[PATCH] x86: Detect CFI support in the assembler at runtime

... instead of using a CONFIG option. The config option still controls
if the resulting executable actually has unwind information.

This is useful to prevent compilation errors when users select
CONFIG_STACK_UNWIND on old binutils and also allows to use
CFI in the future for non kernel debugging applications.

Cc: jbeulich@novell.com
Cc: sam@ravnborg.org

Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 7 insertions, 0 deletions

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 3d523899fdc0..7adef12a0c26 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -63,6 +63,13 @@ as-option = $(shell if $(CC) $(CFLAGS) $(1) -Wa,-Z -c -o /dev/null \
              -xassembler /dev/null > /dev/null 2>&1; then echo "$(1)"; \
              else echo "$(2)"; fi ;)
 
+# as-instr
+# Usage: cflags-y += $(call as-instr, instr, option1, option2)
+
+as-instr = $(shell if echo -e "$(1)" | $(AS) -Z -o astest$$$$.out \
+                   2>&1 >/dev/null ; then echo "$(2)"; else echo "$(3)"; fi; \
+                   rm -f astest$$$$.out)
+
 # cc-option
 # Usage: cflags-y += $(call cc-option, -march=winchip-c6, -march=i586)