+static int resp_xdwriteread(struct scsi_cmnd *scp, unsigned long long lba,
+ unsigned int num, struct sdebug_dev_info *devip)
+{
+ int i, j, ret = -1;
+ unsigned char *kaddr, *buf;
+ unsigned int offset;
+ struct scatterlist *sg;
+ struct scsi_data_buffer *sdb = scsi_in(scp);
+
+ /* better not to use temporary buffer. */
+ buf = kmalloc(scsi_bufflen(scp), GFP_ATOMIC);
+ if (!buf)
+ return ret;
+
+ offset = 0;
+ scsi_for_each_sg(scp, sg, scsi_sg_count(scp), i) {
+ kaddr = (unsigned char *)kmap_atomic(sg_page(sg), KM_USER0);
+ if (!kaddr)
+ goto out;
+
+ memcpy(buf + offset, kaddr + sg->offset, sg->length);
+ offset += sg->length;
+ kunmap_atomic(kaddr, KM_USER0);
+ }
+
+ offset = 0;
+ for_each_sg(sdb->table.sgl, sg, sdb->table.nents, i) {
+ kaddr = (unsigned char *)kmap_atomic(sg_page(sg), KM_USER0);
+ if (!kaddr)
+ goto out;
+
+ for (j = 0; j < sg->length; j++)
+ *(kaddr + sg->offset + j) ^= *(buf + offset + j);
+
+ offset += sg->length;
+ kunmap_atomic(kaddr, KM_USER0);
+ }
+ ret = 0;
+out:
+ kfree(buf);
+
+ return ret;
+}
+