[PATCH] x86/boot: Fix if_changed build flip/flop

[Kees Cook <keescook@chromium.org>]

The if_changed kbuild function can only be used once per target. If not
it will effectively always trigger, flipping back and forth between the
two commands getting recorded. Instead, merge the two commands into a
single function to get stable build artifacts (i.e. .vmlinux.cmd).

Reported-by: Dirk Gouders <dirk@gouders.net>
Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Fixes: 98f78525371b ("x86/boot: Refuse to build with data relocations")
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/boot/compressed/Makefile | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index fa42f895fdde..169c2feda14a 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -106,9 +106,13 @@ define cmd_check_data_rel
 	done
 endef
 
+# We need to run two commands under "if_changed", so merge them into a
+# single invocation.
+quiet_cmd_check-and-link-vmlinux = LD      $@
+      cmd_check-and-link-vmlinux = $(cmd_check_data_rel); $(cmd_ld)
+
 $(obj)/vmlinux: $(vmlinux-objs-y) FORCE
-	$(call if_changed,check_data_rel)
-	$(call if_changed,ld)
+	$(call if_changed,check-and-link-vmlinux)
 
 OBJCOPYFLAGS_vmlinux.bin :=  -R .comment -S
 $(obj)/vmlinux.bin: vmlinux FORCE
-- 
2.17.1


-- 
Kees Cook
Pixel Security