linux/Documentation/process/changes.rst, branch v5.19

scripts/check-local-export: avoid 'wait $!' for process substitution

2022-06-09T18:47:13Z

Bash 4.4, released in 2016, supports 'wait $!' to check the exit status of a process substitution, but it seems too new. Some people using older bash versions (on CentOS 7, Ubuntu 16.04, etc.) reported an error like this: ./scripts/check-local-export: line 54: wait: pid 17328 is not a child of this shell I used the process substitution to avoid a pipeline, which executes each command in a subshell. If the while-loop is executed in the subshell context, variable changes within are lost after the subshell terminates. Fortunately, Bash 4.2, released in 2011, supports the 'lastpipe' option, which makes the last element of a pipeline run in the current shell process. Switch to the pipeline with 'lastpipe' solution, and also set 'pipefail' to catch errors from ${NM}. Add the bash requirement to Documentation/process/changes.rst. Fixes: 31cb50b5590f ("kbuild: check static EXPORT_SYMBOL* by script instead of modpost") Reported-by: Tetsuo Handa Reported-by: Michael Ellerman Reported-by: Wang Yugui Tested-by: Tetsuo Handa Tested-by: Jon Hunter Acked-by: Nick Desaulniers Tested-by: Sedat Dilek # LLVM-14 (x86-64) Signed-off-by: Masahiro Yamada

Docs: Replace version by 'current' in changes.rst

2022-04-22T15:47:25Z

The file 'Documentation/process/changes.rst' states the listed requirements are for the 4.x kernel version. However, there are requirements updated for the 5.x version, as there might be in other future versions. This patch updates it to 'latest' so the document won't be outdated in the future. Signed-off-by: Bruno Moreira-Guedes Signed-off-by: Jonathan Corbet

Docs: Add cpio requirement to changes.rst

2022-04-22T15:47:25Z

The install target requires cpio to run the `kernel/gen_kheaders.sh` script, but it's missing in the requirements list at 'Documentation/process/changes.rst'. This patch adds it to the list. Signed-off-by: Bruno Moreira-Guedes Signed-off-by: Jonathan Corbet

Merge tag 'kbuild-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

2022-01-19T09:15:19Z

Pull Kbuild updates from Masahiro Yamada: - Add new kconfig target 'make mod2noconfig', which will be useful to speed up the build and test iteration. - Raise the minimum supported version of LLVM to 11.0.0 - Refactor certs/Makefile - Change the format of include/config/auto.conf to stop double-quoting string type CONFIG options. - Fix ARCH=sh builds in dash - Separate compression macros for general purposes (cmd_bzip2 etc.) and the ones for decompressors (cmd_bzip2_with_size etc.) - Misc Makefile cleanups * tag 'kbuild-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (34 commits) kbuild: add cmd_file_size arch: decompressor: remove useless vmlinux.bin.all-y kbuild: rename cmd_{bzip2,lzma,lzo,lz4,xzkern,zstd22} kbuild: drop $(size_append) from cmd_zstd sh: rename suffix-y to suffix_y doc: kbuild: fix default in `imply` table microblaze: use built-in function to get CPU_{MAJOR,MINOR,REV} certs: move scripts/extract-cert to certs/ kbuild: do not quote string values in include/config/auto.conf kbuild: do not include include/config/auto.conf from shell scripts certs: simplify $(srctree)/ handling and remove config_filename macro kbuild: stop using config_filename in scripts/Makefile.modsign certs: remove misleading comments about GCC PR certs: refactor file cleaning certs: remove unneeded -I$(srctree) option for system_certificates.o certs: unify duplicated cmd_extract_certs and improve the log certs: use $< and $@ to simplify the key generation rule kbuild: remove headers_check stub kbuild: move headers_check.pl to usr/include/ certs: use if_changed to re-generate the key when the key type is changed ...

Documentation: Raise the minimum supported version of LLVM to 11.0.0

2021-12-02T08:24:32Z

LLVM versions prior to 11.0.0 have a harder time with dead code elimination, which can cause issues with commonly used expressions such as BUILD_BUG_ON and the bitmask functions/macros in bitfield.h (see the first two issues links below). Whenever there is an issue within LLVM that has been resolved in a later release, the only course of action is to gate the problematic configuration or source code on the toolchain verson or raise the minimum supported version of LLVM for building the kernel, as LLVM has a limited support lifetime compared to GCC. GCC major releases will typically see a few point releases across a two year period on average whereas LLVM major releases are only supported until the next major release and will only see one or two point releases within that timeframe. For example, GCC 8.1 was released in May 2018 and GCC 8.5 was released in May 2021, whereas LLVM 12.0.0 was released in April 2021 and its only point release, 12.0.1, was released in July 2021, giving a minimal window for fixes to be backported. To resolve these build errors around improper dead code elimination, raise the minimum supported version of LLVM for building the kernel to 11.0.0. Doing so is a more proper solution than mucking around with core kernel macros that have always worked with GCC or disabling drivers for using these macros in a proper manner. This type of issue may continue to crop up and require patching, which creates more debt for bumping the minimum supported version in the future. This should have a minimal impact to distributions. Using a script to pull several different Docker images and check the output of 'clang --version': archlinux:latest: clang version 13.0.0 debian:oldoldstable-slim: clang version 3.8.1-24 (tags/RELEASE_381/final) debian:oldstable-slim: clang version 7.0.1-8+deb10u2 (tags/RELEASE_701/final) debian:stable-slim: Debian clang version 11.0.1-2 debian:testing-slim: Debian clang version 11.1.0-4 debian:unstable-slim: Debian clang version 11.1.0-4 fedora:34: clang version 12.0.1 (Fedora 12.0.1-1.fc34) fedora:latest: clang version 13.0.0 (Fedora 13.0.0-3.fc35) fedora:rawhide: clang version 13.0.0 (Fedora 13.0.0-5.fc36) opensuse/leap:15.2: clang version 9.0.1 opensuse/leap:latest: clang version 11.0.1 opensuse/tumbleweed:latest: clang version 13.0.0 ubuntu:bionic: clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final) ubuntu:latest: clang version 10.0.0-4ubuntu1 ubuntu:hirsute: Ubuntu clang version 12.0.0-3ubuntu1~21.04.2 ubuntu:rolling: Ubuntu clang version 13.0.0-2 ubuntu:devel: Ubuntu clang version 13.0.0-9 In every case, the distribution's version of clang is either older than the current minimum supported version of LLVM 10.0.1 or equal to or greater than the proposed 11.0.0 so nothing should change. Another benefit of this change is LLVM=1 works better with arm64 and x86_64 since commit f12b034afeb3 ("scripts/Makefile.clang: default to LLVM_IAS=1") enabled the integrated assembler by default, which only works well with clang 11+ (clang-10 required it to be disabled to successfully build a kernel). Link: https://github.com/ClangBuiltLinux/linux/issues/1293 Link: https://github.com/ClangBuiltLinux/linux/issues/1506 Link: https://github.com/ClangBuiltLinux/linux/issues/1511 Link: https://github.com/llvm/llvm-project/commit/fa496ce3c6774097080c8a9cb808da56f383b938 Link: https://groups.google.com/g/clang-built-linux/c/mPQb9_ZWW0s/m/W7o6S-QTBAAJ Link: https://github.com/ClangBuiltLinux/misc-scripts Signed-off-by: Nathan Chancellor Reviewed-by: Miguel Ojeda Reviewed-by: Mark Brown Reviewed-by: Nick Desaulniers Reviewed-by: Kees Cook Signed-off-by: Masahiro Yamada

Documentation: Add minimum pahole version

2021-11-29T21:48:00Z

A report was made in https://github.com/acmel/dwarves/issues/26 about pahole not being listed in the process/changes.rst file as being needed for building the kernel, address that. Link: https://github.com/acmel/dwarves/issues/26 Acked-by: Andrii Nakryiko Acked-by: Daniel Borkmann Cc: Alexei Starovoitov Cc: Jiri Olsa Link: http://lore.kernel.org/lkml/YZPQ6+u2wTHRfR+W@kernel.org Signed-off-by: Arnaldo Carvalho de Melo Link: https://lore.kernel.org/r/YZfzQ0DvHD5o26Bt@kernel.org Signed-off-by: Jonathan Corbet

docs: Update Sphinx requirements

2021-11-15T09:47:22Z

Commit f546ff0c0c07 ("Move our minimum Sphinx version to 1.7") raised the minimum version to 1.7. For pdfdocs, sphinx_pre_install says: note: If you want pdf, you need at least Sphinx 2.4.4. , and current requirements.txt installs Sphinx 2.4.4. Update Sphinx versions mentioned in docs and remove a note on earlier Sphinx versions. Update zh_CN and it_IT translations as well. Signed-off-by: Akira Yokosawa Cc: Federico Vaga Cc: Alex Shi Reviewed-by: Alex Shi Signed-off-by: Jonathan Corbet

Documentation: raise minimum supported version of GCC to 5.1

2021-09-13T17:18:28Z

commit fad7cd3310db ("nbd: add the check to prevent overflow in __nbd_ioctl()") raised an issue from the fallback helpers added in commit f0907827a8a9 ("compiler.h: enable builtin overflow checkers and add fallback code") Specifically, the helpers for checking whether the results of a multiplication overflowed (__unsigned_mul_overflow, __signed_add_overflow) use the division operator when !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW. This is problematic for 64b operands on 32b hosts. Also, because the macro is type agnostic, it is very difficult to write a similarly type generic macro that dispatches to one of: * div64_s64 * div64_u64 * div_s64 * div_u64 Raising the minimum supported versions allows us to remove all of the fallback helpers for !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW, instead dispatching the compiler builtins. arm64 has already raised the minimum supported GCC version to 5.1, do this for all targets now. See the link below for the previous discussion. Link: https://lore.kernel.org/all/20210909182525.372ee687@canb.auug.org.au/ Link: https://lore.kernel.org/lkml/CAK7LNASs6dvU6D3jL2GG3jW58fXfaj6VNOe55NJnTB8UPuk2pA@mail.gmail.com/ Link: https://github.com/ClangBuiltLinux/linux/issues/1438 Reported-by: Stephen Rothwell Reported-by: Nathan Chancellor Suggested-by: Rasmus Villemoes Signed-off-by: Nick Desaulniers Reviewed-by: Kees Cook Reviewed-by: Nathan Chancellor Signed-off-by: Linus Torvalds

oprofiled version output line removed from the list

2021-05-03T23:23:06Z

Oprofiled version output line removed from the list. Signed-off-by: Bhaskar Chowdhury Link: https://lore.kernel.org/r/8d1928ff2fea29d67143d235839a5e845e4402c9.1619181632.git.unixbhaskar@gmail.com Signed-off-by: Jonathan Corbet

Documentation: add minimum clang/llvm version

2020-08-31T22:30:20Z

Based on a vote at the LLVM BoF at Plumbers 2020, we decided to start small, supporting just one formal upstream release of LLVM for now. We can probably widen the support window of supported versions over time. Also, note that LLVM's release process is different than GCC's. GCC tends to have 1 major release per year while releasing minor updates to the past 3 major versions. LLVM tends to support one major release and one minor release every six months. Signed-off-by: Nick Desaulniers Tested-by: Gustavo A. R. Silva Tested-by: Nathan Chancellor Reviewed-by: Kees Cook Reviewed-by: Nathan Chancellor Reviewed-by: Masahiro Yamada Acked-by: Will Deacon Link: https://lore.kernel.org/r/20200826191555.3350406-1-ndesaulniers@google.com Signed-off-by: Jonathan Corbet