linux/scripts/Makefile.extrawarn, branch v6.14

Merge tag 'kbuild-fixes-v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

2025-02-09T18:05:32Z

Pull Kbuild fixes from Masahiro Yamada: - Suppress false-positive -Wformat-{overflow,truncation}-non-kprintf warnings regardless of the W= option - Avoid CONFIG_TRIM_UNUSED_KSYMS dropping symbols passed to symbol_get() - Fix a build regression of the Debian linux-headers package * tag 'kbuild-fixes-v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: kbuild: install-extmod-build: add missing quotation marks for CC variable kbuild: fix misspelling in scripts/Makefile.lib kbuild: keep symbols for symbol_get() even with CONFIG_TRIM_UNUSED_KSYMS scripts/Makefile.extrawarn: Do not show clang's non-kprintf warnings at W=1

kbuild: Move -Wenum-enum-conversion to W=2

2025-02-08T03:49:07Z

-Wenum-enum-conversion was strengthened in clang-19 to warn for C, which caused the kernel to move it to W=1 in commit 75b5ab134bb5 ("kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1") because there were numerous instances that would break builds with -Werror. Unfortunately, this is not a full solution, as more and more developers, subsystems, and distributors are building with W=1 as well, so they continue to see the numerous instances of this warning. Since the move to W=1, there have not been many new instances that have appeared through various build reports and the ones that have appeared seem to be following similar existing patterns, suggesting that most instances of this warning will not be real issues. The only alternatives for silencing this warning are adding casts (which is generally seen as an ugly practice) or refactoring the enums to macro defines or a unified enum (which may be undesirable because of type safety in other parts of the code). Move the warning to W=2, where warnings that occur frequently but may be relevant should reside. Cc: stable@vger.kernel.org Fixes: 75b5ab134bb5 ("kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1") Link: https://lore.kernel.org/ZwRA9SOcOjjLJcpi@google.com/ Signed-off-by: Nathan Chancellor Acked-by: Arnd Bergmann Signed-off-by: Linus Torvalds

scripts/Makefile.extrawarn: Do not show clang's non-kprintf warnings at W=1

2025-02-05T15:58:02Z

Clang's -Wformat-overflow and -Wformat-truncation have chosen to check '%p' unlike GCC but it does not know about the kernel's pointer extensions in lib/vsprintf.c, so the developers split that part of the warning out for the kernel to disable because there will always be false positives. Commit 908dd508276d ("kbuild: enable -Wformat-truncation on clang") did disabled these warnings but only in a block that would be called when W=1 was not passed, so they would appear with W=1. Move the disabling of the non-kprintf warnings to a block that always runs so that they are never seen, regardless of warning level. Fixes: 908dd508276d ("kbuild: enable -Wformat-truncation on clang") Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202501291646.VtwF98qd-lkp@intel.com/ Signed-off-by: Nathan Chancellor Signed-off-by: Masahiro Yamada

kbuild: Use -fzero-init-padding-bits=all

2025-01-30T16:48:34Z

GCC 15 introduces a regression in "= { 0 }" style initialization of unions that Linux has depended on for eliminating uninitialized variable contents. GCC does not seem likely to fix it[1], instead suggesting[2] that affected projects start using -fzero-init-padding-bits=unions. To avoid future surprises beyond just the current situation with unions, enable -fzero-init-padding-bits=all when available (GCC 15+). This will correctly zero padding bits in unions and structs that might have been left uninitialized, and will make sure there is no immediate regression in union initializations. As seen in the stackinit KUnit selftest union cases, which were passing before, were failing under GCC 15: not ok 18 test_small_start_old_zero ok 29 test_small_start_dynamic_partial # SKIP XFAIL uninit bytes: 63 ok 32 test_small_start_assigned_dynamic_partial # SKIP XFAIL uninit bytes: 63 ok 67 test_small_start_static_partial # SKIP XFAIL uninit bytes: 63 ok 70 test_small_start_static_all # SKIP XFAIL uninit bytes: 56 ok 73 test_small_start_dynamic_all # SKIP XFAIL uninit bytes: 56 ok 82 test_small_start_assigned_static_partial # SKIP XFAIL uninit bytes: 63 ok 85 test_small_start_assigned_static_all # SKIP XFAIL uninit bytes: 56 ok 88 test_small_start_assigned_dynamic_all # SKIP XFAIL uninit bytes: 56 The above all now pass again with -fzero-init-padding-bits=all added. This also fixes the following cases for struct initialization that had been XFAIL until now because there was no compiler support beyond the larger "-ftrivial-auto-var-init=zero" option: ok 38 test_small_hole_static_all # SKIP XFAIL uninit bytes: 3 ok 39 test_big_hole_static_all # SKIP XFAIL uninit bytes: 124 ok 40 test_trailing_hole_static_all # SKIP XFAIL uninit bytes: 7 ok 42 test_small_hole_dynamic_all # SKIP XFAIL uninit bytes: 3 ok 43 test_big_hole_dynamic_all # SKIP XFAIL uninit bytes: 124 ok 44 test_trailing_hole_dynamic_all # SKIP XFAIL uninit bytes: 7 ok 58 test_small_hole_assigned_static_all # SKIP XFAIL uninit bytes: 3 ok 59 test_big_hole_assigned_static_all # SKIP XFAIL uninit bytes: 124 ok 60 test_trailing_hole_assigned_static_all # SKIP XFAIL uninit bytes: 7 ok 62 test_small_hole_assigned_dynamic_all # SKIP XFAIL uninit bytes: 3 ok 63 test_big_hole_assigned_dynamic_all # SKIP XFAIL uninit bytes: 124 ok 64 test_trailing_hole_assigned_dynamic_all # SKIP XFAIL uninit bytes: 7 All of the above now pass when built under GCC 15. Tests can be seen with: ./tools/testing/kunit/kunit.py run stackinit --arch=x86_64 \ --make_option CC=gcc-15 Clang continues to fully initialize these kinds of variables[3] without additional flags. Suggested-by: Jakub Jelinek Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118403 [1] Link: https://lore.kernel.org/linux-toolchains/Z0hRrrNU3Q+ro2T7@tucnak/ [2] Link: https://github.com/llvm/llvm-project/commit/7a086e1b2dc05f54afae3591614feede727601fa [3] Reviewed-by: Nathan Chancellor Acked-by: Masahiro Yamada Link: https://lore.kernel.org/r/20250127191031.245214-3-kees@kernel.org Signed-off-by: Kees Cook

kbuild: enable -Wcast-function-type-strict unconditionally

2024-05-19T21:36:16Z

All known function cast warnings are now addressed, so the warning can be enabled globally to catch new ones more quickly. Link: https://lkml.kernel.org/r/20240415122037.1983124-6-arnd@kernel.org Signed-off-by: Arnd Bergmann Reviewed-by: Kees Cook Cc: Masahiro Yamada Cc: Nathan Chancellor Cc: Nicolas Schier Signed-off-by: Andrew Morton

kbuild: enable -Wformat-truncation on clang

2024-05-19T21:36:16Z

This warning option still produces output on gcc but is now clean when building with clang, so enable it conditionally on the compiler for now. As far as I can tell, the remaining warnings with gcc are the result of analysing the code more deeply across inlining, while clang only does this within a function. Link: https://lore.kernel.org/lkml/20240326230511.GA2796782@dev-arch.thelio-3990X/ Link: https://lore.kernel.org/linux-patches/20231002-disable-wformat-truncation-overflow-non-kprintf-v1-1-35179205c8d9@kernel.org/ Link: https://lkml.kernel.org/r/20240415122037.1983124-5-arnd@kernel.org Signed-off-by: Arnd Bergmann Cc: Kees Cook Cc: Masahiro Yamada Cc: Nathan Chancellor Cc: Nicolas Schier Signed-off-by: Andrew Morton

kbuild: turn on -Wrestrict by default

2024-05-19T21:36:16Z

All known -Wrestrict warnings are addressed now, so don't disable the warning any more. Link: https://lkml.kernel.org/r/20240415122037.1983124-4-arnd@kernel.org Signed-off-by: Arnd Bergmann Cc: Kees Cook Cc: Masahiro Yamada Cc: Nathan Chancellor Cc: Nicolas Schier Signed-off-by: Andrew Morton

kbuild: remove redundant extra warning flags

2024-05-19T21:36:16Z

There is no point in turning individual options off and then on again, or vice versa, as the last one always wins. Now that -Wextra always gets passed first, remove all the redundant lines about warnings that are implied by either -Wall or -Wextra, and keep only the last one that disables it in some configurations. This should not have any effect but keep the Makefile more readable and the command line shorter. Link: https://lkml.kernel.org/r/20240415122037.1983124-3-arnd@kernel.org Signed-off-by: Arnd Bergmann Cc: Kees Cook Cc: Masahiro Yamada Cc: Nathan Chancellor Cc: Nicolas Schier Signed-off-by: Andrew Morton

kbuild: turn on -Wextra by default

2024-05-19T21:36:15Z

Patch series "kbuild: enable more warnings by default", v3. All the warning fixes I sent for these warnings have been merged into mainline or linux-next, so let's turn them on by default. This patch (of 6): The -Wextra option controls a number of different warnings that differ slightly by compiler version. Some are useful in general, others are better left at W=1 or higher. Based on earlier work, the ones that should be disabled by default are left for the higher warning levels already, and a lot of the useful ones have no remaining output when enabled. Move the -Wextra option up into the set of default-enabled warnings and just rely on the individual ones getting disabled as needed. The -Wunused warning was always grouped with this, so turn it on by default as well, except for the -Wunused-parameter warning that really has no value at all for the kernel since many interfaces have intentionally unused arguments. Link: https://lkml.kernel.org/r/20240415122037.1983124-1-arnd@kernel.org Link: https://lkml.kernel.org/r/20240415122037.1983124-2-arnd@kernel.org Signed-off-by: Arnd Bergmann Acked-by: Nathan Chancellor Cc: Kees Cook Cc: Masahiro Yamada Cc: Nicolas Schier Signed-off-by: Andrew Morton

kbuild: make -Woverride-init warnings more consistent

2024-03-31T02:32:26Z

The -Woverride-init warn about code that may be intentional or not, but the inintentional ones tend to be real bugs, so there is a bit of disagreement on whether this warning option should be enabled by default and we have multiple settings in scripts/Makefile.extrawarn as well as individual subsystems. Older versions of clang only supported -Wno-initializer-overrides with the same meaning as gcc's -Woverride-init, though all supported versions now work with both. Because of this difference, an earlier cleanup of mine accidentally turned the clang warning off for W=1 builds and only left it on for W=2, while it's still enabled for gcc with W=1. There is also one driver that only turns the warning off for newer versions of gcc but not other compilers, and some but not all the Makefiles still use a cc-disable-warning conditional that is no longer needed with supported compilers here. Address all of the above by removing the special cases for clang and always turning the warning off unconditionally where it got in the way, using the syntax that is supported by both compilers. Fixes: 2cd3271b7a31 ("kbuild: avoid duplicate warning options") Signed-off-by: Arnd Bergmann Acked-by: Hamza Mahfooz Acked-by: Jani Nikula Acked-by: Andrew Jeffery Signed-off-by: Jani Nikula Reviewed-by: Linus Walleij Signed-off-by: Masahiro Yamada