diff mbox series

[v2,14/28] kbuild: lto: remove duplicate dependencies from .mod files

Message ID 20200903203053.3411268-15-samitolvanen@google.com (mailing list archive)
State New, archived
Headers show
Series [v2,01/28] x86/boot/compressed: Disable relocation relaxation | expand

Commit Message

Sami Tolvanen Sept. 3, 2020, 8:30 p.m. UTC 
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@google.com>
---
 scripts/Makefile.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Kees Cook Sept. 3, 2020, 10:29 p.m. UTC | #1 
On Thu, Sep 03, 2020 at 01:30:39PM -0700, Sami Tolvanen wrote:
> 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@google.com>

Reviewed-by: Kees Cook <keescook@chromium.org>
diff mbox series

Patch

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index b8f1f0d65a73..3bb36b4b853c 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -286,7 +286,7 @@  endef
 
 # List module undefined symbols (or empty line if not enabled)
 ifdef CONFIG_TRIM_UNUSED_KSYMS
-cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | xargs echo
+cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | sort -u | xargs echo
 else
 cmd_undef_syms = echo
 endif