From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752539AbdASNYM (ORCPT ); Thu, 19 Jan 2017 08:24:12 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:46542 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751262AbdASNYL (ORCPT ); Thu, 19 Jan 2017 08:24:11 -0500 Date: Thu, 19 Jan 2017 14:23:52 +0100 From: Greg KH To: Manuel =?iso-8859-1?Q?Sch=F6lling?= Cc: jslaby@suse.com, kilobyte@angband.pl, lkml14@scotdoyle.com, rdunlap@infradead.org, shorne@gmail.com, andrey_utkin@fastmail.com, akpm@linux-foundation.org, paul.burton@imgtec.com, daniel.vetter@ffwll.ch, tj@kernel.org, hdegoede@redhat.com, linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org Subject: Re: [PATCH v10 3/4] console: Add persistent scrollback buffers for all VGA consoles Message-ID: <20170119132352.GB29998@kroah.com> References: <201701112105.R6Zog6jw%fengguang.wu@intel.com> <20170113200758.9880-4-manuel.schoelling@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170113200758.9880-4-manuel.schoelling@gmx.de> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 13, 2017 at 09:07:57PM +0100, Manuel Schölling wrote: > Add a scrollback buffers for each VGA console. The benefit is that > the scrollback history is not flushed when switching between consoles > but is persistent. > The buffers are allocated on demand when a new console is opened. > > This breaks tools like clear_console that rely on flushing the > scrollback history by switching back and forth between consoles > which is why this feature is disabled by default. > Use the escape sequence \e[3J instead for flushing the buffer. > > Signed-off-by: Manuel Schölling > Reviewed-by: Andrey Utkin > Tested-by: Andrey Utkin > Tested-by: Adam Borowski > --- > drivers/video/console/Kconfig | 25 +++++++- > drivers/video/console/vgacon.c | 142 ++++++++++++++++++++++++++--------------- > 2 files changed, 111 insertions(+), 56 deletions(-) > > diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig > index c3f1fb9ee820..f500e58f7636 100644 > --- a/drivers/video/console/Kconfig > +++ b/drivers/video/console/Kconfig > @@ -43,9 +43,28 @@ config VGACON_SOFT_SCROLLBACK_SIZE > range 1 1024 > default "64" > help > - Enter the amount of System RAM to allocate for the scrollback > - buffer. Each 64KB will give you approximately 16 80x25 > - screenfuls of scrollback buffer > + Enter the amount of System RAM to allocate for scrollback > + buffers of VGA consoles. Each 64KB will give you approximately > + 16 80x25 screenfuls of scrollback buffer. > + > +config VGACON_SOFT_SCROLLBACK_PERSISTENT > + bool "Persistent Scrollback History for each console" > + depends on VGACON_SOFT_SCROLLBACK > + default n > + help > + Say Y here if the scrollback history should persist when switching > + between consoles. Otherwise, the scrollback history will be flushed > + each time the console is switched. > + > + This feature might break your tool of choice to flush the scrollback > + buffer, e.g. clear(1) will work fine but Debian's clear_console(1) > + will be broken, which might cause security issues. > + You can use the escape sequence \e[3J instead if this feature is > + activated. This issue is the one that makes me the most worried. Why doesn't clear_console() work anymore? Why doesn't it use \e[3J ? thanks, greg k-h From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Date: Thu, 19 Jan 2017 13:23:52 +0000 Subject: Re: [PATCH v10 3/4] console: Add persistent scrollback buffers for all VGA consoles Message-Id: <20170119132352.GB29998@kroah.com> List-Id: References: <201701112105.R6Zog6jw%fengguang.wu@intel.com> <20170113200758.9880-4-manuel.schoelling@gmx.de> In-Reply-To: <20170113200758.9880-4-manuel.schoelling@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: Manuel =?iso-8859-1?Q?Sch=F6lling?= Cc: jslaby@suse.com, kilobyte@angband.pl, lkml14@scotdoyle.com, rdunlap@infradead.org, shorne@gmail.com, andrey_utkin@fastmail.com, akpm@linux-foundation.org, paul.burton@imgtec.com, daniel.vetter@ffwll.ch, tj@kernel.org, hdegoede@redhat.com, linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org On Fri, Jan 13, 2017 at 09:07:57PM +0100, Manuel Sch=F6lling wrote: > Add a scrollback buffers for each VGA console. The benefit is that > the scrollback history is not flushed when switching between consoles > but is persistent. > The buffers are allocated on demand when a new console is opened. >=20 > This breaks tools like clear_console that rely on flushing the > scrollback history by switching back and forth between consoles > which is why this feature is disabled by default. > Use the escape sequence \e[3J instead for flushing the buffer. >=20 > Signed-off-by: Manuel Sch=F6lling > Reviewed-by: Andrey Utkin > Tested-by: Andrey Utkin > Tested-by: Adam Borowski > --- > drivers/video/console/Kconfig | 25 +++++++- > drivers/video/console/vgacon.c | 142 ++++++++++++++++++++++++++---------= ------ > 2 files changed, 111 insertions(+), 56 deletions(-) >=20 > diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig > index c3f1fb9ee820..f500e58f7636 100644 > --- a/drivers/video/console/Kconfig > +++ b/drivers/video/console/Kconfig > @@ -43,9 +43,28 @@ config VGACON_SOFT_SCROLLBACK_SIZE > range 1 1024 > default "64" > help > - Enter the amount of System RAM to allocate for the scrollback > - buffer. Each 64KB will give you approximately 16 80x25 > - screenfuls of scrollback buffer > + Enter the amount of System RAM to allocate for scrollback > + buffers of VGA consoles. Each 64KB will give you approximately > + 16 80x25 screenfuls of scrollback buffer. > + > +config VGACON_SOFT_SCROLLBACK_PERSISTENT > + bool "Persistent Scrollback History for each console" > + depends on VGACON_SOFT_SCROLLBACK > + default n > + help > + Say Y here if the scrollback history should persist when switching > + between consoles. Otherwise, the scrollback history will be flushed > + each time the console is switched. > + > + This feature might break your tool of choice to flush the scrollback > + buffer, e.g. clear(1) will work fine but Debian's clear_console(1) > + will be broken, which might cause security issues. > + You can use the escape sequence \e[3J instead if this feature is > + activated. This issue is the one that makes me the most worried. Why doesn't clear_console() work anymore? Why doesn't it use \e[3J ? thanks, greg k-h