| Message ID | 1526537830-22606-1-git-send-email-yamada.masahiro@socionext.com |
|---|---|
| Headers | show |
| Series | kconfig: move compiler capability tests to Kconfig | expand |
On Thu, 17 May 2018 15:16:39 +0900 Masahiro Yamada <yamada.masahiro@socionext.com> wrote: > [Introduction] > > The motivation of this work is to move the compiler option tests to > Kconfig from Makefile. A number of kernel features require the > compiler support. Enabling such features blindly in Kconfig ends up > with a lot of nasty build-time testing in Makefiles. If a chosen > feature turns out unsupported by the compiler, what the build system > can do is either to disable it (silently!) or to forcibly break the > build, despite Kconfig has let the user to enable it. By moving the > compiler capability tests to Kconfig, Kconfig entries will be visible > only when they are available. > > [Major Changes in V4] Do you have a git tree for v4? I can test it with the powerpc patches. The new scripting capability in kconfig has allowed us to already improve the config process on powerpc: https://marc.info/?l=linuxppc-embedded&m=152648110727868&w=2 I'm sure there's more clever things we can do with it but I haven't had time to think about it yet. One thing that comes to mind is that It might be nice to show the option as disabled, then the user could upgrade their compiler to get the options they want. Anyway v3 worked fine for me, the documentation is really nice, I could implement the above patch without any problem despite being a kbuild dummy. Thanks for the series, ack from me. Thanks, Nick
2018-05-17 16:51 GMT+09:00 Nicholas Piggin <npiggin@gmail.com>: > On Thu, 17 May 2018 15:16:39 +0900 > Masahiro Yamada <yamada.masahiro@socionext.com> wrote: > >> [Introduction] >> >> The motivation of this work is to move the compiler option tests to >> Kconfig from Makefile. A number of kernel features require the >> compiler support. Enabling such features blindly in Kconfig ends up >> with a lot of nasty build-time testing in Makefiles. If a chosen >> feature turns out unsupported by the compiler, what the build system >> can do is either to disable it (silently!) or to forcibly break the >> build, despite Kconfig has let the user to enable it. By moving the >> compiler capability tests to Kconfig, Kconfig entries will be visible >> only when they are available. >> >> [Major Changes in V4] > > Do you have a git tree for v4? I can test it with the powerpc patches. > > The new scripting capability in kconfig has allowed us to already > improve the config process on powerpc: > > https://marc.info/?l=linuxppc-embedded&m=152648110727868&w=2 > > I'm sure there's more clever things we can do with it but I haven't > had time to think about it yet. One thing that comes to mind is that > It might be nice to show the option as disabled, then the user could > upgrade their compiler to get the options they want. > > Anyway v3 worked fine for me, the documentation is really nice, I > could implement the above patch without any problem despite being a > kbuild dummy. Thanks for the series, ack from me. For easier review and test, I pushed v4 to the following branch: git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git kconfig-shell-v4 -- Best Regards Masahiro Yamada
Hi reviewers, 2018-05-17 23:22 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: > 2018-05-17 16:51 GMT+09:00 Nicholas Piggin <npiggin@gmail.com>: >> On Thu, 17 May 2018 15:16:39 +0900 >> Masahiro Yamada <yamada.masahiro@socionext.com> wrote: >> >>> [Introduction] >>> >>> The motivation of this work is to move the compiler option tests to >>> Kconfig from Makefile. A number of kernel features require the >>> compiler support. Enabling such features blindly in Kconfig ends up >>> with a lot of nasty build-time testing in Makefiles. If a chosen >>> feature turns out unsupported by the compiler, what the build system >>> can do is either to disable it (silently!) or to forcibly break the >>> build, despite Kconfig has let the user to enable it. By moving the >>> compiler capability tests to Kconfig, Kconfig entries will be visible >>> only when they are available. >>> >>> [Major Changes in V4] >> >> Do you have a git tree for v4? I can test it with the powerpc patches. >> >> The new scripting capability in kconfig has allowed us to already >> improve the config process on powerpc: >> >> https://marc.info/?l=linuxppc-embedded&m=152648110727868&w=2 >> >> I'm sure there's more clever things we can do with it but I haven't >> had time to think about it yet. One thing that comes to mind is that >> It might be nice to show the option as disabled, then the user could >> upgrade their compiler to get the options they want. >> >> Anyway v3 worked fine for me, the documentation is really nice, I >> could implement the above patch without any problem despite being a >> kbuild dummy. Thanks for the series, ack from me. > > > For easier review and test, > I pushed v4 to the following branch: > > > git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git > kconfig-shell-v4 > Planned change for v5 --------------------- I am thinking of more simplification for v5. This is my thought. V4 supported the _lazy_ expansion and 'if' function. If you have ever looked into GNU Make source code, you may know some functions lazily expand arguments. https://git.savannah.gnu.org/cgit/make.git/tree/src/function.c#n2339 "foreach", "if", "or", "and" are specified with "EXP? = 0". Those 4 functions expand arguments as-needed. For example, $(if $(cond),$(yes-case),$(no-case)) The 'if' function receive arguments before expansion, then expands $(cond) first. $(yes-case) is expanded only when $(cond) turns out to be a non-empty string. In this case, $(no-case) is not evaluated at all. $(error msg), if it is evaluated, immediately terminates Makefile parsing That's why $(error ) in Makefile are generally used in the either of the following forms: ifeq ... $(error blah blah) endif OR $(if $(cond),$(error blah blah)) This does not work in user-defined functions. $(call my-func,$(cond),$(error blah blah)) This always terminates parsing regardless of $(cond). Because the 'call' function is specified with "EXP? = 1", arguments are expanded (i.e. evaluated) before they are passed to the 'call' function. Let's say, you implemented your helper macros based on the 'if' built-in function, like follows: # return $(2) or $(3), depending on the gcc version. gcc-ifversion = $(if $(shell test $(gcc-version) -ge $(1) && echo y),$(2),$(3)) In this case, both $(2) and $(3) are evaluated before the condition part is checked. So, we end up with unneeded calculation where we know $(2) and $(3) are exclusively used. We can exploit the laziness only when we use the 'if' function in raw form. This use cases are limited. We use helper macros anyway, and the advantage of the lazy expansion disappear in user-defined functions. After consideration, I am reluctant to implement the lazy expansion (at least until we find it is necessary). To keep the source code simple, I do not want to implement what we may or may not need. At this moment, I am not so sure whether it is useful. So, here is a planned change in v5: Kconfig expands arguments before passing them to a function. This means, $(error blah blah) would never be useful. I will remove "error" and "warning" built-in functions. Instead, I will add "error-on" and "warning-on" built-in functions. - $(error-on,<cond>,<message>) If <cond> contains any character, it terminates file parsing, showing <message> to stderr. - $(warning-on,<cond>,<message>) If <cond> contains any character, show <message> to stderr. I will remove 'if' function too. If we give up its laziness, we can implement it as a user-defined function. -- Best Regards Masahiro Yamada
[Introduction] The motivation of this work is to move the compiler option tests to Kconfig from Makefile. A number of kernel features require the compiler support. Enabling such features blindly in Kconfig ends up with a lot of nasty build-time testing in Makefiles. If a chosen feature turns out unsupported by the compiler, what the build system can do is either to disable it (silently!) or to forcibly break the build, despite Kconfig has let the user to enable it. By moving the compiler capability tests to Kconfig, Kconfig entries will be visible only when they are available. [Major Changes in V4] - In V4, I slightly change the syntax of a function call. I chose grammatical consistency and simplicity. Anyway, Kconfig is deviating from Make behavior already. In v3, a function call looked like this: $(func-name arg1,arg2,arg3) In v4, a function is invoked like follows: $(func-name,arg1,arg2,arg3) The difference is that the function name and the first argument are separated by a comma. - V3 supported single-letter variable like $X. V4 dropped it because we do not need multiple ways to do the same thing. You must always enclose a variable name like $(X). - Support lazy argument expansion. This is necessary for implementing 'if', 'and', 'or' functions as in Make. - Add more built-in functions: 'if', 'error', 'filename', 'lineno' - Error out if a recursive variable references itself eventually. For example, X = $(X) ends up with a circular expansion. It must be terminated since the expansion would continue eternally. - Update Documentation and unit-tests, accordingly. [Major Changes in V3] This version looks more like Make. - Use = operator instead of 'macro' keyword to define a user-defined function. - 'Recursively expanded variable' is implemented as a side-effect. A variable is a function with zero argument. - Support simply expanded variable which is defined by := operator - Support += operator. Probably, this feature will be useful to accumulate compiler flags. At least, Clang needs some prerequisite flags such as triplet to test other compiler flags. - Support $(info ...) and $(warning ...) built-in functions, which were useful while I was debugging this. - Add documentation - Add unit tests - Collect helpers to scripts/Kconfig.include [Old Versions] V3: https://lkml.org/lkml/2018/4/13/37 V2: https://lkml.org/lkml/2018/2/16/610 V1: https://lkml.org/lkml/2018/2/16/610 RFC: https://lkml.org/lkml/2018/2/8/429 Masahiro Yamada (31): kbuild: remove kbuild cache kbuild: remove CONFIG_CROSS_COMPILE support kconfig: reference environment variables directly and remove 'option env=' kconfig: remove string expansion in file_lookup() kconfig: remove string expansion for mainmenu after yyparse() kconfig: remove sym_expand_string_value() kconfig: add built-in function support kconfig: add 'shell' built-in function kconfig: replace $(UNAME_RELEASE) with function call kconfig: begin PARAM state only when seeing a command keyword kconfig: support user-defined function and recursively expanded variable kconfig: support simply expanded variable kconfig: support append assignment operator kconfig: expand lefthand side of assignment statement kconfig: add 'info', 'warning', and 'error' built-in functions kconfig: add 'if' built-in function kconfig: add 'filename' and 'lineno' built-in variables kconfig: error out if a recursive variable references itself Documentation: kconfig: document a new Kconfig macro language kconfig: test: add Kconfig macro language tests kconfig: show compiler version text in the top comment kconfig: add basic helper macros to scripts/Kconfig.include stack-protector: test compiler capability in Kconfig and drop AUTO mode kconfig: add CC_IS_GCC and GCC_VERSION kconfig: add CC_IS_CLANG and CLANG_VERSION gcov: remove CONFIG_GCOV_FORMAT_AUTODETECT kcov: test compiler capability in Kconfig and correct dependency gcc-plugins: move GCC version check for PowerPC to Kconfig gcc-plugins: test plugin support in Kconfig and clean up Makefile gcc-plugins: allow to enable GCC_PLUGINS for COMPILE_TEST arm64: move GCC version check for ARCH_SUPPORTS_INT128 to Kconfig Documentation/kbuild/kconfig-language.txt | 8 - Documentation/kbuild/kconfig-macro-language.txt | 252 ++++++++ Kconfig | 10 +- MAINTAINERS | 3 +- Makefile | 105 +--- arch/Kconfig | 49 +- arch/arm64/Kconfig | 1 + arch/arm64/Makefile | 6 - arch/powerpc/Kconfig | 2 +- arch/sh/Kconfig | 4 +- arch/sparc/Kconfig | 4 +- arch/um/Kconfig.common | 4 - arch/x86/Kconfig | 15 +- arch/x86/um/Kconfig | 10 +- init/Kconfig | 40 +- kernel/gcov/Kconfig | 17 +- kernel/gcov/Makefile | 2 - lib/Kconfig.debug | 11 +- scripts/Kbuild.include | 101 +--- scripts/Kconfig.include | 27 + scripts/Makefile.gcc-plugins | 91 +-- scripts/Makefile.kcov | 10 +- scripts/clang-version.sh | 18 +- scripts/gcc-plugins/Makefile | 1 + scripts/gcc-x86_32-has-stack-protector.sh | 7 +- scripts/gcc-x86_64-has-stack-protector.sh | 5 - scripts/kconfig/confdata.c | 33 +- scripts/kconfig/kconf_id.c | 1 - scripts/kconfig/lkc.h | 4 - scripts/kconfig/lkc_proto.h | 15 +- scripts/kconfig/menu.c | 3 - scripts/kconfig/preprocess.c | 651 +++++++++++++++++++++ scripts/kconfig/symbol.c | 109 ---- .../kconfig/tests/preprocess/builtin_func/Kconfig | 29 + .../tests/preprocess/builtin_func/__init__.py | 8 + .../tests/preprocess/builtin_func/expected_stderr | 7 + .../tests/preprocess/builtin_func/expected_stdout | 1 + .../tests/preprocess/circular_expansion/Kconfig | 3 + .../preprocess/circular_expansion/__init__.py | 10 + .../preprocess/circular_expansion/expected_stderr | 1 + scripts/kconfig/tests/preprocess/escape/Kconfig | 21 + .../kconfig/tests/preprocess/escape/__init__.py | 7 + .../tests/preprocess/escape/expected_stderr | 5 + scripts/kconfig/tests/preprocess/variable/Kconfig | 48 ++ .../kconfig/tests/preprocess/variable/__init__.py | 7 + .../tests/preprocess/variable/expected_stderr | 9 + scripts/kconfig/util.c | 22 +- scripts/kconfig/zconf.l | 95 ++- scripts/kconfig/zconf.y | 46 +- 49 files changed, 1366 insertions(+), 572 deletions(-) create mode 100644 Documentation/kbuild/kconfig-macro-language.txt create mode 100644 scripts/Kconfig.include create mode 100644 scripts/kconfig/preprocess.c create mode 100644 scripts/kconfig/tests/preprocess/builtin_func/Kconfig create mode 100644 scripts/kconfig/tests/preprocess/builtin_func/__init__.py create mode 100644 scripts/kconfig/tests/preprocess/builtin_func/expected_stderr create mode 100644 scripts/kconfig/tests/preprocess/builtin_func/expected_stdout create mode 100644 scripts/kconfig/tests/preprocess/circular_expansion/Kconfig create mode 100644 scripts/kconfig/tests/preprocess/circular_expansion/__init__.py create mode 100644 scripts/kconfig/tests/preprocess/circular_expansion/expected_stderr create mode 100644 scripts/kconfig/tests/preprocess/escape/Kconfig create mode 100644 scripts/kconfig/tests/preprocess/escape/__init__.py create mode 100644 scripts/kconfig/tests/preprocess/escape/expected_stderr create mode 100644 scripts/kconfig/tests/preprocess/variable/Kconfig create mode 100644 scripts/kconfig/tests/preprocess/variable/__init__.py create mode 100644 scripts/kconfig/tests/preprocess/variable/expected_stderr -- 2.7.4