Users of GNU ld (BFD) from binutils 2.39+ will observe multiple instances of a new warning when linking kernels in the form: ld: warning: vmlinux: missing .note.GNU-stack section implies executable stack ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker ld: warning: vmlinux has a LOAD segment with RWX permissions Generally, we would like to avoid the stack being executable. Because there could be a need for the stack to be executable, assembler sources have to opt-in to this security feature via explicit creation of the .note.GNU-stack feature (which compilers create by default) or command line flag --noexecstack. Or we can simply tell the linker the production of such sections is irrelevant and to link the stack as --noexecstack. LLVM's LLD linker defaults to -z noexecstack, so this flag isn't strictly necessary when linking with LLD, only BFD, but it doesn't hurt to be explicit here for all linkers IMO. --no-warn-rwx-segments is currently BFD specific and only available in the current latest release, so it's wrapped in an ld-option check. While the kernel makes extensive usage of ELF sections, it doesn't use permissions from ELF segments. Link: https://lore.kernel.org/linux-block/3af4127a-f453-4cf7-f133-a181cce06f73@kernel.dk/ Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107 Link: https://github.com/llvm/llvm-project/issues/57009 Reported-and-tested-by: Jens Axboe <axboe@kernel.dk> Suggested-by: Fangrui Song <maskray@google.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull Kbuild updates from Masahiro Yamada: - Remove the support for -O3 (CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3) - Fix error of rpm-pkg cross-builds - Support riscv for checkstack tool - Re-enable -Wformwat warnings for Clang - Clean up modpost, Makefiles, and misc scripts * tag 'kbuild-v5.20' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (30 commits) modpost: remove .symbol_white_list field entirely modpost: remove unneeded .symbol_white_list initializers modpost: add PATTERNS() helper macro modpost: shorten warning messages in report_sec_mismatch() Revert "Kbuild, lto, workaround: Don't warn for initcall_reference in modpost" modpost: use more reliable way to get fromsec in section_rel(a)() modpost: add array range check to sec_name() modpost: refactor get_secindex() kbuild: set EXIT trap before creating temporary directory modpost: remove unused Elf_Sword macro Makefile.extrawarn: re-enable -Wformat for clang kbuild: add dtbs_prepare target kconfig: Qt5: tell the user which packages are required modpost: use sym_get_data() to get module device_table data modpost: drop executable ELF support checkstack: add riscv support for scripts/checkstack.pl kconfig: shorten the temporary directory name for cc-option scripts: headers_install.sh: Update config leak ignore entries kbuild: error out if $(INSTALL_MOD_PATH) contains % or : kbuild: error out if $(KBUILD_EXTMOD) contains % or : ...
Pull Kselftest updates from Shuah Khan: - timers test build fixes and cleanups for new tool chains - removing khdr from kselftest framework and main Makefile - changes to test output messages to improve reports * tag 'linux-kselftest-next-5.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest: (24 commits) Makefile: replace headers_install with headers for kselftest selftests/landlock: drop deprecated headers dependency selftests: timers: clocksource-switch: adapt to kselftest framework selftests: timers: clocksource-switch: add 'runtime' command line parameter selftests: timers: clocksource-switch: add command line switch to skip sanity check selftests: timers: clocksource-switch: sort includes selftests: timers: clocksource-switch: fix passing errors from child selftests: timers: inconsistency-check: adapt to kselftest framework selftests: timers: nanosleep: adapt to kselftest framework selftests: timers: fix declarations of main() selftests: timers: valid-adjtimex: build fix for newer toolchains Makefile: add headers_install to kselftest targets selftests: drop KSFT_KHDR_INSTALL make target selftests: stop using KSFT_KHDR_INSTALL selftests: drop khdr make target selftests: drivers/dma-buf: Improve message in selftest summary selftests/kcmp: Make the test output consistent and clear selftests:timers: globals don't need initialization to 0 selftests/drivers/gpu: Add error messages to drm_mm.sh selftests/tpm2: increase timeout for kselftests ...
Pull io_uring updates from Jens Axboe: - As per (valid) complaint in the last merge window, fs/io_uring.c has grown quite large these days. io_uring isn't really tied to fs either, as it supports a wide variety of functionality outside of that. Move the code to io_uring/ and split it into files that either implement a specific request type, and split some code into helpers as well. The code is organized a lot better like this, and io_uring.c is now < 4K LOC (me). - Deprecate the epoll_ctl opcode. It'll still work, just trigger a warning once if used. If we don't get any complaints on this, and I don't expect any, then we can fully remove it in a future release (me). - Improve the cancel hash locking (Hao) - kbuf cleanups (Hao) - Efficiency improvements to the task_work handling (Dylan, Pavel) - Provided buffer improvements (Dylan) - Add support for recv/recvmsg multishot support. This is similar to the accept (or poll) support for have for multishot, where a single SQE can trigger everytime data is received. For applications that expect to do more than a few receives on an instantiated socket, this greatly improves efficiency (Dylan). - Efficiency improvements for poll handling (Pavel) - Poll cancelation improvements (Pavel) - Allow specifiying a range for direct descriptor allocations (Pavel) - Cleanup the cqe32 handling (Pavel) - Move io_uring types to greatly cleanup the tracing (Pavel) - Tons of great code cleanups and improvements (Pavel) - Add a way to do sync cancelations rather than through the sqe -> cqe interface, as that's a lot easier to use for some use cases (me). - Add support to IORING_OP_MSG_RING for sending direct descriptors to a different ring. This avoids the usually problematic SCM case, as we disallow those. (me) - Make the per-command alloc cache we use for apoll generic, place limits on it, and use it for netmsg as well (me). - Various cleanups (me, Michal, Gustavo, Uros) * tag 'for-5.20/io_uring-2022-07-29' of git://git.kernel.dk/linux-block: (172 commits) io_uring: ensure REQ_F_ISREG is set async offload net: fix compat pointer in get_compat_msghdr() io_uring: Don't require reinitable percpu_ref io_uring: fix types in io_recvmsg_multishot_overflow io_uring: Use atomic_long_try_cmpxchg in __io_account_mem io_uring: support multishot in recvmsg net: copy from user before calling __get_compat_msghdr net: copy from user before calling __copy_msghdr io_uring: support 0 length iov in buffer select in compat io_uring: fix multishot ending when not polled io_uring: add netmsg cache io_uring: impose max limit on apoll cache io_uring: add abstraction around apoll cache io_uring: move apoll cache to poll.c io_uring: consolidate hash_locked io-wq handling io_uring: clear REQ_F_HASH_LOCKED on hash removal io_uring: don't race double poll setting REQ_F_ASYNC_DATA io_uring: don't miss setting REQ_F_DOUBLE_POLL io_uring: disable multishot recvmsg io_uring: only trace one of complete or overflow ...
Factor out the common prerequisites for DT compilation into the new target, dtbs_prepare. Add comments to explain why include/config/kernel.release is the prerequisite. Our policy is that installation targets must not rebuild anything in the tree. If 'make modules_install' is executed as root, include/config/kernel.release may be owned by root. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> Tested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
If the directory path given to KBUILD_EXTMOD (or M=) contains % or :, the module fails to build. % is used in pattern rules, and : as the separator of dependencies. Bail out with a clearer error message. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
The difference in most compilers between `-O3` and `-O2` is mostly down
to whether loops with statically determinable trip counts are fully
unrolled vs unrolled to a multiple of SIMD width.
This patch is effectively a revert of
commit 15f5db60a137 ("kbuild,arc: add
CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 for ARC") without re-adding
ARCH_CFLAGS
Ever since
commit cfdbc2e16e65 ("ARC: Build system: Makefiles, Kconfig, Linker
script")
ARC has been built with -O3, though the reason for doing so was not
specified in inline comments or the commit message. This commit does not
re-add -O3 to arch/arc/Makefile.
Folks looking to experiment with `-O3` (or any compiler flag for that
matter) may pass them along to the command line invocation of make:
$ make KCFLAGS=-O3
Code that looks to re-add an explicit Kconfig option for `-O3` should
provide:
1. A rigorous and reproducible performance profile of a reasonable
userspace workload that demonstrates a hot loop in the kernel that
would benefit from `-O3` over `-O2`.
2. Disassembly of said loop body before and after.
3. Provides stats on terms of increase in file size.
Link: https://lore.kernel.org/linux-kbuild/CA+55aFz2sNBbZyg-_i8_Ldr2e8o9dfvdSfHHuRzVtP2VMAUWPg@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Replace headers_install with headers as kselftest uses the header files from within the kernel tree rather than from a system-wide installation. We can still run this directly: $ make O=build kselftest-all and when building from the selftests directory: $ make O=build headers $ make O=build -C tools/testing/selftests all Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com> Reported-by: Masahiro Yamada <masahiroy@kernel.org> Acked-by: Shuah Khan <skhan@linuxfoundation.org> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>