scsi: scsi_debug: Improve RDPROTECT/WRPROTECT handling

It is useful for testing purposes to be able to inject errors by writing
bad protection information to media with checking disabled and then
attempting to read it back. Extend scsi_debug's PI verification logic to
give the driver feature parity with commercially available drives. Almost
all devices with PI capability support RDPROTECT and WRPROTECT values of 0,
1, and 3.

Link: https://lore.kernel.org/r/20210609033929.3815-10-martin.petersen@oracle.com
Reviewed-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Message-Id: <20210609033929.3815-10-martin.petersen@oracle.com>

drivers/scsi/scsi_debug.c

@@ -3076,33 +3076,41 @@ static void dif_copy_prot(struct scsi_cmnd *scp, sector_t sector,
 static int prot_verify_read(struct scsi_cmnd *scp, sector_t start_sec,
 			    unsigned int sectors, u32 ei_lba)
 {
+	int ret = 0;
 	unsigned int i;
 	sector_t sector;
 	struct sdeb_store_info *sip = devip2sip((struct sdebug_dev_info *)
 						scp->device->hostdata, true);
 	struct t10_pi_tuple *sdt;
 
 	for (i = 0; i < sectors; i++, ei_lba++) {
-		int ret;
-
 		sector = start_sec + i;
 		sdt = dif_store(sip, sector);
 
 		if (sdt->app_tag == cpu_to_be16(0xffff))
 			continue;
 
-		ret = dif_verify(sdt, lba2fake_store(sip, sector), sector,
-				 ei_lba);
-		if (ret) {
-			dif_errors++;
-			return ret;
+		/*
+		 * Because scsi_debug acts as both initiator and
+		 * target we proceed to verify the PI even if
+		 * RDPROTECT=3. This is done so the "initiator" knows
+		 * which type of error to return. Otherwise we would
+		 * have to iterate over the PI twice.
+		 */
+		if (scp->cmnd[1] >> 5) { /* RDPROTECT */
+			ret = dif_verify(sdt, lba2fake_store(sip, sector),
+					 sector, ei_lba);
+			if (ret) {
+				dif_errors++;
+				break;
+			}
 		}
 	}
 
 	dif_copy_prot(scp, start_sec, sectors, true);
 	dix_reads++;
 
-	return 0;
+	return ret;
 }
 
 static int resp_read_dt0(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
@@ -3196,12 +3204,29 @@ static int resp_read_dt0(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
 
 	/* DIX + T10 DIF */
 	if (unlikely(sdebug_dix && scsi_prot_sg_count(scp))) {
-		int prot_ret = prot_verify_read(scp, lba, num, ei_lba);
-
-		if (prot_ret) {
-			read_unlock(macc_lckp);
-			mk_sense_buffer(scp, ABORTED_COMMAND, 0x10, prot_ret);
-			return illegal_condition_result;
+		switch (prot_verify_read(scp, lba, num, ei_lba)) {
+		case 1: /* Guard tag error */
+			if (cmd[1] >> 5 != 3) { /* RDPROTECT != 3 */
+				read_unlock(macc_lckp);
+				mk_sense_buffer(scp, ABORTED_COMMAND, 0x10, 1);
+				return check_condition_result;
+			} else if (scp->prot_flags & SCSI_PROT_GUARD_CHECK) {
+				read_unlock(macc_lckp);
+				mk_sense_buffer(scp, ILLEGAL_REQUEST, 0x10, 1);
+				return illegal_condition_result;
+			}
+			break;
+		case 3: /* Reference tag error */
+			if (cmd[1] >> 5 != 3) { /* RDPROTECT != 3 */
+				read_unlock(macc_lckp);
+				mk_sense_buffer(scp, ABORTED_COMMAND, 0x10, 3);
+				return check_condition_result;
+			} else if (scp->prot_flags & SCSI_PROT_REF_CHECK) {
+				read_unlock(macc_lckp);
+				mk_sense_buffer(scp, ILLEGAL_REQUEST, 0x10, 3);
+				return illegal_condition_result;
+			}
+			break;
 		}
 	}
 
@@ -3277,9 +3302,11 @@ static int prot_verify_write(struct scsi_cmnd *SCpnt, sector_t start_sec,
 			sdt = piter.addr + ppage_offset;
 			daddr = diter.addr + dpage_offset;
 
-			ret = dif_verify(sdt, daddr, sector, ei_lba);
-			if (ret)
-				goto out;
+			if (SCpnt->cmnd[1] >> 5 != 3) { /* WRPROTECT */
+				ret = dif_verify(sdt, daddr, sector, ei_lba);
+				if (ret)
+					goto out;
+			}
 
 			sector++;
 			ei_lba++;
@@ -3456,12 +3483,29 @@ static int resp_write_dt0(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
 
 	/* DIX + T10 DIF */
 	if (unlikely(sdebug_dix && scsi_prot_sg_count(scp))) {
-		int prot_ret = prot_verify_write(scp, lba, num, ei_lba);
-
-		if (prot_ret) {
-			write_unlock(macc_lckp);
-			mk_sense_buffer(scp, ILLEGAL_REQUEST, 0x10, prot_ret);
-			return illegal_condition_result;
+		switch (prot_verify_write(scp, lba, num, ei_lba)) {
+		case 1: /* Guard tag error */
+			if (scp->prot_flags & SCSI_PROT_GUARD_CHECK) {
+				write_unlock(macc_lckp);
+				mk_sense_buffer(scp, ILLEGAL_REQUEST, 0x10, 1);
+				return illegal_condition_result;
+			} else if (scp->cmnd[1] >> 5 != 3) { /* WRPROTECT != 3 */
+				write_unlock(macc_lckp);
+				mk_sense_buffer(scp, ABORTED_COMMAND, 0x10, 1);
+				return check_condition_result;
+			}
+			break;
+		case 3: /* Reference tag error */
+			if (scp->prot_flags & SCSI_PROT_REF_CHECK) {
+				write_unlock(macc_lckp);
+				mk_sense_buffer(scp, ILLEGAL_REQUEST, 0x10, 3);
+				return illegal_condition_result;
+			} else if (scp->cmnd[1] >> 5 != 3) { /* WRPROTECT != 3 */
+				write_unlock(macc_lckp);
+				mk_sense_buffer(scp, ABORTED_COMMAND, 0x10, 3);
+				return check_condition_result;
+			}
+			break;
 		}
 	}