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
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Pull more non-MM updates from Andrew Morton:
- "two fixes in kho_populate()" fixes a couple of not-major issues in
the kexec handover code (Ran Xiaokai)
- misc singletons
* tag 'mm-nonmm-stable-2026-02-18-19-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
lib/group_cpus: handle const qualifier from clusters allocation type
kho: remove unnecessary WARN_ON(err) in kho_populate()
kho: fix missing early_memunmap() call in kho_populate()
scripts/gdb: implement x86_page_ops in mm.py
objpool: fix the overestimation of object pooling metadata size
selftests/memfd: use IPC semaphore instead of SIGSTOP/SIGCONT
delayacct: fix build regression on accounting tool
Pull more MM updates from Andrew Morton:
- "mm/vmscan: fix demotion targets checks in reclaim/demotion" fixes a
couple of issues in the demotion code - pages were failed demotion
and were finding themselves demoted into disallowed nodes (Bing Jiao)
- "Remove XA_ZERO from error recovery of dup_mmap()" fixes a rare
mapledtree race and performs a number of cleanups (Liam Howlett)
- "mm: add bitmap VMA flag helpers and convert all mmap_prepare to use
them" implements a lot of cleanups following on from the conversion
of the VMA flags into a bitmap (Lorenzo Stoakes)
- "support batch checking of references and unmapping for large folios"
implements batching to greatly improve the performance of reclaiming
clean file-backed large folios (Baolin Wang)
- "selftests/mm: add memory failure selftests" does as claimed (Miaohe
Lin)
* tag 'mm-stable-2026-02-18-19-48' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (36 commits)
mm/page_alloc: clear page->private in free_pages_prepare()
selftests/mm: add memory failure dirty pagecache test
selftests/mm: add memory failure clean pagecache test
selftests/mm: add memory failure anonymous page test
mm: rmap: support batched unmapping for file large folios
arm64: mm: implement the architecture-specific clear_flush_young_ptes()
arm64: mm: support batch clearing of the young flag for large folios
arm64: mm: factor out the address and ptep alignment into a new helper
mm: rmap: support batched checks of the references for large folios
tools/testing/vma: add VMA userland tests for VMA flag functions
tools/testing/vma: separate out vma_internal.h into logical headers
tools/testing/vma: separate VMA userland tests into separate files
mm: make vm_area_desc utilise vma_flags_t only
mm: update all remaining mmap_prepare users to use vma_flags_t
mm: update shmem_[kernel]_file_*() functions to use vma_flags_t
mm: update secretmem to use VMA flags on mmap_prepare
mm: update hugetlbfs to use VMA flags on mmap_prepare
mm: add basic VMA flag operation helper functions
tools: bitmap: add missing bitmap_[subset(), andnot()]
mm: add mk_vma_flags() bitmap flag macro helper
...
In preparation for making the kmalloc family of allocators type aware, we
need to make sure that the returned type from the allocation matches the
type of the variable being assigned. (Before, the allocator would always
return "void *", which can be implicitly cast to any pointer type.)
The assigned type is "const struct cpumask **", but the returned type,
while matching, is not const qualified. To get them exactly matching,
just use the dereferenced pointer for the sizeof().
Link: https://lkml.kernel.org/r/20260206222010.work.349-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
Cc: Wangyang Guo <wangyang.guo@intel.com>
Cc: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull Kbuild fixes from Nathan Chancellor:
- Ensure tools/objtool is cleaned by 'make clean' and 'make mrproper'
- Fix test program for CONFIG_CC_CAN_LINK to avoid a warning, which is
made fatal by -Werror
- Drop explicit LZMA parallel compression in scripts/make_fit.py
- Several fixes for commit 62089b804895 ("kbuild: rpm-pkg: Generate
debuginfo package manually")
* tag 'kbuild-fixes-7.0-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux:
kbuild: rpm-pkg: Disable automatic requires for manual debuginfo package
kbuild: rpm-pkg: Fix manual debuginfo generation when using .src.rpm
kernel: rpm-pkg: Restore find-debuginfo.sh approach to -debuginfo package
kbuild: rpm-pkg: Restrict manual debug package creation
scripts/make_fit.py: Drop explicit LZMA parallel compression
kbuild: Fix CC_CAN_LINK detection
kbuild: Add objtool to top-level clean target
Several subsystems (slub, shmem, ttm, etc.) use page->private but don't
clear it before freeing pages. When these pages are later allocated as
high-order pages and split via split_page(), tail pages retain stale
page->private values.
This causes a use-after-free in the swap subsystem. The swap code uses
page->private to track swap count continuations, assuming freshly
allocated pages have page->private == 0. When stale values are present,
swap_count_continued() incorrectly assumes the continuation list is valid
and iterates over uninitialized page->lru containing LIST_POISON values,
causing a crash:
KASAN: maybe wild-memory-access in range [0xdead000000000100-0xdead000000000107]
RIP: 0010:__do_sys_swapoff+0x1151/0x1860
Fix this by clearing page->private in free_pages_prepare(), ensuring all
freed pages have clean state regardless of previous use.
Link: https://lkml.kernel.org/r/20260207173615.146159-1-mikhail.v.gavrilov@gmail.com
Fixes: 3b8000ae185c ("mm/vmalloc: huge vmalloc backing pages should be split rather than compound")
Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Suggested-by: Zi Yan <ziy@nvidia.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The following pr_warn() provides detailed error and location information,
WARN_ON(err) adds no additional debugging value, so remove the redundant
WARN_ON() call.
Link: https://lkml.kernel.org/r/20260212111146.210086-3-ranxiaokai627@163.com
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull thermal control fix from Rafael Wysocki:
"This fixes a sysfs group leak on DLVR registration failure in the
Intel int340x thermal driver (Kaushlendra Kumar)"
* tag 'thermal-7.0-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
thermal: int340x: Fix sysfs group leak on DLVR registration failure
Stefano reports that after commit 62089b804895 ("kbuild: rpm-pkg:
Generate debuginfo package manually"), building with an rpm package
using rpm 4.20.0 fails with:
RPM build errors:
Dependency tokens must begin with alpha-numeric, '_' or '/': #�) = 0x0d000002
Dependency tokens must begin with alpha-numeric, '_' or '/': �) = 0x0d000000
Dependency tokens must begin with alpha-numeric, '_' or '/': ) = 0x7c0e000000
Unknown rich dependency op 'Hat': (Red Hat 15.2.1-7)) = 0x3130363230322000
Unknown rich dependency op 'Hat': (Red Hat 15.2.1-7)) = 0x4728203a43434800
Unknown rich dependency op 'Hat': (Red Hat 15.2.1-7)) = 0x3130363230322000
Unknown rich dependency op 'Hat': (Red Hat 15.2.1-7)) = 0x4728203a43434800
This error comes from the automatic requirements feature of rpm. The
-debuginfo subpackage has no dependencies, so disable this feature with
'AutoReq: 0' for this subpackage, avoiding the error. This matches the
official %_debug_template macro that rpm provides. While automatic
provides should be default enabled, be explicit like %_debug_template
does.
Additionally, while in the area, add the manual debug information
package to the Development/Debug group, further aligning with
%_debug_template.
Cc: stable@vger.kernel.org
Fixes: 62089b804895 ("kbuild: rpm-pkg: Generate debuginfo package manually")
Reported-by: Stefano Garzarella <sgarzare@redhat.com>
Closes: https://lore.kernel.org/CAGxU2F7FFNgb781_A7a1oL63n9Oy8wsyWceKhUpeZ6mLk=focw@mail.gmail.com/
Tested-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://patch.msgid.link/20260216-improve-manual-debuginfo-template-v1-1-e584b3f8d3be@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
This patch adds a new testcase to validate memory failure handling for
dirty pagecache. This performs similar operations as clean pagecaches
except fsync() is not used to keep pages dirty.
This test helps ensure that memory failure handling for dirty pagecache
works correctly, including proper SIGBUS delivery, page isolation, and
recovery paths.
Link: https://lkml.kernel.org/r/20260206031639.2707102-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: kernel test robot <lkp@intel.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "two fixes in kho_populate()", v3.
This patch (of 2):
kho_populate() returns without calling early_memunmap() on success path,
this will cause early ioremap virtual address space leak.
Link: https://lkml.kernel.org/r/20260212111146.210086-1-ranxiaokai627@163.com
Link: https://lkml.kernel.org/r/20260212111146.210086-2-ranxiaokai627@163.com
Fixes: b50634c5e84a ("kho: cleanup error handling in kho_populate()")
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull more ACPI support updates from Rafael J. Wysocki:
"These are mostly fixes and cleanups on top of the ACPI support updates
merged recently, including two new quirks, an ACPI CPPC library fix,
and fixes and cleanups of a few core ACPI device drivers:
- Add an unused power resource handling quirk for THUNDEROBOT ZERO
(Zhai Can)
- Fix remaining for_each_possible_cpu() in the ACPI CPPC library to
use online CPUs (Sean V Kelley)
- Drop redundant checks from the ACPI notify handler and the driver
remove callback in the ACPI battery driver (Rafael Wysocki)
- Move the creation of the wakeup source during the ACPI button
driver probe to an earlier point to avoid missing a wakeup event
due to a race and clean up system wakeup handling and remove
callback in that driver (Rafael Wysocki)
- Drop unnecessary driver_data pointer clearing from the ACPI EC and
SMBUS HC drivers and make the ACPI backlight (video) driver clear
the device's driver_data pointer on remove (Rafael Wysocki)
- Force enabling of PWM2 on the Yogabook YB1-X90 tablets (Yauhen
Kharuzhy)"
* tag 'acpi-7.0-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
ACPI: PM: Add unused power resource quirk for THUNDEROBOT ZERO
ACPI: driver: Drop driver_data pointer clearing from two drivers
ACPI: video: Clear driver_data pointer on remove
ACPI: button: Tweak acpi_button_remove()
ACPI: button: Tweak system wakeup handling
ACPI: battery: Drop redundant checks from acpi_battery_remove()
ACPI: CPPC: Fix remaining for_each_possible_cpu() to use online CPUs
ACPI: x86: Force enabling of PWM2 on the Yogabook YB1-X90
ACPI: button: Call device_init_wakeup() earlier during probe
ACPI: battery: Drop redundant check from acpi_battery_notify()
When DLVR sysfs group creation fails in proc_thermal_rfim_add(),
the function returns immediately without cleaning up the FIVR group
that may have been created earlier.
Add proper error unwinding to remove the FIVR group before returning
failure.
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://patch.msgid.link/LV3PR11MB876881B77D32A2854AD2908EF563A@LV3PR11MB8768.namprd11.prod.outlook.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Commit 62089b804895 ("kbuild: rpm-pkg: Generate debuginfo package
manually") added uses of OBJCOPY and READELF, variables from Kbuild.
These variables are defined and work properly when using the binrpm-pkg
target because rpmbuild is run within Kbuild. However, these variables
are not defined when building from a source RPM package generated with
the srcrpm-pkg target, breaking the build when generating the debug info
subpackage.
Define a default value for these variables so that these commands
respect the value from Kbuild but continue to work when built from a
source RPM package.
Cc: stable@vger.kernel.org
Fixes: 62089b804895 ("kbuild: rpm-pkg: Generate debuginfo package manually")
Reported-by: Lukas Herbolt <lukas@herbolt.com>
Closes: https://lore.kernel.org/20260212135855.147906-2-lukas@herbolt.com/
Tested-by: Lukas Herbolt <lukas@herbolt.com>
Link: https://patch.msgid.link/20260213-fix-debuginfo-srcrpm-pkg-v1-1-45cd0c0501b9@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
This patch adds a new testcase to validate memory failure handling for
clean pagecache. This test performs similar operations as anonymous pages
except allocating memory using mmap() with a file fd.
This test helps ensure that memory failure handling for clean pagecache
works correctly, including unchanged page content, page isolation, and
recovery paths.
Link: https://lkml.kernel.org/r/20260206031639.2707102-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202601221142.mDWA1ucw-lkp@intel.com/
Cc: David Hildenbrand <david@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Implement all member functions of x86_page_ops strictly following the
logic of aarch64_page_ops.
This includes full support for SPARSEMEM and standard page translation
functions.
This fixes compatibility with 'lx-' commands on x86_64, preventing
AttributeErrors when using lx-pfn_to_page and others.
Link: https://lkml.kernel.org/r/20260202034241.649268-1-hsj0512@snu.ac.kr
Signed-off-by: Seongjun Hong <hsj0512@snu.ac.kr>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull more power management updates from Rafael Wysocki:
"These are mostly fixes on top of the power management updates merged
recently in cpuidle governors, in the Intel RAPL power capping driver
and in the wake IRQ management code:
- Fix the handling of package-scope MSRs in the intel_rapl power
capping driver when called from the PMU subsystem and make it add
all package CPUs to the PMU cpumask to allow tools to read RAPL
events from any CPU in the package (Kuppuswamy Satharayananyan)
- Rework the invalid version check in the intel_rapl_tpmi power
capping driver to account for the fact that on partitioned systems,
multiple TPMI instances may exist per package, but RAPL registers
are only valid on one instance (Kuppuswamy Satharayananyan)
- Describe the new intel_idle.table command line option in the
admin-guide intel_idle documentation (Artem Bityutskiy)
- Fix a crash in the ladder cpuidle governor on systems with only one
(polling) idle state available by making the cpuidle core bypass
the governor in those cases and adjust the other existing governors
to that change (Aboorva Devarajan, Christian Loehle)
- Update kerneldoc comments for wake IRQ management functions that
have not been matching the code (Wang Jiayue)"
* tag 'pm-7.0-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
cpuidle: menu: Remove single state handling
cpuidle: teo: Remove single state handling
cpuidle: haltpoll: Remove single state handling
cpuidle: Skip governor when only one idle state is available
powercap: intel_rapl_tpmi: Remove FW_BUG from invalid version check
PM: sleep: wakeirq: Update outdated documentation comments
Documentation: PM: Document intel_idle.table command line option
powercap: intel_rapl: Expose all package CPUs in PMU cpumask
powercap: intel_rapl: Remove incorrect CPU check in PMU context