[Qemu-devel] Re: [PATCH v2] Build *-user targets as PIE

[Paolo Bonzini]

On 09/03/2009 04:38 PM, Paul Brook wrote:
> > PIE code usually is a bit slower. Approximately, 1% for i386 according to
> > some tests. RISC architectures should be affected less, since they have
> > more registers. On other hand we are getting rid from text relocations on
> > i386 which make executable loading slower. So...
>
> I think you've got that backwards.
> A traditional (fixed address) executable requires no load-time relocation for
> internal references because all addresses are known at static link time. PIE
> require the dynamic linker adjust all absolute addresses.

Yes, but since it's also compiled as PIE, there are no absolute 
addresses.  Previously QEMU was linked -shared but compiled as 
non-position independent code.  I am not sure whether only the 
self-virtualized machine would be subject to relocation, or also the 
outer one (maybe address space virtualization would also have to be 
taken into account?).

Anyway, as far as text relocations are concerned Kirill's pathc cannot 
make things worse.

Paolo