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
Clone this repository
For self-hosted knots, clone URLs may differ based on your setup.
Download tar.gz
Pull erofs fixes from Gao Xiang:
- Mark I/Os as failed when encountering short reads on file-backed
mounts
- Label GFP_NOIO in the BIO completion when the completion is in the
process context, and directly call into the decompression to avoid
deadlocks
- Improve Kconfig descriptions to better highlight the overall efforts
- Fix .fadvise() for page cache sharing
* tag 'erofs-for-7.0-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs:
erofs: fix .fadvise() for page cache sharing
erofs: update the Kconfig description
erofs: add GFP_NOIO in the bio completion if needed
erofs: set fileio bio failed in short read case
Pull RCU fixes from Boqun Feng:
"Fix a regression introduced by commit c27cea4416a3 ("rcu: Re-implement
RCU Tasks Trace in terms of SRCU-fast"): BPF contexts can run with
preemption disabled or scheduler locks held, so call_srcu() must work
in all such contexts.
Fix this by converting SRCU's spinlocks to raw spinlocks and avoiding
scheduler lock acquisition in call_srcu() by deferring to an irq_work
(similar to call_rcu_tasks_generic()), for both tree SRCU and tiny
SRCU.
Also fix a follow-on lockdep splat caused by srcu_node allocation
under the newly introduced raw spinlock by deferring the allocation to
grace-period worker context"
* tag 'rcu-fixes.v7.0-20260325a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux:
srcu: Use irq_work to start GP in tiny SRCU
rcu: Use an intermediate irq_work to start process_srcu()
srcu: Push srcu_node allocation to GP when non-preemptible
srcu: Use raw spinlocks so call_srcu() can be used under preempt_disable()
Currently, .fadvise() doesn't work well if page cache sharing is on
since shared inodes belong to a pseudo fs generated with init_pseudo(),
and sb->s_bdi is the default one &noop_backing_dev_info.
Then, generic_fadvise() will just behave as a no-op if sb->s_bdi is
&noop_backing_dev_info, but as the bdev fs (the bdev fs changes
inode_to_bdi() instead), it's actually NOT a pure memfs.
Let's generate a real bdi for erofs_ishare_mnt instead.
Fixes: d86d7817c042 ("erofs: implement .fadvise for page cache share")
Reviewed-by: Hongbo Li <lihongbo22@huawei.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Pull hardening fixes from Kees Cook:
- fix required Clang version for CC_HAS_COUNTED_BY_PTR (Nathan
Chancellor)
- update Coccinelle script used for kmalloc_obj
* tag 'hardening-v7.0-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
init/Kconfig: Require a release version of clang-22 for CC_HAS_COUNTED_BY_PTR
coccinelle: kmalloc_obj: Remove default GFP_KERNEL arg
Tiny SRCU's srcu_gp_start_if_needed() directly calls schedule_work(),
which acquires the workqueue pool->lock.
This causes a lockdep splat when call_srcu() is called with a scheduler
lock held, due to:
call_srcu() [holding pi_lock]
srcu_gp_start_if_needed()
schedule_work() -> pool->lock
workqueue_init() / create_worker() [holding pool->lock]
wake_up_process() -> try_to_wake_up() -> pi_lock
Also add irq_work_sync() to cleanup_srcu_struct() to prevent a
use-after-free if a queued irq_work fires after cleanup begins.
Tested with rcutorture SRCU-T and no lockdep warnings.
[ Thanks to Boqun for similar fix in patch "rcu: Use an intermediate irq_work
to start process_srcu()" ]
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun@kernel.org>
Refine the description to better highlight its features and use cases.
In addition, add instructions for building it as a module and clarify
the compression option.
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Pull x86 platform driver fixes from Ilpo Järvinen:
"Fixes and New HW Support. The trivial drop of unused gz_chain_head is
not exactly fixes material but it allows other work to avoid problems
so I decided to take it in along with the fixes.
- amd/hsmp: Fix typo in error message
- asus-armoury: Add support for G614FP, GA503QM, GZ302EAC, and GZ302EAC
- asus-nb-wmi: Add DMI quirk for ASUS ROG Flow Z13-KJP GZ302EAC
- hp-wmi: Support for Omen 16-k0xxx, 16-wf1xxx, 16-xf0xxx
- intel-hid: Disable wakeup_mode during hibernation
- ISST:
- Check HWP support before MSR access
- Correct locked bit width
- lenovo: wmi-gamezone: Drop unused gz_chain_head
- olpc-xo175-ec: Fix overflow error message"
* tag 'platform-drivers-x86-v7.0-3' of git://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86:
platform/x86: ISST: Correct locked bit width
platform/x86: intel-hid: disable wakeup_mode during hibernation
platform/x86: asus-armoury: add support for GZ302EA and GZ302EAC
platform/x86: asus-nb-wmi: add DMI quirk for ASUS ROG Flow Z13-KJP GZ302EAC
platform/x86/amd/hsmp: Fix typo in error message
platform/olpc: olpc-xo175-ec: Fix overflow error message to print inlen
platform/x86: lenovo: wmi-gamezone: Drop gz_chain_head
platform/x86: ISST: Check HWP support before MSR access
platform/x86: hp-wmi: Add support for Omen 16-k0xxx (8A4D)
platform/x86: hp-wmi: Add support for Omen 16-wf1xxx (8C76)
platform/x86: hp-wmi: Add Omen 16-xf0xxx (8BCA) support
platform/x86: asus-armoury: add support for G614FP
platform/x86: asus-armoury: add support for GA503QM
MAINTAINERS: change email address of Denis Benato
Commit 150a04d817d8 ("compiler_types.h: Attributes: Add __counted_by_ptr
macro") used Clang 22.0.0 as a minimum supported version for
__counted_by_ptr, which made sense while 22.0.0 was the version of
LLVM's main branch to allow developers to easily test and develop uses
of __counted_by_ptr in their code. However, __counted_by_ptr requires a
change [1] merged towards the end of the 22 development cycle to avoid
errors when applied to void pointers.
In file included from fs/xfs/xfs_attr_inactive.c:18:
fs/xfs/libxfs/xfs_attr.h:59:2: error: 'counted_by' cannot be applied to a pointer with pointee of unknown size because 'void' is an incomplete type
59 | void *buffer __counted_by_ptr(bufsize);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This is disruptive for deployed prerelease clang-22 builds (such as
Android LLVM) or when bisecting between llvmorg-21-init and the fix.
Require a released version of clang-22 (i.e., 21.1.0 or newer) to
enabled __counted_by_ptr to ensure all fixes needed for proper support
are present.
Fixes: 150a04d817d8 ("compiler_types.h: Attributes: Add __counted_by_ptr macro")
Link: https://github.com/llvm/llvm-project/commit/f29955a594aedf5943d492a999b83e8c6b8fafae [1]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20260318-counted_by_ptr-release-clang-22-v1-1-e017da246df0@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
Since commit c27cea4416a3 ("rcu: Re-implement RCU Tasks Trace in terms
of SRCU-fast") we switched to SRCU in BPF. However as BPF instrument can
happen basically everywhere (including where a scheduler lock is held),
call_srcu() now needs to avoid acquiring scheduler lock because
otherwise it could cause deadlock [1]. Fix this by following what the
previous RCU Tasks Trace did: using an irq_work to delay the queuing of
the work to start process_srcu().
[boqun: Apply Joel's feedback]
[boqun: Apply Andrea's test feedback]
Reported-by: Andrea Righi <arighi@nvidia.com>
Closes: https://lore.kernel.org/all/abjzvz_tL_siV17s@gpd4/
Fixes: commit c27cea4416a3 ("rcu: Re-implement RCU Tasks Trace in terms of SRCU-fast")
Link: https://lore.kernel.org/rcu/3c4c5a29-24ea-492d-aeee-e0d9605b4183@nvidia.com/ [1]
Suggested-by: Zqiang <qiang.zhang@linux.dev>
Tested-by: Andrea Righi <arighi@nvidia.com>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Boqun Feng <boqun@kernel.org>
The bio completion path in the process context (e.g. dm-verity)
will directly call into decompression rather than trigger another
workqueue context for minimal scheduling latencies, which can
then call vm_map_ram() with GFP_KERNEL.
Due to insufficient memory, vm_map_ram() may generate memory
swapping I/O, which can cause submit_bio_wait to deadlock
in some scenarios.
Trimmed down the call stack, as follows:
f2fs_submit_read_io
submit_bio //bio_list is initialized.
mmc_blk_mq_recovery
z_erofs_endio
vm_map_ram
__pte_alloc_kernel
__alloc_pages_direct_reclaim
shrink_folio_list
__swap_writepage
submit_bio_wait //bio_list is non-NULL, hang!!!
Use memalloc_noio_{save,restore}() to wrap up this path.
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Jiucheng Xu <jiucheng.xu@amlogic.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Pull Kbuild fixes from Nathan Chancellor:
"This mostly addresses some issues with the awk conversion in
scripts/kconfig/merge_config.sh.
- Fix typo to ensure .builtin-dtbs.S is properly cleaned
- Fix '==' bashism in scripts/kconfig/merge_config.sh
- Fix awk error in scripts/kconfig/merge_config.sh when base
configuration is empty
- Fix inconsistent indentation in scripts/kconfig/merge_config.sh"
* tag 'kbuild-fixes-7.0-3' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux:
scripts: kconfig: merge_config.sh: fix indentation
scripts: kconfig: merge_config.sh: pass output file as awk variable
scripts: kconfig: merge_config.sh: fix unexpected operator warning
kbuild: Delete .builtin-dtbs.S when running make clean
SST-PP locked bit width is set to three bits. It should be only one bit.
Use SST_PP_LOCK_WIDTH define instead of SST_PP_LEVEL_WIDTH.
Fixes: ea009e4769fa ("platform/x86: ISST: Add SST-PP support via TPMI")
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260323153635.3263828-1-srinivas.pandruvada@linux.intel.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Remove any GFP_KERNEL arguments found in the new kmalloc_obj-family
helpers. This captures the script used in commit 189f164e573e ("Convert
remaining multi-line kmalloc_obj/flex GFP_KERNEL uses").
Link: https://patch.msgid.link/20260320175113.work.016-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
When the srcutree.convert_to_big and srcutree.big_cpu_lim kernel boot
parameters specify initialization-time allocation of the srcu_node
tree for statically allocated srcu_struct structures (for example, in
DEFINE_SRCU() at build time instead of init_srcu_struct() at runtime),
init_srcu_struct_nodes() will attempt to dynamically allocate this tree
at the first run-time update-side use of this srcu_struct structure,
but while holding a raw spinlock. Because the memory allocator can
acquire non-raw spinlocks, this can result in lockdep splats.
This commit therefore uses the same SRCU_SIZE_ALLOC trick that is used
when the first run-time update-side use of this srcu_struct structure
happens before srcu_init() is called. The actual allocation then takes
place from workqueue context at the ends of upcoming SRCU grace periods.
[boqun: Adjust the sha1 of the Fixes tag]
Fixes: 175b45ed343a ("srcu: Use raw spinlocks so call_srcu() can be used under preempt_disable()")
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun@kernel.org>
For file-backed mount, IO requests are handled by vfs_iocb_iter_read().
However, it can be interrupted by SIGKILL, returning the number of
bytes actually copied. Unused folios in bio are unexpectedly marked
as uptodate.
vfs_read
filemap_read
filemap_get_pages
filemap_readahead
erofs_fileio_readahead
erofs_fileio_rq_submit
vfs_iocb_iter_read
filemap_read
filemap_get_pages <= detect signal
erofs_fileio_ki_complete <= set all folios uptodate
This patch addresses this by setting short read bio with an error
directly.
Fixes: bc804a8d7e86 ("erofs: handle end of filesystem properly for file-backed mounts")
Reported-by: chenguanyou <chenguanyou@xiaomi.com>
Signed-off-by: Yunlei He <heyunlei@xiaomi.com>
Signed-off-by: Sheng Yong <shengyong1@xiaomi.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Pull kvm fixes from Paolo Bonzini:
"ARM:
- Clear the pending exception state from a vcpu coming out of reset,
as it could otherwise affect the first instruction executed in the
guest
- Fix pointer arithmetic in address translation emulation, so that
the Hardware Access bit is set on the correct PTE instead of some
other location
s390:
- Fix deadlock in new memory management
- Properly handle kernel faults on donated memory
- Fix bounds checking for irq routing, with selftest
- Fix invalid machine checks and log all of them"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
KVM: arm64: Fix the descriptor address in __kvm_at_swap_desc()
KVM: s390: vsie: Avoid injecting machine check on signal
KVM: s390: log machine checks more aggressively
KVM: s390: selftests: Add IRQ routing address offset tests
KVM: s390: Limit adapter indicator access to mapped page
s390/mm: Add missing secure storage access fixups for donated memory
KVM: arm64: Discard PC update state on vcpu reset
KVM: s390: Fix a deadlock