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* x86: Add straight-line-speculation mitigationPeter Zijlstra2021-12-091-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | Make use of an upcoming GCC feature to mitigate straight-line-speculation for x86: https://gcc.gnu.org/g:53a643f8568067d7700a9f2facc8ba39974973d3 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102952 https://bugs.llvm.org/show_bug.cgi?id=52323 It's built tested on x86_64-allyesconfig using GCC-12 and GCC-11. Maintenance overhead of this should be fairly low due to objtool validation. Size overhead of all these additional int3 instructions comes to: text data bss dec hex filename 22267751 6933356 2011368 31212475 1dc43bb defconfig-build/vmlinux 22804126 6933356 1470696 31208178 1dc32f2 defconfig-build/vmlinux.sls Or roughly 2.4% additional text. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lore.kernel.org/r/20211204134908.140103474@infradead.org
* kbuild: reuse $(cmd_objtool) for cmd_cc_lto_link_modulesMasahiro Yamada2021-09-221-11/+17
| | | | | | | | | | | | | | | | | | | | | | | | For CONFIG_LTO_CLANG=y, the objtool processing is not possible at the compilation, hence postponed by the link time. Reuse $(cmd_objtool) for CONFIG_LTO_CLANG=y by defining objtool-enabled properly. For CONFIG_LTO_CLANG=y: objtool-enabled is off for %.o compilation objtool-enabled is on for %.lto link For CONFIG_LTO_CLANG=n: objtool-enabled is on for %.o compilation (but, it depends on OBJECT_FILE_NON_STANDARD) Set part-of-module := y for %.lto.o to avoid repeating --module. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
* kbuild: detect objtool update without using .SECONDEXPANSIONMasahiro Yamada2021-09-221-7/+5
| | | | | | | | | | | | | | | | | | | | | | Redo commit 8852c5524029 ("kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_<obj> := n'") to add the objtool dependency in a cleaner way. Using .SECONDEXPANSION ends up with unreadable code due to escaped dollars. Also, it is not efficient because the second half of Makefile.build is parsed twice every time. Append the objtool dependency to the *.cmd files at the build time. This is what fixdep and gen_ksymdeps.sh already do. So, following the same pattern seems a natural solution. This allows us to drop $$(objtool_dep) entirely. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
* kbuild: factor out OBJECT_FILES_NON_STANDARD check into a macroMasahiro Yamada2021-09-221-6/+6
| | | | | | | | | | | The OBJECT_FILES_NON_STANDARD check is quite long. Factor it out into a new macro, objtool-enabled, to not repeat it. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
* kbuild: store the objtool command in *.cmd filesMasahiro Yamada2021-09-221-9/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | objtool_dep includes include/config/{ORC_UNWINDER,STACK_VALIDATION} so that all the objects are rebuilt when CONFIG_ORC_UNWINDER or CONFIG_STACK_VALIDATION is toggled. BTW, the correct option name is not CONFIG_ORC_UNWINDER, but CONFIG_UNWINDER_ORC. Commit 11af847446ed ("x86/unwind: Rename unwinder config options to 'CONFIG_UNWINDER_*'") missed to adjust this part. So, this dependency has been broken for a long time. As you can see in 'objtool_args', there are more CONFIG options that affect the objtool command line. Adding more and more include/config/* is ugly and unmaintainable. Another issue is that non-standard objects are needlessly rebuilt. Objects specified as OBJECT_FILES_NON_STANDARD is not processed by objtool, but they are rebuilt anyway when CONFIG_STACK_VALIDATION is toggled. This is not a big deal, but better to fix. A cleaner and more precise fix is to include the objtool command in *.cmd files so any command change is naturally detected by if_change. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
* kbuild: rename __objtool_obj and reuse it for cmd_cc_lto_link_modulesMasahiro Yamada2021-09-221-6/+5
| | | | | | | | | | | Rename __objtool_obj to objtool, and move it out of the 'ifndef CONFIG_LTO_CLANG' conditional, so it can be used for cmd_cc_lto_link_modules as well. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
* kbuild: move objtool_args back to scripts/Makefile.buildMasahiro Yamada2021-09-221-0/+10
| | | | | | | | | | | | | | | | | | | | Commit b1a1a1a09b46 ("kbuild: lto: postpone objtool") moved objtool_args to Makefile.lib, so the arguments can be used in Makefile.modfinal as well as Makefile.build. With commit 850ded46c642 ("kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANG"), module LTO linking came back to scripts/Makefile.build again. So, there is no more reason to keep objtool_args in a separate file. Get it back to the original place, close to the objtool command. Remove the stale comment too. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
* kbuild: remove stale *.symversionsMasahiro Yamada2021-09-031-0/+2
| | | | | | | | | | | | | | | | | | | | cmd_update_lto_symversions merges all the existing *.symversions, but some of them might be stale. If the last EXPORT_SYMBOL is removed from a C file, the *.symversions file is not deleted or updated. It contains stale CRCs, but still they will be used for linking the vmlinux or modules. It is not a big deal when the EXPORT_SYMBOL is really removed. However, when the EXPORT_SYMBOL is moved to another file, the same __crc_<symbol> will appear twice in the merged *.symversions, possibly with different CRCs if the function argument is changed at the same time. It would confuse module versioning. If no EXPORT_SYMBOL is found, let's remove *.symversions explicitly. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org>
* kbuild: remove unused quiet_cmd_update_lto_symversionsMasahiro Yamada2021-09-031-1/+0
| | | | | | | | This is not used anywhere because the short log is displayed when it is used through a $(call cmd,...) invocation. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org>
* kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANGSami Tolvanen2021-09-031-1/+26
| | | | | | | | | | | | | | | | | | | | | | 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>
* Kbuild: lto: fix module versionings mismatch in GNU make 3.XLecopzer Chen2021-07-181-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When building modules(CONFIG_...=m), I found some of module versions are incorrect and set to 0. This can be found in build log for first clean build which shows WARNING: EXPORT symbol "XXXX" [drivers/XXX/XXX.ko] version generation failed, symbol will not be versioned. But in second build(incremental build), the WARNING disappeared and the module version becomes valid CRC and make someone who want to change modules without updating kernel image can't insert their modules. The problematic code is + $(foreach n, $(filter-out FORCE,$^), \ + $(if $(wildcard $(n).symversions), \ + ; cat $(n).symversions >> $@.symversions)) For example: rm -f fs/notify/built-in.a.symversions ; rm -f fs/notify/built-in.a; \ llvm-ar cDPrST fs/notify/built-in.a fs/notify/fsnotify.o \ fs/notify/notification.o fs/notify/group.o ... `foreach n` shows nothing to `cat` into $(n).symversions because `if $(wildcard $(n).symversions)` return nothing, but actually they do exist during this line was executed. -rw-r--r-- 1 root root 168580 Jun 13 19:10 fs/notify/fsnotify.o -rw-r--r-- 1 root root 111 Jun 13 19:10 fs/notify/fsnotify.o.symversions The reason is the $(n).symversions are generated at runtime, but Makefile wildcard function expends and checks the file exist or not during parsing the Makefile. Thus fix this by use `test` shell command to check the file existence in runtime. Rebase from both: 1. [https://lore.kernel.org/lkml/20210616080252.32046-1-lecopzer.chen@mediatek.com/] 2. [https://lore.kernel.org/lkml/20210702032943.7865-1-lecopzer.chen@mediatek.com/] Fixes: 38e891849003 ("kbuild: lto: fix module versioning") Co-developed-by: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* Merge tag 'kbuild-v5.14' of ↵Linus Torvalds2021-07-101-2/+0
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild Pull Kbuild updates from Masahiro Yamada: - Increase the -falign-functions alignment for the debug option. - Remove ugly libelf checks from the top Makefile. - Make the silent build (-s) more silent. - Re-compile the kernel if KBUILD_BUILD_TIMESTAMP is specified. - Various script cleanups * tag 'kbuild-v5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (27 commits) scripts: add generic syscallnr.sh scripts: check duplicated syscall number in syscall table sparc: syscalls: use pattern rules to generate syscall headers parisc: syscalls: use pattern rules to generate syscall headers nds32: add arch/nds32/boot/.gitignore kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set kbuild: modpost: Explicitly warn about unprototyped symbols kbuild: remove trailing slashes from $(KBUILD_EXTMOD) kconfig.h: explain IS_MODULE(), IS_ENABLED() kconfig: constify long_opts scripts/setlocalversion: simplify the short version part scripts/setlocalversion: factor out 12-chars hash construction scripts/setlocalversion: add more comments to -dirty flag detection scripts/setlocalversion: remove workaround for old make-kpkg scripts/setlocalversion: remove mercurial, svn and git-svn supports kbuild: clean up ${quiet} checks in shell scripts kbuild: sink stdout from cmd for silent build init: use $(call cmd,) for generating include/generated/compile.h kbuild: merge scripts/mkmakefile to top Makefile sh: move core-y in arch/sh/Makefile to arch/sh/Kbuild ...
| * kbuild: remove libelf checks from top MakefileMasahiro Yamada2021-05-241-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | I do not see a good reason why only the libelf development package must be so carefully checked. Kbuild generally does not check host tools or libraries. For example, x86_64 defconfig fails to build with no libssl development package installed. scripts/extract-cert.c:21:10: fatal error: openssl/bio.h: No such file or directory 21 | #include <openssl/bio.h> | ^~~~~~~~~~~~~~~ To solve the build error, you need to install libssl-dev or openssl-devel package, depending on your distribution. 'apt-file search', 'dnf provides', etc. is your frined to find a proper package to install. This commit removes all the libelf checks from the top Makefile. If libelf is missing, objtool will fail to build in a similar pattern: .../linux/tools/objtool/include/objtool/elf.h:10:10: fatal error: gelf.h: No such file or directory 10 | #include <gelf.h> You need to install libelf-dev, libelf-devel, or elfutils-libelf-devel to proceed. Another remarkable change is, CONFIG_STACK_VALIDATION (without CONFIG_UNWINDER_ORC) previously continued to build with a warning, but now it will treat missing libelf as an error. This is just a one-time installation, so it should not hurt to break a build and make a user install the package. BTW, the traditional way to handle such checks is autotool, but according to [1], I do not expect the kernel build would have similar scripting like './configure' does. [1]: https://lore.kernel.org/lkml/CA+55aFzr2HTZVOuzpHYDwmtRJLsVzE-yqg2DHpHi_9ePsYp5ug@mail.gmail.com/ Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Acked-by: Andrii Nakryiko <andrii@kernel.org>
* | kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_<obj> := n'Josh Poimboeuf2021-05-191-2/+3
|/ | | | | | | | | | | | | | | | | | | | | | | "OBJECT_FILES_NON_STANDARD_vma.o := n" has a dependency bug. When objtool source is updated, the affected object doesn't get re-analyzed by objtool. Peter's new variable-sized jump label feature relies on objtool rewriting the object file. Otherwise the system can fail to boot. That effectively upgrades this minor dependency issue to a major bug. The problem is that variables in prerequisites are expanded early, during the read-in phase. The '$(objtool_dep)' variable indirectly uses '$@', which isn't yet available when the target prerequisites are evaluated. Use '.SECONDEXPANSION:' which causes '$(objtool_dep)' to be expanded in a later phase, after the target-specific '$@' variable has been defined. Fixes: b9ab5ebb14ec ("objtool: Add CONFIG_STACK_VALIDATION option") Fixes: ab3257042c26 ("jump_label, x86: Allow short NOPs") Reported-by: Matthew Wilcox <willy@infradead.org> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
* kbuild: refactor fdtoverlay ruleMasahiro Yamada2021-05-061-1/+1
| | | | | | | | | | | | | Rename overlay-y to multi-dtb-y, which is a consistent name with multi-obj-y. Also, use multi-search to avoid code duplication. Introduce real-dtb-y, which is a consistent name with real-obj-y, to contain primitive blobs compiled from *.dts. This is used to calculate the list of *.dt.yaml files. Set -@ to base DTB without using $(eval ). Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: redo fake deps at include/config/*.hAlexey Dobriyan2021-04-251-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Make include/config/foo/bar.h fake deps files generation simpler. * delete .h suffix those aren't header files, shorten filenames, * delete tolower() Linux filesystems can deal with both upper and lowercase filenames very well, * put everything in 1 directory Presumably 'mkdir -p' split is from dark times when filesystems handled huge directories badly, disks were round adding to seek times. x86_64 allmodconfig lists 12364 files in include/config. ../obj/include/config/ ├── 104_QUAD_8 ├── 60XX_WDT ├── 64BIT ... ├── ZSWAP_DEFAULT_ON ├── ZSWAP_ZPOOL_DEFAULT └── ZSWAP_ZPOOL_DEFAULT_ZBUD 0 directories, 12364 files Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: rename multi-used-* to multi-obj-*Masahiro Yamada2021-04-251-3/+3
| | | | | | | | | | | | I think multi-obj-* is clearer, and more consistent with real-obj-*. Rename as follows: multi-used-y -> multi-obj-y multi-used-m -> multi-obj-m multi-used -> multi-obj-ym Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: split cc-option and friends to scripts/Makefile.compilerMasahiro Yamada2021-04-251-0/+1
| | | | | | | | | | | | | scripts/Kbuild.include is included everywhere, but macros such as cc-option are needed by build targets only. For example, when 'make clean' traverses the tree, it does not need to evaluate $(call cc-option,). Split cc-option, ld-option, etc. to scripts/Makefile.compiler, which is only included from the top Makefile and scripts/Makefile.build. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: prefix $(srctree)/ to some included MakefilesMasahiro Yamada2021-03-151-4/+4
| | | | | | | | | | | | | | | | | 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 <masahiroy@kernel.org>
* Merge tag 'kbuild-v5.12' of ↵Linus Torvalds2021-02-251-1/+0
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild Pull Kbuild updates from Masahiro Yamada: - Fix false-positive build warnings for ARCH=ia64 builds - Optimize dictionary size for module compression with xz - Check the compiler and linker versions in Kconfig - Fix misuse of extra-y - Support DWARF v5 debug info - Clamp SUBLEVEL to 255 because stable releases 4.4.x and 4.9.x exceeded the limit - Add generic syscall{tbl,hdr}.sh for cleanups across arches - Minor cleanups of genksyms - Minor cleanups of Kconfig * tag 'kbuild-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (38 commits) initramfs: Remove redundant dependency of RD_ZSTD on BLK_DEV_INITRD kbuild: remove deprecated 'always' and 'hostprogs-y/m' kbuild: parse C= and M= before changing the working directory kbuild: reuse this-makefile to define abs_srctree kconfig: unify rule of config, menuconfig, nconfig, gconfig, xconfig kconfig: omit --oldaskconfig option for 'make config' kconfig: fix 'invalid option' for help option kconfig: remove dead code in conf_askvalue() kconfig: clean up nested if-conditionals in check_conf() kconfig: Remove duplicate call to sym_get_string_value() Makefile: Remove # characters from compiler string Makefile: reuse CC_VERSION_TEXT kbuild: check the minimum linker version in Kconfig kbuild: remove ld-version macro scripts: add generic syscallhdr.sh scripts: add generic syscalltbl.sh arch: syscalls: remove $(srctree)/ prefix from syscall tables arch: syscalls: add missing FORCE and fix 'targets' to make if_changed work gen_compile_commands: prune some directories kbuild: simplify access to the kernel's version ...
| * kbuild: remove deprecated 'always' and 'hostprogs-y/m'Masahiro Yamada2021-02-241-1/+0
| | | | | | | | | | | | | | These have no more user in the upstream code. The use of them has been warned for a while for external modules. The migration is finished. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* | kbuild: lto: postpone objtoolSami Tolvanen2021-02-231-20/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With LTO, LLVM bitcode won't be compiled into native code until modpost_link, or modfinal for modules. This change postpones calls to objtool until after these steps, and moves objtool_args to Makefile.lib, so the arguments can be reused in Makefile.modfinal. As we didn't have objects to process earlier, we use --duplicate when processing vmlinux.o. This change also disables unreachable instruction warnings with LTO to avoid warnings about the int3 padding between functions. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org>
* | tracing: add support for objtool mcountSami Tolvanen2021-02-231-0/+3
| | | | | | | | | | | | | | This change adds build support for using objtool to generate __mcount_loc sections. Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
* | kbuild: lto: fix module versioningSami Tolvanen2021-01-141-2/+31
| | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20201211184633.3213045-4-samitolvanen@google.com
* | kbuild: add support for Clang LTOSami Tolvanen2021-01-141-1/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com
* | tracing: move function tracer options to KconfigSami Tolvanen2021-01-081-4/+2
|/ | | | | | | | | | | | | | | Move function tracer options to Kconfig to make it easier to add new methods for generating __mcount_loc, and to make the options available also when building kernel modules. Note that FTRACE_MCOUNT_USE_* options are updated on rebuild and therefore, work even if the .config was generated in a different environment. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20201211184633.3213045-2-samitolvanen@google.com
* kbuild: avoid split lines in .mod filesMasahiro Yamada2020-12-061-8/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | "xargs echo" is not a safe way to remove line breaks because the input may exceed the command line limit and xargs may break it up into multiple invocations of echo. This should never happen because scripts/gen_autoksyms.sh expects all undefined symbols are placed in the second line of .mod files. One possible way is to replace "xargs echo" with "sed ':x;N;$!bx;s/\n/ /g'" or something, but I rewrote the code by using awk because it is more readable. This issue was reported by Sami Tolvanen; in his Clang LTO patch set, $(multi-used-m) is no longer an ELF object, but a thin archive that contains LLVM bitcode files. llvm-nm prints out symbols for each archive member separately, which results a lot of dupications, in some places, beyond the system-defined limit. This problem must be fixed irrespective of LTO, and we must ensure zero possibility of having this issue. Link: https://lkml.org/lkml/2020/12/1/1658 Reported-by: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
* treewide: remove DISABLE_LTOSami Tolvanen2020-10-211-1/+1
| | | | | | | | | | | | | | | This change removes all instances of DISABLE_LTO from Makefiles, as they are currently unused, and the preferred method of disabling LTO is to filter out the flags instead. Note added by Masahiro Yamada: DISABLE_LTO was added as preparation for GCC LTO, but GCC LTO was not pulled into the mainline. (https://lkml.org/lkml/2014/4/8/272) Suggested-by: Kees Cook <keescook@chromium.org> Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: sort hostprogs before passing it to ifneqMasahiro Yamada2020-08-101-1/+4
| | | | | | | | | | | | | | | | | | | | | | The conditional: ifneq ($(hostprogs),) ... is evaluated to true if $(hostprogs) does not contain any word but whitespace characters. ifneq ($(strip $(hostprogs)),) ... is a safe way to avoid interpreting whitespace as a non-empty value, but I'd rather want to use the side-effect of $(sort ...) to do the equivalent. $(sort ...) is used in scripts/Makefile.host in order to drop duplication in $(hostprogs). It is also useful to strip excessive spaces. Move $(sort ...) before evaluating the ifneq. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: move host .so build rules to scripts/gcc-plugins/MakefileMasahiro Yamada2020-08-101-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | The host shared library rules are currently implemented in scripts/Makefile.host, but actually GCC-plugin is the only user of them. (The VDSO .so files are built for the target by different build rules) Hence, they do not need to be treewide available. Move all the relevant build rules to scripts/gcc-plugins/Makefile. I also optimized the build steps so *.so is directly built from .c because every upstream plugin is compiled from a single source file. I am still keeping the multi-file plugin support, which Kees Cook mentioned might be needed by out-of-tree plugins. (https://lkml.org/lkml/2019/1/11/1107) If the plugin, foo.so, is compiled from two files foo.c and foo2.c, then you can do like follows: foo-objs := foo.o foo2.o Single-file plugins do not need the *-objs notation. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Acked-by: Kees Cook <keescook@chromium.org>
* kbuild: always create directories of targetsMasahiro Yamada2020-08-101-3/+1
| | | | | | | | | Currently, the directories of objects are automatically created only for O= builds. It should not hurt to cater to this for in-tree builds too. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: run the checker after the compilerLuc Van Oostenryck2020-07-071-2/+2
| | | | | | | | | | | | Since the pre-git time the checker is run first, before the compiler. But if the source file contains some syntax error, the warnings from the compiler are more useful than those from sparse (and other checker most probably too). So move the 'check' command to run after the compiler. Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: update modules.order only when contained modules are updatedMasahiro Yamada2020-06-031-8/+13
| | | | | | | | | | | Make modules.order depend on $(obj-m), and use if_changed to build it. This will avoid unneeded update of modules.order, which will be useful to optimize the modpost stage. Currently, the second pass of modpost is always invoked. By checking the timestamp of modules.order, we can avoid the unneeded modpost. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: refactor tagets caluculation for KBUILD_{BUILTIN,KBUILD_MODULES}Masahiro Yamada2020-06-011-13/+12
| | | | | | | | Remove lib-target, builtin-target, modorder-target, and modtargets. Instead, add targets-for-builtin and targets-for-modules. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: make modules.order rule consistent with built-in.aMasahiro Yamada2020-05-261-4/+6
| | | | | | | | | | | | built-in.a contains the built-in object paths from the current and sub directories. module.order collects the module paths from the current and sub directories. Make their build rules look more symmetrical. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: rename subdir-obj-y to subdir-builtinMasahiro Yamada2020-05-261-4/+5
| | | | | | | | I think subdir-builtin is clearer. While I was here, I made its build rule explicit. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: move subdir-obj-y to scripts/Makefile.buildMasahiro Yamada2020-05-261-0/+2
| | | | | | Save $(addprefix ...) for subdir-obj-y. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: clear KBUILD_MODULES in top Makefile if CONFIG_MODULES=nMasahiro Yamada2020-05-261-1/+1
| | | | | | | Do not try to build any module-related artifacts when CONFIG_MODULES is disabled. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: remove ifdef builtin-target / lib-targetMasahiro Yamada2020-05-261-8/+2
| | | | | | I do not see a good reason to add ifdef here. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: add infrastructure to build userspace programsMasahiro Yamada2020-05-171-0/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Kbuild supports the infrastructure to build host programs, but there was no support to build userspace programs for the target architecture (i.e. the same architecture as the kernel). Sam Ravnborg worked on this in 2014 (https://lkml.org/lkml/2014/7/13/154), but it was not merged. One problem at that time was, there was no good way to know whether $(CC) can link standalone programs. In fact, pre-built kernel.org toolchains [1] are often used for building the kernel, but they do not provide libc. Now, we can handle this cleanly because the compiler capability is evaluated at the Kconfig time. If $(CC) cannot link standalone programs, the relevant options are hidden by 'depends on CC_CAN_LINK'. The implementation just mimics scripts/Makefile.host The userspace programs are compiled with the same flags as the host programs. In addition, it uses -m32 or -m64 if it is found in $(KBUILD_CFLAGS). This new syntax has two usecases. - Sample programs Several userspace programs under samples/ include UAPI headers installed in usr/include. Most of them were previously built for the host architecture just to use the 'hostprogs' syntax. However, 'make headers' always works for the target architecture. This caused the arch mismatch in cross-compiling. To fix this distortion, sample code should be built for the target architecture. - Bpfilter net/bpfilter/Makefile compiles bpfilter_umh as the user mode helper, and embeds it into the kernel. Currently, it overrides HOSTCC with CC to use the 'hostprogs' syntax. This hack should go away. [1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/ Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Acked-by: Sam Ravnborg <sam@ravnborg.org>
* kbuild: link lib-y objects to vmlinux forcibly when CONFIG_MODULES=yMasahiro Yamada2020-04-091-17/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Kbuild supports not only obj-y but also lib-y to list objects linked to vmlinux. The difference between them is that all the objects from obj-y are forcibly linked to vmlinux, whereas the objects from lib-y are linked as needed; if there is no user of a lib-y object, it is not linked. lib-y is intended to list utility functions that may be called from all over the place (and may be unused at all), but it is a problem for EXPORT_SYMBOL(). Even if there is no call-site in the vmlinux, we need to keep exported symbols for the use from loadable modules. Commit 7f2084fa55e6 ("[kbuild] handle exports in lib-y objects reliably") worked around it by linking a dummy object, lib-ksyms.o, which contains references to all the symbols exported from lib.a in that directory. It uses the linker script command, EXTERN. Unfortunately, the meaning of EXTERN of ld.lld is different from that of ld.bfd. Therefore, this does not work with LD=ld.lld (CBL issue #515). Anyway, the build rule of lib-ksyms.o is somewhat tricky. So, I want to get rid of it. At first, I was thinking of accumulating lib-y objects into obj-y (or even replacing lib-y with obj-y entirely), but the lib-y syntax is used beyond the ordinary use in lib/ and arch/*/lib/. Examples: - drivers/firmware/efi/libstub/Makefile builds lib.a, which is linked into vmlinux in the own way (arm64), or linked to the decompressor (arm, x86). - arch/alpha/lib/Makefile builds lib.a which is linked not only to vmlinux, but also to bootloaders in arch/alpha/boot/Makefile. - arch/xtensa/boot/lib/Makefile builds lib.a for use from arch/xtensa/boot/boot-redboot/Makefile. One more thing, adding everything to obj-y would increase the vmlinux size of allnoconfig (or tinyconfig). For less impact, I tweaked the destination of lib.a at the top Makefile; when CONFIG_MODULES=y, lib.a goes to KBUILD_VMLINUX_OBJS, which is forcibly linked to vmlinux, otherwise lib.a goes to KBUILD_VMLINUX_LIBS as before. The size impact for normal usecases is quite small since at lease one symbol in every lib-y object is eventually called by someone. In case you are intrested, here are the figures. x86_64_defconfig: text data bss dec hex filename 19566602 5422072 1589328 26578002 1958c52 vmlinux.before 19566932 5422104 1589328 26578364 1958dbc vmlinux.after The case with the biggest impact is allnoconfig + CONFIG_MODULES=y. ARCH=x86 allnoconfig + CONFIG_MODULES=y: text data bss dec hex filename 1175162 254740 1220608 2650510 28718e vmlinux.before 1177974 254836 1220608 2653418 287cea vmlinux.after Hopefully this is still not a big deal. The per-file trimming with the static library is not so effective after all. If fine-grained optimization is desired, some architectures support CONFIG_LD_DEAD_CODE_DATA_ELIMINATION, which trims dead code per-symbol basis. When LTO is supported in mainline, even better optimization will be possible. Link: https://github.com/ClangBuiltLinux/linux/issues/515 Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reported-by: kbuild test robot <lkp@intel.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
* gcc-plugins: drop support for GCC <= 4.7Masahiro Yamada2020-04-091-1/+1
| | | | | | | | | | | | | | | Nobody was opposed to raising minimum GCC version to 4.8 [1] So, we will drop GCC <= 4.7 support sooner or later. We always use C++ compiler for building plugins for GCC >= 4.8. This commit drops the plugin support for GCC <= 4.7 a bit earlier, which allows us to dump lots of code. [1] https://lkml.org/lkml/2020/1/23/545 Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Acked-by: Kees Cook <keescook@chromium.org>
* kbuild: rename hostprogs-y/always to hostprogs/always-yMasahiro Yamada2020-02-041-3/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | In old days, the "host-progs" syntax was used for specifying host programs. It was renamed to the current "hostprogs-y" in 2004. It is typically useful in scripts/Makefile because it allows Kbuild to selectively compile host programs based on the kernel configuration. This commit renames like follows: always -> always-y hostprogs-y -> hostprogs So, scripts/Makefile will look like this: always-$(CONFIG_BUILD_BIN2C) += ... always-$(CONFIG_KALLSYMS) += ... ... hostprogs := $(always-y) $(always-m) I think this makes more sense because a host program is always a host program, irrespective of the kernel configuration. We want to specify which ones to compile by CONFIG options, so always-y will be handier. The "always", "hostprogs-y", "hostprogs-m" will be kept for backward compatibility for a while. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: use pattern rule for building built-in.a in sub-directoriesMasahiro Yamada2020-01-071-1/+1
| | | | | | | | The built-in.a in a sub-directory is created by descending into that directory. It does not depend on the other sub-directories. Loosen the dependency. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: do not create orphan built-in.a or obj-y objectsMasahiro Yamada2020-01-071-1/+1
| | | | | | | | | | | | | | Both 'obj-y += foo/' and 'obj-m += foo/' request Kbuild to visit the sub-directory foo/, but the difference is that only the former combines foo/built-in.a into the built-in.a of the current directory because everything in sub-directories visited by obj-m is supposed to be modular. So, it makes sense to create built-in.a only if that sub-directory is reachable by the chain of obj-y. Otherwise, built-in.a will not be linked into vmlinux anyway. For the same reason, it is pointless to compile obj-y objects in the directory visited by obj-m. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* kbuild: remove header compile testMasahiro Yamada2019-11-151-9/+0
| | | | | | | | | | | | | | | | There are both positive and negative options about this feature. At first, I thought it was a good idea, but actually Linus stated a negative opinion (https://lkml.org/lkml/2019/9/29/227). I admit it is ugly and annoying. The baseline I'd like to keep is the compile-test of uapi headers. (Otherwise, kernel developers have no way to ensure the correctness of the exported headers.) I will maintain a small build rule in usr/include/Makefile. Remove the other header test functionality. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
* kbuild: make single target builds much fasterMasahiro Yamada2019-11-111-1/+4
| | | | | | | | | Since commit 394053f4a4b3 ("kbuild: make single targets work more correctly"), building single targets is really slow. Speed it up by not descending into unrelated directories. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
* kbuild: reduce KBUILD_SINGLE_TARGETS as descending into subdirectoriesMasahiro Yamada2019-11-111-3/+3
| | | | | | | | KBUILD_SINGLE_TARGETS does not need to contain all the targets. Change it to keep track the targets only from the current directory and its subdirectories. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
* kbuild: remove ar-option and KBUILD_ARFLAGSMasahiro Yamada2019-10-011-1/+1
| | | | | | | | | | | | | | | | Commit 40df759e2b9e ("kbuild: Fix build with binutils <= 2.19") introduced ar-option and KBUILD_ARFLAGS to deal with old binutils. According to Documentation/process/changes.rst, the current minimal supported version of binutils is 2.21 so you can assume the 'D' option is always supported. Not only GNU ar but also llvm-ar supports it. With the 'D' option hard-coded, there is no more user of ar-option or KBUILD_ARFLAGS. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com>
* kbuild: rename KBUILD_ENABLE_EXTRA_GCC_CHECKS to KBUILD_EXTRA_WARNMasahiro Yamada2019-09-061-1/+1
| | | | | | | | | | | | | | | | | | KBUILD_ENABLE_EXTRA_GCC_CHECKS started as a switch to add extra warning options for GCC, but now it is a historical misnomer since we use it also for Clang, DTC, and even kernel-doc. Rename it to more sensible, shorter KBUILD_EXTRA_WARN. For the backward compatibility, KBUILD_ENABLE_EXTRA_GCC_CHECKS is still supported (but not advertised in the documentation). I also fixed up 'make help', and updated the documentation. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com>
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