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 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 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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Calculate the hypervisor's VA size only once to maintain consistency
between the memory layout and MMU initialization logic. Previously the
two would be inconsistent when the kernel is configured for less than
IDMAP_VA_BITS of VA space.
Signed-off-by: Petteri Kangaslampi <pekangas@google.com>
Tested-by: Vincent Donnefort <vdonnefort@google.com>
Link: https://patch.msgid.link/20260113194409.2970324-2-pekangas@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
The value of FPEX32_EL2 has no effect on execution in AArch64 state, and
consequently there's no need for an ISB after writing to it in the hyp
code (which executes in AArch64 state). When performing an exception
return to AArch32 state, the exception return will provide the necessary
context synchronization event.
Remove the redundant ISB.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Will Deacon <will@kernel.org>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260106173707.3292074-4-mark.rutland@arm.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
There's a gap in the KVM_HOST_DATA_FLAG_* indices since the removal of
KVM_HOST_DATA_FLAG_HOST_SVE_ENABLED and
KVM_HOST_DATA_FLAG_HOST_SME_ENABLED in commits:
* 459f059be702 ("KVM: arm64: Remove VHE host restore of CPACR_EL1.ZEN")
* 407a99c4654e ("KVM: arm64: Remove VHE host restore of CPACR_EL1.SMEN")
Shuffle the indices to remove the gap, as Oliver requested at the time of
the removals:
https://lore.kernel.org/linux-arm-kernel/Z6qC4qn47ONfDCSH@linux.dev/
There should be no functional change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Will Deacon <will@kernel.org>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://patch.msgid.link/20260106173707.3292074-3-mark.rutland@arm.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
The comment in fpsimd_lazy_switch_to_host() erroneously says guest traps
for FPSIMD/SVE/SME are disabled by fpsimd_lazy_switch_to_guest(). In
reality, the traps are disabled by __activate_cptr_traps(), and
fpsimd_lazy_switch_to_guest() only manipulates the SVE vector length.
This was mistake; I accidentally copy+pasted the wrong function name in
commit:
59419f10045b ("KVM: arm64: Eagerly switch ZCR_EL{1,2}")
Fix the comment.
Fixes: 59419f10045b ("KVM: arm64: Eagerly switch ZCR_EL{1,2}")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Will Deacon <will@kernel.org>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260106173707.3292074-2-mark.rutland@arm.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
Pull core entry fix from Borislav Petkov:
- Make sure clang inlines trivial local_irq_* helpers
* tag 'core_urgent_for_v6.19_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
entry: Always inline local_irq_{enable,disable}_exit_to_user()
Pull pmdomain fixes from Ulf Hansson:
- mediatek: Fix spinlock recursion fix during probe
- imx: Fix reference count leak during probe
* tag 'pmdomain-v6.19-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/linux-pm:
pmdomain: imx: Fix reference count leak in imx_gpc_probe()
pmdomain: mtk-pm-domains: Fix spinlock recursion fix in probe
clang needs __always_inline instead of inline, even for tiny helpers.
This saves some cycles in system call fast path, and saves 195 bytes
on x86_64 build:
$ size vmlinux.before vmlinux.after
text data bss dec hex filename
34652814 22291961 5875180 62819955 3be8e73 vmlinux.before
34652619 22291961 5875180 62819760 3be8db0 vmlinux.after
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251204153127.1321824-1-edumazet@google.com
Pull perf tool fixes and from Namhyung Kim:
- skip building BPF skeletons if libopenssl is missing
- a couple of test updates
- handle error cases of filename__read_build_id()
- support NVIDIA Olympus for ARM SPE profiling
- update tool headers to sync with the kernel
* tag 'perf-tools-fixes-for-v6.19-2026-01-02' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools:
tools build: Fix the common set of features test wrt libopenssl
tools headers: Sync syscall table with kernel sources
tools headers: Sync linux/socket.h with kernel sources
tools headers: Sync linux/gfp_types.h with kernel sources
tools headers: Sync arm64 headers with kernel sources
tools headers: Sync x86 headers with kernel sources
tools headers: Sync UAPI sound/asound.h with kernel sources
tools headers: Sync UAPI linux/mount.h with kernel sources
tools headers: Sync UAPI linux/fs.h with kernel sources
tools headers: Sync UAPI linux/fcntl.h with kernel sources
tools headers: Sync UAPI KVM headers with kernel sources
tools headers: Sync UAPI drm/drm.h with kernel sources
perf arm-spe: Add NVIDIA Olympus to neoverse list
tools headers arm64: Add NVIDIA Olympus part
perf tests top: Make the test exclusive
perf tests kvm: Avoid leaving perf.data.guest file around
perf symbol: Fix ENOENT case for filename__read_build_id
perf tools: Disable BPF skeleton if no libopenssl found
tools/build: Add a feature test for libopenssl
of_get_child_by_name() returns a node pointer with refcount incremented.
Use the __free() attribute to manage the pgc_node reference, ensuring
automatic of_node_put() cleanup when pgc_node goes out of scope.
This eliminates the need for explicit error handling paths and avoids
reference count leaks.
Fixes: 721cabf6c660 ("soc: imx: move PGC handling to a new GPC driver")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Pull power management fix from Rafael Wysocki:
"Fix a recent regression that affects system suspend testing
at the 'core' level (Rafael Wysocki)"
* tag 'pm-6.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
PM: sleep: Fix suspend_test() at the TEST_CORE level
The recent introduction of the libopenssl feature test forgot to add the
-lssl to the test-all.o target, which made it always fail, fix it.
Noticed by looking at this file after building:
$ cat /tmp/build/perf-tools/feature/test-all.make.output
/usr/bin/ld: /tmp/ccBhO8WH.ltrans0.ltrans.o: in function `main':
/home/acme/git/perf-tools/tools/build/feature/test-libopenssl.c:6:(.text.startup+0x2ed): undefined reference to `OPENSSL_init_ssl'
collect2: error: ld returned 1 exit status
$
It was added only to the individual ssl test, that works:
$ cat /tmp/build/perf-tools/feature/test-libopenssl.make.output
$ ldd /tmp/build/perf-tools/feature/test-libopenssl.bin | grep ssl
libssl.so.3 => /usr/lib64/libssl.so.3 (0x00007fb81eda8000)
$
Fixes: 7678523109d1d9ee ("tools/build: Add a feature test for libopenssl")
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Remove scpsys_get_legacy_regmap(), replacing its usage with
of_find_node_with_property(). Explicitly call of_node_get(np) before each
of_find_node_with_property() to maintain correct node reference counting.
The of_find_node_with_property() function "consumes" its input by calling
of_node_put() internally, whether or not it finds a match. Currently,
dev->of_node (np) is passed multiple times in sequence without incrementing
its reference count, causing it to be decremented multiple times and
risking early memory release.
Adding of_node_get(np) before each call balances the reference count,
preventing premature node release.
Fixes: c1bac49fe91f ("pmdomains: mtk-pm-domains: Fix spinlock recursion in probe")
Cc: stable@vger.kernel.org
Signed-off-by: Macpaul Lin <macpaul.lin@mediatek.com>
Tested-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Pull SCSI fixes from James Bottomley:
"The only core fix is in doc; all the others are in drivers, with the
biggest impacts in libsas being the rollback on error handling and in
ufs coming from a couple of error handling fixes, one causing a crash
if it's activated before scanning and the other fixing W-LUN
resumption"
* tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
scsi: ufs: qcom: Fix confusing cleanup.h syntax
scsi: libsas: Add rollback handling when an error occurs
scsi: device_handler: Return error pointer in scsi_dh_attached_handler_name()
scsi: ufs: core: Fix a deadlock in the frequency scaling code
scsi: ufs: core: Fix an error handler crash
scsi: Revert "scsi: libsas: Fix exp-attached device scan after probe failure scanned in again after probe failed"
scsi: ufs: core: Fix RPMB link error by reversing Kconfig dependencies
scsi: qla4xxx: Use time conversion macros
scsi: qla2xxx: Enable/disable IRQD_NO_BALANCING during reset
scsi: ipr: Enable/disable IRQD_NO_BALANCING during reset
scsi: imm: Fix use-after-free bug caused by unfinished delayed work
scsi: target: sbp: Remove KMSG_COMPONENT macro
scsi: core: Correct documentation for scsi_device_quiesce()
scsi: mpi3mr: Prevent duplicate SAS/SATA device entries in channel 1
scsi: target: Reset t_task_cdb pointer in error case
scsi: ufs: core: Fix EH failure after W-LUN resume error
Pull crypto library fix from Eric Biggers:
"Fix the kunit_run_irq_test() function (which I recently added for the
CRC and crypto tests) to be less timing-dependent.
This fixes flakiness in the polyval kunit test suite"
* tag 'libcrypto-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux:
kunit: Enforce task execution in {soft,hard}irq contexts