[U-Boot] [PATCH] pxe: Allow use of environment variables in append string

[Hans de Goede]

Hi,

On 08/01/2014 09:07 PM, Stephen Warren wrote:
> On 08/01/2014 03:21 AM, Hans de Goede wrote:
>> Use run_command("setenv bootargs <label->append>") so that environment
>> variables (e.g. $console) can be used in append strings.
> 
> I'm slightly worried that this changes the semantics of the append line in the PXE/extlinux config file. Namely, you suddenly have to start worrying about escaping any $ signs or semi-colons etc..

I'm not that worried about $ needing escaping, as I cannot think
of any kernel commandline options using $, maybe they exist but if
they do they are quite rare.

But you make a good point about the ; I know some kernel cmdline
options which use those...

> 
>> diff --git a/common/cmd_pxe.c b/common/cmd_pxe.c
> 
>>       if (!localcmd)
>>           return -ENOENT;
>>
>> -    if (label->append)
>> -        setenv("bootargs", label->append);
>> +    if (label->append) {
>> +        bootargs = malloc(strlen("setenv bootargs ") +
>> +                  strlen(label->append) + 1);
>> +        if (!bootargs)
>> +            return 1;
> 
> Shouldn't this return a -ve error code for consistency with the other pre-existing error case I quoted above.

Yeah this is weird, I copy pasted this from
the label_boot() function, of which is a special version,
also label_boot() is the only caller of label_localboot()
(where this hunk applies), and it does not check the return
value at all...

I could make it -ENOMEM if you prefer.


>> +        strcpy(bootargs, "setenv bootargs ");
>> +        strcat(bootargs, label->append);
>> +        run_command(bootargs, 0);
> 
> Using whatever C function that the shell uses to expand variable references in the command-line, rather than run_command(), would at least avoid the issue of ; in label->append causing part of label->append after the ; to be execututed as a separate command.

Ack, I'll look into that and post a v2 with that change.

> There would still be the issue of $ suddenly meaning something different.

Right, but as said I'm not really worried about that.

Regards,

Hans