Changes in Makefile

eb13a1ff271b0d180687eebb30611b0b276d5193 - random: vDSO: avoid call to memset() when zeroing reserved parameter

Fri, 25 Sep 2026 23:46:32 +0200

random: vDSO: avoid call to memset() when zeroing reserved parameterAfter a recent change in LLVM [1], builds with the random vDSOimplementation, such as PowerPC and RISC-V, fail when checking the vDSO: arch/powerpc/kernel/vdso/vdso32.so.dbg: dynamic relocations are not supported arch/riscv/kernel/vdso/vdso.so.dbg: dynamic relocations are not supportedmemset() is now generated when zeroing params->reserved for some buildsbecause LLVM has an optimization (now run in more instances) that canrecognize at compile time when it is assigning a static value to acontiguous area of memory and turn that into a call to memset(). Bothclang and GCC assume memset() is always available [2].Clang has an internal fiddly hook, -max-store-memset, which we can setto a high number, to disable generating out of line memset calls [3].Similarly, GCC has -finline-stringops=memset to do the same [4], shouldthis issue ever hit future version of GCC. While these options wouldn'tmake sense for normal kernel code, it is fine for the extremely limitedand intentionally compact vDSO code.Link: https://github.com/llvm/llvm-project/commit/90cebef1411617fc3eedd359bdf00cb44b1c2439 [1]Link: https://gcc.gnu.org/onlinedocs/gcc-16.2.0/gcc/Standards.html#index-ffreestanding [2]Link: https://github.com/llvm/llvm-project/commit/b28eeb28bea39148738dc375e8a97072a1907e64 [3]Link: https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-finline-stringops [4]Closes: https://github.com/ClangBuiltLinux/linux/issues/2183Cc: stable@vger.kernel.org # v6.12+Signed-off-by: Nathan Chancellor Signed-off-by: Jason A. Donenfeld List of files: /linux/arch/arm64/kernel/vdso/Makefile

76261fc7d1be3fde06efed859cb10c95b1204055 - stackleak: Split KSTACK_ERASE_CFLAGS from GCC_PLUGINS_CFLAGS

Fri, 18 Jul 2025 01:25:08 +0200

stackleak: Split KSTACK_ERASE_CFLAGS from GCC_PLUGINS_CFLAGSIn preparation for Clang stack depth tracking for KSTACK_ERASE,split the stackleak-specific cflags out of GCC_PLUGINS_CFLAGS intoKSTACK_ERASE_CFLAGS.Link: https://lore.kernel.org/r/20250717232519.2984886-3-kees@kernel.orgSigned-off-by: Kees Cook List of files: /linux/arch/arm64/kernel/vdso/Makefile

127b0e05c1669d240426719b3b9db8a8366eed50 - vdso: Rename included Makefile

Tue, 04 Feb 2025 13:05:36 +0100

vdso: Rename included MakefileAs the Makefile is included into other Makefiles it can not be used todefine objects to be built from the current source directory.However the generic datastore will introduce such a local source file.Rename the included Makefile so it is clear how it is to be used and tomake room for a regular Makefile in lib/vdso/.Signed-off-by: Thomas Weißschuh Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-4-13a4669dfc8c@linutronix.de List of files: /linux/arch/arm64/kernel/vdso/Makefile

712676ea2bb3882a852bcf49862c4247317fc9b2 - arm64: vDSO: Wire up getrandom() vDSO implementation

Tue, 03 Sep 2024 14:09:17 +0200

arm64: vDSO: Wire up getrandom() vDSO implementationHook up the generic vDSO implementation to the aarch64 vDSO data page.The _vdso_rng_data required data is placed within the _vdso_data vvarpage, by using a offset larger than the vdso_data.The vDSO function requires a ChaCha20 implementation that does not writeto the stack, and that can do an entire ChaCha20 permutation. The oneprovided uses NEON on the permute operation, with a fallback to thesyscall for chips that do not support AdvSIMD.This also passes the vdso_test_chacha test along withvdso_test_getrandom. The vdso_test_getrandom bench-single result onNeoverse-N1 shows: vdso: 25000000 times in 0.783884250 seconds libc: 25000000 times in 8.780275399 secondssyscall: 25000000 times in 8.786581518 secondsA small fixup to arch/arm64/include/asm/mman.h was required to avoidpulling kernel code into the vDSO, similar to what's already done inarch/arm64/include/asm/rwonce.h.Signed-off-by: Adhemerval Zanella Reviewed-by: Ard Biesheuvel Acked-by: Will Deacon Signed-off-by: Jason A. Donenfeld List of files: /linux/arch/arm64/kernel/vdso/Makefile

48f6430505c0b0498ee9020ce3cf9558b1caaaeb - arm64/vdso: Remove --hash-style=sysv

Thu, 18 Jul 2024 19:34:23 +0200

arm64/vdso: Remove --hash-style=sysvglibc added support for .gnu.hash in 2006 and .hash has been obsoletedfor more than one decade in many Linux distributions. Using--hash-style=sysv might imply unaddressed issues and confuse readers.Just drop the option and rely on the linker default, which is likely"both", or "gnu" when the distribution really wants to eliminate sysvhash overhead.Similar to commit 6b7e26547fad ("x86/vdso: Emit a GNU hash").Signed-off-by: Fangrui Song Link: https://lore.kernel.org/r/20240718173423.1574395-1-maskray@google.comSigned-off-by: Will Deacon List of files: /linux/arch/arm64/kernel/vdso/Makefile

7f7f6f7ad654b326897c9f54438a06f03454bd0d - Makefile: remove redundant tool coverage variables

Mon, 06 May 2024 15:35:43 +0200

Makefile: remove redundant tool coverage variablesNow Kbuild provides reasonable defaults for objtool, sanitizers, andprofilers.Remove redundant variables.Note:This commit changes the coverage for some objects: - include arch/mips/vdso/vdso-image.o into UBSAN, GCOV, KCOV - include arch/sparc/vdso/vdso-image-*.o into UBSAN - include arch/sparc/vdso/vma.o into UBSAN - include arch/x86/entry/vdso/extable.o into KASAN, KCSAN, UBSAN, GCOV, KCOV - include arch/x86/entry/vdso/vdso-image-*.o into KASAN, KCSAN, UBSAN, GCOV, KCOV - include arch/x86/entry/vdso/vdso32-setup.o into KASAN, KCSAN, UBSAN, GCOV, KCOV - include arch/x86/entry/vdso/vma.o into GCOV, KCOV - include arch/x86/um/vdso/vma.o into KASAN, GCOV, KCOVI believe these are positive effects because all of them are kernelspace objects.Signed-off-by: Masahiro Yamada Reviewed-by: Kees Cook Tested-by: Roberto Sassu List of files: /linux/arch/arm64/kernel/vdso/Makefile

b1992c3772e69a6fd0e3fc81cd4d2820c8b6eca0 - kbuild: use $(src) instead of $(srctree)/$(src) for source directory

Sat, 27 Apr 2024 16:55:02 +0200

kbuild: use $(src) instead of $(srctree)/$(src) for source directoryKbuild conventionally uses $(obj)/ for generated files, and $(src)/ forchecked-in source files. It is merely a convention without any functionaldifference. In fact, $(obj) and $(src) are exactly the same, as definedin scripts/Makefile.build: src := $(obj)When the kernel is built in a separate output directory, $(src) doesnot accurately reflect the source directory location. While Kbuildresolves this discrepancy by specifying VPATH=$(srctree) to search forsource files, it does not cover all cases. For example, when adding aheader search path for local headers, -I$(srctree)/$(src) is typicallypassed to the compiler.This introduces inconsistency between upstream and downstream Makefilesbecause $(src) is used instead of $(srctree)/$(src) for the latter.To address this inconsistency, this commit changes the semantics of$(src) so that it always points to the directory in the source tree.Going forward, the variables used in Makefiles will have the followingmeanings: $(obj) - directory in the object tree $(src) - directory in the source tree (changed by this commit) $(objtree) - the top of the kernel object tree $(srctree) - the top of the kernel source treeConsequently, $(srctree)/$(src) in upstream Makefiles need to be replacedwith $(src).Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier List of files: /linux/arch/arm64/kernel/vdso/Makefile

56769ba4b297a629148eb24d554aef72d1ddfd9e - kbuild: unify vdso_install rules

Sat, 14 Oct 2023 12:54:35 +0200

kbuild: unify vdso_install rulesCurrently, there is no standard implementation for vdso_install,leading to various issues: 1. Code duplication Many architectures duplicate similar code just for copying files to the install destination. Some architectures (arm, sparc, x86) create build-id symlinks, introducing more code duplication. 2. Unintended updates of in-tree build artifacts The vdso_install rule depends on the vdso files to install. It may update in-tree build artifacts. This can be problematic, as explained in commit 19514fc665ff ("arm, kbuild: make "make install" not depend on vmlinux"). 3. Broken code in some architectures Makefile code is often copied from one architecture to another without proper adaptation. 'make vdso_install' for parisc does not work. 'make vdso_install' for s390 installs vdso64, but not vdso32.To address these problems, this commit introduces a generic vdso_installrule.Architectures that support vdso_install need to define vdso-install-yin arch/*/Makefile. vdso-install-y lists the files to install.For example, arch/x86/Makefile looks like this: vdso-install-$(CONFIG_X86_64) += arch/x86/entry/vdso/vdso64.so.dbg vdso-install-$(CONFIG_X86_X32_ABI) += arch/x86/entry/vdso/vdsox32.so.dbg vdso-install-$(CONFIG_X86_32) += arch/x86/entry/vdso/vdso32.so.dbg vdso-install-$(CONFIG_IA32_EMULATION) += arch/x86/entry/vdso/vdso32.so.dbgThese files will be installed to $(MODLIB)/vdso/ with the .dbg suffix,if exists, stripped away.vdso-install-y can optionally take the second field after the colonseparator. This is needed because some architectures install a vdsofile as a different base name.The following is a snippet from arch/arm64/Makefile. vdso-install-$(CONFIG_COMPAT_VDSO) += arch/arm64/kernel/vdso32/vdso.so.dbg:vdso32.soThis will rename vdso.so.dbg to vdso32.so during installation. If sucharchitectures change their implementation so that the base names match,this workaround will go away.Signed-off-by: Masahiro Yamada Acked-by: Sven Schnelle # s390Reviewed-by: Nicolas Schier Reviewed-by: Guo Ren Acked-by: Helge Deller # pariscAcked-by: Catalin Marinas Acked-by: Russell King (Oracle) List of files: /linux/arch/arm64/kernel/vdso/Makefile

aff69273af61f5d1c8fb401d6f19148d11629b41 - vdso: Improve cmd_vdso_check to check all dynamic relocations

Fri, 10 Mar 2023 20:07:50 +0100

vdso: Improve cmd_vdso_check to check all dynamic relocationsThe actual intention is that no dynamic relocation exists in the VDSO. Forthis the VDSO build validates that the resulting .so file does not have anyrelocations which are specified via $(ARCH_REL_TYPE_ABS) per architecture,which is fragile as e.g. ARM64 lacks an entry for R_AARCH64_RELATIVE. Asideof that ARCH_REL_TYPE_ABS is a misnomer as it checks for relativerelocations too.However, some GNU ld ports produce unneeded R_*_NONE relocation entries. Ifa port fails to determine the exact .rel[a].dyn size, the trailing zerosbecome R_*_NONE relocations. E.g. ld's powerpc port recently fixedhttps://sourceware.org/bugzilla/show_bug.cgi?id=29540). R_*_NONE aregenerally a no-op in the dynamic loaders. So just ignore them.Remove the ARCH_REL_TYPE_ABS defines and just validate that the resulting.so file does not contain any R_* relocation entries except R_*_NONE.Signed-off-by: Fangrui Song Signed-off-by: Thomas Gleixner Tested-by: Vincenzo Frascino # for aarch64Reviewed-by: Christophe Leroy Reviewed-by: Vincenzo Frascino # for vDSO, aarch64Acked-by: Michael Ellerman (powerpc)Link: https://lore.kernel.org/r/20230310190750.3323802-1-maskray@google.com List of files: /linux/arch/arm64/kernel/vdso/Makefile

e1789d7c752ed001cf1a4bbbd624f70a7dd3c6db - kbuild: upgrade the orphan section warning to an error if CONFIG_WERROR is set

Tue, 25 Oct 2022 09:30:23 +0200

kbuild: upgrade the orphan section warning to an error if CONFIG_WERROR is setAndrew Cooper suggested upgrading the orphan section warning to a hard linkerror. However Nathan Chancellor said outright turning the warning into anerror with no escape hatch might be too aggressive, as we have had thesewarnings triggered by new compiler generated sections, and suggested turningorphan sections into an error only if CONFIG_WERROR is set. Kees Cook echoedand emphasized that the mandate from Linus is that we should avoid breakingbuilds. It wrecks bisection, it causes problems across compiler versions, etc.Thus upgrade the orphan section warning to a hard link error only ifCONFIG_WERROR is set.Suggested-by: Andrew Cooper Suggested-by: Nathan Chancellor Signed-off-by: Xin Li Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221025073023.16137-2-xin3.li@intel.com List of files: /linux/arch/arm64/kernel/vdso/Makefile

f143ff397a3f991e8b48542f77aad900845f436e - treewide: Filter out CC_FLAGS_CFI

Thu, 08 Sep 2022 23:54:43 +0200

treewide: Filter out CC_FLAGS_CFIIn preparation for removing CC_FLAGS_CFI from CC_FLAGS_LTO, explicitlyfilter out CC_FLAGS_CFI in all the makefiles where we currently filterout CC_FLAGS_LTO.Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Tested-by: Kees Cook Tested-by: Nathan Chancellor Acked-by: Peter Zijlstra (Intel) Tested-by: Peter Zijlstra (Intel) Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220908215504.3686827-2-samitolvanen@google.com List of files: /linux/arch/arm64/kernel/vdso/Makefile

e0ab20b20a1bb53d61feedb1fd6c23cbbed11d18 - arm64: vdso: enable orphan handling for VDSO

Tue, 10 May 2022 11:58:32 +0200

arm64: vdso: enable orphan handling for VDSOLike vmlinux, enable orphan-handling for the VDSO. This can catchsubtle errors that might arise from unexpected sections being included.Signed-off-by: Joey Gouly Cc: Catalin Marinas Cc: Will Deacon Cc: Masahiro Yamada Cc: Vincenzo Frascino Cc: Kees Cook Reviewed-by: Kees Cook Reviewed-by: Vincenzo Frascino Link: https://lore.kernel.org/r/20220510095834.32394-3-joey.gouly@arm.comSigned-off-by: Will Deacon List of files: /linux/arch/arm64/kernel/vdso/Makefile

0bf13a84362e750a90008af259b098d7c0e0755b - Merge tag 'kernel-hardening-v5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Tue, 24 May 2022 21:27:09 +0200

Merge tag 'kernel-hardening-v5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linuxPull kernel hardening updates from Kees Cook: - usercopy hardening expanded to check other allocation types (Matthew Wilcox, Yuanzheng Song) - arm64 stackleak behavioral improvements (Mark Rutland) - arm64 CFI code gen improvement (Sami Tolvanen) - LoadPin LSM block dev API adjustment (Christoph Hellwig) - Clang randstruct support (Bill Wendling, Kees Cook)* tag 'kernel-hardening-v5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (34 commits) loadpin: stop using bdevname mm: usercopy: move the virt_addr_valid() below the is_vmalloc_addr() gcc-plugins: randstruct: Remove cast exception handling af_unix: Silence randstruct GCC plugin warning niu: Silence randstruct warnings big_keys: Use struct for internal payload gcc-plugins: Change all version strings match kernel randomize_kstack: Improve docs on requirements/rationale lkdtm/stackleak: fix CONFIG_GCC_PLUGIN_STACKLEAK=n arm64: entry: use stackleak_erase_on_task_stack() stackleak: add on/off stack variants lkdtm/stackleak: check stack boundaries lkdtm/stackleak: prevent unexpected stack usage lkdtm/stackleak: rework boundary management lkdtm/stackleak: avoid spurious failure stackleak: rework poison scanning stackleak: rework stack high bound handling stackleak: clarify variable names stackleak: rework stack low bound handling stackleak: remove redundant check ... List of files: /linux/arch/arm64/kernel/vdso/Makefile

205f3991a273cac6008ef4db3d1c0dc54d14fb56 - arm64: vdso: fix makefile dependency on vdso.so

Tue, 10 May 2022 12:27:21 +0200

arm64: vdso: fix makefile dependency on vdso.soThere is currently no dependency for vdso*-wrap.S on vdso*.so, which means thatyou can get a build that uses a stale vdso*-wrap.o.In commit a5b8ca97fbf8, the file that includes the vdso.so was moved and renamedfrom arch/arm64/kernel/vdso/vdso.S to arch/arm64/kernel/vdso-wrap.S, when thishappened the Makefile was not updated to force the dependcy on vdso.so.Fixes: a5b8ca97fbf8 ("arm64: do not descend to vdso directories twice")Signed-off-by: Joey Gouly Cc: Masahiro Yamada Cc: Vincenzo Frascino Cc: Catalin Marinas Cc: Will Deacon Link: https://lore.kernel.org/r/20220510102721.50811-1-joey.gouly@arm.comSigned-off-by: Will Deacon List of files: /linux/arch/arm64/kernel/vdso/Makefile

613f4b3ed7902d1dbbc6ade6401e452a63dfbc21 - randstruct: Split randstruct Makefile and CFLAGS

Tue, 03 May 2022 22:55:01 +0200

randstruct: Split randstruct Makefile and CFLAGSTo enable the new Clang randstruct implementation[1], moverandstruct into its own Makefile and split the CFLAGS fromGCC_PLUGINS_CFLAGS into RANDSTRUCT_CFLAGS.[1] https://reviews.llvm.org/D121556Cc: linux-hardening@vger.kernel.orgSigned-off-by: Kees Cook Link: https://lore.kernel.org/r/20220503205503.3054173-5-keescook@chromium.org List of files: /linux/arch/arm64/kernel/vdso/Makefile

58cd4a088e8917b4092c7011d499e277e04a6644 - arm64: vdso: Fix "no previous prototype" warning

Fri, 21 Jan 2022 13:12:34 +0100

arm64: vdso: Fix "no previous prototype" warningIf compiling the arm64 kernel with W=1 the following warning is produced:| arch/arm64/kernel/vdso/vgettimeofday.c:9:5: error: no previous prototype for ‘__kernel_clock_gettime’ [-Werror=missing-prototypes]| 9 | int __kernel_clock_gettime(clockid_t clock,| | ^~~~~~~~~~~~~~~~~~~~~~| arch/arm64/kernel/vdso/vgettimeofday.c:15:5: error: no previous prototype for ‘__kernel_gettimeofday’ [-Werror=missing-prototypes]| 15 | int __kernel_gettimeofday(struct __kernel_old_timeval *tv,| | ^~~~~~~~~~~~~~~~~~~~~| arch/arm64/kernel/vdso/vgettimeofday.c:21:5: error: no previous prototype for ‘__kernel_clock_getres’ [-Werror=missing-prototypes]| 21 | int __kernel_clock_getres(clockid_t clock_id,| | ^~~~~~~~~~~~~~~~~~~~~This patch removes "-Wmissing-prototypes" and "-Wmissing-declarations" compilersflags from the compilation of vgettimeofday.c to make possible to build thekernel with CONFIG_WERROR enabled.Cc: Will Deacon Reported-by: Marc Kleine-Budde Signed-off-by: Vincenzo Frascino Tested-by: Marc Kleine-Budde Link: https://lore.kernel.org/r/20220121121234.47273-1-vincenzo.frascino@arm.comSigned-off-by: Catalin Marinas List of files: /linux/arch/arm64/kernel/vdso/Makefile

dd03762ab608e058c8f390ad9cf667e490089796 - arm64: Enable KCSAN

Sat, 11 Dec 2021 14:17:34 +0100

arm64: Enable KCSANThis patch enables KCSAN for arm64, with updates to build rulesto not use KCSAN for several incompatible compilation units.Recent GCC version(at least GCC10) made outline-atomics as thedefault option(unlike Clang), which will cause linker errorsfor kernel/kcsan/core.o. Disables the out-of-line atomics byno-outline-atomics to fix the linker errors.Meanwhile, as Mark said[1], some latent issues are needed to befixed which isn't just a KCSAN problem, we make the KCSAN dependson EXPERT for now.Tested selftest and kcsan_test(built with GCC11 and Clang 13),and all passed.[1] https://lkml.kernel.org/r/YadiUPpJ0gADbiHQ@FVFF77S0Q05NAcked-by: Marco Elver # kernel/kcsanTested-by: Joey Gouly Signed-off-by: Kefeng Wang Link: https://lore.kernel.org/r/20211211131734.126874-1-wangkefeng.wang@huawei.com[catalin.marinas@arm.com: added comment to justify EXPERT]Signed-off-by: Catalin Marinas List of files: /linux/arch/arm64/kernel/vdso/Makefile

34688c76911e4fe7d405ace8b42f565878922045 - arm64: vdso: remove -nostdlib compiler flag

Sun, 07 Nov 2021 17:18:02 +0100

arm64: vdso: remove -nostdlib compiler flagThe -nostdlib option requests the compiler to not use the standardsystem startup files or libraries when linking. It is effective onlywhen $(CC) is used as a linker driver.Since commit 691efbedc60d ("arm64: vdso: use $(LD) instead of $(CC)to link VDSO"), $(LD) is directly used, hence -nostdlib is unneeded.Signed-off-by: Masahiro Yamada Link: https://lore.kernel.org/r/20211107161802.323125-1-masahiroy@kernel.orgSigned-off-by: Will Deacon List of files: /linux/arch/arm64/kernel/vdso/Makefile

79db4d2293eba2ce6265a341bedf6caecad5eeb3 - Merge tag 'clang-lto-v5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Tue, 23 Feb 2021 18:28:51 +0100

Merge tag 'clang-lto-v5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linuxPull clang LTO updates from Kees Cook: "Clang Link Time Optimization. This is built on the work done preparing for LTO by arm64 folks, tracing folks, etc. This includes the core changes as well as the remaining pieces for arm64 (LTO has been the default build method on Android for about 3 years now, as it is the prerequisite for the Control Flow Integrity protections). While x86 LTO enablement is done, it depends on some pending objtool clean-ups. It's possible that I'll send a "part 2" pull request for LTO that includes x86 support. For merge log posterity, and as detailed in commit dc5723b02e52 ("kbuild: add support for Clang LTO"), here is the lt;dr to do an LTO build: make LLVM=1 LLVM_IAS=1 defconfig scripts/config -e LTO_CLANG_THIN make LLVM=1 LLVM_IAS=1 (To do a cross-compile of arm64, add "CROSS_COMPILE=aarch64-linux-gnu-" and "ARCH=arm64" to the "make" command lines.) Summary: - Clang LTO build infrastructure and arm64-specific enablement (Sami Tolvanen) - Recursive build CC_FLAGS_LTO fix (Alexander Lobakin)"* tag 'clang-lto-v5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: kbuild: prevent CC_FLAGS_LTO self-bloating on recursive rebuilds arm64: allow LTO to be selected arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS arm64: vdso: disable LTO drivers/misc/lkdtm: disable LTO for rodata.o efi/libstub: disable LTO scripts/mod: disable LTO for empty.c modpost: lto: strip .lto from module names PCI: Fix PREL32 relocations for LTO init: lto: fix PREL32 relocations init: lto: ensure initcall ordering kbuild: lto: add a default list of used symbols kbuild: lto: merge module sections kbuild: lto: limit inlining kbuild: lto: fix module versioning kbuild: add support for Clang LTO tracing: move function tracer options to Kconfig List of files: /linux/arch/arm64/kernel/vdso/Makefile

a5b8ca97fbf8300a5e21c393df25ce6f521e7939 - arm64: do not descend to vdso directories twice

Fri, 18 Dec 2020 03:45:40 +0100

arm64: do not descend to vdso directories twicearm64 descends into each vdso directory twice; first in vdso_prepare,second during the ordinary build process.PPC mimicked it and uncovered a problem [1]. In the first descend,Kbuild directly visits the vdso directories, therefore it does notinherit subdir-ccflags-y from upper directories.This means the command line parameters may differ between the two.If it happens, the offset values in the generated headers might bedifferent from real offsets of vdso.so in the kernel.This potential danger should be avoided. The vdso directories arebuilt in the vdso_prepare stage, so the second descend is unneeded.[1]: https://lore.kernel.org/linux-kbuild/CAK7LNARAkJ3_-4gX0VA2UkapbOftuzfSTVMBbgbw=HD8n7N+7w@mail.gmail.com/T/#ma10dcb961fda13f36d42d58fa6cb2da988b7e73aSigned-off-by: Masahiro Yamada Link: https://lore.kernel.org/r/20201218024540.1102650-1-masahiroy@kernel.orgSigned-off-by: Will Deacon List of files: /linux/arch/arm64/kernel/vdso/Makefile