Messages in this thread | | | Date | Tue, 18 Feb 2014 10:44:30 -0800 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH] vt: detect and ignore OSC codes. |
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On Sun, Feb 16, 2014 at 03:37:59AM +0100, Adam Borowski wrote: > On Thu, Feb 13, 2014 at 10:39:12AM -0800, Greg Kroah-Hartman wrote: > > On Wed, Jan 15, 2014 at 07:21:04AM +0100, Adam Borowski wrote: > > > These can be used to send commands consisting of an arbitrary string to the > > > terminal, most often used to set a terminal's window title or to redefine > > > the colour palette. Our console doesn't use OSC, unlike everything else, > > > which can lead to junk being displayed if a process sends such a code > > > unconditionally. > > > > > > Not following Ecma-48, this commit recognizes 7-bit forms (ESC ] ... 0x07, > > > ESC ] .. ESC \) but not 8-bit (0x9D ... 0x9C). > > > > > > Signed-off-by: Adam Borowski <kilobyte@angband.pl> > > > > Where is this documented? > > It's a mix of Ecma-48 and undocumented practice. Ecma-48 says: > > # 8.3.89 > # OSC - OPERATING SYSTEM COMMAND > # Notation: (C1) > # Representation: 0x9D or ESC 0x5D (]) > # > # OSC is used as the opening delimiter of a control string for operating > # system use. The command string following may consist of a sequence of > # bit combinations in the range 0x08 to 0x0D and 0x20 to 0x7E. The > # control string is closed by the terminating delimiter STRING TERMINATOR > # (ST). The interpretation of the command string depends on the relevant > # operating system. > > # 8.3.143 > # ST - STRING TERMINATOR > # Notation: (C1) > # Representation: 0x9C or ESC 0x5C (\) > # > # ST is used as the closing delimiter of a control string opened by > # APPLICATION PROGRAM COMMAND (APC), DEVICE CONTROL STRING (DCS), > # OPERATING SYSTEM COMMAND (OSC), PRIVACY MESSAGE (PM), or START OF STRING > # (SOS). > > ... which doesn't define the behaviour for characters 0x00..0x07, 0x0E..0x1F > or 0x7F..0xFF. Somehow, using 0x07 for termination became a widespread > idiom, used more often than proper ESC \. For this reason, implementations > I know all recognize 0x07 as a terminator. The behaviour for other > characters differs, ie, is truly undefined. > > As, unlike what Ecma-48 says, using 8-bit characters in a window title is a > reasonable thing to do, I'd allow 0x80..0xFF as non-terminators. I have no > idea what to do with remaining control characters: the current patch allows > them to be interpreted, as it's usually the case for control characters > inside terminal codes. I did not research other implementation here. > > I did not recognize 0x9C as ST for two reasons: 1. it'd break non-ASCII > characters that happen to include this byte, and 2. Linux already fails to > recognize 8-bit control codes (with one exception: 0x9B stands for ESC [). > > > Should I put the above explanation somewhere? As a comment? In the commit > message? Or does it need to be elaborated even further?
In the commit message would be best.
> > > @@ -2023,6 +2029,8 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c) > > > return; > > > default: > > > vc->vc_state = ESnormal; > > > + case ESosc: > > > + return; > > > > Why below the default: case? > > Just to shave a line and a return statement. From your objection, I guess > this goes against the coding standards, right?
Yes it does.
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