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| author | Sami Tolvanen <samitolvanen@google.com> | 2021-02-23 13:59:52 -0800 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2021-02-23 14:10:44 -0800 |
| commit | 5e95325fbbbdea96de91e7bdb05fe95a3031e37d (patch) | |
| tree | 20a72533b15f1fac23f09b881d1e3ec63c1f2a31 | |
| parent | b33fff07e3e3817d94dbec7bf2040070ecd96d16 (diff) | |
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>
| -rw-r--r-- | Makefile | 3 |
1 files changed, 2 insertions, 1 deletions
@@ -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 |