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Subject[PATCH v6 08/10] kbuild: make *.mod rule robust against too long argument error
Like built-in.a, the command length of the *.mod rule scales with
the depth of the directory times the number of objects in the Makefile.

Add $(obj)/ by the shell command (awk) instead of by Make's builtin

In-tree modules still have some room to the limit (ARG_MAX=2097152),
but this is more future-proof for big modules in a deep directory.

For example, you can build i915 as a module (CONFIG_DRM_I915=m) and
compare drivers/gpu/drm/i915/.i915.mod.cmd with/without this commit.

The issue is more critical for external modules because the M= path
can be very long as Jeff Johnson reported before [1].


Signed-off-by: Masahiro Yamada <>
Reviewed-by: Nicolas Schier <>
Tested-by: Nathan Chancellor <>

(no changes since v2)

Changes in v2:
- New patch

scripts/ | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/ b/scripts/
index 8f1a355df7aa..f546b5f1f33f 100644
--- a/scripts/
+++ b/scripts/
@@ -270,8 +270,8 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
$(call if_changed_rule,cc_o_c)
$(call cmd,force_checksrc)

-cmd_mod = echo $(addprefix $(obj)/, $(call real-search, $*.o, .o, -objs -y -m)) | \
- $(AWK) -v RS='( |\n)' '!x[$$0]++' > $@
+cmd_mod = echo $(call real-search, $*.o, .o, -objs -y -m) | \
+ $(AWK) -v RS='( |\n)' '!x[$$0]++ { print("$(obj)/"$$0) }' > $@

$(obj)/%.mod: FORCE
$(call if_changed,mod)
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