user/sven/linux.git/scripts/Makefile.modpost, branch v5.12.7

kbuild: generate Module.symvers only when vmlinux exists

2021-05-19T08:56:20Z

[ Upstream commit 69bc8d386aebbd91a6bb44b6d33f77c8dfa9ed8c ] 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 Signed-off-by: Sasha Levin

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

modpost: remove -s option

2020-06-06T14:38:13Z

The -s option was added by commit 8d8d8289df65 ("kbuild: do not do section mismatch checks on vmlinux in 2nd pass"). Now that the second pass does not parse vmlinux, this option is unneeded. Signed-off-by: Masahiro Yamada

modpost: show warning if any of symbol dump files is missing

2020-06-06T14:38:12Z

If modpost fails to load a symbol dump file, it cannot check unresolved symbols, hence module dependency will not be added. Nor CRCs can be added. Currently, external module builds check only $(objtree)/Module.symvers, but it should check files specified by KBUILD_EXTRA_SYMBOLS as well. Move the warning message from the top Makefile to scripts/Makefile.modpost and print the warning if any dump file is missing. Signed-off-by: Masahiro Yamada

modpost: invoke modpost only when input files are updated

2020-06-06T14:38:12Z

Currently, the second pass of modpost is always invoked when you run 'make' or 'make modules' even if none of modules is changed. Use if_changed to invoke it only when it is necessary. Signed-off-by: Masahiro Yamada

modpost: generate vmlinux.symvers and reuse it for the second modpost

2020-06-06T14:38:12Z

The full build runs modpost twice, first for vmlinux.o and second for modules. The first pass dumps all the vmlinux symbols into Module.symvers, but the second pass parses vmlinux again instead of reusing the dump file, presumably because it needs to avoid accumulating stale symbols. Loading symbol info from a dump file is faster than parsing an ELF object. Besides, modpost deals with various issues to parse vmlinux in the second pass. A solution is to make the first pass dumps symbols into a separate file, vmlinux.symvers. The second pass reads it, and parses module .o files. The merged symbol information is dumped into Module.symvers in the same way as before. This makes further modpost cleanups possible. Also, it fixes the problem of 'make vmlinux', which previously overwrote Module.symvers, throwing away module symbols. I slightly touched scripts/link-vmlinux.sh so that vmlinux is re-linked when you cross this commit. Otherwise, vmlinux.symvers would not be generated. Signed-off-by: Masahiro Yamada

modpost: refactor -i option calculation

2020-06-06T14:38:12Z

Prepare to use -i for in-tree modpost as well. Signed-off-by: Masahiro Yamada