46 lines
1.8 KiB
Diff
46 lines
1.8 KiB
Diff
From: Masahiro Yamada <yamada.masahiro@socionext.com>
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Date: Fri, 30 Mar 2018 13:15:26 +0900
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Subject: kbuild: use -fmacro-prefix-map to make __FILE__ a relative path
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Origin: https://git.kernel.org/linus/a73619a845d5625079cc1b3b820f44c899618388
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The __FILE__ macro is used everywhere in the kernel to locate the file
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printing the log message, such as WARN_ON(), etc. If the kernel is
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built out of tree, this can be a long absolute path, like this:
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WARNING: CPU: 1 PID: 1 at /path/to/build/directory/arch/arm64/kernel/foo.c:...
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This is because Kbuild runs in the objtree instead of the srctree,
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then __FILE__ is expanded to a file path prefixed with $(srctree)/.
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Commit 9da0763bdd82 ("kbuild: Use relative path when building in a
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subdir of the source tree") improved this to some extent; $(srctree)
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becomes ".." if the objtree is a child of the srctree.
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For other cases of out-of-tree build, __FILE__ is still the absolute
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path. It also means the kernel image depends on where it was built.
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A brand-new option from GCC, -fmacro-prefix-map, solves this problem.
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If your compiler supports it, __FILE__ is the relative path from the
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srctree regardless of O= option. This provides more readable log and
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more reproducible builds.
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Please note __FILE__ is always an absolute path for external modules.
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Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
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---
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Makefile | 3 +++
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1 file changed, 3 insertions(+)
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--- a/Makefile
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+++ b/Makefile
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@@ -857,6 +857,9 @@ KBUILD_CFLAGS += $(call cc-option,-Wer
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# Require designated initializers for all marked structures
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KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
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+# change __FILE__ to the relative path from the srctree
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+KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
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+
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# use the deterministic mode of AR if available
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KBUILD_ARFLAGS := $(call ar-option,D)
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