user/sven/linux.git/scripts/Makefile.modpost, branch v5.16

kbuild: Fix comment typo in scripts/Makefile.modpost

2021-09-19T01:14:19Z

Change comment "create one .mod.c file pr. module" to "create one .mod.c file per module" Signed-off-by: Ramji Jiyani Signed-off-by: Masahiro Yamada

kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANG

2021-09-02T23:12:39Z

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 Reviewed-by: Alexander Lobakin Tested-by: Alexander Lobakin Signed-off-by: Masahiro Yamada

kbuild: fix false-positive modpost warning when all symbols are trimmed

2021-04-24T20:17:53Z

Nathan reports that the mips defconfig emits the following warning: WARNING: modpost: Symbol info of vmlinux is missing. Unresolved symbol check will be entirely skipped. This false-positive happens when CONFIG_TRIM_UNUSED_KSYMS is enabled, but no CONFIG option is set to 'm'. Commit a0590473c5e6 ("nfs: fix PNFS_FLEXFILE_LAYOUT Kconfig default") turned the last 'm' into 'y' for the mips defconfig, and uncovered this issue. In this case, the module feature itself is enabled, but we have no module to build. As a result, CONFIG_TRIM_UNUSED_KSYMS drops all the instances of EXPORT_SYMBOL. Then, modpost wrongly assumes vmlinux is missing because vmlinux.symvers is empty. (As another false-positive case, you can create a module that does not use any symbol of vmlinux). The current behavior is to entirely suppress the unresolved symbol warnings when vmlinux is missing just because there are too many. I found the origin of this code in the historical git tree. [1] If this is a matter of noisiness, I think modpost can display the first 10 warnings, and the number of suppressed warnings at the end. You will get a bit noisier logs when you run 'make modules' without vmlinux, but such warnings are better to show because you never know the resulting modules are actually loadable or not. This commit changes the following: - If any of input *.symver files is missing, pass -w option to let the module build keep going with warnings instead of errors. - If there are too many (10+) unresolved symbol warnings, show only the first 10, and also the number of suppressed warnings. [1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=1cc0e0529569bf6a94f6d49770aa6d4b599d2c46 Reported-by: Nathan Chancellor Signed-off-by: Masahiro Yamada

kbuild: do not set -w for vmlinux.o modpost

2021-04-24T20:17:38Z

The -w option is meaningless for the first pass of modpost (vmlinux.o). We know there are unresolved symbols in vmlinux.o, hence we skip check_exports() and other checks when mod->is_vmlinux is set. See the following part in the for-loop. if (mod->is_vmlinux || mod->from_dump) continue; Signed-off-by: Masahiro Yamada

kbuild: generate Module.symvers only when vmlinux exists

2021-04-24T20:17:02Z

The external module build shows the following warning if Module.symvers is missing in the kernel tree. WARNING: Symbol version dump "Module.symvers" is missing. Modules may not have dependencies or modversions. I think this is an important heads-up because the resulting modules may not work as expected. This happens when you did not build the entire kernel tree, for example, you might have prepared the minimal setups for external modules by 'make defconfig && make modules_preapre'. A problem is that 'make modules' creates Module.symvers even without vmlinux. In this case, that warning is suppressed since Module.symvers already exists in spite of its incomplete content. The incomplete (i.e. invalid) Module.symvers should not be created. This commit changes the second pass of modpost to dump symbols into modules-only.symvers. The final Module.symvers is created by concatenating vmlinux.symvers and modules-only.symvers if both exist. Module.symvers is supposed to collect symbols from both vmlinux and modules. It might be a bit confusing, and I am not quite sure if it is an official interface, but presumably it is difficult to rename it because some tools (e.g. kmod) parse it. Signed-off-by: Masahiro Yamada

kbuild: prefix $(srctree)/ to some included Makefiles

2021-03-15T10:20:48Z

VPATH is used in Kbuild to make pattern rules search for prerequisites in both $(objtree) and $(srctree). Some of *.c, *.S files are not real sources, but generated by tools such as flex, bison, perl. In contrast, I doubt the benefit of --include-dir=$(abs_srctree) because it is always clear which Makefiles are real sources, and which are not. So, my hope is to add $(srctree)/ prefix to all check-in Makefiles, then remove --include-dir=$(abs_srctree) flag in the future. I am touching only some Kbuild core parts for now. Treewide fixes will be needed to achieve this goal. Signed-off-by: Masahiro Yamada

kbuild: lto: fix module versioning

2021-01-14T16:21:08Z

With CONFIG_MODVERSIONS, version information is linked into each compilation unit that exports symbols. With LTO, we cannot use this method as all C code is compiled into LLVM bitcode instead. This change collects symbol versions into .symversions files and merges them in link-vmlinux.sh where they are all linked into vmlinux.o at the same time. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20201211184633.3213045-4-samitolvanen@google.com

kbuild: add support for Clang LTO

2021-01-14T16:21:08Z

This change adds build system support for Clang's Link Time Optimization (LTO). With -flto, instead of ELF object files, Clang produces LLVM bitcode, which is compiled into native code at link time, allowing the final binary to be optimized globally. For more details, see: https://llvm.org/docs/LinkTimeOptimization.html The Kconfig option CONFIG_LTO_CLANG is implemented as a choice, which defaults to LTO being disabled. To use LTO, the architecture must select ARCH_SUPPORTS_LTO_CLANG and support: - compiling with Clang, - compiling all assembly code with Clang's integrated assembler, - and linking with LLD. While using CONFIG_LTO_CLANG_FULL results in the best runtime performance, the compilation is not scalable in time or memory. CONFIG_LTO_CLANG_THIN enables ThinLTO, which allows parallel optimization and faster incremental builds. ThinLTO is used by default if the architecture also selects ARCH_SUPPORTS_LTO_CLANG_THIN: https://clang.llvm.org/docs/ThinLTO.html To enable LTO, LLVM tools must be used to handle bitcode files, by passing LLVM=1 and LLVM_IAS=1 options to make: $ make LLVM=1 LLVM_IAS=1 defconfig $ scripts/config -e LTO_CLANG_THIN $ make LLVM=1 LLVM_IAS=1 To prepare for LTO support with other compilers, common parts are gated behind the CONFIG_LTO option, and LTO can be disabled for specific files by filtering out CC_FLAGS_LTO. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com

kbuild: remove redundant FORCE definition in scripts/Makefile.modpost

2020-08-02T14:09:16Z

The same code exists a few lines above. Fixes: 436b2ac603d5 ("modpost: invoke modpost only when input files are updated") Signed-off-by: Masahiro Yamada

modpost: move -d option in scripts/Makefile.modpost

2020-06-06T14:38:13Z

Collect options for modules into a single place. Signed-off-by: Masahiro Yamada