RFA/RFC: vCont for the remote protocol [client]

Daniel Jacobowitz
2003-09-29T15:28:35Z

Hi all,

Here's the client-side support for the new vCont resume packet that Andrew
and I worked out on gdb@:
http://sources.redhat.com/ml/gdb/2003-09/msg00259.html

Documentation and gdbserver support will follow momentarily. Highlights:
- The protocol and gdbserver implementations support freezing threads,
et cetera. The GDB part doesn't, because that requires substantial
poking and prodding at the target interface for target_resume; but
this cuts down one of the barriers should someone want to implement it.
- I replaced most of remote_async_resume with a call to remote_resume
after verifying that they were exactly identical.

Thoughts? OK, desired protocol changes, ?

--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer

2003-09-29 Daniel Jacobowitz <drow@mvista.com>

* remote.c (remote_protocol_vcont): New variable.
(set_remote_protocol_vcont_packet_cmd): New function.
(show_remote_protocol_vcont_packet_cmd): New function.
(init_all_packet_configs): Handle remote_protocol_vcont.
(remote_vcont_resume): New function.
(remote_resume): Use it.
(remote_async_resume): Call remote_resume.
(_initialize_remote): Add verbose-resume packet commands.

Index: remote.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/remote.c,v
retrieving revision 1.115
diff -u -p -r1.115 remote.c
--- remote.c 21 Sep 2003 01:26:45 -0000 1.115
+++ remote.c 29 Sep 2003 14:26:08 -0000
@@ -749,6 +749,23 @@ packet_ok (const char *buf, struct packe
}
}

+/* Should we try the 'vCont' (descriptive resume) request? */
+static struct packet_config remote_protocol_vcont;
+
+static void
+set_remote_protocol_vcont_packet_cmd (char *args, int from_tty,
+ struct cmd_list_element *c)
+{
+ update_packet_config (&remote_protocol_vcont);
+}
+
+static void
+show_remote_protocol_vcont_packet_cmd (char *args, int from_tty,
+ struct cmd_list_element *c)
+{
+ show_packet_config_cmd (&remote_protocol_vcont);
+}
+
/* Should we try the 'qSymbol' (target symbol lookup service) request? */
static struct packet_config remote_protocol_qSymbol;

@@ -2190,6 +2207,7 @@ init_all_packet_configs (void)
update_packet_config (&remote_protocol_E);
update_packet_config (&remote_protocol_P);
update_packet_config (&remote_protocol_qSymbol);
+ update_packet_config (&remote_protocol_vcont);
for (i = 0; i < NR_Z_PACKET_TYPES; i++)
update_packet_config (&remote_protocol_Z[i]);
/* Force remote_write_bytes to check whether target supports binary
@@ -2503,6 +2521,75 @@ bin2hex (const char *bin, char *hex, int
return i;
}
\f
+/* Resume the remote inferior by using a "vCont" packet. The thread
+ to be resumed is PTID; STEP and SIGGNAL indicate whether the
+ resumed thread should be single-stepped and/or signalled. If PTID's
+ PID is -1, then all threads are resumed; the thread to be stepped and/or
+ signalled is given in the global INFERIOR_PTID. This function returns
+ non-zero iff it resumes the inferior.
+
+ This function issues a strict subset of all possible vCont commands at the
+ moment. */
+
+static int
+remote_vcont_resume (ptid_t ptid, int step, enum target_signal siggnal)
+{
+ struct remote_state *rs = get_remote_state ();
+ int pid = PIDGET (ptid);
+ char *buf = alloca (rs->remote_packet_size);
+
+ if (remote_protocol_vcont.support == PACKET_DISABLE)
+ return 0;
+
+ /* If we could generate a wider range of packets, we'd have to worry
+ about overflowing BUF. Should there be a generic
+ "multi-part-packet" packet? */
+
+ if (PIDGET (inferior_ptid) == MAGIC_NULL_PID)
+ {
+ /* MAGIC_NULL_PTID means that we don't have any active threads, so we
+ don't have any PID numbers the inferior will understand. Make sure
+ to only send forms that do not specify a PID. */
+ if (step && siggnal != TARGET_SIGNAL_0)
+ sprintf (buf, "vCont:S%02x", siggnal);
+ else if (step)
+ sprintf (buf, "vCont:s");
+ else if (siggnal != TARGET_SIGNAL_0)
+ sprintf (buf, "vCont:C%02x", siggnal);
+ else
+ sprintf (buf, "vCont:c");
+ }
+ else if (pid == -1)
+ {
+ /* Resume all threads, with preference for INFERIOR_PTID. */
+ if (step && siggnal != TARGET_SIGNAL_0)
+ sprintf (buf, "vCont:S%02x:%x;c", siggnal, PIDGET (inferior_ptid));
+ else if (step)
+ sprintf (buf, "vCont:s:%x;c", PIDGET (inferior_ptid));
+ else if (siggnal != TARGET_SIGNAL_0)
+ sprintf (buf, "vCont:C%02x:%x;c", siggnal, PIDGET (inferior_ptid));
+ else
+ sprintf (buf, "vCont:c");
+ }
+ else
+ {
+ /* Scheduler locking; resume only PTID. */
+ if (step && siggnal != TARGET_SIGNAL_0)
+ sprintf (buf, "vCont:S%02x:%x", siggnal, pid);
+ else if (step)
+ sprintf (buf, "vCont:s:%x", pid);
+ else if (siggnal != TARGET_SIGNAL_0)
+ sprintf (buf, "vCont:C%02x:%x", siggnal, pid);
+ else
+ sprintf (buf, "vCont:c:%x", pid);
+ }
+
+ putpkt (buf);
+ getpkt (buf, rs->remote_packet_size, 0);
+
+ return (packet_ok (buf, &remote_protocol_vcont) == PACKET_OK);
+}
+
/* Tell the remote machine to resume. */

static enum target_signal last_sent_signal = TARGET_SIGNAL_0;
@@ -2517,20 +2604,24 @@ remote_resume (ptid_t ptid, int step, en
int pid = PIDGET (ptid);
char *p;

+ last_sent_signal = siggnal;
+ last_sent_step = step;
+
+ /* The vCont packet doesn't need to specify threads via Hc. */
+ if (remote_vcont_resume (ptid, step, siggnal))
+ return;
+
+ /* All other supported resume packets do use Hc, so call set_thread. */
if (pid == -1)
set_thread (0, 0); /* run any thread */
else
set_thread (pid, 0); /* run this thread */

- last_sent_signal = siggnal;
- last_sent_step = step;
-
/* A hook for when we need to do something at the last moment before
resumption. */
if (target_resume_hook)
(*target_resume_hook) ();

-
/* The s/S/c/C packets do not return status. So if the target does
not support the S or C packets, the debug agent returns an empty
string which is detected in remote_wait(). This protocol defect
@@ -2602,91 +2693,8 @@ remote_resume (ptid_t ptid, int step, en
static void
remote_async_resume (ptid_t ptid, int step, enum target_signal siggnal)
{
- struct remote_state *rs = get_remote_state ();
- char *buf = alloca (rs->remote_packet_size);
- int pid = PIDGET (ptid);
- char *p;
-
- if (pid == -1)
- set_thread (0, 0); /* run any thread */
- else
- set_thread (pid, 0); /* run this thread */
-
- last_sent_signal = siggnal;
- last_sent_step = step;
-
- /* A hook for when we need to do something at the last moment before
- resumption. */
- if (target_resume_hook)
- (*target_resume_hook) ();
-
- /* The s/S/c/C packets do not return status. So if the target does
- not support the S or C packets, the debug agent returns an empty
- string which is detected in remote_wait(). This protocol defect
- is fixed in the e/E packets. */
-
- if (step && step_range_end)
- {
- /* If the target does not support the 'E' packet, we try the 'S'
- packet. Ideally we would fall back to the 'e' packet if that
- too is not supported. But that would require another copy of
- the code to issue the 'e' packet (and fall back to 's' if not
- supported) in remote_wait(). */
-
- if (siggnal != TARGET_SIGNAL_0)
- {
- if (remote_protocol_E.support != PACKET_DISABLE)
- {
- p = buf;
- *p++ = 'E';
- *p++ = tohex (((int) siggnal >> 4) & 0xf);
- *p++ = tohex (((int) siggnal) & 0xf);
- *p++ = ',';
- p += hexnumstr (p, (ULONGEST) step_range_start);
- *p++ = ',';
- p += hexnumstr (p, (ULONGEST) step_range_end);
- *p++ = 0;
-
- putpkt (buf);
- getpkt (buf, (rs->remote_packet_size), 0);
-
- if (packet_ok (buf, &remote_protocol_E) == PACKET_OK)
- goto register_event_loop;
- }
- }
- else
- {
- if (remote_protocol_e.support != PACKET_DISABLE)
- {
- p = buf;
- *p++ = 'e';
- p += hexnumstr (p, (ULONGEST) step_range_start);
- *p++ = ',';
- p += hexnumstr (p, (ULONGEST) step_range_end);
- *p++ = 0;
-
- putpkt (buf);
- getpkt (buf, (rs->remote_packet_size), 0);
+ remote_resume (ptid, step, siggnal);

- if (packet_ok (buf, &remote_protocol_e) == PACKET_OK)
- goto register_event_loop;
- }
- }
- }
-
- if (siggnal != TARGET_SIGNAL_0)
- {
- buf[0] = step ? 'S' : 'C';
- buf[1] = tohex (((int) siggnal >> 4) & 0xf);
- buf[2] = tohex ((int) siggnal & 0xf);
- buf[3] = '\0';
- }
- else
- strcpy (buf, step ? "s" : "c");
-
- putpkt (buf);
-
-register_event_loop:
/* We are about to start executing the inferior, let's register it
with the event loop. NOTE: this is the one place where all the
execution commands end up. We could alternatively do this in each
@@ -6019,6 +6027,7 @@ show_remote_cmd (char *args, int from_tt
show_remote_protocol_E_packet_cmd (args, from_tty, NULL);
show_remote_protocol_P_packet_cmd (args, from_tty, NULL);
show_remote_protocol_qSymbol_packet_cmd (args, from_tty, NULL);
+ show_remote_protocol_vcont_packet_cmd (args, from_tty, NULL);
show_remote_protocol_binary_download_cmd (args, from_tty, NULL);
}

@@ -6191,6 +6200,13 @@ in a memory packet.\n",

add_info ("remote-process", remote_info_process,
"Query the remote system for process info.");
+
+ add_packet_config_cmd (&remote_protocol_vcont,
+ "vCont", "verbose-resume",
+ set_remote_protocol_vcont_packet_cmd,
+ show_remote_protocol_vcont_packet_cmd,
+ &remote_set_cmdlist, &remote_show_cmdlist,
+ 0);

add_packet_config_cmd (&remote_protocol_qSymbol,
"qSymbol", "symbol-lookup",