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 -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html