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Rui Qi 8ac35bac70 riscv: stacktrace: Remove bogus -0x4 offset in non-FP walk_stackframe
In the non-frame-pointer version of walk_stackframe, each value read
from the stack is treated as a potential return address and has 0x4
subtracted before being used as the program counter. This was intended
to convert the return address (the instruction after a call) back to
the call site, but it is incorrect:

1. RISC-V has variable-length instructions due to the RVC (compressed
   instruction) extension. A call instruction can be either 4 bytes
   (regular) or 2 bytes (compressed, e.g. c.jal). Subtracting a fixed
   0x4 assumes all call instructions are 4 bytes, which is wrong for
   compressed instructions.

2. Stack traces conventionally report return addresses, not call sites.
   Other architectures (ARM64, x86, ARM) do not subtract instruction
   size from return addresses in their stack unwinding code.

3. The frame-pointer version of walk_stackframe already dropped the
   -0x4 offset. Commit b785ec129b ("riscv/ftrace: Add
   HAVE_FUNCTION_GRAPH_RET_ADDR_PTR support") replaced "pc =
   frame->ra - 0x4" with ftrace_graph_ret_addr(), and the commit
   message explicitly noted that "the original calculation, pc =
   frame->ra - 4, is buggy when the instruction at the return address
   happened to be a compressed inst." The non-FP version was simply
   overlooked.

Remove the bogus -0x4 offset to match the FP version and the
conventions used by other architectures.

Fixes: 5d8544e2d0 ("RISC-V: Generic library routines and assembly")
Signed-off-by: Rui Qi <qirui.001@bytedance.com>
Link: https://patch.msgid.link/20260603115329.791603-2-qirui.001@bytedance.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>
2026-06-06 23:48:15 -06:00
arch riscv: stacktrace: Remove bogus -0x4 offset in non-FP walk_stackframe 2026-06-06 23:48:15 -06:00
block block: align down bounces bios 2026-05-13 13:55:18 -06:00
certs Clang build fixes for 7.1 2026-04-24 09:29:51 -07:00
crypto This push contains the following changes: 2026-05-02 12:31:43 -07:00
Documentation RISC-V updates for v7.1-rc4 2026-05-17 09:33:49 -07:00
drivers virt: sev-guest: Do not use host-controlled page order in cleanup path 2026-05-17 11:45:07 -07:00
fs five client fixes 2026-05-15 14:52:17 -07:00
include Fix ARM64-specific rseq regressions, by Mark Rutland. 2026-05-17 10:59:32 -07:00
init memblock: updates for 7.0-rc1 2026-04-18 11:29:14 -07:00
io_uring io_uring-7.1-20260515 2026-05-15 12:34:02 -07:00
ipc Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kernel tracing fixes for 7.1: 2026-05-17 12:02:31 -07:00
lib Fix potential garbage reads in the vDSO gettimeofday code, 2026-05-17 11:07:09 -07:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm This push contains the following changes: 2026-05-15 10:38:37 -07:00
net An important patch from Hristo that squashes a folio reference leak 2026-05-15 14:48:09 -07:00
rust Rust fixes for v7.1 2026-05-09 11:24:02 -07:00
samples soc: drivers for 7.1 2026-04-16 20:34:34 -07:00
scripts gcc-plugins: Always define CONST_CAST_GIMPLE and CONST_CAST_TREE 2026-05-14 09:24:32 -07:00
security selinux: shrink critical section in sel_write_load() 2026-05-05 16:02:28 -04:00
sound ALSA: hda/ca0132: Disable auto-detect on manual output select 2026-05-15 11:19:48 +02:00
tools selftests/riscv: fix compiler output flag spacing in all Makefiles 2026-06-06 20:17:52 -06:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt KVM: Reject wrapped offset in kvm_reset_dirty_gfn() 2026-05-12 22:16:16 +02:00
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -08:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add myself 2026-04-02 16:48:25 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rust: provide an option to inline C helpers into Rust 2026-03-30 02:03:52 +02:00
.mailmap MAINTAINERS: update Tomasz Jeznach's email address 2026-05-15 07:30:28 +02:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS Delete some obsolete networking code 2026-04-24 09:41:58 -07:00
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS IOMMU Fixes for Linux v7.1-rc3: 2026-05-15 15:22:26 -07:00
Makefile Linux 7.1-rc4 2026-05-17 13:59:58 -07:00
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -07:00

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