[PATCH RFC 17/43] x86/pie: Enable stack protector only if per-cpu stack canary is supported

[Hou Wenlong]

Since -fPIE option is not incompatible with -mcmode=kernel option, PIE
kernel would drop -mcmodel=kernel option. However, GCC would use %fs as
segment register for stack protector when -mcmodel=kernel option is
dropped. So only enable stack protector for PIE kernel if per-cpu stack
canary is supported.

Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
Cc: Thomas Garnier <thgarnie@xxxxxxxxxxxx>
Cc: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
---
 arch/x86/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 55cce8cdf9bd..b26941ef50ee 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -403,6 +403,7 @@ config PGTABLE_LEVELS
 
 config CC_HAS_SANE_STACKPROTECTOR
 	bool
+	default CC_HAS_CUSTOMIZED_STACKPROTECTOR if X86_PIE
 	default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) if 64BIT
 	default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC) $(CLANG_FLAGS))
 	help
-- 
2.31.1