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Thomas Weißschuh
546e9289c7
With CONFIG_CC_OPTIMIZE_FOR_SIZE=y, GCC may decide not to inline __cvdso_clock_getres_common(). This introduces spurious internal function calls in the vDSO fastpath. Furthermore, with automatic stack variable initialization (CONFIG_INIT_STACK_ALL_ZERO or CONFIG_INIT_STACK_ALL_PATTERN) GCC can emit a call to memset() which is not valid in the vDSO. Mark __cvdso_clock_getres_common() as __always_inline to avoid both issues. Paradoxically the inlining even reduces the size of the code: $ ./scripts/bloat-o-meter arch/powerpc/kernel/vdso/vgettimeofday-32.o.before arch/powerpc/kernel/vdso/vgettimeofday-32.o.after add/remove: 0/1 grow/shrink: 1/1 up/down: 52/-148 (-96) Function old new delta __c_kernel_clock_getres_time64 92 144 +52 __c_kernel_clock_getres 136 132 -4 __cvdso_clock_getres_common 144 - -144 Total: Before=2788, After=2692, chg -3.44% With CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y the functions are always inlined and therefore the behaviour stays the same. See also the equivalent change for clock_gettime() in commitb91c8c42ff("lib/vdso: Force inlining of __cvdso_clock_gettime_common()"). Fixes:21bbfd7404("x86/vdso: Provide clock_getres_time64() for x86-32") Fixes:1149dcdfc9("ARM: VDSO: Provide clock_getres_time64()") Fixes:f10c2e72b5("arm64: vdso32: Provide clock_getres_time64()") Fixes:bec06cd6a1("MIPS: vdso: Provide getres_time64() for 32-bit ABIs") Fixes:759a1f9737("powerpc/vdso: Provide clock_getres_time64()") Reported-by: Sverdlin, Alexander <alexander.sverdlin@siemens.com> Suggested-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@kernel.org> Link: https://lore.kernel.org/lkml/230c749f-ebd6-4829-93ee-601d88000a45@kernel.org/ Link: https://patch.msgid.link/20260123-vdso-clock_getres-inline-v1-1-4d6203b90cd3@linutronix.de Closes: https://lore.kernel.org/lkml/f45316f65a46da638b3c6aa69effd8980e6677b9.camel@siemens.com/
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst