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authorLinus Torvalds <torvalds@linux-foundation.org>2021-02-23 12:21:58 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-02-23 12:21:58 -0800
commit5cf0fd591f2e7833405bdc7ce2176c3502e8a11e (patch)
tree95d351a2e2e7c891506cae075367b8d0fe9c6ef5
parent21a6ab2131ab0644eeef70507e20273338bf065c (diff)
Kbuild: disable TRIM_UNUSED_KSYMS option
The removal of EXPORT_UNUSED_SYMBOL() in commit 367948220fce looks like (and was sold as) a no-op, but it actually had a rather serious and subtle side effect: the UNUSED_SYMBOLS option not only enabled the removed (unused) functionality, it also _disabled_ the TRIM_UNUSED_KSYMS functionality. And it turns out that TRIM_UNUSED_KSYMS is a huge time waste, and takes up a third of the kernel build time for me. For no actual upside, since no distro is likely to ever be able to enable it (because they all support external kernel modules). Rather than re-enable EXPORT_UNUSED_SYMBOL, this just disables the TRIM_UNUSED_KSYMS option by marking it broken. I'm tempted to just remove the support entirely, but maybe somebody has a use-case and can fix the behavior of it. I could have just disabled it for COMPILE_TEST, but it really smells like the TRIM_UNUSED_KSYMS option is badly done and not really useful, so this takes the more direct approach - let's see if anybody ever actually notices or complains. Cc: Miroslav Benes <mbenes@suse.cz> Cc: Emil Velikov <emil.l.velikov@gmail.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Jessica Yu <jeyu@kernel.org> Fixes: 367948220fce ("module: remove EXPORT_UNUSED_SYMBOL*") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--init/Kconfig1
1 files changed, 1 insertions, 0 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 8a2c0e41f1bb..ba8bd5256980 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -2274,6 +2274,7 @@ config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
config TRIM_UNUSED_KSYMS
bool "Trim unused exported kernel symbols"
+ depends on BROKEN
help
The kernel and some modules make many symbols available for
other modules to use via EXPORT_SYMBOL() and variants. Depending

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