[Qemu-devel] [PATCH v3 0/3]: QMP: Human Monitor passthrough

[Qemu-devel] [PATCH v3 0/3]: QMP: Human Monitor passthrough

[Luiz Capitulino]

Simple example:

-> { "execute": "human-monitor-command", "arguments": { "command-line": "print /i 10+25" } }
<- { "return": "35\r\n" }

Please, check individual patches for details. Also note that this series
depends on the script improvements one.

Also, Markus suggestion of having an assert() in qemu_chr_close() have not
been added this series because I don't know what to assert(). But that's an
incremental change anyway and should prevent this series from being merged.

changelog
---------

v2 -> v3

- Renamed command name to human-monitor-command
- Fixed buggy error reporting when cpu-index is invalid
- Make qemu_chr_mem_to_qs() return a string when outbuf is empty
- Introduced qemu_chr_mem_osize() along with some cleanups

v1 -> v2

- A number of small cleanups and clarifications

Thanks.

[Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver

[Luiz Capitulino]

This driver handles in-memory chardev operations. That's, all writes
to this driver are stored in an internal buffer and it doesn't talk
to the external world in any way.

Right now it's very simple: it supports only writes. But it can be
easily extended to support more operations.

This is going to be used by the monitor's "HMP passthrough via QMP"
feature, which needs to run monitor handlers without a backing
device.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 qemu-char.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 qemu-char.h |    7 ++++++
 2 files changed, 77 insertions(+), 0 deletions(-)

diff --git a/qemu-char.c b/qemu-char.c
index 88997f9..36d23c6 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2275,6 +2275,76 @@ static CharDriverState *qemu_chr_open_socket(QemuOpts *opts)
     return NULL;
 }
 
+/***********************************************************/
+/* Memory chardev */
+typedef struct {
+    size_t outbuf_size;
+    size_t outbuf_capacity;
+    uint8_t *outbuf;
+} MemoryDriver;
+
+static int mem_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
+{
+    MemoryDriver *d = chr->opaque;
+
+    /* TODO: the QString implementation has the same code, we should
+     * introduce a generic way to do this in cutils.c */
+    if (d->outbuf_capacity < d->outbuf_size + len) {
+        /* grow outbuf */
+        d->outbuf_capacity += len;
+        d->outbuf_capacity *= 2;
+        d->outbuf = qemu_realloc(d->outbuf, d->outbuf_capacity);
+    }
+
+    memcpy(d->outbuf + d->outbuf_size, buf, len);
+    d->outbuf_size += len;
+
+    return len;
+}
+
+void qemu_chr_init_mem(CharDriverState *chr)
+{
+    MemoryDriver *d;
+
+    d = qemu_malloc(sizeof(*d));
+    d->outbuf_size = 0;
+    d->outbuf_capacity = 4096;
+    d->outbuf = qemu_mallocz(d->outbuf_capacity);
+
+    memset(chr, 0, sizeof(*chr));
+    chr->opaque = d;
+    chr->chr_write = mem_chr_write;
+}
+
+/* assumes the stored data is a string */
+QString *qemu_chr_mem_to_qs(CharDriverState *chr)
+{
+    MemoryDriver *d = chr->opaque;
+
+    if (d->outbuf_size == 0) {
+        return qstring_new();
+    }
+
+    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
+}
+
+/* NOTE: this driver can not be closed with qemu_chr_close()! */
+void qemu_chr_close_mem(CharDriverState *chr)
+{
+    MemoryDriver *d = chr->opaque;
+
+    qemu_free(d->outbuf);
+    qemu_free(chr->opaque);
+    chr->opaque = NULL;
+    chr->chr_write = NULL;
+}
+
+size_t qemu_chr_mem_osize(const CharDriverState *chr)
+{
+    const MemoryDriver *d = chr->opaque;
+    return d->outbuf_size;
+}
+
 QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
 {
     char host[65], port[33], width[8], height[8];
diff --git a/qemu-char.h b/qemu-char.h
index 18ad12b..e6ee6c4 100644
--- a/qemu-char.h
+++ b/qemu-char.h
@@ -6,6 +6,7 @@
 #include "qemu-option.h"
 #include "qemu-config.h"
 #include "qobject.h"
+#include "qstring.h"
 
 /* character device */
 
@@ -100,6 +101,12 @@ CharDriverState *qemu_chr_open_eventfd(int eventfd);
 
 extern int term_escape_char;
 
+/* memory chardev */
+void qemu_chr_init_mem(CharDriverState *chr);
+void qemu_chr_close_mem(CharDriverState *chr);
+QString *qemu_chr_mem_to_qs(CharDriverState *chr);
+size_t qemu_chr_mem_osize(const CharDriverState *chr);
+
 /* async I/O support */
 
 int qemu_set_fd_handler2(int fd,
-- 
1.7.3.2.164.g6f10c

Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver

[Markus Armbruster]

Luiz Capitulino <lcapitulino@redhat.com> writes:

> This driver handles in-memory chardev operations. That's, all writes
> to this driver are stored in an internal buffer and it doesn't talk
> to the external world in any way.
>
> Right now it's very simple: it supports only writes. But it can be
> easily extended to support more operations.
>
> This is going to be used by the monitor's "HMP passthrough via QMP"
> feature, which needs to run monitor handlers without a backing
> device.
>
> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
> ---
>  qemu-char.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  qemu-char.h |    7 ++++++
>  2 files changed, 77 insertions(+), 0 deletions(-)
>
> diff --git a/qemu-char.c b/qemu-char.c
> index 88997f9..36d23c6 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -2275,6 +2275,76 @@ static CharDriverState *qemu_chr_open_socket(QemuOpts *opts)
>      return NULL;
>  }
>  
> +/***********************************************************/
> +/* Memory chardev */
> +typedef struct {
> +    size_t outbuf_size;
> +    size_t outbuf_capacity;
> +    uint8_t *outbuf;
> +} MemoryDriver;
> +
> +static int mem_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
> +{
> +    MemoryDriver *d = chr->opaque;
> +
> +    /* TODO: the QString implementation has the same code, we should
> +     * introduce a generic way to do this in cutils.c */
> +    if (d->outbuf_capacity < d->outbuf_size + len) {
> +        /* grow outbuf */
> +        d->outbuf_capacity += len;
> +        d->outbuf_capacity *= 2;
> +        d->outbuf = qemu_realloc(d->outbuf, d->outbuf_capacity);
> +    }
> +
> +    memcpy(d->outbuf + d->outbuf_size, buf, len);
> +    d->outbuf_size += len;
> +
> +    return len;
> +}
> +
> +void qemu_chr_init_mem(CharDriverState *chr)
> +{
> +    MemoryDriver *d;
> +
> +    d = qemu_malloc(sizeof(*d));
> +    d->outbuf_size = 0;
> +    d->outbuf_capacity = 4096;
> +    d->outbuf = qemu_mallocz(d->outbuf_capacity);
> +
> +    memset(chr, 0, sizeof(*chr));
> +    chr->opaque = d;
> +    chr->chr_write = mem_chr_write;
> +}
> +
> +/* assumes the stored data is a string */

This could indicate a problem.  See my reply in the thread for v2.

> +QString *qemu_chr_mem_to_qs(CharDriverState *chr)
> +{
> +    MemoryDriver *d = chr->opaque;
> +
> +    if (d->outbuf_size == 0) {
> +        return qstring_new();
> +    }

Why is this necessary?  Is qstring_from_substr() broken for empty
substrings?  If it is, it ought to be fixed!

> +
> +    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
> +}
> +
> +/* NOTE: this driver can not be closed with qemu_chr_close()! */
> +void qemu_chr_close_mem(CharDriverState *chr)
> +{
> +    MemoryDriver *d = chr->opaque;
> +
> +    qemu_free(d->outbuf);
> +    qemu_free(chr->opaque);
> +    chr->opaque = NULL;
> +    chr->chr_write = NULL;
> +}
> +
> +size_t qemu_chr_mem_osize(const CharDriverState *chr)
> +{
> +    const MemoryDriver *d = chr->opaque;
> +    return d->outbuf_size;
> +}
> +
>  QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
>  {
>      char host[65], port[33], width[8], height[8];
> diff --git a/qemu-char.h b/qemu-char.h
> index 18ad12b..e6ee6c4 100644
> --- a/qemu-char.h
> +++ b/qemu-char.h
> @@ -6,6 +6,7 @@
>  #include "qemu-option.h"
>  #include "qemu-config.h"
>  #include "qobject.h"
> +#include "qstring.h"
>  
>  /* character device */
>  
> @@ -100,6 +101,12 @@ CharDriverState *qemu_chr_open_eventfd(int eventfd);
>  
>  extern int term_escape_char;
>  
> +/* memory chardev */
> +void qemu_chr_init_mem(CharDriverState *chr);
> +void qemu_chr_close_mem(CharDriverState *chr);
> +QString *qemu_chr_mem_to_qs(CharDriverState *chr);
> +size_t qemu_chr_mem_osize(const CharDriverState *chr);
> +
>  /* async I/O support */
>  
>  int qemu_set_fd_handler2(int fd,

Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver

[Luiz Capitulino]

On Fri, 12 Nov 2010 11:21:57 +0100
Markus Armbruster <armbru@redhat.com> wrote:

> Luiz Capitulino <lcapitulino@redhat.com> writes:
> 
> > This driver handles in-memory chardev operations. That's, all writes
> > to this driver are stored in an internal buffer and it doesn't talk
> > to the external world in any way.
> >
> > Right now it's very simple: it supports only writes. But it can be
> > easily extended to support more operations.
> >
> > This is going to be used by the monitor's "HMP passthrough via QMP"
> > feature, which needs to run monitor handlers without a backing
> > device.
> >
> > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
> > ---
> >  qemu-char.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  qemu-char.h |    7 ++++++
> >  2 files changed, 77 insertions(+), 0 deletions(-)
> >
> > diff --git a/qemu-char.c b/qemu-char.c
> > index 88997f9..36d23c6 100644
> > --- a/qemu-char.c
> > +++ b/qemu-char.c
> > @@ -2275,6 +2275,76 @@ static CharDriverState *qemu_chr_open_socket(QemuOpts *opts)
> >      return NULL;
> >  }
> >  
> > +/***********************************************************/
> > +/* Memory chardev */
> > +typedef struct {
> > +    size_t outbuf_size;
> > +    size_t outbuf_capacity;
> > +    uint8_t *outbuf;
> > +} MemoryDriver;
> > +
> > +static int mem_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
> > +{
> > +    MemoryDriver *d = chr->opaque;
> > +
> > +    /* TODO: the QString implementation has the same code, we should
> > +     * introduce a generic way to do this in cutils.c */
> > +    if (d->outbuf_capacity < d->outbuf_size + len) {
> > +        /* grow outbuf */
> > +        d->outbuf_capacity += len;
> > +        d->outbuf_capacity *= 2;
> > +        d->outbuf = qemu_realloc(d->outbuf, d->outbuf_capacity);
> > +    }
> > +
> > +    memcpy(d->outbuf + d->outbuf_size, buf, len);
> > +    d->outbuf_size += len;
> > +
> > +    return len;
> > +}
> > +
> > +void qemu_chr_init_mem(CharDriverState *chr)
> > +{
> > +    MemoryDriver *d;
> > +
> > +    d = qemu_malloc(sizeof(*d));
> > +    d->outbuf_size = 0;
> > +    d->outbuf_capacity = 4096;
> > +    d->outbuf = qemu_mallocz(d->outbuf_capacity);
> > +
> > +    memset(chr, 0, sizeof(*chr));
> > +    chr->opaque = d;
> > +    chr->chr_write = mem_chr_write;
> > +}
> > +
> > +/* assumes the stored data is a string */
> 
> This could indicate a problem.  See my reply in the thread for v2.

Replied, but I can't see the problem.

> > +QString *qemu_chr_mem_to_qs(CharDriverState *chr)
> > +{
> > +    MemoryDriver *d = chr->opaque;
> > +
> > +    if (d->outbuf_size == 0) {
> > +        return qstring_new();
> > +    }
> 
> Why is this necessary?  Is qstring_from_substr() broken for empty
> substrings?  If it is, it ought to be fixed!

qstring_from_substr() takes a character range; outbuf_size stores a size,
not a string length. So we do:

> > +    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);

If outbuf_size is 0, we'll be passing a negative value down.

> > +}
> > +
> > +/* NOTE: this driver can not be closed with qemu_chr_close()! */
> > +void qemu_chr_close_mem(CharDriverState *chr)
> > +{
> > +    MemoryDriver *d = chr->opaque;
> > +
> > +    qemu_free(d->outbuf);
> > +    qemu_free(chr->opaque);
> > +    chr->opaque = NULL;
> > +    chr->chr_write = NULL;
> > +}
> > +
> > +size_t qemu_chr_mem_osize(const CharDriverState *chr)
> > +{
> > +    const MemoryDriver *d = chr->opaque;
> > +    return d->outbuf_size;
> > +}
> > +
> >  QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
> >  {
> >      char host[65], port[33], width[8], height[8];
> > diff --git a/qemu-char.h b/qemu-char.h
> > index 18ad12b..e6ee6c4 100644
> > --- a/qemu-char.h
> > +++ b/qemu-char.h
> > @@ -6,6 +6,7 @@
> >  #include "qemu-option.h"
> >  #include "qemu-config.h"
> >  #include "qobject.h"
> > +#include "qstring.h"
> >  
> >  /* character device */
> >  
> > @@ -100,6 +101,12 @@ CharDriverState *qemu_chr_open_eventfd(int eventfd);
> >  
> >  extern int term_escape_char;
> >  
> > +/* memory chardev */
> > +void qemu_chr_init_mem(CharDriverState *chr);
> > +void qemu_chr_close_mem(CharDriverState *chr);
> > +QString *qemu_chr_mem_to_qs(CharDriverState *chr);
> > +size_t qemu_chr_mem_osize(const CharDriverState *chr);
> > +
> >  /* async I/O support */
> >  
> >  int qemu_set_fd_handler2(int fd,
> 

Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver

[Markus Armbruster]

Luiz Capitulino <lcapitulino@redhat.com> writes:

> On Fri, 12 Nov 2010 11:21:57 +0100
> Markus Armbruster <armbru@redhat.com> wrote:
>
>> Luiz Capitulino <lcapitulino@redhat.com> writes:
[...]
>> > +QString *qemu_chr_mem_to_qs(CharDriverState *chr)
>> > +{
>> > +    MemoryDriver *d = chr->opaque;
>> > +
>> > +    if (d->outbuf_size == 0) {
>> > +        return qstring_new();
>> > +    }
>> 
>> Why is this necessary?  Is qstring_from_substr() broken for empty
>> substrings?  If it is, it ought to be fixed!
>
> qstring_from_substr() takes a character range; outbuf_size stores a size,
> not a string length. So we do:
>
>> > +    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
>
> If outbuf_size is 0, we'll be passing a negative value down.

What's wrong with that?

[...]

Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver

[Luiz Capitulino]

On Fri, 12 Nov 2010 15:16:33 +0100
Markus Armbruster <armbru@redhat.com> wrote:

> Luiz Capitulino <lcapitulino@redhat.com> writes:
> 
> > On Fri, 12 Nov 2010 11:21:57 +0100
> > Markus Armbruster <armbru@redhat.com> wrote:
> >
> >> Luiz Capitulino <lcapitulino@redhat.com> writes:
> [...]
> >> > +QString *qemu_chr_mem_to_qs(CharDriverState *chr)
> >> > +{
> >> > +    MemoryDriver *d = chr->opaque;
> >> > +
> >> > +    if (d->outbuf_size == 0) {
> >> > +        return qstring_new();
> >> > +    }
> >> 
> >> Why is this necessary?  Is qstring_from_substr() broken for empty
> >> substrings?  If it is, it ought to be fixed!
> >
> > qstring_from_substr() takes a character range; outbuf_size stores a size,
> > not a string length. So we do:
> >
> >> > +    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
> >
> > If outbuf_size is 0, we'll be passing a negative value down.
> 
> What's wrong with that?

Although it's going to work with the current QString implementation, I don't
think it's it's a good idea to rely on a negative index.

Maybe, we could have:

return qstring_from_substr((char *) d->outbuf, 0,
                            d->outbuf_size > 0 ? d->outbuf_size - 1 : 0);

A bit harder to read, but makes the function smaller.

Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver

[Markus Armbruster]

Luiz Capitulino <lcapitulino@redhat.com> writes:

> On Fri, 12 Nov 2010 15:16:33 +0100
> Markus Armbruster <armbru@redhat.com> wrote:
>
>> Luiz Capitulino <lcapitulino@redhat.com> writes:
>> 
>> > On Fri, 12 Nov 2010 11:21:57 +0100
>> > Markus Armbruster <armbru@redhat.com> wrote:
>> >
>> >> Luiz Capitulino <lcapitulino@redhat.com> writes:
>> [...]
>> >> > +QString *qemu_chr_mem_to_qs(CharDriverState *chr)
>> >> > +{
>> >> > +    MemoryDriver *d = chr->opaque;
>> >> > +
>> >> > +    if (d->outbuf_size == 0) {
>> >> > +        return qstring_new();
>> >> > +    }
>> >> 
>> >> Why is this necessary?  Is qstring_from_substr() broken for empty
>> >> substrings?  If it is, it ought to be fixed!
>> >
>> > qstring_from_substr() takes a character range; outbuf_size stores a size,
>> > not a string length. So we do:
>> >
>> >> > +    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
>> >
>> > If outbuf_size is 0, we'll be passing a negative value down.
>> 
>> What's wrong with that?
>
> Although it's going to work with the current QString implementation, I don't
> think it's it's a good idea to rely on a negative index.

How should I extract the substring of S beginning at index B with length
L?  If I cant't do this for any B, L with interval [B,B+L-1] fully
within [0,length(S)], then the API is flawed, and ought to be replaced.

> Maybe, we could have:
>
> return qstring_from_substr((char *) d->outbuf, 0,
>                             d->outbuf_size > 0 ? d->outbuf_size - 1 : 0);
>
> A bit harder to read, but makes the function smaller.

Err, doesn't qstring_from_substr(s, 0, 0) extract a substring of length
1?

Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver

[Luiz Capitulino]

On Fri, 12 Nov 2010 16:04:39 +0100
Markus Armbruster <armbru@redhat.com> wrote:

> Luiz Capitulino <lcapitulino@redhat.com> writes:
> 
> > On Fri, 12 Nov 2010 15:16:33 +0100
> > Markus Armbruster <armbru@redhat.com> wrote:
> >
> >> Luiz Capitulino <lcapitulino@redhat.com> writes:
> >> 
> >> > On Fri, 12 Nov 2010 11:21:57 +0100
> >> > Markus Armbruster <armbru@redhat.com> wrote:
> >> >
> >> >> Luiz Capitulino <lcapitulino@redhat.com> writes:
> >> [...]
> >> >> > +QString *qemu_chr_mem_to_qs(CharDriverState *chr)
> >> >> > +{
> >> >> > +    MemoryDriver *d = chr->opaque;
> >> >> > +
> >> >> > +    if (d->outbuf_size == 0) {
> >> >> > +        return qstring_new();
> >> >> > +    }
> >> >> 
> >> >> Why is this necessary?  Is qstring_from_substr() broken for empty
> >> >> substrings?  If it is, it ought to be fixed!
> >> >
> >> > qstring_from_substr() takes a character range; outbuf_size stores a size,
> >> > not a string length. So we do:
> >> >
> >> >> > +    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
> >> >
> >> > If outbuf_size is 0, we'll be passing a negative value down.
> >> 
> >> What's wrong with that?
> >
> > Although it's going to work with the current QString implementation, I don't
> > think it's it's a good idea to rely on a negative index.
> 
> How should I extract the substring of S beginning at index B with length
> L?  If I cant't do this for any B, L with interval [B,B+L-1] fully
> within [0,length(S)], then the API is flawed, and ought to be replaced.

Not sure we're talking about the same problem, anymore. When you said:

> >> What's wrong with that?

What did you mean? Did you mean 'let's not decrement outbuf_size' or did
you mean 'let's pass -1 anyway'?

Both seem wrong to me: the substring [0,-1] should be invalid and not
decrementing outbuf_size is wrong, because it contains the buffer size and
qstring_from_substr() will consume an additional char from the buffer (which
should be '\0' today, but we shouldn't count on that).

> 
> > Maybe, we could have:
> >
> > return qstring_from_substr((char *) d->outbuf, 0,
> >                             d->outbuf_size > 0 ? d->outbuf_size - 1 : 0);
> >
> > A bit harder to read, but makes the function smaller.
> 
> Err, doesn't qstring_from_substr(s, 0, 0) extract a substring of length
> 1?

Yeah, it's a bug. But that doesn't change my suggestion, can we do this way?

This should fix the bug (not even compiled tested):

diff --git a/qstring.c b/qstring.c
index 4e2ba08..72a25de 100644
--- a/qstring.c
+++ b/qstring.c
@@ -42,10 +42,10 @@ QString *qstring_from_substr(const char *str, int start, int end)
 
     qstring = qemu_malloc(sizeof(*qstring));
 
-    qstring->length = end - start + 1;
-    qstring->capacity = qstring->length;
+    qstring->length = end - start;
+    qstring->capacity = qstring->length + 1;
 
-    qstring->string = qemu_malloc(qstring->capacity + 1);
+    qstring->string = qemu_malloc(qstring->capacity);
     memcpy(qstring->string, str + start, qstring->length);
     qstring->string[qstring->length] = 0;

Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver

[Markus Armbruster]

Luiz Capitulino <lcapitulino@redhat.com> writes:

> On Fri, 12 Nov 2010 16:04:39 +0100
> Markus Armbruster <armbru@redhat.com> wrote:
>
>> Luiz Capitulino <lcapitulino@redhat.com> writes:
>> 
>> > On Fri, 12 Nov 2010 15:16:33 +0100
>> > Markus Armbruster <armbru@redhat.com> wrote:
>> >
>> >> Luiz Capitulino <lcapitulino@redhat.com> writes:
>> >> 
>> >> > On Fri, 12 Nov 2010 11:21:57 +0100
>> >> > Markus Armbruster <armbru@redhat.com> wrote:
>> >> >
>> >> >> Luiz Capitulino <lcapitulino@redhat.com> writes:
>> >> [...]
>> >> >> > +QString *qemu_chr_mem_to_qs(CharDriverState *chr)
>> >> >> > +{
>> >> >> > +    MemoryDriver *d = chr->opaque;
>> >> >> > +
>> >> >> > +    if (d->outbuf_size == 0) {
>> >> >> > +        return qstring_new();
>> >> >> > +    }
>> >> >> 
>> >> >> Why is this necessary?  Is qstring_from_substr() broken for empty
>> >> >> substrings?  If it is, it ought to be fixed!
>> >> >
>> >> > qstring_from_substr() takes a character range; outbuf_size stores a size,
>> >> > not a string length. So we do:
>> >> >
>> >> >> > +    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
>> >> >
>> >> > If outbuf_size is 0, we'll be passing a negative value down.
>> >> 
>> >> What's wrong with that?
>> >
>> > Although it's going to work with the current QString implementation, I don't
>> > think it's it's a good idea to rely on a negative index.
>> 
>> How should I extract the substring of S beginning at index B with length
>> L?  If I cant't do this for any B, L with interval [B,B+L-1] fully
>> within [0,length(S)], then the API is flawed, and ought to be replaced.
>
> Not sure we're talking about the same problem, anymore. When you said:
>
>> >> What's wrong with that?
>
> What did you mean? Did you mean 'let's not decrement outbuf_size' or did
> you mean 'let's pass -1 anyway'?

Yes, what's wrong with qstring_from_substr(S, 0, -1)?

Its function comment is imprecise, it doesn't tell us whether the END-th
character is included in the substring or not.

The code, however, is clear enough: it *is* included.  And the unit test
checks that.

Therefore, qstring_from_substr("abc", 0, 0) returns the qstring "a".

> Both seem wrong to me: the substring [0,-1] should be invalid

Why?

How do you express "the empty substring starting at 0" then?

>                                                               and not
> decrementing outbuf_size is wrong, because it contains the buffer size and
> qstring_from_substr() will consume an additional char from the buffer (which
> should be '\0' today, but we shouldn't count on that).
>
>> 
>> > Maybe, we could have:
>> >
>> > return qstring_from_substr((char *) d->outbuf, 0,
>> >                             d->outbuf_size > 0 ? d->outbuf_size - 1 : 0);
>> >
>> > A bit harder to read, but makes the function smaller.
>> 
>> Err, doesn't qstring_from_substr(s, 0, 0) extract a substring of length
>> 1?
>
> Yeah, it's a bug. But that doesn't change my suggestion, can we do this way?
>
> This should fix the bug (not even compiled tested):
>
> diff --git a/qstring.c b/qstring.c
> index 4e2ba08..72a25de 100644
> --- a/qstring.c
> +++ b/qstring.c
> @@ -42,10 +42,10 @@ QString *qstring_from_substr(const char *str, int start, int end)
>  
>      qstring = qemu_malloc(sizeof(*qstring));
>  
> -    qstring->length = end - start + 1;
> -    qstring->capacity = qstring->length;
> +    qstring->length = end - start;
> +    qstring->capacity = qstring->length + 1;
>  
> -    qstring->string = qemu_malloc(qstring->capacity + 1);
> +    qstring->string = qemu_malloc(qstring->capacity);
>      memcpy(qstring->string, str + start, qstring->length);
>      qstring->string[qstring->length] = 0;

I suspect this will fail your unit test.

Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver

[Luiz Capitulino]

On Fri, 12 Nov 2010 17:06:16 +0100
Markus Armbruster <armbru@redhat.com> wrote:

> Luiz Capitulino <lcapitulino@redhat.com> writes:
> 
> > On Fri, 12 Nov 2010 16:04:39 +0100
> > Markus Armbruster <armbru@redhat.com> wrote:
> >
> >> Luiz Capitulino <lcapitulino@redhat.com> writes:
> >> 
> >> > On Fri, 12 Nov 2010 15:16:33 +0100
> >> > Markus Armbruster <armbru@redhat.com> wrote:
> >> >
> >> >> Luiz Capitulino <lcapitulino@redhat.com> writes:
> >> >> 
> >> >> > On Fri, 12 Nov 2010 11:21:57 +0100
> >> >> > Markus Armbruster <armbru@redhat.com> wrote:
> >> >> >
> >> >> >> Luiz Capitulino <lcapitulino@redhat.com> writes:
> >> >> [...]
> >> >> >> > +QString *qemu_chr_mem_to_qs(CharDriverState *chr)
> >> >> >> > +{
> >> >> >> > +    MemoryDriver *d = chr->opaque;
> >> >> >> > +
> >> >> >> > +    if (d->outbuf_size == 0) {
> >> >> >> > +        return qstring_new();
> >> >> >> > +    }
> >> >> >> 
> >> >> >> Why is this necessary?  Is qstring_from_substr() broken for empty
> >> >> >> substrings?  If it is, it ought to be fixed!
> >> >> >
> >> >> > qstring_from_substr() takes a character range; outbuf_size stores a size,
> >> >> > not a string length. So we do:
> >> >> >
> >> >> >> > +    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
> >> >> >
> >> >> > If outbuf_size is 0, we'll be passing a negative value down.
> >> >> 
> >> >> What's wrong with that?
> >> >
> >> > Although it's going to work with the current QString implementation, I don't
> >> > think it's it's a good idea to rely on a negative index.
> >> 
> >> How should I extract the substring of S beginning at index B with length
> >> L?  If I cant't do this for any B, L with interval [B,B+L-1] fully
> >> within [0,length(S)], then the API is flawed, and ought to be replaced.
> >
> > Not sure we're talking about the same problem, anymore. When you said:
> >
> >> >> What's wrong with that?
> >
> > What did you mean? Did you mean 'let's not decrement outbuf_size' or did
> > you mean 'let's pass -1 anyway'?
> 
> Yes, what's wrong with qstring_from_substr(S, 0, -1)?
> 
> Its function comment is imprecise, it doesn't tell us whether the END-th
> character is included in the substring or not.
> 
> The code, however, is clear enough: it *is* included.  And the unit test
> checks that.
> 
> Therefore, qstring_from_substr("abc", 0, 0) returns the qstring "a".
> 
> > Both seem wrong to me: the substring [0,-1] should be invalid
> 
> Why?
> 
> How do you express "the empty substring starting at 0" then?

I didn't consider that when I wrote the code, so it's a matter a defining
the behavior we want it to have.


> 
> >                                                               and not
> > decrementing outbuf_size is wrong, because it contains the buffer size and
> > qstring_from_substr() will consume an additional char from the buffer (which
> > should be '\0' today, but we shouldn't count on that).
> >
> >> 
> >> > Maybe, we could have:
> >> >
> >> > return qstring_from_substr((char *) d->outbuf, 0,
> >> >                             d->outbuf_size > 0 ? d->outbuf_size - 1 : 0);
> >> >
> >> > A bit harder to read, but makes the function smaller.
> >> 
> >> Err, doesn't qstring_from_substr(s, 0, 0) extract a substring of length
> >> 1?
> >
> > Yeah, it's a bug. But that doesn't change my suggestion, can we do this way?
> >
> > This should fix the bug (not even compiled tested):
> >
> > diff --git a/qstring.c b/qstring.c
> > index 4e2ba08..72a25de 100644
> > --- a/qstring.c
> > +++ b/qstring.c
> > @@ -42,10 +42,10 @@ QString *qstring_from_substr(const char *str, int start, int end)
> >  
> >      qstring = qemu_malloc(sizeof(*qstring));
> >  
> > -    qstring->length = end - start + 1;
> > -    qstring->capacity = qstring->length;
> > +    qstring->length = end - start;
> > +    qstring->capacity = qstring->length + 1;
> >  
> > -    qstring->string = qemu_malloc(qstring->capacity + 1);
> > +    qstring->string = qemu_malloc(qstring->capacity);
> >      memcpy(qstring->string, str + start, qstring->length);
> >      qstring->string[qstring->length] = 0;
> 
> I suspect this will fail your unit test.

Haven't checked it yet, but maybe it has to be fixed too.

[Qemu-devel] [PATCH 2/3] QMP: Introduce Human Monitor passthrough command

[Luiz Capitulino]

This command allows QMP clients to execute HMP commands.

Please, check the documentation added to the qmp-commands.hx file
for additional details about the interface and its limitations.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 monitor.c       |   38 ++++++++++++++++++++++++++++++++++++++
 qmp-commands.hx |   45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+), 0 deletions(-)

diff --git a/monitor.c b/monitor.c
index 8cee35d..ec31eac 100644
--- a/monitor.c
+++ b/monitor.c
@@ -491,6 +491,44 @@ static int do_qmp_capabilities(Monitor *mon, const QDict *params,
     return 0;
 }
 
+static int mon_set_cpu(int cpu_index);
+static void handle_user_command(Monitor *mon, const char *cmdline);
+
+static int do_hmp_passthrough(Monitor *mon, const QDict *params,
+                              QObject **ret_data)
+{
+    int ret = 0;
+    Monitor *old_mon, hmp;
+    CharDriverState mchar;
+
+    memset(&hmp, 0, sizeof(hmp));
+    qemu_chr_init_mem(&mchar);
+    hmp.chr = &mchar;
+
+    old_mon = cur_mon;
+    cur_mon = &hmp;
+
+    if (qdict_haskey(params, "cpu-index")) {
+        ret = mon_set_cpu(qdict_get_int(params, "cpu-index"));
+        if (ret < 0) {
+            cur_mon = old_mon;
+            qerror_report(QERR_INVALID_PARAMETER_VALUE, "cpu-index", "a CPU number");
+            goto out;
+        }
+    }
+
+    handle_user_command(&hmp, qdict_get_str(params, "command-line"));
+    cur_mon = old_mon;
+
+    if (qemu_chr_mem_osize(hmp.chr) > 0) {
+        *ret_data = QOBJECT(qemu_chr_mem_to_qs(hmp.chr));
+    }
+
+out:
+    qemu_chr_close_mem(hmp.chr);
+    return ret;
+}
+
 static int compare_cmd(const char *name, const char *list)
 {
     const char *p, *pstart;
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 793cf1c..e5f157f 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -761,6 +761,51 @@ Example:
 
 Note: This command must be issued before issuing any other command.
 
+EQMP
+
+    {
+        .name       = "human-monitor-command",
+        .args_type  = "command-line:s,cpu-index:i?",
+        .params     = "",
+        .help       = "",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_hmp_passthrough,
+    },
+
+SQMP
+human-monitor-command
+---------------------
+
+Execute a Human Monitor command.
+
+Arguments: 
+
+- command-line: the command name and its arguments, just like the
+                Human Monitor's shell (json-string)
+- cpu-index: select the CPU number to be used by commands which access CPU
+             data, like 'info registers'. The Monitor selects CPU 0 if this
+             argument is not provided (json-int, optional)
+
+Example:
+
+-> { "execute": "human-monitor-command", "arguments": { "command-line": "info kvm" } }
+<- { "return": "kvm support: enabled\r\n" }
+
+Notes:
+
+(1) The Human Monitor is NOT an stable interface, this means that command
+    names, arguments and responses can change or be removed at ANY time.
+    Applications that rely on long term stability guarantees should NOT
+    use this command
+
+(2) Limitations:
+
+    o This command is stateless, this means that commands that depend
+      on state information (such as getfd) might not work
+
+    o Commands that prompt the user for data (eg. 'cont' when the block
+      device is encrypted) don't currently work
+
 3. Query Commands
 =================
 
-- 
1.7.3.2.164.g6f10c

[Qemu-devel] [PATCH 3/3] QMP/qmp-shell: Introduce HMP mode

[Luiz Capitulino]

In which qmp-shell will exclusively use the HMP passthrough feature,
this is useful for testing.

Example:

    # ./qmp-shell -H qmp-sock
    Welcome to the HMP shell!
    Connected to QEMU 0.13.50

    (QEMU) info network
    VLAN 0 devices:
      user.0: net=10.0.2.0, restricted=n
        e1000.0: model=e1000,macaddr=52:54:00:12:34:56
        Devices not on any VLAN:
    (QEMU)

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 QMP/qmp-shell |   75 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 74 insertions(+), 1 deletions(-)

diff --git a/QMP/qmp-shell b/QMP/qmp-shell
index 1fb7e76..5135590 100755
--- a/QMP/qmp-shell
+++ b/QMP/qmp-shell
@@ -145,6 +145,72 @@ class QMPShell(qmp.QEMUMonitorProtocol):
         else:
             return self._execute_cmd(cmdline)
 
+class HMPShell(QMPShell):
+    def __init__(self, address):
+        QMPShell.__init__(self, address)
+        self.__cpu_index = 0
+
+    def __cmd_completion(self):
+        for cmd in self.__cmd_passthrough('help')['return'].split('\r\n'):
+            if cmd and cmd[0] != '[' and cmd[0] != '\t':
+                name = cmd.split()[0] # drop help text
+                if name == 'info':
+                    continue
+                if name.find('|') != -1:
+                    # Command in the form 'foobar|f' or 'f|foobar', take the
+                    # full name
+                    opt = name.split('|')
+                    if len(opt[0]) == 1:
+                        name = opt[1]
+                    else:
+                        name = opt[0]
+                self._completer.append(name)
+                self._completer.append('help ' + name) # help completion
+
+    def __info_completion(self):
+        for cmd in self.__cmd_passthrough('info')['return'].split('\r\n'):
+            if cmd:
+                self._completer.append('info ' + cmd.split()[1])
+
+    def __other_completion(self):
+        # special cases
+        self._completer.append('help info')
+
+    def _fill_completion(self):
+        self.__cmd_completion()
+        self.__info_completion()
+        self.__other_completion()
+
+    def __cmd_passthrough(self, cmdline):
+        return self.cmd_obj({ 'execute': 'human-monitor-command', 'arguments':
+                              { 'command-line': cmdline,
+                                'cpu-index': self.__cpu_index } })
+
+    def _execute_cmd(self, cmdline):
+        if cmdline.split()[0] == "cpu":
+            # trap the cpu command, it requires special setting
+            try:
+                self.__cpu_index = int(cmdline.split()[1])
+            except ValueError:
+                print 'cpu command takes an integer argument'
+                return True
+        resp = self.__cmd_passthrough(cmdline)
+        if resp is None:
+            print 'Disconnected'
+            return False
+        assert 'return' in resp or 'error' in resp
+        if 'return' in resp:
+            # Success
+            if len(resp['return']) > 0:
+                print resp['return'],
+        else:
+            # Error
+            print '%s: %s' % (resp['error']['class'], resp['error']['desc'])
+        return True
+
+    def show_banner(self):
+        QMPShell.show_banner(self, msg='Welcome to the HMP shell!')
+
 def die(msg):
     sys.stderr.write('ERROR: %s\n' % msg)
     sys.exit(1)
@@ -156,9 +222,16 @@ def fail_cmdline(option=None):
     sys.exit(1)
 
 def main():
+    addr = ''
     try:
         if len(sys.argv) == 2:
             qemu = QMPShell(sys.argv[1])
+            addr = sys.argv[1]
+        elif len(sys.argv) == 3:
+            if sys.argv[1] != '-H':
+                fail_cmdline(sys.argv[1])
+            qemu = HMPShell(sys.argv[2])
+            addr = sys.argv[2]
         else:
                 fail_cmdline()
     except QMPShellBadPort:
@@ -171,7 +244,7 @@ def main():
     except qmp.QMPCapabilitiesError:
         die('Could not negotiate capabilities')
     except qemu.error:
-        die('Could not connect to %s' % sys.argv[1])
+        die('Could not connect to %s' % addr)
 
     qemu.show_banner()
     while qemu.read_exec_command('(QEMU) '):
-- 
1.7.3.2.164.g6f10c