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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Include <linux/io.h> to avoid depending on <linux/backlight.h>
for including it. Declares __raw_readb() and __raw_writeb().
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202510282206.wI0HrqcK-lkp@intel.com/
Fixes: 243ce64b2b37 ("backlight: Do not include <linux/fb.h> in header file")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Daniel Thompson (RISCstar) <danielt@kernel.org>
Cc: Simona Vetter <simona.vetter@ffwll.ch>
Cc: Lee Jones <lee@kernel.org>
Cc: Daniel Thompson <danielt@kernel.org>
Cc: Jingoo Han <jingoohan1@gmail.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Reviewed-by: Daniel Thompson (RISCstar) <danielt@kernel.org>
Signed-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Pull fsverity fixes from Eric Biggers:
- Fix a build error on parisc
- Remove the non-large-folio-aware function fsverity_verify_page()
* tag 'fsverity-for-linus' of git://git.kernel.org/pub/scm/fs/fsverity/linux:
fsverity: fix build error by adding fsverity_readahead() stub
fsverity: remove fsverity_verify_page()
f2fs: make f2fs_verify_cluster() partially large-folio-aware
f2fs: remove unnecessary ClearPageUptodate in f2fs_verify_cluster()
Pull crypto library fix from Eric Biggers:
"Fix a big endian specific issue in the PPC64-optimized AES code"
* tag 'libcrypto-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux:
lib/crypto: powerpc/aes: Fix rndkey_from_vsx() on big endian CPUs
hppa-linux-gcc 9.5.0 generates a call to fsverity_readahead() in
f2fs_readahead() when CONFIG_FS_VERITY=n, because it fails to do the
expected dead code elimination based on vi always being NULL. Fix the
build error by adding an inline stub for fsverity_readahead(). Since
it's just for opportunistic readahead, just make it a no-op.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202602180838.pwICdY2r-lkp@intel.com/
Fixes: 45dcb3ac9832 ("f2fs: consolidate fsverity_info lookup")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20260218012244.18536-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Stephen retired and stepped back from -next maintainership, update his
entry in CREDITS to recognise his 18 years of hard work making it what
it is today and all the impact it's had on our development process.
Also update to his current GnuPG key while we're here.
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I finally got a big endian PPC64 kernel to boot in QEMU. The PPC64 VSX
optimized AES library code does work in that case, with the exception of
rndkey_from_vsx() which doesn't take into account that the order in
which the VSX code stores the round key words depends on the endianness.
So fix rndkey_from_vsx() to do the right thing on big endian CPUs.
Fixes: 7cf2082e74ce ("lib/crypto: powerpc/aes: Migrate POWER8 optimized code into library")
Link: https://lore.kernel.org/r/20260216022104.332991-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Now that fsverity_verify_page() has no callers, remove it.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20260218010630.7407-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
The x509 public key code gained a dependency on the sha256 hash
implementation, causing a rare link time failure in randconfig
builds:
arm-linux-gnueabi-ld: crypto/asymmetric_keys/x509_public_key.o: in function `x509_get_sig_params':
x509_public_key.c:(.text.x509_get_sig_params+0x12): undefined reference to `sha256'
arm-linux-gnueabi-ld: (sha256): Unknown destination type (ARM/Thumb) in crypto/asymmetric_keys/x509_public_key.o
x509_public_key.c:(.text.x509_get_sig_params+0x12): dangerous relocation: unsupported relocation
Select the necessary library code from Kconfig.
Fixes: 2c62068ac86b ("x509: Separately calculate sha256 for blacklist")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull sysctl updates from Joel Granados:
- Remove macros from proc handler converters
Replace the proc converter macros with "regular" functions. Though it
is more verbose than the macro version, it helps when debugging and
better aligns with coding-style.rst.
- General cleanup
Remove superfluous ctl_table forward declarations. Const qualify the
memory_allocation_profiling_sysctl and loadpin_sysctl_table arrays.
Add missing kernel doc to proc_dointvec_conv.
- Testing
This series was run through sysctl selftests/kunit test suite in
x86_64. And went into linux-next after rc4, giving it a good 3 weeks
of testing
* tag 'sysctl-7.00-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl:
sysctl: replace SYSCTL_INT_CONV_CUSTOM macro with functions
sysctl: Replace unidirectional INT converter macros with functions
sysctl: Add kernel doc to proc_douintvec_conv
sysctl: Replace UINT converter macros with functions
sysctl: Add CONFIG_PROC_SYSCTL guards for converter macros
sysctl: clarify proc_douintvec_minmax doc
sysctl: Return -ENOSYS from proc_douintvec_conv when CONFIG_PROC_SYSCTL=n
sysctl: Remove unused ctl_table forward declarations
loadpin: Implement custom proc_handler for enforce
alloc_tag: move memory_allocation_profiling_sysctls into .rodata
sysctl: Add missing kernel-doc for proc_dointvec_conv
f2fs_verify_cluster() is the only remaining caller of the
non-large-folio-aware function fsverity_verify_page(). To unblock the
removal of that function, change f2fs_verify_cluster() to verify the
entire folio of each page and mark it up-to-date.
Note that this doesn't actually make f2fs_verify_cluster()
large-folio-aware, as it is still passed an array of pages. Currently,
it's never called with large folios.
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20260218010630.7407-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Align to the commit bf4afc53b77a ("Convert 'alloc_obj' family to use the
new default GFP_KERNEL argument") update the 'kmalloc_obj' declaration
for userspace to fix below compile error:
In file included from arch/arm/boot/compressed/../../../../lib/decompress_unxz.c:241,
from arch/arm/boot/compressed/decompress.c:56:
arch/arm/boot/compressed/../../../../lib/xz/xz_dec_stream.c: In function 'xz_dec_init':
arch/arm/boot/compressed/../../../../lib/xz/xz_dec_stream.c:787:28: error: implicit declaration of function 'kmalloc_obj'; did you mean 'kmalloc'? [-Wimplicit-function-declaration]
787 | struct xz_dec *s = kmalloc_obj(*s);
| ^~~~~~~~~~~
| kmalloc
Signed-off-by: Haiyue Wang <haiyuewa@163.com>
Fixes: 69050f8d6d07 ("treewide: Replace kmalloc with kmalloc_obj for non-scalar types")
Fixes: bf4afc53b77a ("Convert 'alloc_obj' family to use the new default GFP_KERNEL argument")
Reviewed-by: Kees Cook <kees@kernel.org>
Acked-by: Lasse Collin <lasse.collin@tukaani.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull turbostat fix from Len Brown:
"Fix a recent AMD regression due to errant code cleanup"
* tag 'turbostat-2026.02.14-AMD-RAPL-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux:
tools/power turbostat: Fix AMD RAPL regression
Remove SYSCTL_INT_CONV_CUSTOM and replace it with proc_int_conv. This
converter function expects a negp argument as it can take on negative
values. Update all jiffies converters to use explicit function calls.
Remove SYSCTL_CONV_IDENTITY as it is no longer used.
Signed-off-by: Joel Granados <joel.granados@kernel.org>
Remove the unnecessary clearing of PG_uptodate. It's guaranteed to
already be clear.
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20260218010630.7407-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Pull RTC updates from Alexandre Belloni:
- loongson: Loongson-2K0300 support
- s35390a: nvmem support
- zynqmp: rework calibration
* tag 'rtc-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux:
rtc: ds1390: fix number of bytes read from RTC
rtc: class: Remove duplicate check for alarm
rtc: optee: simplify OP-TEE context match
rtc: interface: Alarm race handling should not discard preceding error
rtc: s35390a: implement nvmem support
rtc: loongson: Add Loongson-2K0300 support
dt-bindings: rtc: loongson: Document Loongson-2K0300 compatible
dt-bindings: rtc: loongson: Correct Loongson-1C interrupts property
dt-bindings: rtc: renesas,rz-rtca3: Add RZ/V2N support
dt-bindings: rtc: cpcap: convert to schema
rtc: zynqmp: use dynamic max and min offset ranges
rtc: zynqmp: rework set_offset
rtc: zynqmp: rework read_offset
rtc: zynqmp: check calibration max value
rtc: zynqmp: correct frequency value
rtc: amlogic-a4: Remove IRQF_ONESHOT
rtc: pcf8563: use correct of_node for output clock
rtc: max31335: use correct CONFIG symbol in IS_REACHABLE()
rtc: nvvrs: Add ARCH_TEGRA to the NV VRS RTC driver