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Message-ID: <20251006193839.1350626-1-elsk@google.com>
Date: Mon, 6 Oct 2025 19:38:38 +0000
From: HONG Yifan <elsk@...gle.com>
To: Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas.schier@...ux.dev>
Cc: Masahiro Yamada <masahiroy@...nel.org>, HONG Yifan <elsk@...gle.com>, kernel-team@...roid.com,
linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] kbuild: use $(obj)/ instead of $(src)/ for COPY
Similar to
commit 9a0ebe5011f4 ("kbuild: use $(obj)/ instead of $(src)/ for common pattern rules")
This change updates the COPY rule to use $(obj) instead of $(src). This
makes Kbuild rules like
always-y += libfoo/.foo.o.cmd
work when the user provides libfoo/.foo.o.cmd_shipped, even when obj and
src is different and src is an absolute path. This is useful when foo.o
and .foo.o.cmd are checked-in as prebuilts.
(Admittedly, `always-y += libfoo/.foo.o.cmd` is not recommended in
kbuild/modules.rst, "Several Subdirectories".)
For example, if
obj=.
src=/some/path
then the original rule
$(obj)/%: $(src)/%_shipped
expands to
./%: /some/path/%_shipped
And when matching against the above example, the stem is just `bar.o`
[^1] so the following is looked up:
libfoo/.foo.o.cmd: libfoo//some/path/.foo.o.cmd_shipped
... and it cannot be matched.
With this change, the rule expands to
./%: ./%_shipped
... and it should work, at least for files that does not have a more
specific pattern rule.
NOTE: that after this change, code like
bar-y += libfoo/foo.o
... with libfoo/foo.o_shipped provided still DOES NOT work, because
the pattern rule $(obj)/%.o takes priority. For .o_shipped files,
the user still needs an explicit `$(obj)/%.o: $(obj)/%.o_shipped` rule
in its own Kbuild file.
[^1]: https://www.gnu.org/software/make/manual/html_node/Pattern-Match.html
Signed-off-by: HONG Yifan <elsk@...gle.com>
---
scripts/Makefile.lib | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 1d581ba5df66..e066b7b00bcc 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -272,7 +272,7 @@ endef
quiet_cmd_copy = COPY $@
cmd_copy = cat $< > $@
-$(obj)/%: $(src)/%_shipped
+$(obj)/%: $(obj)/%_shipped
$(call cmd,copy)
# Touch a file
--
2.51.0.618.g983fd99d29-goog
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