linux/Documentation/process/changes.rst

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Documentation: raise minimum supported version of GCC to 5.1 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 <sfr@canb.auug.org.au> Reported-by: Nathan Chancellor <nathan@kernel.org> Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-10 16:40:38 -07:00
Documentation: Raise the minimum supported version of LLVM to 11.0.0 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 <nathan@kernel.org> Reviewed-by: Miguel Ojeda <ojeda@kernel.org> Reviewed-by: Mark Brown <broonie@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-11-29 09:57:58 -07:00
docs: add Rust documentation Most of the documentation for Rust is written within the source code itself, as it is idiomatic for Rust projects. This applies to both the shared infrastructure at `rust/` as well as any other Rust module (e.g. drivers) written across the kernel. However, these documents contain general information that does not fit particularly well in the source code, like the Quick Start guide. It also contains a few other small changes elsewhere in the documentation folder. Reviewed-by: Kees Cook <keescook@chromium.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: Wu XiangCheng <bobwxc@email.cn> Signed-off-by: Wu XiangCheng <bobwxc@email.cn> 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: Yuki Okushi <jtitor@2k36.org> Signed-off-by: Yuki Okushi <jtitor@2k36.org> Co-developed-by: Wei Liu <wei.liu@kernel.org> Signed-off-by: Wei Liu <wei.liu@kernel.org> Co-developed-by: Daniel Xu <dxu@dxuuu.xyz> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Co-developed-by: Julian Merkle <me@jvmerkle.de> Signed-off-by: Julian Merkle <me@jvmerkle.de> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2021-07-03 17:23:16 +02:00
kbuild: prepare to remove C files pre-generated by flex and bison In Linux build system convention, pre-generated files are version- controlled with a "_shipped" suffix. During the kernel building, they are simply shipped (copied) removing the suffix. This approach can reduce external tool dependency for the kernel build, but it is tedious to manually regenerate such artifacts from developers' point of view. (We need to do "make REGENERATE_PARSERS=1" every time we touch real source files such as *.l, *.y) Some months ago, I sent out RFC patches to run flex, bison, and gperf during the build. In the review and test, Linus noticed gperf-3.1 had changed the lookup function prototype. Then, the use of gperf in kernel was entirely removed by commit bb3290d91695 ("Remove gperf usage from toolchain"). This time, I tested several versions of flex and bison, and I was not hit by any compatibility issue except a flaw in flex-2.6.3; if you generate lexer for dtc and genksyms with flex-2.6.3, you will see "yywrap redefined" warning. This was not intentional, but a bug, fixed by flex-2.6.4. Otherwise, both flex and bison look fairly stable for a long time. This commit prepares some build rules to remove the _shipped files. Also, document minimal requirement for flex and bison. Rationale for the minimal version: The -Wmissing-prototypes option of GCC warns "no previous prototype" for lexers generated by flex-2.5.34 or older, so I chose 2.5.35 as the required version for flex. Flex-2.5.35 was released in 2008. Bison looks more stable. I did not see any problem with bison-2.0, released in 2004. I did not test bison-1.x, but bison-2.0 should be old enough. Tested flex versions: 2.5.35 2.5.36 2.5.37 2.5.39 2.6.0 2.6.1 2.6.2 2.6.3 (*) 2.6.4 (*) flex-2.6.3 causes "yywrap redefined" warning Tested bison versions: 2.0 2.1 2.2 2.3 2.4 2.4.1 2.5.1 2.6 2.6.1 2.6.2 2.6.3 2.6.4 2.6.5 2.7 2.7.1 3.0 3.0.1 3.0.2 3.0.3 3.0.4 Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-12-10 01:02:29 +09:00
docs: add Rust documentation Most of the documentation for Rust is written within the source code itself, as it is idiomatic for Rust projects. This applies to both the shared infrastructure at `rust/` as well as any other Rust module (e.g. drivers) written across the kernel. However, these documents contain general information that does not fit particularly well in the source code, like the Quick Start guide. It also contains a few other small changes elsewhere in the documentation folder. Reviewed-by: Kees Cook <keescook@chromium.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: Wu XiangCheng <bobwxc@email.cn> Signed-off-by: Wu XiangCheng <bobwxc@email.cn> 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: Yuki Okushi <jtitor@2k36.org> Signed-off-by: Yuki Okushi <jtitor@2k36.org> Co-developed-by: Wei Liu <wei.liu@kernel.org> Signed-off-by: Wei Liu <wei.liu@kernel.org> Co-developed-by: Daniel Xu <dxu@dxuuu.xyz> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Co-developed-by: Julian Merkle <me@jvmerkle.de> Signed-off-by: Julian Merkle <me@jvmerkle.de> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2021-07-03 17:23:16 +02:00
kbuild: prepare to remove C files pre-generated by flex and bison In Linux build system convention, pre-generated files are version- controlled with a "_shipped" suffix. During the kernel building, they are simply shipped (copied) removing the suffix. This approach can reduce external tool dependency for the kernel build, but it is tedious to manually regenerate such artifacts from developers' point of view. (We need to do "make REGENERATE_PARSERS=1" every time we touch real source files such as *.l, *.y) Some months ago, I sent out RFC patches to run flex, bison, and gperf during the build. In the review and test, Linus noticed gperf-3.1 had changed the lookup function prototype. Then, the use of gperf in kernel was entirely removed by commit bb3290d91695 ("Remove gperf usage from toolchain"). This time, I tested several versions of flex and bison, and I was not hit by any compatibility issue except a flaw in flex-2.6.3; if you generate lexer for dtc and genksyms with flex-2.6.3, you will see "yywrap redefined" warning. This was not intentional, but a bug, fixed by flex-2.6.4. Otherwise, both flex and bison look fairly stable for a long time. This commit prepares some build rules to remove the _shipped files. Also, document minimal requirement for flex and bison. Rationale for the minimal version: The -Wmissing-prototypes option of GCC warns "no previous prototype" for lexers generated by flex-2.5.34 or older, so I chose 2.5.35 as the required version for flex. Flex-2.5.35 was released in 2008. Bison looks more stable. I did not see any problem with bison-2.0, released in 2004. I did not test bison-1.x, but bison-2.0 should be old enough. Tested flex versions: 2.5.35 2.5.36 2.5.37 2.5.39 2.6.0 2.6.1 2.6.2 2.6.3 (*) 2.6.4 (*) flex-2.6.3 causes "yywrap redefined" warning Tested bison versions: 2.0 2.1 2.2 2.3 2.4 2.4.1 2.5.1 2.6 2.6.1 2.6.2 2.6.3 2.6.4 2.6.5 2.7 2.7.1 3.0 3.0.1 3.0.2 3.0.3 3.0.4 Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-12-10 01:02:29 +09:00
docs: add Rust documentation Most of the documentation for Rust is written within the source code itself, as it is idiomatic for Rust projects. This applies to both the shared infrastructure at `rust/` as well as any other Rust module (e.g. drivers) written across the kernel. However, these documents contain general information that does not fit particularly well in the source code, like the Quick Start guide. It also contains a few other small changes elsewhere in the documentation folder. Reviewed-by: Kees Cook <keescook@chromium.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: Wu XiangCheng <bobwxc@email.cn> Signed-off-by: Wu XiangCheng <bobwxc@email.cn> 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: Yuki Okushi <jtitor@2k36.org> Signed-off-by: Yuki Okushi <jtitor@2k36.org> Co-developed-by: Wei Liu <wei.liu@kernel.org> Signed-off-by: Wei Liu <wei.liu@kernel.org> Co-developed-by: Daniel Xu <dxu@dxuuu.xyz> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Co-developed-by: Julian Merkle <me@jvmerkle.de> Signed-off-by: Julian Merkle <me@jvmerkle.de> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2021-07-03 17:23:16 +02:00
docs: add Rust documentation Most of the documentation for Rust is written within the source code itself, as it is idiomatic for Rust projects. This applies to both the shared infrastructure at `rust/` as well as any other Rust module (e.g. drivers) written across the kernel. However, these documents contain general information that does not fit particularly well in the source code, like the Quick Start guide. It also contains a few other small changes elsewhere in the documentation folder. Reviewed-by: Kees Cook <keescook@chromium.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: Wu XiangCheng <bobwxc@email.cn> Signed-off-by: Wu XiangCheng <bobwxc@email.cn> 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: Yuki Okushi <jtitor@2k36.org> Signed-off-by: Yuki Okushi <jtitor@2k36.org> Co-developed-by: Wei Liu <wei.liu@kernel.org> Signed-off-by: Wei Liu <wei.liu@kernel.org> Co-developed-by: Daniel Xu <dxu@dxuuu.xyz> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Co-developed-by: Julian Merkle <me@jvmerkle.de> Signed-off-by: Julian Merkle <me@jvmerkle.de> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2021-07-03 17:23:16 +02:00
kbuild: prepare to remove C files pre-generated by flex and bison In Linux build system convention, pre-generated files are version- controlled with a "_shipped" suffix. During the kernel building, they are simply shipped (copied) removing the suffix. This approach can reduce external tool dependency for the kernel build, but it is tedious to manually regenerate such artifacts from developers' point of view. (We need to do "make REGENERATE_PARSERS=1" every time we touch real source files such as *.l, *.y) Some months ago, I sent out RFC patches to run flex, bison, and gperf during the build. In the review and test, Linus noticed gperf-3.1 had changed the lookup function prototype. Then, the use of gperf in kernel was entirely removed by commit bb3290d91695 ("Remove gperf usage from toolchain"). This time, I tested several versions of flex and bison, and I was not hit by any compatibility issue except a flaw in flex-2.6.3; if you generate lexer for dtc and genksyms with flex-2.6.3, you will see "yywrap redefined" warning. This was not intentional, but a bug, fixed by flex-2.6.4. Otherwise, both flex and bison look fairly stable for a long time. This commit prepares some build rules to remove the _shipped files. Also, document minimal requirement for flex and bison. Rationale for the minimal version: The -Wmissing-prototypes option of GCC warns "no previous prototype" for lexers generated by flex-2.5.34 or older, so I chose 2.5.35 as the required version for flex. Flex-2.5.35 was released in 2008. Bison looks more stable. I did not see any problem with bison-2.0, released in 2004. I did not test bison-1.x, but bison-2.0 should be old enough. Tested flex versions: 2.5.35 2.5.36 2.5.37 2.5.39 2.6.0 2.6.1 2.6.2 2.6.3 (*) 2.6.4 (*) flex-2.6.3 causes "yywrap redefined" warning Tested bison versions: 2.0 2.1 2.2 2.3 2.4 2.4.1 2.5.1 2.6 2.6.1 2.6.2 2.6.3 2.6.4 2.6.5 2.7 2.7.1 3.0 3.0.1 3.0.2 3.0.3 3.0.4 Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-12-10 01:02:29 +09:00