[Bug target/61904] Incorrect stack red-zoning on x86-64 code generation

[torvalds@linux-foundation.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61904

--- Comment #10 from Linus Torvalds <torvalds@linux-foundation.org> ---
(In reply to Andrew Pinski from comment #9)
> 
> The bad compiler versions are 4.5.0 (when debug_insn came in) to 4.8.3 and
> 4.9.0 and 4.9.1.

Ok, so we have no reasonable way of avoiding the problem compiler version. I
had hoped that we could just do a warning if people use 4.9.0/1, since they
aren't very common yet.

Ugh. We had one suggestion of having some post-compile checking pass, but that
one was (so far) just handwaving ("objdump + perl-script"). It doesn't sound
very pleasant.

The problem is that these things are a bitch to debug - they turn into these
completely impossible kernel oopses or corruption, and we were just very lucky
that this one case happened to be repeatable and pinpoint for two people. Are
there others? We have no way of knowing..

Anyway, thanks for the quick resolution, even if I'm now rather nervous about
existing compilers..