Re: [Qemu-devel] [PATCH] s390-ccw: print carriage return with new lines

[Halil Pasic <pasic@linux.vnet.ibm.com>]

On 10/20/2017 12:25 PM, Christian Borntraeger wrote:
> From: "Collin L. Walling" <walling@linux.vnet.ibm.com>
> 
> 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
> 

The check for buffer overflow was not there previously, or?

Maybe integrate that in the commit message too.

> Signed-off-by: Collin L. Walling <walling@linux.vnet.ibm.com>
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  pc-bios/s390-ccw/s390-ccw.h |  3 +++
>  pc-bios/s390-ccw/sclp.c     | 17 ++++++++++++++---
>  2 files changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/pc-bios/s390-ccw/s390-ccw.h b/pc-bios/s390-ccw/s390-ccw.h
> index 25d4d21..a8bd204 100644
> --- a/pc-bios/s390-ccw/s390-ccw.h
> +++ b/pc-bios/s390-ccw/s390-ccw.h
> @@ -33,6 +33,9 @@ typedef unsigned long long __u64;
>  #ifndef EBUSY
>  #define EBUSY   2
>  #endif
> +#ifndef EFBIG
> +#define EFBIG   3
> +#endif
>  #ifndef NULL
>  #define NULL    0
>  #endif
> diff --git a/pc-bios/s390-ccw/sclp.c b/pc-bios/s390-ccw/sclp.c
> index b1fc8ff..4795259 100644
> --- a/pc-bios/s390-ccw/sclp.c
> +++ b/pc-bios/s390-ccw/sclp.c
> @@ -76,17 +76,28 @@ static int _strlen(const char *str)
>  long write(int fd, const void *str, size_t len)
>  {
>      WriteEventData *sccb = (void *)_sccb;
> +    const char *p;
> +    size_t data_len = 0;
> 
>      if (fd != 1 && fd != 2) {
>          return -EIO;
>      }
> 
> -    sccb->h.length = sizeof(WriteEventData) + len;
> +    for (p = str; *p; ++p) {
> +        if (data_len > SCCB_DATA_LEN - 1) {
> +            return -EFBIG;
> +        }

We could also do a partial write or do more that one
sclp_service_call calls.

I don't think EFBIG is entirely correct here. From the man page:
"""
       EFBIG  An attempt was made to write a file that exceeds the implementa-
              tion-defined maximum file size or the process’s file size limit,
              or to write at a position past the maximum allowed offset.
"""

That's not what we have here IMHO.

> +        if (*p == '\n') {
> +            sccb->data[data_len++] = '\r';
> +        }
> +        sccb->data[data_len++] = *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);
> 

Otherwise LGTM

Halil