Re: [Qemu-devel] [PATCH v2] s390-ccw: print carriage return with new lines

[Alexander Graf]

On 26.10.17 20:52, Collin L. Walling wrote:
> 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: Collin L. Walling <address@hidden>
> Signed-off-by: Christian Borntraeger <address@hidden>
> ---
>  pc-bios/s390-ccw/sclp.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/pc-bios/s390-ccw/sclp.c b/pc-bios/s390-ccw/sclp.c
> index 486fce1..f8ad5ae 100644
> --- a/pc-bios/s390-ccw/sclp.c
> +++ b/pc-bios/s390-ccw/sclp.c
> @@ -68,17 +68,27 @@ void sclp_setup(void)
>  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 = len; i > 0; i--) {

Where did the bounds check go? If you write(max) before, you were
writing max bytes. If you do it now, you end up writing max + n bytes
and potentially overflow the array, no?


Alex

> +        if (*p == '\n') {
> +            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);
>  
>