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Guenter Roeck 90d77b30a6
ARM: integrator: Fix early initialization
Starting with commit bdb249fce9 ("ARM: integrator: read counter using
syscon/regmap"), intcp_init_early calls syscon_regmap_lookup_by_compatible
which in turn calls of_syscon_register. This function allocates memory.
Since the memory management code has not been initialized at that time,
the call always fails. It either returns -ENOMEM or crashes as follows.

Unable to handle kernel NULL pointer dereference at virtual address 0000000c when read
[0000000c] *pgd=00000000
Internal error: Oops: 5 [#1] ARM
Modules linked in:
CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.15.0-rc5-00026-g5fcc9bf84ee5 #1 PREEMPT
Hardware name: ARM Integrator/CP (Device Tree)
PC is at __kmalloc_cache_noprof+0xec/0x39c
LR is at __kmalloc_cache_noprof+0x34/0x39c
...
Call trace:
 __kmalloc_cache_noprof from of_syscon_register+0x7c/0x310
 of_syscon_register from device_node_get_regmap+0xa4/0xb0
 device_node_get_regmap from intcp_init_early+0xc/0x40
 intcp_init_early from start_kernel+0x60/0x688
 start_kernel from 0x0

The crash is seen due to a dereferenced pointer which is not supposed to be
NULL but is NULL if the memory management subsystem has not been
initialized. The crash is not seen with all versions of gcc. Some versions
such as gcc 9.x apparently do not dereference the pointer, presumably if
tracing is disabled. The problem has been reproduced with gcc 10.x, 11.x,
and 13.x. Either case, if the crash is not seen, the call to
syscon_regmap_lookup_by_compatible returns -ENOMEM, and
sched_clock_register is never called.

Fix the problem by moving the early initialization code into the standard
machine initialization code.

Fixes: bdb249fce9 ("ARM: integrator: read counter using syscon/regmap")
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/20250518164118.3859567-1-linux@roeck-us.net
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20260505-integrator-fixes-v1-1-56ab9aac59db@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
History 2026-05-07 14:03:21 +02:00
arch ARM: integrator: Fix early initialization 2026-05-07 14:03:21 +02:00
block block: only restrict bio allocation gfp mask asked to block 2026-04-21 11:42:12 -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 Including fixes from netfilter. 2026-04-30 08:45:43 -07:00
drivers drm fixes for 7.1-rc2 2026-05-01 16:56:08 -07:00
fs Description for this pull request: 2026-05-02 12:25:57 -07:00
include drm fixes for 7.1-rc2 2026-05-01 16:56:08 -07:00
init memblock: updates for 7.0-rc1 2026-04-18 11:29:14 -07:00
io_uring io_uring-7.1-20260430 2026-05-01 11:01:31 -07:00
ipc Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kernel Fix lockup in requeue-PI during signal/timeout wakeups, 2026-05-03 08:17:09 -07:00
lib 20 hotfixes. All are for MM (and for MMish maintainers). 9 are cc:stable 2026-05-01 08:45:23 -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 slab fixes for 7.1-rc1 2026-05-03 08:19:57 -07:00
net net/sched: cls_flower: revert unintended changes 2026-04-30 13:47:01 +02:00
rust Char/Misc/IIO/and others driver updates for 7.1-rc1 2026-04-24 13:23:50 -07:00
samples soc: drivers for 7.1 2026-04-16 20:34:34 -07:00
scripts First round of Kbuild fixes for 7.1 2026-04-25 17:04:15 -07:00
security selinux: fix avdcache auditing 2026-04-28 18:13:58 -04:00
sound ALSA: hda/tas2781: Fix incorrect bit update for non-book-zero or book 0 pages >1 2026-04-29 07:51:17 +02:00
tools Assorted arm64, ACPI and kselftest fixes for 7.1-rc2: 2026-05-01 16:32:42 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt Arm: 2026-04-17 07:18:03 -07:00
.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 drm fixes for 7.1-rc2 2026-05-01 16:56:08 -07:00
.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 drm fixes for 7.1-rc2 2026-05-01 16:56:08 -07:00
Makefile Linux 7.1-rc2 2026-05-03 14:21:25 -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