Re: [Xen-devel] [PATCH v1 1/6] docs: add feature document for Xen hypervisor sysfs-like support

[Jan Beulich <jbeulich@xxxxxxxx>]

On 30.09.2019 10:17, Jürgen Groß wrote:
> On 27.09.19 17:19, Ian Jackson wrote:
>> Jürgen Groß writes ("Re: [PATCH v1 1/6] docs: add feature document for Xen 
>> hypervisor sysfs-like support"):
>>> On 27.09.19 15:37, Ian Jackson wrote:
>>>> I think this is ASCII printing characters with the exception of
>>>>     ! " ` $ % ^ & * = + { } ' ~ < > / \ |
>>>>
>>>> I struggle to find a principled explanation for this particular
>>>> exclusion set (apart from /), considering that following are
>>>> included:
>>>>     - @ _ . : ( ) [ ] # , ;
>>>>
>>>> Could we borrow some existing permitted character set ?  If we are
>>>> permitting shell metacharacters why not just permit all printable
>>>> ASCII except / ?
>>>
>>> Hmm, maybe we should allow just the "Posix portable file name character
>>> set"? That would be [-._0-9A-Za-z]. And we should explicitly not allow
>>> the key names "." and "..".
>>
>> I agree about "." and "..".
>>
>> I'm not sure the "Posix portable file name character set" is a very
>> good guide.  Posix will be pretty restricted there.  What is the legal
>> set in a Linux sysfs filename ?
> 
> Everything but "/" and "\0".
> 
>>
>>>> Do you mean "any 7-bit byte", or octet values 32-126 (0x20-0x7e)
>>>> inclusive, or something else ?
>>>
>>> :-)
>>>
>>> As I'd like to support e.g. the .config file contents of the hypervisor
>>> build I guess I need (0x01-0xff) inclusive, right?
>>
>> The .config file I have here does not seem to contain any control
>> characters.  If it did surely that would be a bug?  If you want this
>> you obviously do need to permit newlines and spaces and perhaps tabs
>> too.
> 
> .config can contain user supplied strings. While not making much sense
> to have unprintable characters in there I don't see how to prevent them.

Does / can't kconfig reject them?

Jan

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