s390-ccw: print carriage return with new lines

The sclp console in the s390 bios writes raw data,
leading console emulators (such as virsh console) to
treat a new line ('\n') as just a new line instead
of as a Unix line feed. Because of this, output
appears in a "stair case" pattern.

Let's print \r\n on every occurrence of a new line
in the string passed to write to amend this issue.

This is in sync with the guest Linux code in
drivers/s390/char/sclp_vt220.c which also does a line feed
conversion in the console part of the driver.

This fixes the s390-ccw and s390-netboot output like
$ virsh start test --console
Domain test started
Connected to domain test
Escape character is ^]
Network boot starting...
                          Using MAC address: 02:01:02:03:04:05
                                                                Requesting information via DHCP:  010
Signed-off-by: NCollin L. Walling <walling@linux.vnet.ibm.com>
Message-Id: <1509120893-28054-1-git-send-email-walling@linux.vnet.ibm.com>
Reviewed-by: NHalil Pasic <pasic@linux.vnet.ibm.com>
Acked-by: NCornelia Huck <cohuck@redhat.com>
Reviewed-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>

pc-bios/s390-ccw/sclp.c

@@ -76,17 +76,35 @@ static int _strlen(const char *str)
 long write(int fd, const void *str, size_t len)
 {
     WriteEventData *sccb = (void *)_sccb;
+    const char *p = str;
+    size_t data_len = 0;
+    size_t i;
 
     if (fd != 1 && fd != 2) {
         return -EIO;
     }
 
-    sccb->h.length = sizeof(WriteEventData) + len;
+    for (i = 0; i < len; i++) {
+        if ((data_len + 1) >= SCCB_DATA_LEN) {
+            /* We would overflow the sccb buffer, abort early */
+            len = i;
+            break;
+        }
+
+        if (*p == '\n') {
+            /* Terminal emulators might need \r\n, so generate it */
+            sccb->data[data_len++] = '\r';
+        }
+
+        sccb->data[data_len++] = *p;
+        p++;
+    }
+
+    sccb->h.length = sizeof(WriteEventData) + data_len;
     sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
-    sccb->ebh.length = sizeof(EventBufferHeader) + len;
+    sccb->ebh.length = sizeof(EventBufferHeader) + data_len;
     sccb->ebh.type = SCLP_EVENT_ASCII_CONSOLE_DATA;
     sccb->ebh.flags = 0;
-    memcpy(sccb->data, str, len);
 
     sclp_service_call(SCLP_CMD_WRITE_EVENT_DATA, sccb);