program loading: add optional is_loader_active() callback

Add a way for a loader to indicate if it is active. Such users
of this callback would be vboot which can indicate to the rest
of the system that it isn't active. is_loader_active() also
gives vboot a chance to perform the necessary work to make
said decision.

Change-Id: I6679ac75b19bb1bfff9c2b709da5591986f752ff
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/10022
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/include/program_loading.h

@@ -103,6 +103,9 @@ void platform_prog_run(struct prog *prog);
 
 struct prog_loader_ops {
 	const char *name;
+	/* Determine if the loader is the active one. If so returns 1 else 0
+	 * or < 0 on error. */
+	int (*is_loader_active)(struct prog *prog);
 	/* Returns < 0 on error or 0 on success. This function needs to do
 	 * different things depending on the prog type. See definition
 	 * of struct prog above. */

src/lib/loaders/load_and_run_payload.c

@@ -54,7 +54,24 @@ void payload_load(void)
 	struct prog *payload = &global_payload;
 
 	for (i = 0; i < ARRAY_SIZE(payload_ops); i++) {
+		/* Default loader state is active. */
+		int ret = 1;
+
 		ops = payload_ops[i];
+
+		if (ops->is_loader_active != NULL)
+			ret = ops->is_loader_active(payload);
+
+		if (ret == 0) {
+			printk(BIOS_DEBUG, "%s payload loader inactive.\n",
+				ops->name);
+			continue;
+		} else if (ret < 0) {
+			printk(BIOS_DEBUG, "%s payload loader failure.\n",
+				ops->name);
+			continue;
+		}
+
 		if (ops->prepare(payload) < 0) {
 			printk(BIOS_DEBUG, "%s: could not locate payload.\n",
 				ops->name);

src/lib/loaders/load_and_run_ramstage.c

@@ -83,8 +83,25 @@ void run_ramstage(void)
 	run_ramstage_from_resume(romstage_handoff_find_or_add(), &ramstage);
 
 	for (i = 0; i < ARRAY_SIZE(loaders); i++) {
+		/* Default loader state is active. */
+		int ret = 1;
+
 		ops = loaders[i];
-		printk(BIOS_DEBUG, "Trying %s ramstage loader.\n", ops->name);
+
+		if (ops->is_loader_active != NULL)
+			ret = ops->is_loader_active(&ramstage);
+
+		if (ret == 0) {
+			printk(BIOS_DEBUG, "%s ramstage loader inactive.\n",
+				ops->name);
+			continue;
+		} else if (ret < 0) {
+			printk(BIOS_DEBUG, "%s ramstage loader failure.\n",
+				ops->name);
+			continue;
+		}
+
+		printk(BIOS_DEBUG, "%s ramstage loader active.\n", ops->name);
 		load_ramstage(ops, &ramstage);
 	}
 

src/lib/loaders/load_and_run_romstage.c

@@ -41,11 +41,26 @@ void run_romstage(void)
 	};
 
 	for (i = 0; i < ARRAY_SIZE(loaders); i++) {
+		/* Default loader state is active. */
+		int ret = 1;
 		const struct prog_loader_ops *ops;
 
 		ops = loaders[i];
 
-		printk(BIOS_DEBUG, "Trying %s romstage loader.\n", ops->name);
+		if (ops->is_loader_active != NULL)
+			ret = ops->is_loader_active(&romstage);
+
+		if (ret == 0) {
+			printk(BIOS_DEBUG, "%s romstage loader inactive.\n",
+				ops->name);
+			continue;
+		} else if (ret < 0) {
+			printk(BIOS_DEBUG, "%s romstage loader failure.\n",
+				ops->name);
+			continue;
+		}
+
+		printk(BIOS_DEBUG, "%s romstage loader active.\n", ops->name);
 
 		timestamp_add_now(TS_START_COPYROM);