[PATCH 08/22] kbuild: lto: remove duplicate dependencies from .mod files

Sami Tolvanen samitolvanen at google.com
Wed Jun 24 16:31:46 EDT 2020

With LTO, llvm-nm prints out symbols for each archive member
separately, which results in a lot of duplicate dependencies in the
.mod file when CONFIG_TRIM_UNUSED_SYMS is enabled. When a module
consists of several compilation units, the output can exceed the
default xargs command size limit and split the dependency list to
multiple lines, which results in used symbols getting trimmed.

This change removes duplicate dependencies, which will reduce the
probability of this happening and makes .mod files smaller and
easier to read.

Signed-off-by: Sami Tolvanen <samitolvanen at google.com>
 scripts/Makefile.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 82977350f5a6..82b465ce3ca0 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -291,7 +291,7 @@ endef
 # List module undefined symbols (or empty line if not enabled)
-cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | xargs echo
+cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | sort -u | xargs echo
 cmd_undef_syms = echo

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