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| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2021-05-18 18:59:15 -0500 |
|---|---|---|
| committer | Josh Poimboeuf <jpoimboe@redhat.com> | 2021-05-19 15:07:20 -0500 |
| commit | 8852c552402979508fdc395ae07aa8761aa46045 (patch) | |
| tree | c39b34036a4a25810ecc8dd6b8dbae28231c866c /scripts/Makefile.build | |
| parent | 48001d26c19f02c33795829ec9fc71a0d8d42413 (diff) | |
| download | lwn-8852c552402979508fdc395ae07aa8761aa46045.tar.gz lwn-8852c552402979508fdc395ae07aa8761aa46045.zip | |
kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_<obj> := n'
"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 <willy@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Diffstat (limited to 'scripts/Makefile.build')
| -rw-r--r-- | scripts/Makefile.build | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 949f723efe53..34d257653fb4 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -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)) |