Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935008AbcCPJsQ (ORCPT ); Wed, 16 Mar 2016 05:48:16 -0400 Received: from mail-lf0-f54.google.com ([209.85.215.54]:34263 "EHLO mail-lf0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934953AbcCPJsM (ORCPT ); Wed, 16 Mar 2016 05:48:12 -0400 Date: Wed, 16 Mar 2016 12:48:05 +0300 From: Cyrill Gorcunov To: Jiri Slaby , LKML Cc: Peter Hurley , Greg Kroah-Hartman , Andrey Vagin , Konstantin Khorenko , Vladimir Davydov , Pavel Emelianov Subject: [PATCH v2] tty: n_tty -- Add new TIOCPEEKRAW ioctl to peek unread data Message-ID: <20160316094805.GK2231@uranus.lan> References: <20160312141830.GM1989@uranus.lan> <56E53D96.3010107@suse.cz> <20160313103523.GP1989@uranus.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160313103523.GP1989@uranus.lan> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4336 Lines: 111 On Sun, Mar 13, 2016 at 01:35:23PM +0300, Cyrill Gorcunov wrote: > On Sun, Mar 13, 2016 at 11:14:46AM +0100, Jiri Slaby wrote: > > On 03/12/2016, 03:18 PM, Cyrill Gorcunov wrote: > > > --- linux-ml.git.orig/include/uapi/asm-generic/ioctls.h > > > +++ linux-ml.git/include/uapi/asm-generic/ioctls.h > > > @@ -77,6 +77,7 @@ > > > #define TIOCGPKT _IOR('T', 0x38, int) /* Get packet mode state */ > > > #define TIOCGPTLCK _IOR('T', 0x39, int) /* Get Pty lock state */ > > > #define TIOCGEXCL _IOR('T', 0x40, int) /* Get exclusive mode state */ > > > +#define TIOCPEEKRAW _IOR('T', 0x41, void *) > > > > Hi, this is not 32/64bit compatible and would need a compat ioctl number > > and a wrapper. Since it is char *, could you make it just 'char'? > > Hi Jiri, sure, thanks! Lets wait for more feedback, maybe there some > other more elegant solution possible, which I failed to invent. Here is an updated one. Hopefully I didn't miss anything. Any comments are highly appreciated. --- From: Cyrill Gorcunov Subject: [PATCH v2] tty: n_tty -- Add new TIOCPEEKRAW ioctl to peek unread data Currently when we checkpoint PTY connections we ignore data queued inside read buffer of ldisk, such data is barely lost after the restore. So we would like to have an ability to dump and restore it. Here is a new ioctl code which simply copies data from read buffer into the userspace without any additional processing (just like terminal is sitting in a raw mode). The idea behind is when we checkpointing PTY pairs we peek this unread data into images on disk and on restore phase we find the linked peer and write it back thus reading peer will see it in read buffer. I tried several approaches (including simply reuse of canon_copy_from_read_buf and copy_from_read_buf) but it not always do the trick: for example if data queued doesn't have \n symbol the input_available_p helper returns false and I shouldn't call for the helpers above. So I end up in plain copying. v2: - Use @char in ioctl definition. Signed-off-by: Cyrill Gorcunov CC: Jiri Slaby CC: Peter Hurley CC: Greg Kroah-Hartman CC: Andrey Vagin CC: Pavel Emelianov CC: Vladimir Davydov CC: Konstantin Khorenko --- drivers/tty/n_tty.c | 22 ++++++++++++++++++++++ include/uapi/asm-generic/ioctls.h | 1 + 2 files changed, 23 insertions(+) Index: linux-ml.git/drivers/tty/n_tty.c =================================================================== --- linux-ml.git.orig/drivers/tty/n_tty.c +++ linux-ml.git/drivers/tty/n_tty.c @@ -2485,6 +2485,26 @@ static unsigned long inq_canon(struct n_ return nr; } +static ssize_t n_tty_peek_raw(struct tty_struct *tty, unsigned char __user *buf) +{ + struct n_tty_data *ldata = tty->disc_data; + ssize_t retval; + + if (!mutex_trylock(&ldata->atomic_read_lock)) + return -EAGAIN; + + down_read(&tty->termios_rwsem); + retval = read_cnt(ldata); + if (retval) { + const unsigned char *from = read_buf_addr(ldata, ldata->read_tail); + if (copy_to_user(buf, from, retval)) + retval = -EFAULT; + } + up_read(&tty->termios_rwsem); + mutex_unlock(&ldata->atomic_read_lock); + return retval; +} + static int n_tty_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg) { @@ -2502,6 +2522,8 @@ static int n_tty_ioctl(struct tty_struct retval = read_cnt(ldata); up_write(&tty->termios_rwsem); return put_user(retval, (unsigned int __user *) arg); + case TIOCPEEKRAW: + return n_tty_peek_raw(tty, (unsigned char __user *) arg); default: return n_tty_ioctl_helper(tty, file, cmd, arg); } Index: linux-ml.git/include/uapi/asm-generic/ioctls.h =================================================================== --- linux-ml.git.orig/include/uapi/asm-generic/ioctls.h +++ linux-ml.git/include/uapi/asm-generic/ioctls.h @@ -77,6 +77,7 @@ #define TIOCGPKT _IOR('T', 0x38, int) /* Get packet mode state */ #define TIOCGPTLCK _IOR('T', 0x39, int) /* Get Pty lock state */ #define TIOCGEXCL _IOR('T', 0x40, int) /* Get exclusive mode state */ +#define TIOCPEEKRAW _IOR('T', 0x41, char) #define FIONCLEX 0x5450 #define FIOCLEX 0x5451