user/sven/linux.git/scripts/Makefile.build, branch v6.0.18

kbuild: remove sed command from cmd_ar_builtin

2022-07-27T12:17:59Z

Replace a pipeline of echo and sed with printf to decrease process forks. Signed-off-by: Masahiro Yamada Reviewed-by: Nick Desaulniers

kbuild: avoid regex RS for POSIX awk

2022-06-07T16:27:26Z

In 22f26f21774f8 awk was added to deduplicate *.mod files. The awk invocation passes -v RS='( |\n)' to match a space or newline character as the record separator. Unfortunately, POSIX states[1] > If RS contains more than one character, the results are unspecified. Some implementations (such as the One True Awk[2] used by the BSDs) do not treat RS as a regular expression. When awk does not support regex RS, build failures such as the following are produced (first error using allmodconfig): CC [M] arch/x86/events/intel/uncore.o CC [M] arch/x86/events/intel/uncore_nhmex.o CC [M] arch/x86/events/intel/uncore_snb.o CC [M] arch/x86/events/intel/uncore_snbep.o CC [M] arch/x86/events/intel/uncore_discovery.o LD [M] arch/x86/events/intel/intel-uncore.o ld: cannot find uncore_nhmex.o: No such file or directory ld: cannot find uncore_snb.o: No such file or directory ld: cannot find uncore_snbep.o: No such file or directory ld: cannot find uncore_discovery.o: No such file or directory make[3]: *** [scripts/Makefile.build:422: arch/x86/events/intel/intel-uncore.o] Error 1 make[2]: *** [scripts/Makefile.build:487: arch/x86/events/intel] Error 2 make[1]: *** [scripts/Makefile.build:487: arch/x86/events] Error 2 make: *** [Makefile:1839: arch/x86] Error 2 To avoid this, use printf(1) to produce a newline between each object path, instead of the space produced by echo(1), so that the default RS can be used by awk. [1]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/awk.html [2]: https://github.com/onetrueawk/awk Fixes: 22f26f21774f ("kbuild: get rid of duplication in *.mod files") Signed-off-by: Kevin Locke Signed-off-by: Masahiro Yamada

kbuild: factor out the common objtool arguments

2022-06-04T21:20:57Z

scripts/Makefile.build and scripts/link-vmlinux.sh have similar setups for the objtool arguments. It was difficult to factor out them because all the vmlinux build rules were written in a shell script. It is somewhat tedious to touch the two files every time a new objtool option is supported. To reduce the code duplication, move the objtool for vmlinux.o into scripts/Makefile.vmlinux_o. Then, move the common macros to Makefile.lib so they are shared between Makefile.build and Makefile.vmlinux_o. Signed-off-by: Masahiro Yamada Tested-by: Sedat Dilek # LLVM-14 (x86-64)

kbuild: rebuild multi-object modules when objtool is updated

2022-06-01T14:07:29Z

When CONFIG_LTO_CLANG or CONFIG_X86_KERNEL_IBT is enabled, objtool for multi-object modules is postponed until the objects are linked together. Make sure to re-run objtool and re-link multi-object modules when objtool is updated. Signed-off-by: Masahiro Yamada Reviewed-by: Kees Cook Acked-by: Josh Poimboeuf Tested-by: Nathan Chancellor Reviewed-by: Nicolas Schier Tested-by: Sedat Dilek # LLVM-14 (x86-64)

kbuild: make *.mod rule robust against too long argument error

2022-06-01T14:07:29Z

Like built-in.a, the command length of the *.mod rule scales with the depth of the directory times the number of objects in the Makefile. Add $(obj)/ by the shell command (awk) instead of by Make's builtin function. In-tree modules still have some room to the limit (ARG_MAX=2097152), but this is more future-proof for big modules in a deep directory. For example, you can build i915 as a module (CONFIG_DRM_I915=m) and compare drivers/gpu/drm/i915/.i915.mod.cmd with/without this commit. The issue is more critical for external modules because the M= path can be very long as Jeff Johnson reported before [1]. [1] https://lore.kernel.org/linux-kbuild/4c02050c4e95e4cb8cc04282695f8404@codeaurora.org/ Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier Tested-by: Nathan Chancellor Tested-by: Sedat Dilek # LLVM-14 (x86-64)

kbuild: make built-in.a rule robust against too long argument error

2022-06-01T14:07:29Z

Kbuild runs at the top of objtree instead of changing the working directory to subdirectories. I think this design is nice overall but some commands have a scalability issue. The build command of built-in.a is one of them whose length scales with: O(D * N) Here, D is the length of the directory path (i.e. $(obj)/ prefix), N is the number of objects in the Makefile, O() is the big O notation. The deeper directory the Makefile directory is located, the more easily it will hit the too long argument error. We can make it better. Trim the $(obj)/ by Make's builtin function, and restore it by a shell command (sed). With this, the command length scales with: O(D + N) In-tree modules still have some room to the limit (ARG_MAX=2097152), but this is more future-proof for big modules in a deep directory. For example, you can build i915 as builtin (CONFIG_DRM_I915=y) and compare drivers/gpu/drm/i915/.built-in.a.cmd with/without this commit. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier Tested-by: Nathan Chancellor Tested-by: Sedat Dilek # LLVM-14 (x86-64)

kbuild: check static EXPORT_SYMBOL* by script instead of modpost

2022-06-01T14:07:02Z

The 'static' specifier and EXPORT_SYMBOL() are an odd combination. Commit 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions") tried to detect it, but this check has false negatives. Here is the sample code. Makefile: obj-y += foo1.o foo2.o foo1.c: #include static void foo(void) {} EXPORT_SYMBOL(foo); foo2.c: void foo(void) {} foo1.c exports the static symbol 'foo', but modpost cannot catch it because it is fooled by foo2.c, which has a global symbol with the same name. s->is_static is cleared if a global symbol with the same name is found somewhere, but EXPORT_SYMBOL() and the global symbol do not necessarily belong to the same compilation unit. This check should be done per compilation unit, but I do not know how to do it in modpost. modpost runs against vmlinux.o or modules, which merges multiple objects, then forgets their origin. modpost cannot parse individual objects because they may not be ELF but LLVM IR when CONFIG_LTO_CLANG=y. Add a simple bash script to parse the output from ${NM}. This works for CONFIG_LTO_CLANG=y because llvm-nm can dump symbols of LLVM IR files. Revert 15bfc2348d54. Signed-off-by: Masahiro Yamada Reviewed-by: Nick Desaulniers Tested-by: Nathan Chancellor Tested-by: Sedat Dilek # LLVM-14 (x86-64)

kbuild: do not create *.prelink.o for Clang LTO or IBT

2022-05-29T09:39:35Z

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 Reviewed-by: Nicolas Schier Tested-by: Nathan Chancellor Reviewed-by: Sami Tolvanen Tested-by: Sedat Dilek # LLVM-14 (x86-64) Acked-by: Josh Poimboeuf

kbuild: replace $(linked-object) with CONFIG options

2022-05-29T09:39:35Z

*.prelink.o is created when CONFIG_LTO_CLANG or CONFIG_X86_KERNEL_IBT is enabled. Replace $(linked-object) with $(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT) so you will get a quick idea of when the --link option is passed. No functional change is intended. Signed-off-by: Masahiro Yamada Acked-by: Josh Poimboeuf Reviewed-by: Nick Desaulniers Tested-by: Sedat Dilek # LLVM-14

Merge tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

2022-05-26T19:09:50Z

Pull Kbuild updates from Masahiro Yamada: - Add HOSTPKG_CONFIG env variable to allow users to override pkg-config - Support W=e as a shorthand for KCFLAGS=-Werror - Fix CONFIG_IKHEADERS build to support toybox cpio - Add scripts/dummy-tools/pahole to ease distro packagers' life - Suppress false-positive warnings from checksyscalls.sh for W=2 build - Factor out the common code of arch/*/boot/install.sh into scripts/install.sh - Support 'kernel-install' tool in scripts/prune-kernel - Refactor module-versioning to link the symbol versions at the final link of vmlinux and modules - Remove CONFIG_MODULE_REL_CRCS because module-versioning now works in an arch-agnostic way - Refactor modpost, Makefiles * tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (56 commits) genksyms: adjust the output format to modpost kbuild: stop merging *.symversions kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS modpost: extract symbol versions from *.cmd files modpost: add sym_find_with_module() helper modpost: change the license of EXPORT_SYMBOL to bool type modpost: remove left-over cross_compile declaration kbuild: record symbol versions in *.cmd files kbuild: generate a list of objects in vmlinux modpost: move *.mod.c generation to write_mod_c_files() modpost: merge add_{intree_flag,retpoline,staging_flag} to add_header scripts/prune-kernel: Use kernel-install if available kbuild: factor out the common installation code into scripts/install.sh modpost: split new_symbol() to symbol allocation and hash table addition modpost: make sym_add_exported() always allocate a new symbol modpost: make multiple export error modpost: dump Module.symvers in the same order of modules.order modpost: traverse the namespace_list in order modpost: use doubly linked list for dump_lists modpost: traverse unresolved symbols in order ...