Re: [Qemu-devel] [PATCH v6 4/8] module: implement module loading function

[Daniel P. Berrange]

On Thu, Sep 12, 2013 at 09:36:43AM +0400, Michael Tokarev wrote:
> 12.09.2013 07:02, Fam Zheng wrote.
> >On Wed, 09/11 11:46, Richard Henderson wrote:
> >>On 09/11/2013 08:48 AM, Daniel P. Berrange wrote:
> >>>We know the precise list of valid modules when building QEMU,
> >>>so IMHO, this should just explicitly load each known module
> >>>name, and *not* readdir. Also it should do something along the
> >>>lines suggested their of poisoning exported symbols with a
> >>>build hash to guarantee the modules loaded match the original
> >>>binary and that the symbols change on every rebuild.
> >>
> >>We need not mangle the symbols, which could be complicated to
> >>actually implement, and irritating to work around within gdb.
> >>
> >Agree with this, some id or hash check should be enough.
> 
> A solution which I proposed at the very beginning -- to export
> a "hashed" init function from modules, and call it from the
> main executable.  Like, instead of, say, qemu_module_init(),
> call qemu_module_init_0xdeadbeaf(), where 0xdeadbeaf is a
> hash of some build-dependent value.  This should be enough
> to keep it going.
> 
> Ofcourse, if a module lacks this function, it should not be
> loaded.

Yep, that would be a reasonable way todo this. THe current
patches use attribute(constructor) so QEMU doesn't actually
call any explicit init function after dlopen()ing. That could
easily be changed though. 

Daniel
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