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When CONFIG_TRIM_UNUSED_KSYMS is enabled, Kbuild recursively traverses the directory tree to determine which EXPORT_SYMBOL to trim. If an EXPORT_SYMBOL turns out to be unused by anyone, Kbuild begins the second traverse, where some source files are recompiled with their EXPORT_SYMBOL() tuned into a no-op. Linus stated negative opinions about this slowness in commits: -5cf0fd591f("Kbuild: disable TRIM_UNUSED_KSYMS option") -a555bdd0c5("Kbuild: enable TRIM_UNUSED_KSYMS again, with some guarding") We can do this better now. The final data structures of EXPORT_SYMBOL are generated by the modpost stage, so modpost can selectively emit KSYMTAB entries that are really used by modules. Commitf73edc8951("kbuild: unify two modpost invocations") is another ground-work to do this in a one-pass algorithm. With the list of modules, modpost sets sym->used if it is used by a module. modpost emits KSYMTAB only for symbols with sym->used==true. BTW, Nicolas explained why the trimming was implemented with recursion: https://lore.kernel.org/all/2o2rpn97-79nq-p7s2-nq5-8p83391473r@syhkavp.arg/ Actually, we never achieved that level of optimization where the chain reaction of trimming comes into play because: - CONFIG_LTO_CLANG cannot remove any unused symbols - CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is enabled only for vmlinux, but not modules If deeper trimming is required, we need to revisit this, but I guess that is unlikely to happen. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
175 lines
2.0 KiB
Plaintext
175 lines
2.0 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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#
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# NOTE! Don't add files that are generated in specific
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# subdirectories here. Add them in the ".gitignore" file
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# in that subdirectory instead.
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#
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# NOTE! Please use 'git ls-files -i -c --exclude-per-directory=.gitignore'
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# command after changing this file, to see if there are
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# any tracked files which get ignored after the change.
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#
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# Normal rules (sorted alphabetically)
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#
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.*
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*.a
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*.asn1.[ch]
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*.bin
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*.bz2
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*.c.[012]*.*
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*.cover
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*.dt.yaml
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*.dtb
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*.dtbo
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*.dtb.S
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*.dtbo.S
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*.dwo
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*.elf
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*.gcno
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*.gz
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*.i
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*.ko
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*.lex.c
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*.ll
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*.lst
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*.lz4
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*.lzma
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*.lzo
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*.mbx
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*.mod
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*.mod.c
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*.o
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*.o.*
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*.patch
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*.rmeta
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*.rpm
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*.rsi
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*.s
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*.so
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*.so.dbg
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*.su
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*.symtypes
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*.symversions
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*.tab.[ch]
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*.tar
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*.xz
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*.zst
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Module.symvers
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modules.order
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#
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# Top-level generic files
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#
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/linux
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/modules-only.symvers
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/vmlinux
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/vmlinux.32
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/vmlinux.map
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/vmlinux.symvers
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/vmlinux-gdb.py
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/vmlinuz
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/System.map
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/Module.markers
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/modules.builtin
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/modules.builtin.modinfo
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/modules.nsdeps
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#
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# RPM spec file (make rpm-pkg)
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#
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/*.spec
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/rpmbuild/
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#
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# Debian directory (make deb-pkg)
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#
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/debian/
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#
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# Snap directory (make snap-pkg)
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#
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/snap/
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#
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# tar directory (make tar*-pkg)
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#
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/tar-install/
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#
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# We don't want to ignore the following even if they are dot-files
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#
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!.clang-format
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!.cocciconfig
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!.get_maintainer.ignore
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!.gitattributes
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!.gitignore
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!.kunitconfig
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!.mailmap
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!.rustfmt.toml
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#
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# Generated include files
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#
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/include/config/
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/include/generated/
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/arch/*/include/generated/
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# stgit generated dirs
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patches-*
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# quilt's files
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patches
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series
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# ctags files
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tags
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TAGS
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# cscope files
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cscope.*
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ncscope.*
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# gnu global files
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GPATH
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GRTAGS
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GSYMS
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GTAGS
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# id-utils files
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ID
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*.orig
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*~
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\#*#
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#
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# Leavings from module signing
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#
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extra_certificates
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signing_key.pem
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signing_key.priv
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signing_key.x509
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x509.genkey
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# Kconfig presets
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/all.config
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/alldef.config
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/allmod.config
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/allno.config
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/allrandom.config
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/allyes.config
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# Kconfig savedefconfig output
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/defconfig
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# Kdevelop4
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*.kdev4
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# Clang's compilation database file
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/compile_commands.json
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# Documentation toolchain
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sphinx_*/
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# Rust analyzer configuration
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/rust-project.json
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