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

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 03/26/2014 04:11 PM, Ian Campbell wrote:
> On Wed, 2014-03-26 at 16:01 +0000, Julien Grall wrote:
>> On 03/26/2014 03:47 PM, Ian Campbell wrote:
>>> On Wed, 2014-03-26 at 15:38 +0000, Julien Grall wrote:
>>>> On 03/26/2014 10:39 AM, Ian Campbell wrote:
>>>>> 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?
>>>>
>>>> I've tried to compile a same compilation unit with gcc and clang. gcc is
>>>> inlining the call to __aebi_*.
>>>
>>> That is orthogonal to the question I asked.
>>>
>>> What in a clang based system normally provides __aeabi_*?
>>>
>>> Your choices are "a libclang thing", "the libc", "something else".
>>
>> Sorry I spent the last couple of hours to try to find who is providing
>> the __aebi_* functions.
>>
>> For userspace binary it's providing by the glibc.
> 
> Are we not telling clang not to use with libc (via --nostdlib or
> similar)? I thought we did for gcc too but I can't actually see the
> code. Actually maybe I wouldn't expect it to suppress this sort of
> thing.

We directly use ld to link the binary. So no need of --nosdtlib
--nolibgcc (see arch/arm/Makefile $(TARGET)-syms).

> I see __eabi_memset even in a gcc based glibc, so I think this isn't
> clang specific, just differences in the optmisers/inliners etc.
> 
> Anyhow, it looks like this is actually part of the ABI spec:
> http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ihi0043d/index.html
> 
> The correct wording for the commit message would therefore be something
> like "Provide __aeabi_memset et al which are required by EABI and which
> compilers expect to be provided by the libc implementation", or
> something like that.

Thanks I will rework the commit message.

-- 
Julien Grall

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