Messages in this thread Patch in this message |  | | From | Masahiro Yamada <> | Subject | [PATCH v2 23/26] kbuild: make built-in.a rule robust against too long argument error | Date | Sun, 1 May 2022 17:40:29 +0900 |
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Kbuild runs at the top of objtree instead of changing the working directory to subdirectories. I think this design is nice overall but some commands have a scapability issue.
The build command of built-in.a is one of them whose length scales with:
O(D * N)
Here, D is the length of the directory path (i.e. $(obj)/ prefix), N is the number of objects in the Makefile, O() is the big O notation.
The deeper directory the Makefile directory is located, the more easily it will hit the too long argument error.
We can make it better. Trim the $(obj)/ by Make's builtin function, and restore it by a shell command (sed).
With this, the command length scales with:
O(D + N)
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 builtin (CONFIG_DRM_I915=y) and compare drivers/gpu/drm/i915/.built-in.a.cmd with/without this commit.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> ---
Changes in v2: - New patch
scripts/Makefile.build | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build index cc8f362f58e2..a9236add4864 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -370,7 +370,10 @@ $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ; # quiet_cmd_ar_builtin = AR $@ - cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs) + cmd_ar_builtin = rm -f $@; \ + echo $(patsubst $(obj)/%,%,$(real-prereqs)) | \ + sed -E 's:([^ ]+):$(obj)/\1:g' | \ + xargs $(AR) cDPrST $@ $(obj)/built-in.a: $(real-obj-y) FORCE $(call if_changed,ar_builtin) -- 2.32.0
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