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Alexei Starovoitov
b236134f70
Ihor Solodrai says: ==================== bpf: Kernel functions with KF_IMPLICIT_ARGS This series implements a generic "implicit arguments" feature for BPF kernel functions. For context see prior work [1][2]. A mechanism is created for kfuncs to have arguments that are not visible to the BPF programs, and are provided to the kernel function implementation by the verifier. This mechanism is then used in the kfuncs that have a parameter with __prog annotation [3], which is the current way of passing struct bpf_prog_aux pointer to kfuncs. The function with implicit arguments is defined by KF_IMPLICIT_ARGS flag in BTF_IDS_FLAGS set. In this series, only a pointer to struct bpf_prog_aux can be implicit, although it is simple to extend this to more types. The verifier handles a kfunc with KF_IMPLICIT_ARGS by resolving it to a different (actual) BTF prototype early in verification (patch #3). A <kfunc>_impl function generated in BTF for a kfunc with implicit args does not have a "bpf_kfunc" decl tag, and a kernel address. The verifier will reject a program trying to call such an _impl kfunc. The usage of <kfunc>_impl functions in BPF is only allowed for kfuncs with an explicit kernel (or kmodule) declaration, that is in "legacy" cases. As of this series, there are no legacy kernel functions, as all __prog users are migrated to KF_IMPLICIT_ARGS. However the implementation allows for legacy cases support in principle. The series removes the following BPF kernel functions: - bpf_stream_vprintk_impl - bpf_task_work_schedule_resume_impl - bpf_task_work_schedule_signal_impl - bpf_wq_set_callback_impl This will break existing BPF programs calling these functions (the verifier will not load them) on new kernels. To mitigate, BPF users are advised to use the following pattern [4]: if (xxx_impl) xxx_impl(..., NULL); else xxx(...); Which can be wrapped in a macro. The series consists of the following patches: - patches #1 and #2 are non-functional refactoring in kernel/bpf - patch #3 defines KF_IMPLICIT_ARGS flag and teaches the verifier about it - patches #4-#5 implement btf2btf transformation in resolve_btfids - patch #6 adds selftests specific to KF_IMPLICIT_ARGS feature - patches #7-#11 migrate the current users of __prog argument to KF_IMPLICIT_ARGS - patch #12 removes __prog arg suffix support from the kernel - patch #13 updates the docs [1] https://lore.kernel.org/bpf/20251029190113.3323406-1-ihor.solodrai@linux.dev/ [2] https://lore.kernel.org/bpf/20250924211716.1287715-1-ihor.solodrai@linux.dev/ [3] https://docs.kernel.org/bpf/kfuncs.html#prog-annotation [4] https://lore.kernel.org/bpf/CAEf4BzbgPfRm9BX=TsZm-TsHFAHcwhPY4vTt=9OT-uhWqf8tqw@mail.gmail.com/ --- v2->v3: - resolve_btfids: Use dynamic reallocation for btf2btf_context arrays (Andrii) - resolve_btfids: Add missing free() for btf2btf_context arrays (AI) - Other nits in resolve_btfids (Andrii, Eduard) v2: https://lore.kernel.org/bpf/20260116201700.864797-1-ihor.solodrai@linux.dev/ v1->v2: - Replace the following kernel functions with KF_IMPLICIT_ARGS version: - bpf_stream_vprintk_impl -> bpf_stream_vprintk - bpf_task_work_schedule_resume_impl -> bpf_task_work_schedule_resume - bpf_task_work_schedule_signal_impl -> bpf_task_work_schedule_signal - bpf_wq_set_callback_impl -> bpf_wq_set_callback_impl - Remove __prog arg suffix support from the verifier - Rework btf2btf implementation in resolve_btfids - Do distill base and sort before BTF_ids patching - Collect kfuncs based on BTF decl tags, before BTF_ids are patched - resolve_btfids: use dynamic memory for intermediate data (Andrii) - verifier: reset .subreg_def for caller saved registers on kfunc call (Eduard) - selftests/hid: remove Makefile changes (Benjamin) - selftests/bpf: Add a patch (#11) migrating struct_ops_assoc test to KF_IMPLICIT_ARGS - Various nits across the series (Alexei, Andrii, Eduard) v1: https://lore.kernel.org/bpf/20260109184852.1089786-1-ihor.solodrai@linux.dev/ --- ==================== Link: https://patch.msgid.link/20260120222638.3976562-1-ihor.solodrai@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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