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[PATCH, BFD, LD, AArch64, 0/4] Add support for AArch64 BTI and PAC in the linker

Nick Clifton nickc@redhat.com
Mon Mar 11 12:30:00 GMT 2019 
Hi Sudi,

>>>> does -z ibt warn on x86_64?
>>>
>>> No - it does not.  

>> Maybe that comes automatically from the compiler driver though a quick
>> grep doesn't find me anything in the x86 backend.

Hmm, true - I cannot find it either.


> My understanding on this is a bit different though! Take 
> property-x86-ibt4.d test for example where a source without IBT note is 
> linked with -z ibt and it gives out an IBT note (and no error/warning). 
> Have I missed something?

Nope, it must be me.  


>>>     * With --bti specified, BTI is enabled in the output provided that
>>>       the BTI note was found in all of the input files.  If one or more

>> I feel this option is superfluous.

Hmm, OK,

> I agree that --force-bti looks like a more appropriate name for the 
> option. I am open to the idea of dropping --bti-nowarn 
> (--force-bti-nowarn) assuming that if need be, users can ignore the 
> warnings and go on doing what they want anyway.
> 
> @Nick, I hope that even though staying co-ordinated with x86_64 is 
> desirable (to me as well in my personal opinion), our reasoning on the 
> differences is convincing enough!

It is.   :-)

OK, lets go with enabling BTI automatically, providing that all of
the inputs have the required notes.  The --force-bti option does
what it says, but generates warnings for any input that does not
have a note.

I still think that --force-bti-nowarn would be a dangerous option
to have, but if your toolchain guys really think that it is necessary
then I am not going to object to it any longer.

Patch series with the revised option name(s) approved.

Cheers
  Nick
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