Now that Kconfig has the capability to run shell command when
generating CONFIG_* we can use it in some cases to test CFLAGS.

CONFIG_INDIRECT_THUNK is a good example that wants to exist both in
Makefile and as a C macro, which Kconfig do. So use Kconfig to
generate CONFIG_INDIRECT_THUNK and have the CFLAGS depends on that.

Signed-off-by: Anthony PERARD <anthony.per...@citrix.com>
Acked-by: Andrew Cooper <andrew.coop...@citrix.com>
---
 xen/arch/x86/Kconfig  | 3 +++
 xen/arch/x86/Rules.mk | 4 +---
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index f853c0456404..8149362bdef3 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -31,6 +31,9 @@ config ARCH_DEFCONFIG
        string
        default "arch/x86/configs/x86_64_defconfig"
 
+config INDIRECT_THUNK
+       def_bool $(cc-option,-mindirect-branch-register)
+
 menu "Architecture Features"
 
 source "arch/Kconfig"
diff --git a/xen/arch/x86/Rules.mk b/xen/arch/x86/Rules.mk
index 92fdbe9d6822..a2c257fb95b2 100644
--- a/xen/arch/x86/Rules.mk
+++ b/xen/arch/x86/Rules.mk
@@ -71,11 +71,9 @@ CFLAGS += -DGCC_HAS_VISIBILITY_ATTRIBUTE
 endif
 
 # Compile with thunk-extern, indirect-branch-register if avaiable.
-ifneq ($(call cc-option,$(CC),-mindirect-branch-register,n),n)
+ifeq ($(CONFIG_INDIRECT_THUNK),y)
 CFLAGS += -mindirect-branch=thunk-extern -mindirect-branch-register
-CFLAGS += -DCONFIG_INDIRECT_THUNK
 CFLAGS += -fno-jump-tables
-export CONFIG_INDIRECT_THUNK=y
 endif
 
 # If supported by the compiler, reduce stack alignment to 8 bytes. But allow
-- 
Anthony PERARD


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