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| author |   Masahiro Yamada <masahiroy@kernel.org> | 2022-05-27 19:01:52 +0900 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2022-06-01 23:07:29 +0900 |
| commit | cd968b97c49214e6557381bddddacbd0e0fb696e (patch) | |
| tree | c7df9e88fd1767e7e335ea3ab0104d9fdde163b4 /scripts | |
| parent | kbuild: check static EXPORT_SYMBOL* by script instead of modpost (diff) | |
| download | linux-dev-cd968b97c49214e6557381bddddacbd0e0fb696e.tar.xz linux-dev-cd968b97c49214e6557381bddddacbd0e0fb696e.zip | |
kbuild: make built-in.a rule robust against too long argument error
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 scalability 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>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
Diffstat (limited to 'scripts')
| -rw-r--r-- | scripts/Makefile.build | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/scripts/Makefile.build b/scripts/Makefile.build index b6ae652a943f..3c1e20e4a4fc 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -377,9 +377,14 @@ $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ; # # Rule to compile a set of .o files into one .a file (without symbol table) # +# To make this rule robust against "Argument list too long" error, +# remove $(obj)/ prefix, and restore it by a shell command. 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) |