_state == ESosc && c>=8 && c<=13) /* ... except for OSC */ + if (ansi_control_string(vc->vc_state) && c >= 8 && c <= 13) return; switch (c) { case 0: return; case 7: - if (vc->vc_state == ESosc) + if (ansi_control_string(vc->vc_state)) vc->vc_state = ESnormal; else if (vc->vc_bell_duration) kd_mksound(vc->vc_bell_pitch, vc->vc_bell_duration); @@ -2207,6 +2215,12 @@ static void do_con_trol(struct tty_struc case ']': vc->vc_state = ESnonstd; return; + case '_': + vc->vc_state = ESapc; + return; + case '^': + vc->vc_state = ESpm; + return; case '%': vc->vc_state = ESpercent; return; @@ -2224,6 +2238,9 @@ static void do_con_trol(struct tty_struc if (vc->state.x < VC_TABSTOPS_COUNT) set_bit(vc->state.x, vc->vc_tab_stop); return; + case 'P': + vc->vc_state = ESdcs; + return; case 'Z': respond_ID(tty); return; @@ -2520,8 +2537,14 @@ static void do_con_trol(struct tty_struc vc_setGx(vc, 1, c); vc->vc_state = ESnormal; return; + case ESapc: + return; case ESosc: return; + case ESpm: + return; + case ESdcs: + return; default: vc->vc_state = ESnormal; }