On Mon, Nov 12, 2018 at 7:54 AM, Masahiro Yamada <[email protected]> wrote: > On Mon, Nov 12, 2018 at 5:29 PM Kees Cook <[email protected]> wrote: >> >> On Sun, Nov 11, 2018 at 9:06 PM, Masahiro Yamada >> <[email protected]> wrote: >> > gcc-x86_64-has-stack-protector.sh was introduced by commit 4f7fd4d7a791 >> > ("[PATCH] Add the -fstack-protector option to the CFLAGS") in 2006 >> > to work around buggy compilers. >> > >> > gcc-x86_32-has-stack-protector.sh was introduced by commit 60a5317ff0f4 >> > ("x86: implement x86_32 stack protector"), which did not clearly state >> > whether compilers were still producing broken code at that time. >> > >> > Now, the minimum reuquired GCC version is 4.6, which was released in >> > 2011. Probably, we can dump these old compiler checks. >> >> NAK. We need to keep this because we've seen recent regressions with >> stack protection (e.g. gcc briefly used global instead of tls for the >> canary, which silently broke the use of stack protectors). Since the >> gcc/kernel "API" for the canary is so fragile we need to keep these >> tests to make sure things end up where they're expected. > > Thanks for your feedback. > > I did not know this is still fragile even after ten years time. > > One more curious thing is, x86 is the only arch ever > that has had this kind of script check.
Presently, yes -- x86 is the only arch with non-global canaries, though something may be coming soon for arm64. However, that case may be more detectable with cc-option. The trouble with gcc was that the default switched at one point. :( -- Kees Cook
