transport: validate the transport id's from the driver

Verify that it contains only valid transports.

While JTAG and SWD are the more permissive transports, the
respective 'dapdirect' versions are slightly limited, and the
respective 'hla' versions are even more limited.
A driver should not provide two version of the same transport.
Verify that only one JTAG and only one SWD transport is present.
Verify that the preferred transport is valid too.

Change-Id: Iace2f881dd65fc763e81b33e6a7113961a7008af
Signed-off-by: Antonio Borneo <[email protected]>
Reviewed-on: https://review.openocd.org/c/openocd/+/8676
Tested-by: jenkins
Reviewed-by: zapb <[email protected]>
Reviewed-by: Jan Matyas <[email protected]>

Author: borneoa

src/transport/transport.c

@@ -125,21 +125,37 @@ static int transport_select(struct command_context *ctx, const char *name)
 int allow_transports(struct command_context *ctx, unsigned int transport_ids,
 	unsigned int transport_preferred_id)
 {
-	/* NOTE:  caller is required to provide only a list
-	 * of *valid* transports
-	 *
-	 * REVISIT should we validate that?  and insist there's
-	 * at least one valid element in that list?
-	 *
-	 * ... allow removals, e.g. external strapping prevents use
-	 * of one transport; C code should be definitive about what
-	 * can be used when all goes well.
-	 */
 	if (allowed_transports || session) {
 		LOG_ERROR("Can't modify the set of allowed transports.");
 		return ERROR_FAIL;
 	}
 
+	/* validate the values in transport_ids and transport_preferred_id */
+	if (transport_ids == 0 || (transport_ids & ~TRANSPORT_VALID_MASK) != 0) {
+		LOG_ERROR("BUG: Unknown transport IDs %lu", transport_ids & ~TRANSPORT_VALID_MASK);
+		return ERROR_FAIL;
+	}
+
+	if ((transport_ids & transport_preferred_id) == 0
+		|| !IS_PWR_OF_2(transport_preferred_id)) {
+		LOG_ERROR("BUG: Invalid adapter transport_preferred_id");
+		return ERROR_FAIL;
+	}
+
+	unsigned int mask = transport_ids &
+		(TRANSPORT_JTAG | TRANSPORT_HLA_JTAG | TRANSPORT_DAPDIRECT_JTAG);
+	if (mask && !IS_PWR_OF_2(mask)) {
+		LOG_ERROR("BUG: Multiple JTAG transports");
+		return ERROR_FAIL;
+	}
+
+	mask = transport_ids &
+		(TRANSPORT_SWD | TRANSPORT_HLA_SWD | TRANSPORT_DAPDIRECT_SWD);
+	if (mask && !IS_PWR_OF_2(mask)) {
+		LOG_ERROR("BUG: Multiple SWD transports");
+		return ERROR_FAIL;
+	}
+
 	allowed_transports = transport_ids;
 	preferred_transport = transport_preferred_id;