[openssl-dev] arch (ARM) capabilities

[Andy Polyakov]

>> I want something more programmatic, more general. I want to deliver
>> a piece of software that will run on ARM architectures and will
>> issue a warning or something like that if the user does not have an
>> OpenSSL library set to work with ARM Crypto Extension.
> 
> What does "set to work" mean? Compiled with support for ARMv8 extensions
> or actually uses them? While there is no direct means to tell either,
> there are indirect methods that you might find usable. To see if it's
> compiled with support for ARMv8 you might be able to use dlsym to lookup
> either of symbols specific to ARMv8 code. As for those subroutines
> actually being used, if you trust OpenSSL capability detection, you can
> simply look at /proc/cpuinfo, or replicate OpenSSL's detection.

I'd say that if it is that important, then it would be more appropriate
to bundle OpenSSL copy with your application. I mean if faith in
system-provided code is that low, then you'd have to answer questions if
you can trust that target code is actually called despite its presence
and should-be-called detection. And then the only way to be sure that it
works as advertised is to bundle own copy and debug it to verify that
everything is in shape.