Re: [Qemu-devel] Raspbian in QEMU

[Stefan Weil]

Am 12.03.2014 19:05, schrieb Peter Hanzel:
> Thanks.
> 
> Now it makes sense. Also google now works and led me to
> https://github.com/bavison/arm-mem.
> And there is SETEND used.
> 

It might be possible to handle that special case in QEMU without
implementing setend:

That instruction is only used in the implementation of function memcmp.
When TCG detects a setend instruction, it could check whether the
surrounding code has the signature of that memcmp implementation and add
code which calls a memcmp helper function. The setend instruction and
all the following code of memcmp would be handled as if it were a single
special multi byte machine instruction.

Is that special accelerated implementation of memcmp used in lots of ARM
systems, or is it only used for Raspberry PI? From the copyright in
memcpy.S I'd guess that it is RPi specific, so maybe the need for a QEMU
hack is not urgent enough.

Stefan

PS. Link to previous discussion on setend:
https://lists.gnu.org/archive/html/qemu-trivial/2013-08/msg00086.html
I cc Richard because he was / is involved, too.