[llvm-dev] retpoline mitigation and 6.0

Chandler Carruth via llvm-dev llvm-dev at lists.llvm.org
Tue Feb 6 14:08:39 PST 2018


So, I was waiting to hear a definitive response on whether using aliases is
hard, and didn't see one here, which is why I haven't responded further.

However, a colleauge pointed me at an LKML thread where it seems there *is*
a definitive response?

I'm really looking for clear direction: we can try to implement custom
naming, but it will add undesirable complexity to the compiler. Do we need
it for the kernel? I have to ask because I genuinely don't know what is or
isn't reasonable in the kernel.

On Sat, Feb 3, 2018 at 6:36 AM David Woodhouse <dwmw2 at infradead.org> wrote:

> It's *only* the external thunk where it absolutely
> *does* become an ABI, where we care about consistency.


In the future, if there is such a powerful need for consistency, it would
be good to actually engage with more than one compiler community. =/ As I
said, I tried to talk to the GCC developers and made no progress but also
heard no strong arguments that this kind of consistency was actually
necessary.

I really do want to produce a feature that addresses the kernel's needs,
but we need to know what they are and have some chance to figure out how to
find a solution that also doesn't cause problems for the compiler. This is
just a note for the future though, the retpoline stuff is above.
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