target: use correct target in target-prefixed commands and event handlers

This change contains an alternative to Matthias Welwarsky's #4130
(target-prefixed commands) and to #4293 (event handlers).

get_current_target() must retrieve the target associated to the current
command. If no target associated, the current target of the command
context is used as a fallback.

Many Tcl event handlers work with the current target as if it were
the target issuing the event.

current_target in command_context is a number and has to be converted
to a pointer in every get_current_target() call.

The solution:
- Replace current_target in command_context by a target pointer
- Add another target pointer current_target_override
- get_current_target() returns current_target_override if set, otherwise
	current_target
- Save, set and restore current_target_override to the current prefix
	in run_command()
- Save, set and restore current_target_override to the event invoking
	target in target_handle_event()

While on it use calloc when allocating a new command_context.

Change-Id: I9a82102e94dcac063743834a1d28da861b2e74ea
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Suggested-by: Matthias Welwarsky <matthias.welwarsky@sysgo.com>
Reviewed-on: http://openocd.zylin.com/4295
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

doc/openocd.texi

@@ -4217,6 +4217,9 @@ Calling this twice with two different event names assigns
 two different handlers, but calling it twice with the
 same event name assigns only one handler.
 
+Current target is temporarily overridden to the event issuing target
+before handler code starts and switched back after handler is done.
+
 @item @code{-work-area-backup} (@option{0}|@option{1}) -- says
 whether the work area gets backed up; by default,
 @emph{it is not backed up.}

src/helper/command.c

@@ -608,7 +608,23 @@ static int run_command(struct command_context *context,
 		.argc = num_words - 1,
 		.argv = words + 1,
 	};
+	/* Black magic of overridden current target:
+	 * If the command we are going to handle has a target prefix,
+	 * override the current target temporarily for the time
+	 * of processing the command.
+	 * current_target_override is used also for event handlers
+	 * therefore we prevent touching it if command has no prefix.
+	 * Previous override is saved and restored back to ensure
+	 * correct work when run_command() is re-entered. */
+	struct target *saved_target_override = context->current_target_override;
+	if (c->jim_handler_data)
+		context->current_target_override = c->jim_handler_data;
+
 	int retval = c->handler(&cmd);
+
+	if (c->jim_handler_data)
+		context->current_target_override = saved_target_override;
+
 	if (retval == ERROR_COMMAND_SYNTAX_ERROR) {
 		/* Print help for command */
 		char *full_name = command_name(c, ' ');
@@ -643,6 +659,8 @@ int command_run_line(struct command_context *context, char *line)
 	 * happen when the Jim Tcl interpreter is provided by eCos for
 	 * instance.
 	 */
+	context->current_target_override = NULL;
+
 	Jim_Interp *interp = context->interp;
 	Jim_DeleteAssocData(interp, "context");
 	retcode = Jim_SetAssocData(interp, "context", NULL, context);
@@ -1269,14 +1287,10 @@ static const struct command_registration command_builtin_handlers[] = {
 
 struct command_context *command_init(const char *startup_tcl, Jim_Interp *interp)
 {
-	struct command_context *context = malloc(sizeof(struct command_context));
+	struct command_context *context = calloc(1, sizeof(struct command_context));
 	const char *HostOs;
 
 	context->mode = COMMAND_EXEC;
-	context->commands = NULL;
-	context->current_target = 0;
-	context->output_handler = NULL;
-	context->output_handler_priv = NULL;
 
 	/* Create a jim interpreter if we were not handed one */
 	if (interp == NULL) {

src/helper/command.h

@@ -49,7 +49,15 @@ struct command_context {
 	Jim_Interp *interp;
 	enum command_mode mode;
 	struct command *commands;
-	int current_target;
+	struct target *current_target;
+		/* The target set by 'targets xx' command or the latest created */
+	struct target *current_target_override;
+		/* If set overrides current_target
+		 * It happens during processing of
+		 *	1) a target prefixed command
+		 *	2) an event handler
+		 * Pay attention to reentrancy when setting override.
+		 */
 	command_output_handler_t output_handler;
 	void *output_handler_priv;
 };
@@ -168,6 +176,11 @@ struct command {
 	command_handler_t handler;
 	Jim_CmdProc *jim_handler;
 	void *jim_handler_data;
+		/* Currently used only for target of target-prefixed cmd.
+		 * Native OpenOCD commands use jim_handler_data exclusively
+		 * as a target override.
+		 * Jim handlers outside of target cmd tree can use
+		 * jim_handler_data for any handler specific data */
 	enum command_mode mode;
 	struct command *next;
 };

src/server/tcl_server.c

@@ -157,7 +157,7 @@ static int tcl_new_connection(struct connection *connection)
 
 	connection->priv = tclc;
 
-	struct target *target = get_target_by_num(connection->cmd_ctx->current_target);
+	struct target *target = get_current_target(connection->cmd_ctx);
 	if (target != NULL)
 		tclc->tc_laststate = target->state;
 

src/target/target.c

@@ -510,7 +510,9 @@ struct target *get_target_by_num(int num)
 
 struct target *get_current_target(struct command_context *cmd_ctx)
 {
-	struct target *target = get_target_by_num(cmd_ctx->current_target);
+	struct target *target = cmd_ctx->current_target_override
+		? cmd_ctx->current_target_override
+		: cmd_ctx->current_target;
 
 	if (target == NULL) {
 		LOG_ERROR("BUG: current_target out of bounds");
@@ -2505,7 +2507,10 @@ static int find_target(struct command_context *cmd_ctx, const char *name)
 		return ERROR_FAIL;
 	}
 
-	cmd_ctx->current_target = target->target_number;
+	cmd_ctx->current_target = target;
+	if (cmd_ctx->current_target_override)
+		cmd_ctx->current_target_override = target;
+
 	return ERROR_OK;
 }
 
@@ -2533,7 +2538,7 @@ COMMAND_HANDLER(handle_targets_command)
 		else
 			state = "tap-disabled";
 
-		if (CMD_CTX->current_target == target->target_number)
+		if (CMD_CTX->current_target == target)
 			marker = '*';
 
 		/* keep columns lined up to match the headers above */
@@ -4441,17 +4446,28 @@ void target_handle_event(struct target *target, enum target_event e)
 
 	for (teap = target->event_action; teap != NULL; teap = teap->next) {
 		if (teap->event == e) {
-			LOG_DEBUG("target: (%d) %s (%s) event: %d (%s) action: %s",
+			LOG_DEBUG("target(%d): %s (%s) event: %d (%s) action: %s",
 					   target->target_number,
 					   target_name(target),
 					   target_type_name(target),
 					   e,
 					   Jim_Nvp_value2name_simple(nvp_target_event, e)->name,
 					   Jim_GetString(teap->body, NULL));
+
+			/* Override current target by the target an event
+			 * is issued from (lot of scripts need it).
+			 * Return back to previous override as soon
+			 * as the handler processing is done */
+			struct command_context *cmd_ctx = current_command_context(teap->interp);
+			struct target *saved_target_override = cmd_ctx->current_target_override;
+			cmd_ctx->current_target_override = target;
+
 			if (Jim_EvalObj(teap->interp, teap->body) != JIM_OK) {
 				Jim_MakeErrorMessage(teap->interp);
 				command_print(NULL, "%s\n", Jim_GetString(Jim_GetResult(teap->interp), NULL));
 			}
+
+			cmd_ctx->current_target_override = saved_target_override;
 		}
 	}
 }
@@ -5529,7 +5545,7 @@ static int target_create(Jim_GetOptInfo *goi)
 	target = calloc(1, sizeof(struct target));
 	/* set target number */
 	target->target_number = new_target_number();
-	cmd_ctx->current_target = target->target_number;
+	cmd_ctx->current_target = target;
 
 	/* allocate memory for each unique target type */
 	target->type = calloc(1, sizeof(struct target_type));