[RFA] Reverse Debugging, 2/5

Michael Snyder
2008-10-01T19:19:29Z

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This patch (#2) adds a target implementation of reverse debugging
(for the "remote" target), implementing the new target_ops methods
and changing remote_wait and remote_resume to make use of them.

Adding this patch on top of patch #1 causes no change in gdb
behavior, since nothing invokes the new methods. Tested under
RHEL native with no change in results.

2008-09-30 Michael Snyder <msnyder@vmware.com>
Remote interface for reverse debugging.
* remote.c (remote_get_execdir, remote_set_execdir): New methods.
(remote_vcont_resume): Jump out if attempting reverse execution.
(remote_resume): Check for reverse exec direction, and send
appropriate command to target.
(remote_wait): Check target response for NO_HISTORY status.
Also check for empty reply (target doesn't understand "bs" or "bc).
(_initialize_remote): Add new methods to remote target vector.

Index: remote.c
===================================================================
RCS file: /cvs/src/src/gdb/remote.c,v
retrieving revision 1.310
diff -u -p -r1.310 remote.c
--- remote.c 22 Sep 2008 15:21:30 -0000 1.310
+++ remote.c 30 Sep 2008 18:23:30 -0000
@@ -3385,7 +3385,15 @@ remote_resume (ptid_t ptid, int step, en
set_continue_thread (ptid);

buf = rs->buf;
- if (siggnal != TARGET_SIGNAL_0)
+ if (target_get_execution_direction () == EXEC_REVERSE)
+ {
+ /* We don't pass signals to the target in reverse exec mode. */
+ if (info_verbose && siggnal != TARGET_SIGNAL_0)
+ warning (" - Can't pass signal %d to target in reverse: ignored.\n",
+ siggnal);
+ strcpy (buf, step ? "bs" : "bc");
+ }
+ else if (siggnal != TARGET_SIGNAL_0)
{
buf[0] = step ? 'S' : 'C';
buf[1] = tohex (((int) siggnal >> 4) & 0xf);
@@ -3651,8 +3659,15 @@ remote_wait (ptid_t ptid, struct target_
/* We're out of sync with the target now. Did it continue or not?
Not is more likely, so report a stop. */
warning (_("Remote failure reply: %s"), buf);
- status->kind = TARGET_WAITKIND_STOPPED;
- status->value.sig = TARGET_SIGNAL_0;
+ if (buf[1] == '0' && buf[2] == '6')
+ {
+ status->kind = TARGET_WAITKIND_NO_HISTORY;
+ }
+ else
+ {
+ status->kind = TARGET_WAITKIND_STOPPED;
+ status->value.sig = TARGET_SIGNAL_0;
+ }
goto got_status;
case 'F': /* File-I/O request. */
remote_fileio_request (buf);
@@ -7545,6 +7560,35 @@ remote_command (char *args, int from_tty
help_list (remote_cmdlist, "remote ", -1, gdb_stdout);
}

+/* Reverse execution.
+ TODO: set up as a capability. */
+static enum exec_direction_kind remote_execdir = EXEC_FORWARD;
+
+static enum exec_direction_kind remote_get_execdir (void)
+{
+ if (remote_debug && info_verbose)
+ printf_filtered ("remote execdir is %s\n",
+ remote_execdir == EXEC_FORWARD ? "forward" :
+ remote_execdir == EXEC_REVERSE ? "reverse" :
+ "unknown");
+ return remote_execdir;
+}
+
+static int remote_set_execdir (enum exec_direction_kind dir)
+{
+ if (remote_debug && info_verbose)
+ printf_filtered ("Set remote execdir: %s\n",
+ dir == EXEC_FORWARD ? "forward" :
+ dir == EXEC_REVERSE ? "reverse" :
+ "bad direction");
+
+ /* TODO: check target for capability. */
+ if (dir == EXEC_FORWARD || dir == EXEC_REVERSE)
+ return (remote_execdir = dir);
+ else
+ return EXEC_ERROR;
+}
+
static void
init_remote_ops (void)
{
@@ -7593,6 +7637,8 @@ Specify the serial device it is connecte
remote_ops.to_has_registers = 1;
remote_ops.to_has_execution = 1;
remote_ops.to_has_thread_control = tc_schedlock; /* can lock scheduler */
+ remote_ops.to_get_execdir = remote_get_execdir;
+ remote_ops.to_set_execdir = remote_set_execdir;
remote_ops.to_magic = OPS_MAGIC;
remote_ops.to_memory_map = remote_memory_map;
remote_ops.to_flash_erase = remote_flash_erase;