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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Pull scheduler fix from Ingo Molnar:
"Fix a regression in the deferrable dl_server code that can cause the
dl_server to be stuck"
* tag 'sched-urgent-2026-02-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/deadline: Fix 'stuck' dl_server
Pull objtool fixes from Ingo Molnar:
- Fix a build error on ia32-x86_64 cross builds
- Replace locally open coded ALIGN_UP(), ALIGN_UP_POW2()
and MAX(), which, beyond being duplicates, the
ALIGN_UP_POW2() is also buggy
- Fix objtool klp-diff regression caused by a recent
change to the bug table format
- Fix klp-build vs CONFIG_MODULE_SRCVERSION_ALL build
failure
* tag 'objtool-urgent-2026-02-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
livepatch/klp-build: Fix klp-build vs CONFIG_MODULE_SRCVERSION_ALL
objtool/klp: Fix bug table handling for __WARN_printf()
objtool: Replace custom macros in elf.c with shared ones
objtool: Print bfd_vma as unsigned long long on ia32-x86_64 cross build
Andrea reported the dl_server getting stuck for him. He tracked it
down to a state where dl_server_start() saw dl_defer_running==1, but
the dl_server's job is no longer valid at the time of
dl_server_start().
In the state diagram this corresponds to [4] D->A (or dl_server_stop()
due to no more runnable tasks) followed by [1], which in case of a
lapsed deadline must then be A->B.
Now our A has dl_defer_running==1, while B demands
dl_defer_running==0, therefore it must get cleared when the CBS wakeup
rules demand a replenish.
Fixes: a110a81c52a9 ("sched/deadline: Deferrable dl server")
Reported-by: Andrea Righi arighi@nvidia.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Tested-by: Andrea Righi arighi@nvidia.com
Link: https://lkml.kernel.org/r/20260123161645.2181752-1-arighi@nvidia.com
Link: https://patch.msgid.link/20260130124100.GC1079264@noisy.programming.kicks-ass.net
Pull irq fixes from Ingo Molnar:
"Misc irqchip fixes:
- Fix a regression in the ls-extirq irqchip driver
- Fix an irqchip platform enumeration regression
in the simple-pm-bus driver"
* tag 'irq-urgent-2026-02-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
bus: simple-pm-bus: Probe the Layerscape SCFG node
irqchip/ls-extirq: Convert to a platform driver to make it work again
When building a patch to a single-file kernel module with
CONFIG_MODULE_SRCVERSION_ALL enabled, the klp-build module link fails in
modpost:
Diffing objects
drivers/md/raid0.o: changed function: raid0_run
Building patch module: livepatch-0001-patch-raid0_run.ko
drivers/md/raid0.c: No such file or directory
...
The problem here is that klp-build copied drivers/md/.raid0.o.cmd to the
module build directory, but it didn't also copy over the input source
file listed in the .cmd file:
source_drivers/md/raid0.o := drivers/md/raid0.c
So modpost dies due to the missing .c file which is needed for
calculating checksums for CONFIG_MODULE_SRCVERSION_ALL.
Instead of copying the original .cmd file, just create an empty one.
Modpost only requires that it exists. The original object's build
dependencies are irrelevant for the frankenobjects used by klp-build.
Fixes: 24ebfcd65a87 ("livepatch/klp-build: Introduce klp-build script for generating livepatch modules")
Reported-by: Song Liu <song@kernel.org>
Tested-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/c41b6629e02775e4c1015259aa36065b3fe2f0f3.1769471792.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Pull iommu fixes from Joerg Roedel:
- Fix a performance regression cause by the new Generic IO-Page-Table
code detected in Intel VT-d driver
- Command queue flushing fix for NVidia version of the ARM-SMMU-v3
* tag 'iommu-fixes-v6.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/iommu/linux:
iommu/tegra241-cmdqv: Reset VCMDQ in tegra241_vcmdq_hw_init_user()
iommupt: Only cache flush memory changed by unmap
Make the simple-pm-bus driver probe the Layerscape SCFG dt nodes and
populate platform_device structures from its child dt nodes.
This is now needed because its child interrupt-controller - ls-extirq -
is being handled as a platform_device instead of being initialized
through the IRQCHIP_DECLARE infrastructure which impeded its parent IRQ
retrieval through the blamed commit.
Note that this does not set ONLY_BUS because that enables the
of_platform_populate() call. The extra power management operations which
are enabled by that are not required but harmless.
Fixes: 1b1f04d8271e ("of/irq: Ignore interrupt parent for nodes without interrupts")
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20260122134034.3274053-3-ioana.ciornei@nxp.com
Running objtool klp-diff on a changed function which uses WARN() can
fail with:
vmlinux.o: error: objtool: md_run+0x866: failed to convert reloc sym '__bug_table' to its proper format
The problem is that since commit 5b472b6e5bd9 ("x86_64/bug: Implement
__WARN_printf()"), each __WARN_printf() call site now directly
references its bug table entry. klp-diff errors out when it can't
convert such section-based references to object symbols (because bug
table entries don't have symbols).
Luckily, klp-diff already has code to create symbols for bug table
entries. Move that code earlier, before function diffing.
Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Fixes: 5b472b6e5bd9 ("x86_64/bug: Implement __WARN_printf()")
Reported-by: Song Liu <song@kernel.org>
Tested-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/a8e0a714b9da962858842b9aecd63b4900927c88.1769406850.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Pull SCSI fixes from James Bottomley:
"Only one core change, the rest are drivers.
The core change reorders some state operations in the error handler to
try to prevent missed wake ups of the error handler (which can halt
error processing and effectively freeze the entire system)"
* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
scsi: qla2xxx: Sanitize payload size to prevent member overflow
scsi: target: iscsi: Fix use-after-free in iscsit_dec_session_usage_count()
scsi: target: iscsi: Fix use-after-free in iscsit_dec_conn_usage_count()
scsi: core: Wake up the error handler when final completions race against each other
scsi: storvsc: Process unsupported MODE_SENSE_10
scsi: xen: scsiback: Fix potential memory leak in scsiback_remove()
Pull EFI fix from Ard Biesheuvel:
- Fix regression in efivarfs error propagation
* tag 'efi-fixes-for-v6.19-3' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi:
efivarfs: fix error propagation in efivar_entry_get()
The Enable bits in CMDQV/VINTF/VCMDQ_CONFIG registers do not actually reset
the HW registers. So, the driver explicitly clears all the registers when a
VINTF or VCMDQ is being initialized calling its hw_deinit() function.
However, a userspace VCMDQ is not properly reset, unlike an in-kernel VCMDQ
getting reset in tegra241_vcmdq_hw_init().
Meanwhile, tegra241_vintf_hw_init() calling tegra241_vintf_hw_deinit() will
not deinit any VCMDQ, since there is no userspace VCMDQ mapped to the VINTF
at that stage.
Then, this may result in dirty VCMDQ registers, which can fail the VM.
Like tegra241_vcmdq_hw_init(), reset a VCMDQ in tegra241_vcmdq_hw_init() to
fix this bug. This is required by a host kernel.
Fixes: 6717f26ab1e7 ("iommu/tegra241-cmdqv: Add user-space use support")
Cc: stable@vger.kernel.org
Reported-by: Bao Nguyen <ncqb@google.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Starting with the blamed commit, the ls-extirq driver stopped working. This
is because ls-extirq, being one of the interrupt-map property abusers, does
not pass the DT checks added by the referenced commit, making it unable to
determine its interrupt parent:
irq-ls-extirq: Cannot find parent domain
OF: of_irq_init: Failed to init /soc/syscon@1f70000/interrupt-controller@14
((____ptrval____)), parent 0000000000000000
Instead of reverting the referenced commit, convert the ls-extirq to a
platform driver to avoid the irqchip_init() -> of_irq_init() code path
completely.
As part of the conversion, use the managed resources APIs and
dev_err_probe() so that there is no need for a .remove() callback or for
complicated error handling.
Fixes: 1b1f04d8271e ("of/irq: Ignore interrupt parent for nodes without interrupts")
Co-developed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260122134034.3274053-2-ioana.ciornei@nxp.com
The source file tools/objtool/elf.c defines the macros ALIGN_UP(),
ALIGN_UP_POW2() and MAX(). These macros unnecessarily duplicate
functionality already available under tools/include/, specifically ALIGN(),
roundup_pow_of_two() and max().
More importantly, the definition of ALIGN_UP_POW2() is incorrect when the
input is 1, as it results in a call to __builtin_clz(0), which produces an
undefined result. This issue impacts the function elf_alloc_reloc(). When
adding the first relocation to a section, the function allocates an
undefined number of relocations.
Replace the custom macros with the shared functionality to resolve these
issues.
Fixes: 2c05ca026218 ("objtool: Add elf_create_reloc() and elf_init_reloc()")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Link: https://patch.msgid.link/20260126151356.3924887-1-petr.pavlu@suse.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Pull keys fix from Jarkko Sakkinen.
* tag 'keys-trusted-next-6.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd:
keys/trusted_keys: fix handle passed to tpm_buf_append_name during unseal
In qla27xx_copy_fpin_pkt() and qla27xx_copy_multiple_pkt(), the frame_size
reported by firmware is used to calculate the copy length into
item->iocb. However, the iocb member is defined as a fixed-size 64-byte
array within struct purex_item.
If the reported frame_size exceeds 64 bytes, subsequent memcpy calls will
overflow the iocb member boundary. While extra memory might be allocated,
this cross-member write is unsafe and triggers warnings under
CONFIG_FORTIFY_SOURCE.
Fix this by capping total_bytes to the size of the iocb member (64 bytes)
before allocation and copying. This ensures all copies remain within the
bounds of the destination structure member.
Fixes: 875386b98857 ("scsi: qla2xxx: Add Unsolicited LS Request and Response Support for NVMe")
Signed-off-by: Jiasheng Jiang <jiashengjiangcool@gmail.com>
Reviewed-by: Himanshu Madhani <hmadhani2024@gmail.com>
Link: https://patch.msgid.link/20260106205344.18031-1-jiashengjiangcool@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>