klibc - Jun 2014 - [PATCH] isatty(): use TCGETS instead of TIOCGPGRP, like dietlibc does

While all ?real? ttys may support TIOCGPGRP, /dev/console doesn?t;
using TCGETS here allows Linux booted with init=/bin/mksh-static
to have working interactive command line (PS1, editing, etc).

Reported-by: Dominik George <d.george at tarent.de>
Signed-off-by: Thorsten Glaser <t.glaser at tarent.de>
---
 usr/klibc/isatty.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/usr/klibc/isatty.c b/usr/klibc/isatty.c
index c2e4a4e..2359479 100644
--- a/usr/klibc/isatty.c
+++ b/usr/klibc/isatty.c
@@ -8,8 +8,9 @@
 
 int isatty(int fd)
 {
-	int dummy;
+	struct termios dummy;
 
 	/* All ttys support TIOCGPGRP */
-	return !ioctl(fd, TIOCGPGRP, &dummy);
+	/* except /dev/console which needs TCGETS */
+	return !ioctl(fd, TCGETS, &dummy);
 }
-- 
2.0.0

On 06/11/2014 01:02 AM, Thorsten Glaser wrote:
> While all ?real? ttys may support TIOCGPGRP, /dev/console doesn?t;
> using TCGETS here allows Linux booted with init=/bin/mksh-static
> to have working interactive command line (PS1, editing, etc).
> 
> Reported-by: Dominik George <d.george at tarent.de>
> Signed-off-by: Thorsten Glaser <t.glaser at tarent.de>
> ---
>  usr/klibc/isatty.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/usr/klibc/isatty.c b/usr/klibc/isatty.c
> index c2e4a4e..2359479 100644
> --- a/usr/klibc/isatty.c
> +++ b/usr/klibc/isatty.c
> @@ -8,8 +8,9 @@
>  
>  int isatty(int fd)
>  {
> -	int dummy;
> +	struct termios dummy;
>  
>  	/* All ttys support TIOCGPGRP */
> -	return !ioctl(fd, TIOCGPGRP, &dummy);
> +	/* except /dev/console which needs TCGETS */
> +	return !ioctl(fd, TCGETS, &dummy);
>  }
> 
But is that really a tty, then?  I also understand that virtio console
doesn't support termios, which makes this an ugly bifurcation.  All of
this is stupid, of course...

	-hpa

H. Peter Anvin dixit:
>But is that really a tty, then?  I also understand that virtio console
Hm. Both eglibc and dietlibc return true for isatty on it.
>doesn't support termios, which makes this an ugly bifurcation.  All of
Let me test that? quick? hah not really (CONFIG_VIRTIO_CONSOLE=m)?
ok luckily Ubuntu?s linux-image-3.15.0-5-generic is installable on
Debian stable and has CONFIG_VIRTIO_CONSOLE=y? but no reiserfs module?
gah? ok I could test it.

This works. It has got enough of a tty for mksh-static linked against
klibc to have proper command line editing even with console=hvc0.
>this is stupid, of course...
Fully agreed!

bye,
//mirabilos
-- 
?ah that reminds me, thanks for the stellar entertainment that you and certain
other people provide on the Debian mailing lists ? sole reason I subscribed to
them (I'm not using Debian anywhere) is the entertainment factor ? Debian
does
not strike me as a place for good humour, much less German admin-style humour?