Rust fixes for v7.2 (2nd)

Toolchain and infrastructure:

‘zerocopy’ crates: update to v0.8.54 to fix a modpost error under ‘CONFIG_CC_OPTIMIZE_FOR_SIZE=y’.There are actually two updates in the PR: the one to v0.8.52 is fairly large and was originally not intended for a fixes PR, but the actual fix landed in the v0.8.54 one. Thus I included both here.The v0.8.52 update includes two things upstream added for us: ‘–cfg no_fp_fmt_parse’ to avoid a local workaround, and the new ‘most_traits’ feature.The good news is that, after these updates, the delta with upstream is now trivial: only an identifier prefix change and the SPDX parentheses.
Fix an objtool warning by adding one more ‘noreturn’ function for Rust 1.99.0 (expected 2026-10-01).
Clean up new ‘semicolon_in_expressions_from_macros’ lint errors for Rust 1.99.0 (expected 2026-10-01). The lint can be allowed, but it will be a hard error at some point in the future anyway, so clean it up now.
Locally allow new ‘suspicious_runtime_symbol_definitions’ lint for Rust 1.98.0 (expected 2026-08-20).
Globally allow ‘clippy::unwrap_or_default’ lint since it relies on optimizations – under ‘CONFIG_CC_OPTIMIZE_FOR_SIZE=y’ it does not work well.

‘kernel’ crate:

‘time’ module: fix ‘Delta::as_micros_ceil()’ to round negative values correctly.
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Merge tag ‘rust-fixes-7.2-2’ of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux

Pull rust fixes from Miguel Ojeda: “Toolchain and infrastructure:

‘zerocopy’ crates: update to v0.8.54 to fix a modpost error under ‘CONFIG_CC_OPTIMIZE_FOR_SIZE=y’.

There are actually two updates in the PR: the one to v0.8.52 is fairly large and was originally not intended for a fixes PR, but the actual fix landed in the v0.8.54 one. Thus I included both here.

The v0.8.52 update includes two things upstream added for us: ‘–cfg no_fp_fmt_parse’ to avoid a local workaround, and the new ‘most_traits’ feature.

The good news is that, after these updates, the delta with upstream is now trivial: only an identifier prefix change and the SPDX parentheses.
Fix an objtool warning by adding one more ‘noreturn’ function for Rust 1.99.0 (expected 2026-10-01).
Clean up new ‘semicolon_in_expressions_from_macros’ lint errors for Rust 1.99.0 (expected 2026-10-01). The lint can be allowed, but it will be a hard error at some point in the future anyway, so clean it up now.
Locally allow new ‘suspicious_runtime_symbol_definitions’ lint for Rust 1.98.0 (expected 2026-08-20).
Globally allow ‘clippy::unwrap_or_default’ lint since it relies on optimizations – under ‘CONFIG_CC_OPTIMIZE_FOR_SIZE=y’ it does not work well.

‘kernel’ crate:

‘time’ module: fix ‘Delta::as_micros_ceil()’ to round negative values correctly”

tag ‘rust-fixes-7.2-2’ of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux: rust: time: fix as_micros_ceil() to round correctly for negative Delta rust: device: avoid trailing ; in printing macros objtool/rust: add one more noreturn Rust function for Rust 1.99.0 rust: zerocopy: update to v0.8.54 rust: zerocopy: update to v0.8.52 rust: allow clippy::unwrap_or_default globally rust: allow suspicious_runtime_symbol_definitions lint for Rust >= 1.98

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
AI Coding Assistant - LLMs and AI-powered development tools

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

AI Coding Assistant

CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel:

Documentation/process/coding-assistants.rst

This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with.

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