* [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code
@ 2017-12-06 11:57 Daniel P. Berrange
2017-12-06 14:22 ` Eric Blake
2017-12-08 12:15 ` Dr. David Alan Gilbert
0 siblings, 2 replies; 7+ messages in thread
From: Daniel P. Berrange @ 2017-12-06 11:57 UTC (permalink / raw)
To: qemu-devel
Cc: qemu-block, Kevin Wolf, Max Reitz, Stefan Hajnoczi, Daniel P. Berrange
qemu-io puts the TTY into non-canonical mode, which means no EOF processing is
done and thus getchar() will never return the EOF constant. Instead we have to
check for an explicit Ctrl-D, aka 0x4, to detect EOF and exit the qemu-io
shell. This fixes the regression that prevented Ctrl-D from triggering an exit
of qemu-io that has existed since readline was first added in
commit 0cf17e181798063c3824c8200ba46f25f54faa1a
Author: Stefan Hajnoczi <stefanha@redhat.com>
Date: Thu Nov 14 11:54:17 2013 +0100
qemu-io: use readline.c
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
qemu-io.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/qemu-io.c b/qemu-io.c
index c70bde3eb1..2ea0bfbaf8 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -322,7 +322,9 @@ static char *fetchline_readline(void)
readline_start(readline_state, get_prompt(), 0, readline_func, &line);
while (!line) {
int ch = getchar();
- if (ch == EOF) {
+ /* In non-canon tty mode we get 0x4 (Ctrl-D), not the stdio "EOF"
+ * constant */
+ if (ch == 0x4) {
break;
}
readline_handle_byte(readline_state, ch);
--
2.14.3
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code
2017-12-06 11:57 [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code Daniel P. Berrange
@ 2017-12-06 14:22 ` Eric Blake
2017-12-06 14:25 ` Daniel P. Berrange
2017-12-08 12:15 ` Dr. David Alan Gilbert
1 sibling, 1 reply; 7+ messages in thread
From: Eric Blake @ 2017-12-06 14:22 UTC (permalink / raw)
To: Daniel P. Berrange, qemu-devel
Cc: Kevin Wolf, Stefan Hajnoczi, qemu-block, Max Reitz
[-- Attachment #1: Type: text/plain, Size: 1341 bytes --]
On 12/06/2017 05:57 AM, Daniel P. Berrange wrote:
> qemu-io puts the TTY into non-canonical mode, which means no EOF processing is
> done and thus getchar() will never return the EOF constant. Instead we have to
> check for an explicit Ctrl-D, aka 0x4, to detect EOF and exit the qemu-io
> shell. This fixes the regression that prevented Ctrl-D from triggering an exit
> of qemu-io that has existed since readline was first added in
>
> commit 0cf17e181798063c3824c8200ba46f25f54faa1a
> Author: Stefan Hajnoczi <stefanha@redhat.com>
> Date: Thu Nov 14 11:54:17 2013 +0100
>
> qemu-io: use readline.c
>
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
> qemu-io.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> while (!line) {
> int ch = getchar();
> - if (ch == EOF) {
> + /* In non-canon tty mode we get 0x4 (Ctrl-D), not the stdio "EOF"
> + * constant */
> + if (ch == 0x4) {
Should we instead be looking for a match against the current termios()
c_cc[VEOF] setting, in case the user prefers something other than ^D via
stty? Does readline provide any functionality for automating this?
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code
2017-12-06 14:22 ` Eric Blake
@ 2017-12-06 14:25 ` Daniel P. Berrange
2017-12-06 14:30 ` Eric Blake
0 siblings, 1 reply; 7+ messages in thread
From: Daniel P. Berrange @ 2017-12-06 14:25 UTC (permalink / raw)
To: Eric Blake; +Cc: qemu-devel, Kevin Wolf, Stefan Hajnoczi, qemu-block, Max Reitz
On Wed, Dec 06, 2017 at 08:22:35AM -0600, Eric Blake wrote:
> On 12/06/2017 05:57 AM, Daniel P. Berrange wrote:
> > qemu-io puts the TTY into non-canonical mode, which means no EOF processing is
> > done and thus getchar() will never return the EOF constant. Instead we have to
> > check for an explicit Ctrl-D, aka 0x4, to detect EOF and exit the qemu-io
> > shell. This fixes the regression that prevented Ctrl-D from triggering an exit
> > of qemu-io that has existed since readline was first added in
> >
> > commit 0cf17e181798063c3824c8200ba46f25f54faa1a
> > Author: Stefan Hajnoczi <stefanha@redhat.com>
> > Date: Thu Nov 14 11:54:17 2013 +0100
> >
> > qemu-io: use readline.c
> >
> > Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> > ---
> > qemu-io.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
>
> > while (!line) {
> > int ch = getchar();
> > - if (ch == EOF) {
> > + /* In non-canon tty mode we get 0x4 (Ctrl-D), not the stdio "EOF"
> > + * constant */
> > + if (ch == 0x4) {
>
> Should we instead be looking for a match against the current termios()
> c_cc[VEOF] setting, in case the user prefers something other than ^D via
> stty? Does readline provide any functionality for automating this?
I was afraid someone was going to suggest doing that. I was being lazy by
hardcoding Ctrl-D, but yes the real readline() library will honour the
VEOF value. QEMU though is using a home-grown reimpl of readline...
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code
2017-12-06 14:25 ` Daniel P. Berrange
@ 2017-12-06 14:30 ` Eric Blake
2017-12-06 16:14 ` Markus Armbruster
0 siblings, 1 reply; 7+ messages in thread
From: Eric Blake @ 2017-12-06 14:30 UTC (permalink / raw)
To: Daniel P. Berrange
Cc: qemu-devel, Kevin Wolf, Stefan Hajnoczi, qemu-block, Max Reitz
[-- Attachment #1: Type: text/plain, Size: 924 bytes --]
On 12/06/2017 08:25 AM, Daniel P. Berrange wrote:
>> Should we instead be looking for a match against the current termios()
>> c_cc[VEOF] setting, in case the user prefers something other than ^D via
>> stty? Does readline provide any functionality for automating this?
>
> I was afraid someone was going to suggest doing that. I was being lazy by
> hardcoding Ctrl-D, but yes the real readline() library will honour the
> VEOF value. QEMU though is using a home-grown reimpl of readline...
I understand why we can't use modern libreadline (it is licensed GPLv3+,
making it impossible to use with our GPLv2-only code) - but doesn't BSD
have a readline-alike library with BSD licensing that we could use
instead of implementing readline ourselves? (Was it named libinput?)
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code
2017-12-06 14:30 ` Eric Blake
@ 2017-12-06 16:14 ` Markus Armbruster
0 siblings, 0 replies; 7+ messages in thread
From: Markus Armbruster @ 2017-12-06 16:14 UTC (permalink / raw)
To: Eric Blake
Cc: Daniel P. Berrange, Kevin Wolf, qemu-block, qemu-devel,
Stefan Hajnoczi, Max Reitz
Eric Blake <eblake@redhat.com> writes:
> On 12/06/2017 08:25 AM, Daniel P. Berrange wrote:
>
>>> Should we instead be looking for a match against the current termios()
>>> c_cc[VEOF] setting, in case the user prefers something other than ^D via
>>> stty? Does readline provide any functionality for automating this?
>>
>> I was afraid someone was going to suggest doing that. I was being lazy by
>> hardcoding Ctrl-D, but yes the real readline() library will honour the
>> VEOF value. QEMU though is using a home-grown reimpl of readline...
>
> I understand why we can't use modern libreadline (it is licensed GPLv3+,
> making it impossible to use with our GPLv2-only code) - but doesn't BSD
> have a readline-alike library with BSD licensing that we could use
> instead of implementing readline ourselves? (Was it named libinput?)
We've discussed this before. Short story: we can't use the original due
to our foolish licensing mistake, and the clones don't cut the mustard.
Long story:
http://lists.gnu.org/archive/html/qemu-devel/2016-10/msg02697.html
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code
2017-12-06 11:57 [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code Daniel P. Berrange
2017-12-06 14:22 ` Eric Blake
@ 2017-12-08 12:15 ` Dr. David Alan Gilbert
2017-12-08 13:35 ` Daniel P. Berrange
1 sibling, 1 reply; 7+ messages in thread
From: Dr. David Alan Gilbert @ 2017-12-08 12:15 UTC (permalink / raw)
To: Daniel P. Berrange
Cc: qemu-devel, Kevin Wolf, Stefan Hajnoczi, qemu-block, Max Reitz
* Daniel P. Berrange (berrange@redhat.com) wrote:
> qemu-io puts the TTY into non-canonical mode, which means no EOF processing is
> done and thus getchar() will never return the EOF constant. Instead we have to
> check for an explicit Ctrl-D, aka 0x4, to detect EOF and exit the qemu-io
> shell. This fixes the regression that prevented Ctrl-D from triggering an exit
> of qemu-io that has existed since readline was first added in
>
> commit 0cf17e181798063c3824c8200ba46f25f54faa1a
> Author: Stefan Hajnoczi <stefanha@redhat.com>
> Date: Thu Nov 14 11:54:17 2013 +0100
>
> qemu-io: use readline.c
>
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
> qemu-io.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/qemu-io.c b/qemu-io.c
> index c70bde3eb1..2ea0bfbaf8 100644
> --- a/qemu-io.c
> +++ b/qemu-io.c
> @@ -322,7 +322,9 @@ static char *fetchline_readline(void)
> readline_start(readline_state, get_prompt(), 0, readline_func, &line);
> while (!line) {
> int ch = getchar();
> - if (ch == EOF) {
> + /* In non-canon tty mode we get 0x4 (Ctrl-D), not the stdio "EOF"
> + * constant */
> + if (ch == 0x4) {
Personally I'd have made that EOF or 0x4 - but that's fine
(I don't see the point of reading the ioctl to figure out which EOF
char we're using; it seems to turn a trivial check into something much
more complex)
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> break;
> }
> readline_handle_byte(readline_state, ch);
> --
> 2.14.3
>
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code
2017-12-08 12:15 ` Dr. David Alan Gilbert
@ 2017-12-08 13:35 ` Daniel P. Berrange
0 siblings, 0 replies; 7+ messages in thread
From: Daniel P. Berrange @ 2017-12-08 13:35 UTC (permalink / raw)
To: Dr. David Alan Gilbert
Cc: qemu-devel, Kevin Wolf, Stefan Hajnoczi, qemu-block, Max Reitz
On Fri, Dec 08, 2017 at 12:15:21PM +0000, Dr. David Alan Gilbert wrote:
> * Daniel P. Berrange (berrange@redhat.com) wrote:
> > qemu-io puts the TTY into non-canonical mode, which means no EOF processing is
> > done and thus getchar() will never return the EOF constant. Instead we have to
> > check for an explicit Ctrl-D, aka 0x4, to detect EOF and exit the qemu-io
> > shell. This fixes the regression that prevented Ctrl-D from triggering an exit
> > of qemu-io that has existed since readline was first added in
> >
> > commit 0cf17e181798063c3824c8200ba46f25f54faa1a
> > Author: Stefan Hajnoczi <stefanha@redhat.com>
> > Date: Thu Nov 14 11:54:17 2013 +0100
> >
> > qemu-io: use readline.c
> >
> > Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> > ---
> > qemu-io.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/qemu-io.c b/qemu-io.c
> > index c70bde3eb1..2ea0bfbaf8 100644
> > --- a/qemu-io.c
> > +++ b/qemu-io.c
> > @@ -322,7 +322,9 @@ static char *fetchline_readline(void)
> > readline_start(readline_state, get_prompt(), 0, readline_func, &line);
> > while (!line) {
> > int ch = getchar();
> > - if (ch == EOF) {
> > + /* In non-canon tty mode we get 0x4 (Ctrl-D), not the stdio "EOF"
> > + * constant */
> > + if (ch == 0x4) {
>
> Personally I'd have made that EOF or 0x4 - but that's fine
I thought about that, but it is impossible to get 'EOF' when the terminal
is in raw mode, so there's little point.
> (I don't see the point of reading the ioctl to figure out which EOF
> char we're using; it seems to turn a trivial check into something much
> more complex)
I'd already done the work to read termios settings by time I read this
comment, so I've sent a v2 anyway :-)
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
^ permalink raw reply [flat|nested] 7+ messages in thread
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2017-12-06 11:57 [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code Daniel P. Berrange
2017-12-06 14:22 ` Eric Blake
2017-12-06 14:25 ` Daniel P. Berrange
2017-12-06 14:30 ` Eric Blake
2017-12-06 16:14 ` Markus Armbruster
2017-12-08 12:15 ` Dr. David Alan Gilbert
2017-12-08 13:35 ` Daniel P. Berrange
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