Re: [Qemu-devel] [PATCH v2 0/7] build-sys: Fix iscsi module loading failure

[Stefan Hajnoczi]

On Fri, Aug 22, 2014 at 06:54:16PM +0800, Fam Zheng wrote:
> The iscsi driver doesn't work if built with --enable-modules:
> 
> $ ~/build/last/qemu-img
> Failed to open module: /home/fam/build/master/block-iscsi.so: undefined 
> symbol: qmp_query_uuid
> qemu-img: Not enough arguments
> Try 'qemu-img --help' for more information
> 
> This fixes it by completely linking libqemuutil.a (now qemuutil.o) rather than
> on demand.
> 
> A few stub functions are added into libqemustub to make linker happy.
> 
> Lastly, iqn generation code is moved from iscsi.c to util, so that
> qmp_query_uuid or its stub is not missed.

Did you try ld --just-symbols=filename to include module symbol
dependencies when linking the QEMU binary?

The advantage is that the QEMU binary stays smaller.  And (depending on
whether you consider this a feature or not) it discourages people from
building out-of-tree modules.

Did you compare the before/after binary size with your patch?  Please
use size(1).

It's unfortunate to bloat the binary, not just from a code size
perspective, but also from a security perspective less code is better
(cannot be abused in return-oriented-programming).

Stefan

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