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authorSami Tolvanen <samitolvanen@google.com>2021-02-23 13:59:52 -0800
committerKees Cook <keescook@chromium.org>2021-02-23 14:10:44 -0800
commit5e95325fbbbdea96de91e7bdb05fe95a3031e37d (patch)
tree20a72533b15f1fac23f09b881d1e3ec63c1f2a31 /Makefile
parentb33fff07e3e3817d94dbec7bf2040070ecd96d16 (diff)
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kbuild: lto: force rebuilds when switching CONFIG_LTO
When doing non-clean builds and switching between CONFIG_LTO=n and CONFIG_LTO=y, the build system (correctly) didn't notice that assembly and LTO-excluded C object files were rewritten in place by objtool (to add the .orc_unwind* sections), since their build command lines were the same between CONFIG_LTO=y and CONFIG_LTO=n. The objtool step would fail: vmlinux.o: warning: objtool: file already has .orc_unwind section, skipping make: *** [Makefile:1194: vmlinux] Error 255 Avoid this by making sure the build will see a difference between an LTO and non-LTO build (by including "-fno-lto" in KBUILD_*FLAGS). This will get ignored when CC_FLAGS_LTO is present, and will not be included at all when CONFIG_LTO=n. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'Makefile')
-rw-r--r--Makefile3
1 files changed, 2 insertions, 1 deletions
diff --git a/Makefile b/Makefile
index 3189eacf3185..639873def1fd 100644
--- a/Makefile
+++ b/Makefile
@@ -910,7 +910,8 @@ KBUILD_LDFLAGS += -mllvm -import-instr-limit=5
endif
ifdef CONFIG_LTO
-KBUILD_CFLAGS += $(CC_FLAGS_LTO)
+KBUILD_CFLAGS += -fno-lto $(CC_FLAGS_LTO)
+KBUILD_AFLAGS += -fno-lto
export CC_FLAGS_LTO
endif