On Sun, Feb 11, 2018 at 9:56 AM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
>> - How common are those broken compilers?
>
> I *thought* it was rare (i.e. gcc 4.2) but while working on ..._AUTO I
> found breakage in akpm's 4.4 gcc, and all of Arnd's gccs due to some
> very strange misconfiguration between the gcc build environment and
> other options. So, it turns out this is unfortunately common. The good
> news is that it does NOT appear to happen with most distro compilers,
> though I've seen Android's compiler regress the global vs %gs at least
> once about a year ago.
Hmm. Ok, so it's not *that* common, and won't affect normal people.
That actually sounds like we could just
(a) make gcc 4.5 be the minimum required version
(b) actually error out if we find a bad compiler
Upgrading the minimum required gcc version to 4.5 is pretty much going
to happen _anyway_, because we're starting to rely on "asm goto" for
avoiding speculation.
End result: maybe we can make the configuration phase just use the
standard "does gcc support this flag" logic, and then just have a
separate script that is run to validate that gcc doesn't generate
garbage, and error out loudly if it does.
Linus
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