Re: [Qemu-devel] [PATCH v1 for-2.13 4/4] pc-bios/s390-ccw/net: Add support for .INS config files

[Thomas Huth]

On 19.04.2018 10:02, Viktor VM Mihajlovski wrote:
> On 18.04.2018 14:31, Thomas Huth wrote:
>> The .INS config files can normally be found on CD-ROM ISO images,
>> so by supporting these files, it is now possible to boot directly
>> when the TFTP server is set up with the contents of such an CD-ROM
>> image.
>>
>> Signed-off-by: Thomas Huth <address@hidden>
>> ---
>>  pc-bios/s390-ccw/netmain.c | 51 
>> ++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 51 insertions(+)
>>
>> diff --git a/pc-bios/s390-ccw/netmain.c b/pc-bios/s390-ccw/netmain.c
>> index fa62bfe..e52e17d 100644
>> --- a/pc-bios/s390-ccw/netmain.c
>> +++ b/pc-bios/s390-ccw/netmain.c
>> @@ -441,6 +441,55 @@ static int net_try_pxelinux_cfgs(filename_ip_t *fn_ip)
>>      return -1;
>>  }
>>
>> +/**
>> + * Load via information from a .INS file (which can be found on CD-ROMs
>> + * for example)
>> + */
>> +static int handle_ins_cfg(filename_ip_t *fn_ip, char *cfg, int cfgsize)
>> +{
>> +    char *ptr;
>> +    int rc = -1, llen;
>> +    void *destaddr;
>> +    char *insbuf = cfg;
>> +
>> +    ptr = strchr(insbuf, '\n');
>> +    if (!ptr) {
>> +        puts("Does not seem to be a valid .INS file");
>> +        return -1;
>> +    }
>> +
>> +    *ptr = 0;
>> +    printf("\nParsing .INS file:\n %s\n", &insbuf[2]);
>> +
>> +    insbuf = ptr + 1;
>> +    while (*insbuf && insbuf < cfg + cfgsize) {
>> +        ptr = strchr(insbuf, '\n');
>> +        if (ptr) {
>> +            *ptr = 0;
>> +        }
>> +        llen = strlen(insbuf);
>> +        if (!llen) {
>> +            insbuf = ptr + 1;
>> +            continue;
>> +        }
>> +        ptr = strchr(insbuf, ' ');
>> +        if (!ptr) {
>> +            puts("Missing space separator in .INS file");
>> +            return -1;
>> +        }
>> +        *ptr = 0;
>> +        strncpy((char *)fn_ip->filename, insbuf, sizeof(fn_ip->filename));
>> +        destaddr = (char *)atol(ptr + 1);
>> +        rc = tftp_load(fn_ip, destaddr, (long)_start - (long)destaddr);
>> +        if (rc <= 0) {
>> +            break;
>> +        }
>> +        insbuf += llen + 1;
>> +    }
>> +
>> +    return rc;
>> +}
>> +
>>  static int net_try_direct_tftp_load(filename_ip_t *fn_ip)
>>  {
>>      int rc;
>> @@ -455,6 +504,8 @@ static int net_try_direct_tftp_load(filename_ip_t *fn_ip)
>>          if (!strncasecmp("default", cfgbuf, 7) || !strncmp("# ", cfgbuf, 
>> 2)) {
>>              /* Looks like it is a pxelinux.cfg */
>>              return handle_pxelinux_cfg(fn_ip, cfgbuf, rc);
>> +        } else if (!strncmp("* ", cfgbuf, 2)) {
>> +            return handle_ins_cfg(fn_ip, cfgbuf, rc);
>>          }
>>      }
>>
> You could consider to move the magic matching code into a helper
> function, I could imagine that the detection might grow more complex
> over time and then could clutter the try-load code.
> I.e. something like
> 
> typedef enum {
>       FT_UNKOWN,
>       FT_PXECFG,
>       FT_INSFILE,
> } FileType;
> 
> static FileType probe_file_type(const char * cfgbuf, size_t cfgbuflen)
> {
>         ...
>         if (!strncasecmp("default", cfgbuf, 7) || !strncmp("# ",
>                           cfgbuf, 2)) {
>             /* Looks like it is a pxelinux.cfg */
>             return FT_PXECFG;
>         } else if (!strncmp("* ", cfgbuf, 2)) {
>             return FT_INSFILE;
>         } else {
>           return FT_UNKOWN;
>         }
> }
> 
> ...
>   FileType ft = probe_file_type(cfgbuf, ...);
>   switch (ft)
>   {
>      case FT_PXECFG:
>        return handle_pxelinux_cfg(fn_ip, cfgbuf, rc);
>        break;
>      ...
>      case FT_UNKNOWN:
>        /* got to be a kernel */
>        memmove(...);
>        return rc;
>   }
> ...

I agree that this might be a good refactoring if the list grows bigger,
but as long as we only have these few entries here, it looks a little
bit over-engineered to me, so I'd rather prefer to keep the code in its
current shape right now.

 Thomas