mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-09-22 09:34:56 +02:00
Kumar Kartikeya Dwivedi
2f2223a993
Pu Lehui says: ==================== Mixing bpf2bpf and tailcalls for RV64 In the current RV64 JIT, if we just don't initialize the TCC in subprog, the TCC can be propagated from the parent process to the subprocess, but the updated TCC of the parent process cannot be restored when the subprocess exits. Since the RV64 TCC is initialized before saving the callee saved registers into the stack, we cannot use the callee saved register to pass the TCC, otherwise the original value of the callee saved register will be destroyed. So we implemented mixing bpf2bpf and tailcalls similar to x86_64, i.e. using a non-callee saved register to transfer the TCC between functions, and saving that register to the stack to protect the TCC value. As for the tailcall hierarchy issue, inspired by the s390's low-overhead approach, we store TCC from RV_REG_TCC back to stack after calling bpf2bpf call or calling orig bpf func in bpf trampoline. In addition, some code cleans are also attached to this patchset. Tests test_bpf.ko and test_verifier have passed, as well as the relative testcases of test_progs*. v6: - Add new patch to fix memory leak in bpf_jit_free. (Sashiko) v5: https://lore.kernel.org/bpf/20260707142219.2871758-1-pulehui@huaweicloud.com - Fix TCC value was not restored to RV_REG_TCC upon trampoline exit, resulting in an infinite tail call. (Sashiko) - Fix epilogue not restored TCC value to RV_REG_TCC, resulting in leaf tailcall callee may clobbered RV_REG_TCC. (Sashiko) - Remove patch of `Remove ctx->offset initialization` as it would hit some corner case. (Sashiko) - Fix double-count kcfi insn when tailcall to target. (Sashiko) - Add detail for selftest commit message. (BPF BOT) v4: https://lore.kernel.org/bpf/20260629140048.733346-1-pulehui@huaweicloud.com - Fix tailcall hierarchy issue. - use is_struct_ops_tramp helper in bpf trampoline v3: https://lore.kernel.org/bpf/20240201083351.943121-1-pulehui@huaweicloud.com - Remove duplicate RV_REG_TCC load in epiloguei. (Björn Töpel) v2: https://lore.kernel.org/bpf/20240130040958.230673-1-pulehui@huaweicloud.com - Fix emit restore RV_REG_TCC double times when `flags & BPF_TRAMP_F_CALL_ORIG` - Use bpf_is_subprog helper v1: https://lore.kernel.org/bpf/20230919035711.3297256-1-pulehui@huaweicloud.com ==================== Link: https://patch.msgid.link/20260708064436.2971933-1-pulehui@huaweicloud.com Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.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 * 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