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2024-09-20kbuild: remove append operation on cmd_ld_ko_oThomas Weißschuh1-1/+1
The append operation was introduced in commit b1a1a1a09b46 ("kbuild: lto: postpone objtool") when the command was created from two parts. In commit 850ded46c642 ("kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANG") however the first part was removed again, making the append operation unnecessary. To keep this command definition aligned with all other command definitions, remove the append again. Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-09-07kbuild: compile constant module information only onceThomas Weißschuh1-2/+5
Various information about modules is compiled into the info sections. For that a dedicated .mod.c file is generated by modpost for each module and then linked into the module. However most of the information in the .mod.c is the same for all modules, internal and external. Split the shared information into a dedicated source file that is compiled once and then linked into all modules. This avoids frequent rebuilds for all .mod.c files when using CONFIG_LOCALVERSION_AUTO because the local version ends up in .mod.c through UTS_RELEASE and VERMAGIC_STRING. The modules are still relinked in this case. The code is also easier to maintain as it's now in a proper source file instead of an inline string literal. Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-08-22kbuild: fix typos "prequisites" to "prerequisites"Masahiro Yamada1-1/+1
This typo in scripts/Makefile.build has been present for more than 20 years. It was accidentally copy-pasted to other scripts/Makefile.* files. Fix them all. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
2024-06-22kbuild,bpf: Add module-specific pahole flags for distilled base BTFAlan Maguire1-1/+1
Support creation of module BTF along with distilled base BTF; the latter is stored in a .BTF.base ELF section and supplements split BTF references to base BTF with information about base types, allowing for later relocation of split BTF with a (possibly changed) base. resolve_btfids detects the presence of a .BTF.base section and will use it instead of the base BTF it is passed in BTF id resolution. Modules will be built with a distilled .BTF.base section for external module build, i.e. make -C. -M=path2/module ...while in-tree module build as part of a normal kernel build will not generate distilled base BTF; this is because in-tree modules change with the kernel and do not require BTF relocation for the running vmlinux. Signed-off-by: Alan Maguire <alan.maguire@oracle.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Reviewed-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/bpf/20240620091733.1967885-6-alan.maguire@oracle.com
2024-05-14kbuild: use GCOV_PROFILE and KCSAN_SANITIZE in scripts/Makefile.modfinalMasahiro Yamada1-1/+3
Instead of filtering out the GCOV and KCSAN flags, let's set GCOV_PROFILE and KCSAN_SANITIZE to 'n', as in other Makefiles. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Roberto Sassu <roberto.sassu@huawei.com>
2024-03-31kbuild: Disable KCSAN for autogenerated *.mod.c intermediariesBorislav Petkov (AMD)1-1/+1
When KCSAN and CONSTRUCTORS are enabled, one can trigger the "Unpatched return thunk in use. This should not happen!" catch-all warning. Usually, when objtool runs on the .o objects, it does generate a section .return_sites which contains all offsets in the objects to the return thunks of the functions present there. Those return thunks then get patched at runtime by the alternatives. KCSAN and CONSTRUCTORS add this to the object file's .text.startup section: ------------------- Disassembly of section .text.startup: ... 0000000000000010 <_sub_I_00099_0>: 10: f3 0f 1e fa endbr64 14: e8 00 00 00 00 call 19 <_sub_I_00099_0+0x9> 15: R_X86_64_PLT32 __tsan_init-0x4 19: e9 00 00 00 00 jmp 1e <__UNIQUE_ID___addressable_cryptd_alloc_aead349+0x6> 1a: R_X86_64_PLT32 __x86_return_thunk-0x4 ------------------- which, if it is built as a module goes through the intermediary stage of creating a <module>.mod.c file which, when translated, receives a second constructor: ------------------- Disassembly of section .text.startup: 0000000000000010 <_sub_I_00099_0>: 10: f3 0f 1e fa endbr64 14: e8 00 00 00 00 call 19 <_sub_I_00099_0+0x9> 15: R_X86_64_PLT32 __tsan_init-0x4 19: e9 00 00 00 00 jmp 1e <_sub_I_00099_0+0xe> 1a: R_X86_64_PLT32 __x86_return_thunk-0x4 ... 0000000000000030 <_sub_I_00099_0>: 30: f3 0f 1e fa endbr64 34: e8 00 00 00 00 call 39 <_sub_I_00099_0+0x9> 35: R_X86_64_PLT32 __tsan_init-0x4 39: e9 00 00 00 00 jmp 3e <__ksymtab_cryptd_alloc_ahash+0x2> 3a: R_X86_64_PLT32 __x86_return_thunk-0x4 ------------------- in the .ko file. Objtool has run already so that second constructor's return thunk cannot be added to the .return_sites section and thus the return thunk remains unpatched and the warning rightfully fires. Drop KCSAN flags from the mod.c generation stage as those constructors do not contain data races one would be interested about. Debugged together with David Kaplan <David.Kaplan@amd.com> and Nikolay Borisov <nik.borisov@suse.com>. Reported-by: Paul Menzel <pmenzel@molgen.mpg.de> Closes: https://lore.kernel.org/r/0851a207-7143-417e-be31-8bf2b3afb57d@molgen.mpg.de Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Tested-by: Paul Menzel <pmenzel@molgen.mpg.de> # Dell XPS 13 Reviewed-by: Nikolay Borisov <nik.borisov@suse.com> Reviewed-by: Marco Elver <elver@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-10-28kbuild: remove ARCH_POSTLINK from module buildsMasahiro Yamada1-4/+1
The '%.ko' rule in arch/*/Makefile.postlink does nothing but call the 'true' command. Remove the unneeded code. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
2023-08-10btf, scripts: rust: drop is_rust_module.shAndrea Righi1-2/+0
With commit c1177979af9c ("btf, scripts: Exclude Rust CUs with pahole") we are now able to use pahole directly to identify Rust compilation units (CUs) and exclude them from generating BTF debugging information (when DEBUG_INFO_BTF is enabled). And if pahole doesn't support the --lang-exclude flag, we can't enable both RUST and DEBUG_INFO_BTF at the same time. So, in any case, the script is_rust_module.sh is just redundant and we can drop it. NOTE: we may also be able to drop the "Rust loadable module" mark inside Rust modules, but it seems safer to keep it for now to make sure we are not breaking any external tool that may potentially rely on it. Signed-off-by: Andrea Righi <andrea.righi@canonical.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Eric Curtin <ecurtin@redhat.com> Reviewed-by: Eric Curtin <ecurtin@redhat.com> Reviewed-by: Neal Gompa <neal@gompa.dev> Reviewed-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com> Acked-by: Daniel Xu <dxu@dxuuu.xyz> Link: https://lore.kernel.org/r/20230704052136.155445-1-andrea.righi@canonical.com [ Picked the `Reviewed-by`s from the old patch too. ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2023-06-25kbuild: Disable GCOV for *.mod.oSami Tolvanen1-1/+1
With GCOV_PROFILE_ALL, Clang injects __llvm_gcov_* functions to each object file, including the *.mod.o. As we filter out CC_FLAGS_CFI for *.mod.o, the compiler won't generate type hashes for the injected functions, and therefore indirectly calling them during module loading trips indirect call checking. Enabling CFI for *.mod.o isn't sufficient to fix this issue after commit 0c3e806ec0f9 ("x86/cfi: Add boot time hash randomization"), as *.mod.o aren't processed by objtool, which means any hashes emitted there won't be randomized. Therefore, in addition to disabling CFI for *.mod.o, also disable GCOV, as the object files don't otherwise contain any executable code. Fixes: cf68fffb66d6 ("add support for Clang CFI") Reported-by: Joe Fradley <joefradley@google.com> Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-01-22kbuild: rename cmd_$@ to savedcmd_$@ in *.cmd filesMasahiro Yamada1-1/+1
The cmd-check macro compares $(cmd_$@) and $(cmd_$1), but a pitfall is that you cannot use cmd_<target> as the variable name for the command. For example, the following code will not work in the top Makefile or ./Kbuild. quiet_cmd_foo = GEN $@ cmd_foo = touch $@ targets += foo foo: FORCE $(call if_changed,foo) In this case, both $@ and $1 are expanded to 'foo', so $(cmd_check) is always empty. We do not need to use the same prefix for cmd_$@ and cmd_$1. Rename the former to savedcmd_$@. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2022-12-14kbuild: change module.order to list *.o instead of *.koMasahiro Yamada1-3/+3
scripts/Makefile.build replaces the suffix .o with .ko, then scripts/Makefile.modpost calls the sed command to change .ko back to the original .o suffix. Instead of converting the suffixes back-and-forth, store the .o paths in modules.order, and replace it with .ko in 'make modules_install'. This avoids the unneeded sed command. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
2022-12-13kbuild: add read-file macroMasahiro Yamada1-1/+1
Since GNU Make 4.2, $(file ...) supports the read operater '<', which is useful to read a file without forking a new process. No warning is shown even if the input file is missing. For older Make versions, it falls back to the cat command. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu> Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com> Tested-by: Alexander Lobakin <alexandr.lobakin@intel.com>
2022-12-13kbuild: do not sort after reading modules.orderMasahiro Yamada1-1/+1
modules.order lists modules in the deterministic order (that is why "modules order"), and there is no duplication in the list. $(sort ) is pointless. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2022-10-10Merge tag 'kbuild-v6.1' of ↵Linus Torvalds1-1/+1
git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild Pull Kbuild updates from Masahiro Yamada: - Remove potentially incomplete targets when Kbuid is interrupted by SIGINT etc in case GNU Make may miss to do that when stderr is piped to another program. - Rewrite the single target build so it works more correctly. - Fix rpm-pkg builds with V=1. - List top-level subdirectories in ./Kbuild. - Ignore auto-generated __kstrtab_* and __kstrtabns_* symbols in kallsyms. - Avoid two different modules in lib/zstd/ having shared code, which potentially causes building the common code as build-in and modular back-and-forth. - Unify two modpost invocations to optimize the build process. - Remove head-y syntax in favor of linker scripts for placing particular sections in the head of vmlinux. - Bump the minimal GNU Make version to 3.82. - Clean up misc Makefiles and scripts. * tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (41 commits) docs: bump minimal GNU Make version to 3.82 ia64: simplify esi object addition in Makefile Revert "kbuild: Check if linker supports the -X option" kbuild: rebuild .vmlinux.export.o when its prerequisite is updated kbuild: move modules.builtin(.modinfo) rules to Makefile.vmlinux_o zstd: Fixing mixed module-builtin objects kallsyms: ignore __kstrtab_* and __kstrtabns_* symbols kallsyms: take the input file instead of reading stdin kallsyms: drop duplicated ignore patterns from kallsyms.c kbuild: reuse mksysmap output for kallsyms mksysmap: update comment about __crc_* kbuild: remove head-y syntax kbuild: use obj-y instead extra-y for objects placed at the head kbuild: hide error checker logs for V=1 builds kbuild: re-run modpost when it is updated kbuild: unify two modpost invocations kbuild: move vmlinux.o rule to the top Makefile kbuild: move .vmlinux.objs rule to Makefile.modpost kbuild: list sub-directories in ./Kbuild Makefile.compiler: replace cc-ifversion with compiler-specific macros ...
2022-09-29kbuild: unify two modpost invocationsMasahiro Yamada1-1/+1
Currently, modpost is executed twice; first for vmlinux, second for modules. This commit merges them. Current build flow ================== 1) build obj-y and obj-m objects 2) link vmlinux.o 3) modpost for vmlinux 4) link vmlinux 5) modpost for modules 6) link modules (*.ko) The build steps 1) through 6) are serialized, that is, modules are built after vmlinux. You do not get benefits of parallel builds when scripts/link-vmlinux.sh is being run. New build flow ============== 1) build obj-y and obj-m objects 2) link vmlinux.o 3) modpost for vmlinux and modules 4a) link vmlinux 4b) link modules (*.ko) In the new build flow, modpost is invoked just once. vmlinux and modules are built in parallel. One exception is CONFIG_DEBUG_INFO_BTF_MODULES=y, where modules depend on vmlinux. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2022-09-28Kbuild: add Rust supportMiguel Ojeda1-3/+5
Having most of the new files in place, we now enable Rust support in the build system, including `Kconfig` entries related to Rust, the Rust configuration printer and a few other bits. Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com> Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com> Co-developed-by: Finn Behrens <me@kloenk.de> Signed-off-by: Finn Behrens <me@kloenk.de> Co-developed-by: Adam Bratschi-Kaye <ark.email@gmail.com> Signed-off-by: Adam Bratschi-Kaye <ark.email@gmail.com> Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com> Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com> Co-developed-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Co-developed-by: Sven Van Asbroeck <thesven73@gmail.com> Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com> Co-developed-by: Gary Guo <gary@garyguo.net> Signed-off-by: Gary Guo <gary@garyguo.net> Co-developed-by: Boris-Chengbiao Zhou <bobo1239@web.de> Signed-off-by: Boris-Chengbiao Zhou <bobo1239@web.de> Co-developed-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Co-developed-by: Douglas Su <d0u9.su@outlook.com> Signed-off-by: Douglas Su <d0u9.su@outlook.com> Co-developed-by: Dariusz Sosnowski <dsosnowski@dsosnowski.pl> Signed-off-by: Dariusz Sosnowski <dsosnowski@dsosnowski.pl> Co-developed-by: Antonio Terceiro <antonio.terceiro@linaro.org> Signed-off-by: Antonio Terceiro <antonio.terceiro@linaro.org> Co-developed-by: Daniel Xu <dxu@dxuuu.xyz> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Co-developed-by: Björn Roy Baron <bjorn3_gh@protonmail.com> Signed-off-by: Björn Roy Baron <bjorn3_gh@protonmail.com> Co-developed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com> Signed-off-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2022-05-29kbuild: do not create *.prelink.o for Clang LTO or IBTMasahiro Yamada1-3/+2
When CONFIG_LTO_CLANG=y, additional intermediate *.prelink.o is created for each module. Also, objtool is postponed until LLVM IR is converted to ELF. CONFIG_X86_KERNEL_IBT works in a similar way to postpone objtool until objects are merged together. This commit stops generating *.prelink.o, so the build flow will look similar with/without LTO. The following figures show how the LTO build currently works, and how this commit is changing it. Current build flow ================== [1] single-object module $(LD) $(CC) +objtool $(LD) foo.c --------------------> foo.o -----> foo.prelink.o -----> foo.ko (LLVM IR) (ELF) | (ELF) | foo.mod.o --/ (LLVM IR) [2] multi-object module $(LD) $(CC) $(AR) +objtool $(LD) foo1.c -----> foo1.o -----> foo.o -----> foo.prelink.o -----> foo.ko | (archive) (ELF) | (ELF) foo2.c -----> foo2.o --/ | (LLVM IR) foo.mod.o --/ (LLVM IR) One confusion is that foo.o in multi-object module is an archive despite of its suffix. New build flow ============== [1] single-object module Since there is only one object, there is no need to keep the LLVM IR. Use $(CC)+$(LD) to generate an ELF object in one build rule. When LTO is disabled, $(LD) is unneeded because $(CC) produces an ELF object. $(CC)+$(LD)+objtool $(LD) foo.c ----------------------------> foo.o ---------> foo.ko (ELF) | (ELF) | foo.mod.o --/ (LLVM IR) [2] multi-object module Previously, $(AR) was used to combine LLVM IR files into an archive, but there was no technical reason to do so. Use $(LD) to merge them into a single ELF object. $(LD) $(CC) +objtool $(LD) foo1.c ---------> foo1.o ---------> foo.o ---------> foo.ko | (ELF) | (ELF) foo2.c ---------> foo2.o ----/ | (LLVM IR) foo.mod.o --/ (LLVM IR) Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu> Tested-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Sami Tolvanen <samitolvanen@google.com> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64) Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
2021-11-02kbuild: Unify options for BTF generation for vmlinux and modulesJiri Olsa1-1/+1
Using new PAHOLE_FLAGS variable to pass extra arguments to pahole for both vmlinux and modules BTF data generation. Adding new scripts/pahole-flags.sh script that detect and prints pahole options. [ fixed issues found by kernel test robot ] Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20211029125729.70002-1-jolsa@kernel.org
2021-10-06bpf: Enable TCP congestion control kfunc from modulesKumar Kartikeya Dwivedi1-0/+1
This commit moves BTF ID lookup into the newly added registration helper, in a way that the bbr, cubic, and dctcp implementation set up their sets in the bpf_tcp_ca kfunc_btf_set list, while the ones not dependent on modules are looked up from the wrapper function. This lifts the restriction for them to be compiled as built in objects, and can be loaded as modules if required. Also modify Makefile.modfinal to call resolve_btfids for each module. Note that since kernel kfunc_ids never overlap with module kfunc_ids, we only match the owner for module btf id sets. See following commits for background on use of: CONFIG_X86 ifdef: 569c484f9995 (bpf: Limit static tcp-cc functions in the .BTF_ids list to x86) CONFIG_DYNAMIC_FTRACE ifdef: 7aae231ac93b (bpf: tcp: Limit calling some tcp cc functions to CONFIG_DYNAMIC_FTRACE) Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211002011757.311265-6-memxor@gmail.com
2021-09-03kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANGSami Tolvanen1-19/+2
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>
2021-07-10Merge tag 'kbuild-v5.14' of ↵Linus Torvalds1-2/+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 ...
2021-05-27kbuild: Quote OBJCOPY var to avoid a pahole call break the buildJavier Martinez Canillas1-1/+1
The ccache tool can be used to speed up cross-compilation, by calling the compiler and binutils through ccache. For example, following should work: $ export ARCH=arm64 CROSS_COMPILE="ccache aarch64-linux-gnu-" $ make M=drivers/gpu/drm/rockchip/ but pahole fails to extract the BTF info from DWARF, breaking the build: CC [M] drivers/gpu/drm/rockchip//rockchipdrm.mod.o LD [M] drivers/gpu/drm/rockchip//rockchipdrm.ko BTF [M] drivers/gpu/drm/rockchip//rockchipdrm.ko aarch64-linux-gnu-objcopy: invalid option -- 'J' Usage: aarch64-linux-gnu-objcopy [option(s)] in-file [out-file] Copies a binary file, possibly transforming it in the process ... make[1]: *** [scripts/Makefile.modpost:156: __modpost] Error 2 make: *** [Makefile:1866: modules] Error 2 this fails because OBJCOPY is set to "ccache aarch64-linux-gnu-copy" and later pahole is executed with the following command line: LLVM_OBJCOPY=$(OBJCOPY) $(PAHOLE) -J --btf_base vmlinux $@ which gets expanded to: LLVM_OBJCOPY=ccache aarch64-linux-gnu-objcopy pahole -J ... instead of: LLVM_OBJCOPY="ccache aarch64-linux-gnu-objcopy" pahole -J ... Fixes: 5f9ae91f7c0d ("kbuild: Build kernel module BTFs if BTF is enabled and pahole supports it") Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com> Link: https://lore.kernel.org/bpf/20210526215228.3729875-1-javierm@redhat.com
2021-05-24kbuild: remove libelf checks from top MakefileMasahiro Yamada1-2/+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>
2021-04-09add support for Clang CFISami Tolvanen1-1/+1
This change adds support for Clang’s forward-edge Control Flow Integrity (CFI) checking. With CONFIG_CFI_CLANG, the compiler injects a runtime check before each indirect function call to ensure the target is a valid function with the correct static type. This restricts possible call targets and makes it more difficult for an attacker to exploit bugs that allow the modification of stored function pointers. For more details, see: https://clang.llvm.org/docs/ControlFlowIntegrity.html Clang requires CONFIG_LTO_CLANG to be enabled with CFI to gain visibility to possible call targets. Kernel modules are supported with Clang’s cross-DSO CFI mode, which allows checking between independently compiled components. With CFI enabled, the compiler injects a __cfi_check() function into the kernel and each module for validating local call targets. For cross-module calls that cannot be validated locally, the compiler calls the global __cfi_slowpath_diag() function, which determines the target module and calls the correct __cfi_check() function. This patch includes a slowpath implementation that uses __module_address() to resolve call targets, and with CONFIG_CFI_CLANG_SHADOW enabled, a shadow map that speeds up module look-ups by ~3x. Clang implements indirect call checking using jump tables and offers two methods of generating them. With canonical jump tables, the compiler renames each address-taken function to <function>.cfi and points the original symbol to a jump table entry, which passes __cfi_check() validation. This isn’t compatible with stand-alone assembly code, which the compiler doesn’t instrument, and would result in indirect calls to assembly code to fail. Therefore, we default to using non-canonical jump tables instead, where the compiler generates a local jump table entry <function>.cfi_jt for each address-taken function, and replaces all references to the function with the address of the jump table entry. Note that because non-canonical jump table addresses are local to each component, they break cross-module function address equality. Specifically, the address of a global function will be different in each module, as it's replaced with the address of a local jump table entry. If this address is passed to a different module, it won’t match the address of the same function taken there. This may break code that relies on comparing addresses passed from other components. CFI checking can be disabled in a function with the __nocfi attribute. Additionally, CFI can be disabled for an entire compilation unit by filtering out CC_FLAGS_CFI. By default, CFI failures result in a kernel panic to stop a potential exploit. CONFIG_CFI_PERMISSIVE enables a permissive mode, where the kernel prints out a rate-limited warning instead, and allows execution to continue. This option is helpful for locating type mismatches, but should only be enabled during development. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20210408182843.1754385-2-samitolvanen@google.com
2021-02-23kbuild: lto: postpone objtoolSami Tolvanen1-3/+16
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>
2021-01-14kbuild: add support for Clang LTOSami Tolvanen1-1/+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
2020-11-25kbuild: Skip module BTF generation for out-of-tree external modulesAndrii Nakryiko1-2/+7
In some modes of operation, Kbuild allows to build modules without having vmlinux image around. In such case, generation of module BTF is impossible. This patch changes the behavior to emit a warning about impossibility of generating kernel module BTF, instead of breaking the build. This is especially important for out-of-tree external module builds. In vmlinux-less mode: $ make clean $ make modules_prepare $ touch drivers/acpi/button.c $ make M=drivers/acpi ... CC [M] drivers/acpi/button.o MODPOST drivers/acpi/Module.symvers LD [M] drivers/acpi/button.ko BTF [M] drivers/acpi/button.ko Skipping BTF generation for drivers/acpi/button.ko due to unavailability of vmlinux ... $ readelf -S ~/linux-build/default/drivers/acpi/button.ko | grep BTF -A1 ... empty ... Now with normal build: $ make all ... LD [M] drivers/acpi/button.ko BTF [M] drivers/acpi/button.ko ... $ readelf -S ~/linux-build/default/drivers/acpi/button.ko | grep BTF -A1 [60] .BTF PROGBITS 0000000000000000 00029310 000000000000ab3f 0000000000000000 0 0 1 Fixes: 5f9ae91f7c0d ("kbuild: Build kernel module BTFs if BTF is enabled and pahole supports it") Reported-by: Bruce Allan <bruce.w.allan@intel.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Jessica Yu <jeyu@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Link: https://lore.kernel.org/bpf/20201121070829.2612884-1-andrii@kernel.org
2020-11-11kbuild: Build kernel module BTFs if BTF is enabled and pahole supports itAndrii Nakryiko1-2/+18
Detect if pahole supports split BTF generation, and generate BTF for each selected kernel module, if it does. This is exposed to Makefiles and C code as CONFIG_DEBUG_INFO_BTF_MODULES flag. Kernel module BTF has to be re-generated if either vmlinux's BTF changes or module's .ko changes. To achieve that, I needed a helper similar to if_changed, but that would allow to filter out vmlinux from the list of updated dependencies for .ko building. I've put it next to the only place that uses and needs it, but it might be a better idea to just add it along the other if_changed variants into scripts/Kbuild.include. Each kernel module's BTF deduplication is pretty fast, as it does only incremental BTF deduplication on top of already deduplicated vmlinux BTF. To show the added build time, I've first ran make only just built kernel (to establish the baseline) and then forced only BTF re-generation, without regenerating .ko files. The build was performed with -j60 parallelization on 56-core machine. The final time also includes bzImage building, so it's not a pure BTF overhead. $ time make -j60 ... make -j60 27.65s user 10.96s system 782% cpu 4.933 total $ touch ~/linux-build/default/vmlinux && time make -j60 ... make -j60 123.69s user 27.85s system 1566% cpu 9.675 total So 4.6 seconds real time, with noticeable part spent in compressed vmlinux and bzImage building. To show size savings, I've built my kernel configuration with about 700 kernel modules with full BTF per each kernel module (without deduplicating against vmlinux) and with split BTF against deduplicated vmlinux (approach in this patch). Below are top 10 modules with biggest BTF sizes. And total size of BTF data across all kernel modules. It shows that split BTF "compresses" 115MB down to 5MB total. And the biggest kernel modules get a downsize from 500-570KB down to 200-300KB. FULL BTF ======== $ for f in $(find . -name '*.ko'); do size -A -d $f | grep BTF | awk '{print $2}'; done | awk '{ s += $1 } END { print s }' 115710691 $ for f in $(find . -name '*.ko'); do printf "%s %d\n" $f $(size -A -d $f | grep BTF | awk '{print $2}'); done | sort -nr -k2 | head -n10 ./drivers/gpu/drm/i915/i915.ko 570570 ./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko 520240 ./drivers/gpu/drm/radeon/radeon.ko 503849 ./drivers/infiniband/hw/mlx5/mlx5_ib.ko 491777 ./fs/xfs/xfs.ko 411544 ./drivers/net/ethernet/intel/i40e/i40e.ko 403904 ./drivers/net/ethernet/broadcom/bnx2x/bnx2x.ko 398754 ./drivers/infiniband/core/ib_core.ko 397224 ./fs/cifs/cifs.ko 386249 ./fs/nfsd/nfsd.ko 379738 SPLIT BTF ========= $ for f in $(find . -name '*.ko'); do size -A -d $f | grep BTF | awk '{print $2}'; done | awk '{ s += $1 } END { print s }' 5194047 $ for f in $(find . -name '*.ko'); do printf "%s %d\n" $f $(size -A -d $f | grep BTF | awk '{print $2}'); done | sort -nr -k2 | head -n10 ./drivers/gpu/drm/i915/i915.ko 293206 ./drivers/gpu/drm/radeon/radeon.ko 282103 ./fs/xfs/xfs.ko 222150 ./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko 198503 ./drivers/infiniband/hw/mlx5/mlx5_ib.ko 198356 ./drivers/net/ethernet/broadcom/bnx2x/bnx2x.ko 113444 ./fs/cifs/cifs.ko 109379 ./arch/x86/kvm/kvm.ko 100225 ./drivers/gpu/drm/drm.ko 94827 ./drivers/infiniband/core/ib_core.ko 91188 Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20201110011932.3201430-4-andrii@kernel.org
2020-09-24kbuild: preprocess module linker scriptMasahiro Yamada1-3/+2
There was a request to preprocess the module linker script like we do for the vmlinux one. (https://lkml.org/lkml/2020/8/21/512) The difference between vmlinux.lds and module.lds is that the latter is needed for external module builds, thus must be cleaned up by 'make mrproper' instead of 'make clean'. Also, it must be created by 'make modules_prepare'. You cannot put it in arch/$(SRCARCH)/kernel/, which is cleaned up by 'make clean'. I moved arch/$(SRCARCH)/kernel/module.lds to arch/$(SRCARCH)/include/asm/module.lds.h, which is included from scripts/module.lds.S. scripts/module.lds is fine because 'make clean' keeps all the build artifacts under scripts/. You can add arch-specific sections in <asm/module.lds.h>. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Tested-by: Jessica Yu <jeyu@kernel.org> Acked-by: Will Deacon <will@kernel.org> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: Palmer Dabbelt <palmerdabbelt@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Jessica Yu <jeyu@kernel.org>
2019-08-21kbuild: move modkern_{c,a}flags to Makefile.lib from Makefile.buildMasahiro Yamada1-3/+3
Makefile.lib is included by Makefile.modfinal as well as Makefile.build. Move modkern_cflags to Makefile.lib in order to simplify cmd_cc_o_c in Makefile.modfinal. Move modkern_cflags as well for consistency. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-08-21kbuild: split final module linking out into Makefile.modfinalMasahiro Yamada1-0/+60
I think splitting the modpost and linking modules into separate Makefiles will be useful especially when more complex build steps come in. The main motivation of this commit is to integrate the proposed klp-convert feature cleanly. I moved the logging 'Building modules, stage 2.' to Makefile.modpost to avoid the code duplication although I do not know whether or not this message is needed in the first place. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
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