Re: [Xen-devel] [PATCH 19/34] xen/arm: Provide eabi wrapper for __aeabi_mem* functions

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-03-25 at 18:12 +0000, Julien Grall wrote:
> Hi Ian,
> 
> On 03/25/2014 05:25 PM, Ian Campbell wrote:
> > On Tue, 2014-03-25 at 16:55 +0000, Julien Grall wrote:
> >> Clang doesn't provide function __aebai_mem*, implement generically as a 
> >> wrapper
> >> for mem* function provided by Xen.
> > 
> > Where are the references to these functions coming from if not from the
> > compiler?
> 
> Theses functions are called by the code generated by the compiler.

And who normally provides them when building with clang? Some sort of
libclang I guess?

> Removing this file will result to the following errors:
> 
> /local/home/julien/works/arndale/xen/xen/common/symbols-dummy.o -o 
> /local/home/julien/works/arndale/xen/xen/.xen-syms.0
> prelink.o: In function `dump_node':
> /local/home/julien/works/arndale/xen/xen/common/device_tree.c:259: undefined 
> reference to `__aeabi_memset'
> prelink.o: In function `get_cpu_idle_time':
> /local/home/julien/works/arndale/xen/xen/common/schedule.c:178: undefined 
> reference to `__aeabi_memset'
> prelink.o: In function `construct_dom0':
> /local/home/julien/works/arndale/xen/xen/arch/arm/domain_build.c:1055: 
> undefined reference to `__aeabi_memset'
> prelink.o: In function `wallclock_time':
> /local/home/julien/works/arndale/xen/xen/arch/arm/time.c:267: undefined 
> reference to `__aeabi_memset'
> prelink.o: In function `scheduler_init':
> /local/home/julien/works/arndale/xen/xen/common/schedule.c:1368: undefined 
> reference to `__aeabi_memcpy'
> /local/home/julien/works/arndale/xen/xen/common/schedule.c:1377: undefined 
> reference to `__aeabi_memcpy'
> 
>  
> > Are you sure this isn't something usually provided by some clang
> > equivalent of libgcc?
> 
> Yes. Linux on LLVM has the same issue.

Kernels often use -nostdlib and other options which intentionally
disable the default linkage of libgcc/libclang type libraries.

>  See page 22:
> https://events.linuxfoundation.org/images/stories/pdf/lcjp2012_charlebois.pdf?a
> 
> Regards,
> 



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