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Re: [RFC PATCH, binutils, ARM 10/11] Add support for creating ARM v8-M secure extensions import libraries


On 08/07/16 10:23, Thomas Preudhomme wrote:
> On Thursday 07 July 2016 11:55:28 Richard Earnshaw wrote:
>> On 29/03/16 15:46, Thomas Preudhomme wrote:
>>> On Wednesday 23 December 2015 16:01:50 Thomas Preud'homme wrote:
>>>> Hi,
>>>>
>>>> [Posting patch series as RFC]
>>>>
>>>> This patch is part of a patch series to add support for ARMv8-M security
>>>> extension[1] to GNU ld. This specific patch adds support for creating
>>>> *Secure Gateway* import libraries.
>>>>
>>>> ARM v8-M security extensions require [3] a secure gateway import library
>>>> to
>>>> be generated for non-secure executable to link against entry points in
>>>> secure executable. Such an import library must contain all global
>>>> function
>>>> symbols from the secure executable that have a corresponding special (ie
>>>> prefixed by "__acle_se_") symbol and these symbol should be made
>>>> absolute.
>>>>
>>>> This patch adds support for generating such an import library. It reuses
>>>> the code to generate an import library by requiring the user to add an
>>>> extra --cmse-implib option for him/her to state the intent to create a
>>>> *secure gateway* import library.
>>>>
>>>>
>>>> [1] Software requirements for ARMv8-M security extension are described in
>>>> document ARM-ECM-0359818 [2] [2] Available on http://infocenter.arm.com
>>>> in
>>>> Developer guides and articles > Software development > ARM®v8-M Security
>>>> Extensions: Requirements on Development Tools [3] See requirement 9 of
>>>> ARM-ECM-0359818 [2]
>>>
>>> Please find an updated patch below.
>>
>> One question: What happens if the user tries to use the new option
>> --cmse-implib on a target that doesn't support v8-M SE?  We should get
>> some sensible diagnostic in that case.
> 
> It depends whether the object file has __acle_se symbols or not. If it doesn't 
> (eg. normal armv7-m object file), the following happens:
> 
> ./ld/ld-new: implib.lib: no symbol found for import library
> ./ld/ld-new: implib.lib: failed to generate import library
> 
> Indeed, there is no entry function so the import library would be empty. This 
> is a generic error message, it could be improved indeed with specific logic to 
> detect such a case.
> 
> If one of the object file has an __acle_se symbol but is still not v8-m, the 
> following happens:
> 
> ./ld/ld-new: cmse-implib.o: Special symbol `__acle_se_exported_entry_veneer2' 
> only allowed for ARMv8-M architecture or later
> ./ld/ld-new: cannot size stub section: Invalid operation
> 
> Are the messages enough in your opinion or should we improve the wordings?
> 

No, I think that's sufficient.  Patch OK.

R.

> Best regards,
> 
> Thomas
> 


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