[PATCH] x86: Skip ISA check for always_inline in system headers

[Jakub Jelinek]

On Thu, Mar 25, 2021 at 03:40:51PM +0100, Richard Biener wrote:
> I think the "proper" way to do this is to have 'open' above end up
> refering to the out-of-line 'open' in the DSO, _not_ to emit the
> fortification wrapper out-of-line.  But then, yes, it shouldn't
> be always-inline then.  It should be like the former extern inline
> extension.

It is extern inline __attribute__((gnu_inline, always_inline, artificial))
I think.  But the always_inline is completely intentional there,
we don't want the decision whether to inline it or not being done based on
its size, amount of functions already inlined into the caller before,
whether the call is cold or hot, etc.  It is a matter of security.
If it is taking address, we want the library routine in that case, sure.

> But we have existing issues with [target] options differing and existing old
> uses of always_inline (like the fortification wrappers).  Adding a new attribute
> will not fix those issues.  Do you propose to not fix them and instead only
> fix the new general_regs_only always-inline function glibc wants to add?

Yes.
Basically solve the problem for the fortification wrappers and rdtsc or
whatever other always inlines don't really require any specific
target/optimize options.

> IMHO we have to fix the existing always_inline and we need a _new_
> attribute to get the desired diagnostics on intrinsics.  Something
> like __attribute__((need_target("avx"))) for AVX intrinsics?

Or, if we go this route in addition to adding
at least a new attributes for the "diagnose taking address without
direct call", we'd need probably not just that,
but also pragma way to specify it for a lot of functions together,
otherwise it would be a maintainance nightmare.

	Jakub