Commit: d77698df39a5 ("x86/build: Specify stack alignment for clang") intended to use the same stack alignment for clang as with gcc. The two compilers use different options to configure the stack alignment (gcc: -mpreferred-stack-boundary=n, clang: -mstack-alignment=n). The above commit assumes that the clang option uses the same parameter type as gcc, i.e. that the alignment is specified as 2^n. However clang interprets the value of this option literally to use an alignment of n, in consequence the stack remains misaligned. Change the values used with -mstack-alignment to be the actual alignment instead of a power of two. cc-option isn't used here with the typical pattern of KBUILD_CFLAGS += $(call cc-option ...). The reason is that older gcc versions don't support the -mpreferred-stack-boundary option, since cc-option doesn't verify whether the alternative option is valid it would incorrectly select the clang option -mstack-alignment.. Signed-off-by: Matthias Kaehlcke <mka@chromium.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Bernhard.Rosenkranzer@linaro.org Cc: Greg Hackmann <ghackmann@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Michael Davidson <md@google.com> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephen Hines <srhines@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dianders@chromium.org Link: http://lkml.kernel.org/r/20170817004740.170588-1-mka@chromium.org Signed-off-by: Ingo Molnar <mingo@kernel.org>