From 8454cfe408413489635e5fd91bffb3998919f211 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Tue, 18 May 2021 18:59:15 -0500 Subject: [PATCH] kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_ := n' [ Upstream commit 8852c552402979508fdc395ae07aa8761aa46045 ] "OBJECT_FILES_NON_STANDARD_vma.o := n" has a dependency bug. When objtool source is updated, the affected object doesn't get re-analyzed by objtool. Peter's new variable-sized jump label feature relies on objtool rewriting the object file. Otherwise the system can fail to boot. That effectively upgrades this minor dependency issue to a major bug. The problem is that variables in prerequisites are expanded early, during the read-in phase. The '$(objtool_dep)' variable indirectly uses '$@', which isn't yet available when the target prerequisites are evaluated. Use '.SECONDEXPANSION:' which causes '$(objtool_dep)' to be expanded in a later phase, after the target-specific '$@' variable has been defined. Fixes: b9ab5ebb14ec ("objtool: Add CONFIG_STACK_VALIDATION option") Fixes: ab3257042c26 ("jump_label, x86: Allow short NOPs") Reported-by: Matthew Wilcox Signed-off-by: Josh Poimboeuf Signed-off-by: Sasha Levin --- scripts/Makefile.build | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 03df22412f86..1261f75cb4e7 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -257,7 +257,8 @@ define rule_as_o_S endef # Built-in and composite module parts -$(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE +.SECONDEXPANSION: +$(obj)/%.o: $(src)/%.c $(recordmcount_source) $$(objtool_dep) FORCE $(call if_changed_rule,cc_o_c) $(call cmd,force_checksrc) @@ -340,7 +341,7 @@ cmd_modversions_S = \ fi endif -$(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE +$(obj)/%.o: $(src)/%.S $$(objtool_dep) FORCE $(call if_changed_rule,as_o_S) targets += $(filter-out $(subdir-obj-y), $(real-obj-y)) $(real-obj-m) $(lib-y)