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kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_<obj> := n'

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"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: b9ab5ebb14 ("objtool: Add CONFIG_STACK_VALIDATION option")
Fixes: ab3257042c ("jump_label, x86: Allow short NOPs")
Reported-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
This commit is contained in:
Josh Poimboeuf 2021-05-18 18:59:15 -05:00
parent 48001d26c1
commit 8852c55240
1 changed files with 3 additions and 2 deletions
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5
scripts/Makefile.build
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@ -268,7 +268,8 @@ 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) $$(objtool_dep) FORCE
$(call if_changed_rule,cc_o_c)
$(call cmd,force_checksrc)
@ -349,7 +350,7 @@ cmd_modversions_S = \
fi
endif
$(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
$(obj)/%.o: $(src)/%.S $$(objtool_dep) FORCE
$(call if_changed_rule,as_o_S)
targets += $(filter-out $(subdir-builtin), $(real-obj-y))