tree ed580e8080a047597b44f12afc534adc3dce43c3
parent 560706d5d2589ef510f5436d69ab510a351b8cf7
author Ard Biesheuvel <ard.biesheuvel@linaro.org> 1547809087 +0100
committer Kees Cook <keescook@chromium.org> 1548022000 -0800

gcc-plugins: arm_ssp_per_task_plugin: fix for GCC 9+

GCC 9 reworks the way the references to the stack canary are
emitted, to prevent the value from being spilled to the stack
before the final comparison in the epilogue, defeating the
purpose, given that the spill slot is under control of the
attacker that we are protecting ourselves from.

Since our canary value address is obtained without accessing
memory (as opposed to pre-v7 code that will obtain it from a
literal pool), it is unlikely (although not guaranteed) that
the compiler will spill the canary value in the same way, so
let's just disable this improvement when building with GCC9+.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Kees Cook <keescook@chromium.org>