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2021-09-03kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANGSami Tolvanen1-12/+0
With CONFIG_LTO_CLANG, we currently link modules into native code just before modpost, which means with TRIM_UNUSED_KSYMS enabled, we still look at the LLVM bitcode in the .o files when generating the list of used symbols. As the bitcode doesn't yet have calls to compiler intrinsics and llvm-nm doesn't see function references that only exist in function-level inline assembly, we currently need a whitelist for TRIM_UNUSED_KSYMS to work with LTO. This change moves module LTO linking to happen earlier, and thus avoids the issue with LLVM bitcode and TRIM_UNUSED_KSYMS entirely, allowing us to also drop the whitelist from gen_autoksyms.sh. Link: https://github.com/ClangBuiltLinux/linux/issues/1369 Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Alexander Lobakin <alobakin@pm.me> Tested-by: Alexander Lobakin <alobakin@pm.me> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-02-28kbuild: fix UNUSED_KSYMS_WHITELIST for Clang LTOMasahiro Yamada1-9/+26
Commit fbe078d397b4 ("kbuild: lto: add a default list of used symbols") does not work as expected if the .config file has already specified CONFIG_UNUSED_KSYMS_WHITELIST="my/own/white/list" before enabling CONFIG_LTO_CLANG. So, the user-supplied whitelist and LTO-specific white list must be independent of each other. I refactored the shell script so CONFIG_MODVERSIONS and CONFIG_CLANG_LTO handle whitelists in the same way. Fixes: fbe078d397b4 ("kbuild: lto: add a default list of used symbols") Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
2021-02-12kbuild: fix CONFIG_TRIM_UNUSED_KSYMS build for ppc64Masahiro Yamada1-0/+3
Stephen Rothwell reported a build error on ppc64 when CONFIG_TRIM_UNUSED_KSYMS is enabled. Jessica Yu pointed out the cause of the error with the reference to the ppc64 ELF ABI: "Symbol names with a dot (.) prefix are reserved for holding entry point addresses. The value of a symbol named ".FN", if it exists, is the entry point of the function "FN". As it turned out, CONFIG_TRIM_UNUSED_KSYMS has never worked for ppc64, but this issue has been unnoticed until recently because this option depends on !UNUSED_SYMBOLS hence is disabled by all{mod,yes}config. (Then, it was uncovered by another patch removing UNUSED_SYMBOLS.) Removing the dot prefix in scripts/gen_autoksyms.sh fixes the issue. Please note it must be done before 'sort -u' because modules have both ._mcount and _mcount undefined when CONFIG_FUNCTION_TRACER=y. Link: https://lore.kernel.org/lkml/20210209210843.3af66662@canb.auug.org.au/ Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Tested-by: Jessica Yu <jeyu@kernel.org>
2020-03-03kbuild: generate autoksyms.h earlyQuentin Perret1-1/+2
When doing a cold build, autoksyms.h starts empty, and is updated late in the build process to have visibility over the symbols used by in-tree drivers. But since the symbol whitelist is known upfront, it can be used to pre-populate autoksyms.h and maximize the amount of code that can be compiled to its final state in a single pass, hence reducing build time. Do this by using gen_autoksyms.sh to initialize autoksyms.h instead of creating an empty file. Acked-by: Nicolas Pitre <nico@fluxnic.net> Tested-by: Matthias Maennich <maennich@google.com> Reviewed-by: Matthias Maennich <maennich@google.com> Signed-off-by: Quentin Perret <qperret@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-03-03kbuild: split adjust_autoksyms.sh in two partsQuentin Perret1-0/+51
In order to prepare the ground for a build-time optimization, split adjust_autoksyms.sh into two scripts: one that generates autoksyms.h based on all currently available information (whitelist, and .mod files), and the other to inspect the diff between two versions of autoksyms.h and trigger appropriate rebuilds. Acked-by: Nicolas Pitre <nico@fluxnic.net> Tested-by: Matthias Maennich <maennich@google.com> Reviewed-by: Matthias Maennich <maennich@google.com> Signed-off-by: Quentin Perret <qperret@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>