[Qemu-devel] Re: PRoot: A Step Forward for QEMU User-Mode

[Cédric VINCENT]

Hi Riku,

Riku Voipio <riku.voipio <at> iki.fi> writes:
> 
> Similar thing is done with scratchbox2, but with LD_PRELOAD instead of
> ptrace. LD_PRELOAD for all around the corners (static binaries etc) and
> the slowdown is major. ptrace would make at least the former problem
> go away.
> 
> However, why do it behind Qemu's back anyway? In linux-user we already pass
> most filesystem access via path() function. Any needed filesystem redirections
> could be done there within Qemu itself.

I first tried to fix the path translation mechanism in QEMU but it has
introduced too many changes and the validation was not that easy.
Finally it was more convenient to resolve this problematic in an
external tool, hence PRoot.

I don't think we will merge its path translation mechanism [1] and its
interpreter support [2] back into QEMU since PRoot currently works
fine with any version of QEMU, however I will be glad to help you to
do so, if you wish.

We didn't benchmark the performance of PRoot yet but we know there's
plenty of room for improvement however we will not address that point
until next year.  I would say this is not an issue for now since most
of the CPU time is generally consumed by the emulated application
itself.

Regards,
Cédric.

[1] man 7 path_resolution
[2] man 2 execve