[6/7] Implement multiple-filesystem support for remote targets
Commit Message
This commit allows GDB to access executables and shared libraries
on remote targets where the inferior and the remote stub do not
share a common filesystem. A new packet "vFile:setfs" is added
to the remote protocol and the three remote hostio functions with
filename arguments are modified to send "vFile:setfs" packets as
necessary.
gdb/ChangeLog:
* remote.c (struct remote_state) <fs_pid>: New field.
(new_remote_state): Initialize the above.
(PACKET_vFile_setfs): New enum value.
(remote_fs_pid): New static variable.
(remote_hostio_set_fs_deferred): New function.
(remote_hostio_set_filesystem): Likewise.
(remote_hostio_open): Call the above.
(remote_hostio_unlink): Likewise.
(remote_hostio_readlink): Likewise.
(init_remote_ops): Initialize to_fileio_set_fs.
(_initialize_remote): Register new "set/show remote
hostio-setfs-packet" command.
* NEWS: Mention that GDB and gdbserver support attaching to
processes in different mount namespaces on GNU/Linux systems.
Announce new vFile:setfs packet.
gdb/doc/ChangeLog:
* gdb.texinfo (Remote Configuration): Document the
"set/show remote hostio-setfs-packet" command.
(Host I/O Packets): Document the vFile:setfs packet.
---
gdb/ChangeLog | 18 +++++++++++++++
gdb/NEWS | 8 +++++++
gdb/doc/ChangeLog | 6 +++++
gdb/doc/gdb.texinfo | 11 +++++++++
gdb/remote.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 101 insertions(+), 0 deletions(-)
Comments
> From: Gary Benson <gbenson@redhat.com>
> Date: Thu, 16 Apr 2015 13:19:50 +0100
>
> gdb/doc/ChangeLog:
>
> * gdb.texinfo (Remote Configuration): Document the
> "set/show remote hostio-setfs-packet" command.
> (Host I/O Packets): Document the vFile:setfs packet.
> ---
> gdb/ChangeLog | 18 +++++++++++++++
> gdb/NEWS | 8 +++++++
> gdb/doc/ChangeLog | 6 +++++
> gdb/doc/gdb.texinfo | 11 +++++++++
I think the patch for the docs leaves too much unsaid to be useful.
E.g., after reading it, I was left as clueless as before regarding
what this feature is about. What is a "mount namespace", for
starters? What does it mean to "set a filesystem"?
Please consider explaining a bit of background about this in the
manual.
Thanks.
On 04/16/2015 01:19 PM, Gary Benson wrote:
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -367,6 +367,12 @@ struct remote_state
>
> /* The branch trace configuration. */
> struct btrace_config btrace_config;
> +
> + /* The argument to the last "vFile:setfs:" packet we sent, used
> + to avoid sending repeated unnecessary "vFile:setfs:" packets.
> + Initialized to -1 to indicate that no "vFile:setfs:" packet
> + has yet been sent. */
> + int fs_pid;
> };
>
> +/* Process ID of inferior whose filesystem remote_hostio functions
> + that take FILENAME arguments will use. Zero means to use the
> + remote stub's filesystem. */
> +
> +static int remote_fs_pid = 0;
What's the rationale for not putting this one in "struct remote_state" ?
Thanks,
Pedro Alves
On 04/16/2015 01:19 PM, Gary Benson wrote:
> diff --git a/gdb/NEWS b/gdb/NEWS
> index 62cbdcb..a9f05e4 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -42,6 +42,10 @@
> (no "set sysroot" or "file" commands are required). See "New remote
> packets" below.
>
> +* GDB and gdbserver now support attaching to processes running in
> + different mount namespaces from the debugger on GNU/Linux systems.
> + See "New remote packets" below.
Reading this, I'm left wondering what this really means, because I
think we could already attach before. What the user needed to do before
was point the "set sysroot" somewhere, while now, if the sysroot
is left to "target:", that's no longer necessary. Is that right?
Thanks,
Pedro Alves
Pedro Alves wrote:
> On 04/16/2015 01:19 PM, Gary Benson wrote:
> > --- a/gdb/remote.c
> > +++ b/gdb/remote.c
> > @@ -367,6 +367,12 @@ struct remote_state
> >
> > /* The branch trace configuration. */
> > struct btrace_config btrace_config;
> > +
> > + /* The argument to the last "vFile:setfs:" packet we sent, used
> > + to avoid sending repeated unnecessary "vFile:setfs:" packets.
> > + Initialized to -1 to indicate that no "vFile:setfs:" packet
> > + has yet been sent. */
> > + int fs_pid;
> > };
> >
>
> > +/* Process ID of inferior whose filesystem remote_hostio functions
> > + that take FILENAME arguments will use. Zero means to use the
> > + remote stub's filesystem. */
> > +
> > +static int remote_fs_pid = 0;
>
> What's the rationale for not putting this one in "struct
> remote_state" ?
I don't have one :) Would you prefer it there?
Cheers,
Gary
Pedro Alves wrote:
> On 04/16/2015 01:19 PM, Gary Benson wrote:
> > diff --git a/gdb/NEWS b/gdb/NEWS
> > index 62cbdcb..a9f05e4 100644
> > --- a/gdb/NEWS
> > +++ b/gdb/NEWS
> > @@ -42,6 +42,10 @@
> > (no "set sysroot" or "file" commands are required). See "New remote
> > packets" below.
> >
> > +* GDB and gdbserver now support attaching to processes running in
> > + different mount namespaces from the debugger on GNU/Linux systems.
> > + See "New remote packets" below.
>
> Reading this, I'm left wondering what this really means, because I
> think we could already attach before. What the user needed to do
> before was point the "set sysroot" somewhere, while now, if the
> sysroot is left to "target:", that's no longer necessary. Is that
> right?
Yeah, it's more about accessing files than attaching per se.
I think I need to spend some time rewriting the docs for this
series...
Cheers,
Gary
On 04/17/2015 04:59 PM, Gary Benson wrote:
> Pedro Alves wrote:
>> On 04/16/2015 01:19 PM, Gary Benson wrote:
>>> --- a/gdb/remote.c
>>> +++ b/gdb/remote.c
>>> @@ -367,6 +367,12 @@ struct remote_state
>>>
>>> /* The branch trace configuration. */
>>> struct btrace_config btrace_config;
>>> +
>>> + /* The argument to the last "vFile:setfs:" packet we sent, used
>>> + to avoid sending repeated unnecessary "vFile:setfs:" packets.
>>> + Initialized to -1 to indicate that no "vFile:setfs:" packet
>>> + has yet been sent. */
>>> + int fs_pid;
>>> };
>>>
>>
>>> +/* Process ID of inferior whose filesystem remote_hostio functions
>>> + that take FILENAME arguments will use. Zero means to use the
>>> + remote stub's filesystem. */
>>> +
>>> +static int remote_fs_pid = 0;
>>
>> What's the rationale for not putting this one in "struct
>> remote_state" ?
>
> I don't have one :) Would you prefer it there?
It's not really about personal preference: if on a
multi-remote-connections world the flag would be remote connection
specific, it should be in remote_state. It seemed that way
to me, but if it isn't, then it should be left a global.
Thanks,
Pedro Alves
Pedro Alves wrote:
> On 04/17/2015 04:59 PM, Gary Benson wrote:
> > Pedro Alves wrote:
> >> On 04/16/2015 01:19 PM, Gary Benson wrote:
> > > > --- a/gdb/remote.c
> > > > +++ b/gdb/remote.c
> > > > @@ -367,6 +367,12 @@ struct remote_state
> > > >
> > > > /* The branch trace configuration. */
> > > > struct btrace_config btrace_config;
> > > > +
> > > > + /* The argument to the last "vFile:setfs:" packet we sent, used
> > > > + to avoid sending repeated unnecessary "vFile:setfs:" packets.
> > > > + Initialized to -1 to indicate that no "vFile:setfs:" packet
> > > > + has yet been sent. */
> > > > + int fs_pid;
> > > > };
> > > >
> > >
> > > > +/* Process ID of inferior whose filesystem remote_hostio functions
> > > > + that take FILENAME arguments will use. Zero means to use the
> > > > + remote stub's filesystem. */
> > > > +
> > > > +static int remote_fs_pid = 0;
> > >
> > > What's the rationale for not putting this one in "struct
> > > remote_state" ?
> >
> > I don't have one :) Would you prefer it there?
>
> It's not really about personal preference: if on a
> multi-remote-connections world the flag would be remote connection
> specific, it should be in remote_state. It seemed that way to me,
> but if it isn't, then it should be left a global.
Ah, it is probably connection-specific, I'll move it.
Cheers,
Gary
@@ -42,6 +42,10 @@
(no "set sysroot" or "file" commands are required). See "New remote
packets" below.
+* GDB and gdbserver now support attaching to processes running in
+ different mount namespaces from the debugger on GNU/Linux systems.
+ See "New remote packets" below.
+
* Python Scripting
** gdb.Objfile objects have a new attribute "username",
@@ -116,6 +120,10 @@ qXfer:exec-file:read
Return the full absolute name of the file that was executed to
create a process running on the remote system.
+vFile:setfs:
+ Set the filesystem accessed by vFile: packets with filename
+ arguments.
+
* The info record command now shows the recording format and the
branch tracing configuration for the current thread when using
the btrace record target.
@@ -19889,6 +19889,10 @@ are:
@tab @code{vFile:fstat}
@tab Host I/O
+@item @code{hostio-setfs-packet}
+@tab @code{vFile:setfs}
+@tab Host I/O
+
@item @code{noack-packet}
@tab @code{QStartNoAckMode}
@tab Packet acknowledgment
@@ -37533,6 +37537,13 @@ An empty response indicates that this operation is not recognized.
These are the supported Host I/O operations:
@table @samp
+@item vFile:setfs: @var{pid}
+Set the filesystem accessed by @code{vFile} packets with
+@var{filename} arguments to the filesystem as seen by process
+@var{pid}. If @var{pid} is zero, set the filesystem to that
+seen by the remote stub. Return 0 on success, or -1 if an
+error occurs.
+
@item vFile:open: @var{filename}, @var{flags}, @var{mode}
Open a file at @var{filename} and return a file descriptor for it, or
return -1 if an error occurs. The @var{filename} is a string,
@@ -367,6 +367,12 @@ struct remote_state
/* The branch trace configuration. */
struct btrace_config btrace_config;
+
+ /* The argument to the last "vFile:setfs:" packet we sent, used
+ to avoid sending repeated unnecessary "vFile:setfs:" packets.
+ Initialized to -1 to indicate that no "vFile:setfs:" packet
+ has yet been sent. */
+ int fs_pid;
};
/* Private data that we'll store in (struct thread_info)->private. */
@@ -409,6 +415,7 @@ new_remote_state (void)
result->buf = xmalloc (result->buf_size);
result->remote_traceframe_number = -1;
result->last_sent_signal = GDB_SIGNAL_0;
+ result->fs_pid = -1;
return result;
}
@@ -1243,6 +1250,7 @@ enum {
PACKET_Z2,
PACKET_Z3,
PACKET_Z4,
+ PACKET_vFile_setfs,
PACKET_vFile_open,
PACKET_vFile_pread,
PACKET_vFile_pwrite,
@@ -9879,6 +9887,46 @@ remote_hostio_send_command (int command_bytes, int which_packet,
return ret;
}
+/* Process ID of inferior whose filesystem remote_hostio functions
+ that take FILENAME arguments will use. Zero means to use the
+ remote stub's filesystem. */
+
+static int remote_fs_pid = 0;
+
+/* Implementation of to_fileio_set_fs. */
+
+static void
+remote_hostio_set_fs_deferred (struct target_ops *self, int pid)
+{
+ remote_fs_pid = pid;
+}
+
+/* Set the filesystem remote_hostio functions that take FILENAME
+ arguments will use. */
+
+static void
+remote_hostio_set_filesystem (void)
+{
+ struct remote_state *rs = get_remote_state ();
+
+ if (rs->fs_pid == -1 || remote_fs_pid != rs->fs_pid)
+ {
+ char *p = rs->buf;
+ int left = get_remote_packet_size () - 1;
+ int remote_errno;
+ char arg[9];
+
+ remote_buffer_add_string (&p, &left, "vFile:setfs:");
+
+ xsnprintf (arg, sizeof (arg), "%x", remote_fs_pid);
+ remote_buffer_add_string (&p, &left, arg);
+
+ if (remote_hostio_send_command (p - rs->buf, PACKET_vFile_setfs,
+ &remote_errno, NULL, NULL) == 0)
+ rs->fs_pid = remote_fs_pid;
+ }
+}
+
/* Return nonzero if the filesystem accessed by the target_fileio_*
methods is the local filesystem, zero otherwise. */
@@ -9901,6 +9949,8 @@ remote_hostio_open (struct target_ops *self,
char *p = rs->buf;
int left = get_remote_packet_size () - 1;
+ remote_hostio_set_filesystem ();
+
remote_buffer_add_string (&p, &left, "vFile:open:");
remote_buffer_add_bytes (&p, &left, (const gdb_byte *) filename,
@@ -10015,6 +10065,8 @@ remote_hostio_unlink (struct target_ops *self,
char *p = rs->buf;
int left = get_remote_packet_size () - 1;
+ remote_hostio_set_filesystem ();
+
remote_buffer_add_string (&p, &left, "vFile:unlink:");
remote_buffer_add_bytes (&p, &left, (const gdb_byte *) filename,
@@ -10040,6 +10092,8 @@ remote_hostio_readlink (struct target_ops *self,
int read_len;
char *ret;
+ remote_hostio_set_filesystem ();
+
remote_buffer_add_string (&p, &left, "vFile:readlink:");
remote_buffer_add_bytes (&p, &left, (const gdb_byte *) filename,
@@ -11756,6 +11810,7 @@ Specify the serial device it is connected to\n\
remote_ops.to_supports_multi_process = remote_supports_multi_process;
remote_ops.to_supports_disable_randomization
= remote_supports_disable_randomization;
+ remote_ops.to_fileio_set_fs = remote_hostio_set_fs_deferred;
remote_ops.to_filesystem_is_local = remote_filesystem_is_local;
remote_ops.to_fileio_open = remote_hostio_open;
remote_ops.to_fileio_pwrite = remote_hostio_pwrite;
@@ -12322,6 +12377,9 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
add_packet_config_cmd (&remote_protocol_packets[PACKET_qTStatus],
"qTStatus", "trace-status", 0);
+ add_packet_config_cmd (&remote_protocol_packets[PACKET_vFile_setfs],
+ "vFile:setfs", "hostio-setfs", 0);
+
add_packet_config_cmd (&remote_protocol_packets[PACKET_vFile_open],
"vFile:open", "hostio-open", 0);