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

[Ian Jackson <ian.jackson@xxxxxxxxxx>]

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 ?

> > 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.

Ian.

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