[CFR] mge driver / elf reloc

[Warner Losh]

On Jul 20, 2014, at 5:10 PM, John-Mark Gurney <jmg at funkthat.com> wrote:

> Tim Kientzle wrote this message on Sun, Jul 20, 2014 at 15:25 -0700:
>> 
>> On Jul 20, 2014, at 3:05 PM, John-Mark Gurney <jmg at funkthat.com> wrote:
>> 
>>> Ian Lepore wrote this message on Sat, Jul 19, 2014 at 16:54 -0600:
>>>> Sorry to take so long to reply to this, I'm trying to get caught up.  I
>>>> see you've already committed the mge fixes.  I think the ELF alignment
>>>> fix looks good and should also be committed.
>>> 
>>> So, re the elf alignment...
>>> 
>>> I think we should get a set of macros that handle load/stores to/from
>>> unaligned addresses that are transparent to the caller....  I need
>>> these for some other code I'm writing... 
>>> 
>>> I thought Open/Net had these available, but I can't seem to find them
>>> right now...
>> 
>> $ man 9 byteorder
>> 
>> is most of what you want, lacking only some aliases to pick
>> the correct macro for native byte order.
> 
> Um, those doesn't help if you want native endian order…

Ummm, yes they do. enc converts from native order. dec decodes to native byte
order. They are more general cases than the ntoh* functions that are more traditional
since they also work on byte streams that may not be completely aligned when
sitting in memory. Which is what you are asking for.

> Also, only the enc/dec functions are documented to work on non-aligned
> address, so that doesn't help in most cases…

They work on all addresses. They are even documented to work on any address:

     The be16enc(), be16dec(), be32enc(), be32dec(), be64enc(), be64dec(),
     le16enc(), le16dec(), le32enc(), le32dec(), le64enc(), and le64dec()
     functions encode and decode integers to/from byte strings on any align-
     ment in big/little endian format.

So they are quite useful in general. Peeking under the covers at the implementation
also shows they will work for any alignment, so I’m having trouble understanding
where this objection is really coming from.

Warner

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