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 runtime verifier fix from Steven Rostedt:
- Fix multiple definition of __pcpu_unique_da_mon_this
After refactoring monitors, we used static per-cpu variables with the
same names across different per-cpu monitors. This is explicitly
disallowed for modules on some architectures (alpha) or if
CONFIG_DEBUG_FORCE_WEAK_PER_CPU is enabled (e.g. Fedora's debug
kernel). Make sure all those variables have different names to avoid
compilation issues.
* tag 'trace-rv-7.0-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
rv: Fix multiple definition of __pcpu_unique_da_mon_this
Conversion performed via this Coccinelle script:
// SPDX-License-Identifier: GPL-2.0-only
// Options: --include-headers-for-types --all-includes --include-headers --keep-comments
virtual patch
@gfp depends on patch && !(file in "tools") && !(file in "samples")@
identifier ALLOC = {kmalloc_obj,kmalloc_objs,kmalloc_flex,
kzalloc_obj,kzalloc_objs,kzalloc_flex,
kvmalloc_obj,kvmalloc_objs,kvmalloc_flex,
kvzalloc_obj,kvzalloc_objs,kvzalloc_flex};
@@
ALLOC(...
- , GFP_KERNEL
)
$ make coccicheck MODE=patch COCCI=gfp.cocci
Build and boot tested x86_64 with Fedora 42's GCC and Clang:
Linux version 6.19.0+ (user@host) (gcc (GCC) 15.2.1 20260123 (Red Hat 15.2.1-7), GNU ld version 2.44-12.fc42) #1 SMP PREEMPT_DYNAMIC 1970-01-01
Linux version 6.19.0+ (user@host) (clang version 20.1.8 (Fedora 20.1.8-4.fc42), LLD 20.1.8) #1 SMP PREEMPT_DYNAMIC 1970-01-01
Signed-off-by: Kees Cook <kees@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The refactoring in commit 30984ccf31b7 ("rv: Refactor da_monitor to
minimise macros") replaced per-monitor unique variable names
(da_mon_##name) with a fixed name (da_mon_this).
While this works for 'static' variables (each translation unit gets its
own copy), DEFINE_PER_CPU internally generates a non-static dummy
variable __pcpu_unique_<n> for each per-cpu definition. The requirement
for this variable to be unique although static exists for modules on
specific architectures (alpha) and if the kernel is built with
CONFIG_DEBUG_FORCE_WEAK_PER_CPU (e.g. Fedora's debug kernel).
When multiple per-cpu monitors (e.g. sco and sts) are built-in
simultaneously, they all produce the same __pcpu_unique_da_mon_this
symbol, causing a link error:
ld: kernel/trace/rv/monitors/sts/sts.o: multiple definition of
`__pcpu_unique_da_mon_this';
kernel/trace/rv/monitors/sco/sco.o: first defined here
Fix this by introducing a DA_MON_NAME macro that expands to a
per-monitor unique name (da_mon_<MONITOR_NAME>) via the existing
CONCATENATE helper. This restores the uniqueness that was present
before the refactoring.
Fixes: 30984ccf31b7 ("rv: Refactor da_monitor to minimise macros")
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Link: https://lore.kernel.org/r/20260216172707.1441516-1-mikhail.v.gavrilov@gmail.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
This converts some of the visually simpler cases that have been split
over multiple lines. I only did the ones that are easy to verify the
resulting diff by having just that final GFP_KERNEL argument on the next
line.
Somebody should probably do a proper coccinelle script for this, but for
me the trivial script actually resulted in an assertion failure in the
middle of the script. I probably had made it a bit _too_ trivial.
So after fighting that far a while I decided to just do some of the
syntactically simpler cases with variations of the previous 'sed'
scripts.
The more syntactically complex multi-line cases would mostly really want
whitespace cleanup anyway.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Update documentation reference to reflect the file rename.
Monitor synthesis documentation was renamed in commit f40a7c060207
("Documentation/rv: Prepare monitor synthesis document for LTL inclusion")
from da_monitor_synthesis.rst to monitor_synthesis.rst.
Signed-off-by: Shubham Sharma <slopixelz@gmail.com>
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Link: https://lore.kernel.org/r/20251230075337.11993-1-slopixelz@gmail.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
This is the exact same thing as the 'alloc_obj()' version, only much
smaller because there are a lot fewer users of the *alloc_flex()
interface.
As with alloc_obj() version, this was done entirely with mindless brute
force, using the same script, except using 'flex' in the pattern rather
than 'objs*'.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The monitor container source files contained a declaration and a
definition for the rv_monitor variable. The former is superfluous and
can be removed.
Remove the variable declaration from the template as well as the
existing monitor containers.
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20251126104241.291258-9-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
This was done entirely with mindless brute force, using
git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'
to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.
Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.
For the same reason the 'flex' versions will be done as a separate
conversion.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The header files generated by dot2c currently create enums for states
and events assigning the first element to 0. This is superfluous as it
happens automatically if no value is specified.
Also it doesn't add a comma to the last enum elements, which slightly
complicates the diff if states or events are added.
Remove the assignment to 0 and add a comma to last elements, this
simplifies the logic for the code generator.
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20251126104241.291258-8-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Most simple allocations use GFP_KERNEL, and with the new allocation
helpers being introduced, let's just take advantage of that to simplify
that default case.
It's a numbers game:
git grep 'alloc_obj(' |
sed 's/.*\(GFP_[_A-Z]*\).*/\1/' |
sort | uniq -c | sort -n | tail
shows that about 90% of all those new allocator instances just use that
standard GFP_KERNEL.
Those helpers are already macros, and we can easily just make it be the
default case when the gfp argument is missing.
And yes, we could do that for all the legacy interfaces too, but let's
keep it to just the new ones at least for now, since those all got
converted recently anyway, so this is not any "extra" noise outside of
that limited conversion.
And, in fact, I want to do this before doing the -rc1 release, exactly
so that we don't get extra merge conflicts.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
str.join() can do what __buff_to_string() does. Therefore replace
__buff_to_string() to make the scripts more pythonic.
Also clean and remove some intermediate functions.
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20251126104241.291258-7-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Commit 69050f8d6d07 ("treewide: Replace kmalloc with kmalloc_obj for
non-scalar types") started using the new allocation helpers, and in the
process showed that they were completely non-working.
The overflow logic in overflows_flex_counter_type() is completely the
wrong way around, and that broke __alloc_flex() completely. By chance,
the resulting code was then such a mess that clang generated
sufficiently garbage code that objtool warned about it all. Which made
it somewhat quicker to narrow things down.
While fixing overflows_flex_counter_type() would presumably fix this
all, I'm excising the whole broken overflow logic from __alloc_flex(),
because we don't want that kind of code in basic allocation functions
anyway.
That (no longer) broken overflows_flex_counter_type() thing needs to be
inserted into the actual __set_flex_counter() logic in the unlikely case
that we ever want this at all. And made conditional.
Fixes: 81cee9166a90 ("compiler_types: Introduce __flex_counter() and family")
Fixes: 69050f8d6d07 ("treewide: Replace kmalloc with kmalloc_obj for non-scalar types")
Cc: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/all/CAHk-=whEd020BYzGTzYrENjD9Z5_82xx6h8HsQvH5xDSnv0=Hw@mail.gmail.com/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Functions in automata.py, dot2c.py and dot2k.py don't have type
annotations and it can get complicated to remember how to use them.
Add minimal type annotations.
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20251126104241.291258-6-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Pull kmalloc_obj conversion from Kees Cook:
"This does the tree-wide conversion to kmalloc_obj() and friends using
coccinelle, with a subsequent small manual cleanup of whitespace
alignment that coccinelle does not handle.
This uncovered a clang bug in __builtin_counted_by_ref(), so the
conversion is preceded by disabling that for current versions of
clang. The imminent clang 22.1 release has the fix.
I've done allmodconfig build tests for x86_64, arm64, i386, and arm. I
did defconfig builds for alpha, m68k, mips, parisc, powerpc, riscv,
s390, sparc, sh, arc, csky, xtensa, hexagon, and openrisc"
* tag 'kmalloc_obj-treewide-v7.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
kmalloc_obj: Clean up after treewide replacements
treewide: Replace kmalloc with kmalloc_obj for non-scalar types
compiler_types: Disable __builtin_counted_by_ref for Clang
Previous changes refactored the da_monitor header file to avoid using
macros. This implies a few changes in how to import and use da_monitor
helpers:
DECLARE_DA_MON_<TYPE>(name, type) is substituted by
#define RV_MON_TYPE RV_MON_<TYPE>
Update the rvgen templates to reflect the changes.
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20251126104241.291258-5-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Pull perf tools updates from Arnaldo Carvalho de Melo:
- Introduce 'perf sched stats' tool with record/report/diff workflows
using schedstat counters
- Add a faster libdw based addr2line implementation and allow selecting
it or its alternatives via 'perf config addr2line.style='
- Data-type profiling fixes and improvements including the ability to
select fields using 'perf report''s -F/-fields, e.g.:
'perf report --fields overhead,type'
- Add 'perf test' regression tests for Data-type profiling with C and
Rust workloads
- Fix srcline printing with inlines in callchains, make sure this has
coverage in 'perf test'
- Fix printing of leaf IP in LBR callchains
- Fix display of metrics without sufficient permission in 'perf stat'
- Print all machines in 'perf kvm report -vvv', not just the host
- Switch from SHA-1 to BLAKE2s for build ID generation, remove SHA-1
code
- Fix 'perf report's histogram entry collapsing with '-F' option
- Use system's cacheline size instead of a hardcoded value in 'perf
report'
- Allow filtering conversion by time range in 'perf data'
- Cover conversion to CTF using 'perf data' in 'perf test'
- Address newer glibc const-correctness (-Werror=discarded-qualifiers)
issues
- Fixes and improvements for ARM's CoreSight support, simplify ARM SPE
event config in 'perf mem', update docs for 'perf c2c' including the
ARM events it can be used with
- Build support for generating metrics from arch specific python
script, add extra AMD, Intel, ARM64 metrics using it
- Add AMD Zen 6 events and metrics
- Add JSON file with OpenHW Risc-V CVA6 hardware counters
- Add 'perf kvm' stats live testing
- Add more 'perf stat' tests to 'perf test'
- Fix segfault in `perf lock contention -b/--use-bpf`
- Fix various 'perf test' cases for s390
- Build system cleanups, bump minimum shellcheck version to 0.7.2
- Support building the capstone based annotation routines as a plugin
- Allow passing extra Clang flags via EXTRA_BPF_FLAGS
* tag 'perf-tools-for-v7.0-1-2026-02-21' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools: (255 commits)
perf test script: Add python script testing support
perf test script: Add perl script testing support
perf script: Allow the generated script to be a path
perf test: perf data --to-ctf testing
perf test: Test pipe mode with data conversion --to-json
perf json: Pipe mode --to-ctf support
perf json: Pipe mode --to-json support
perf check: Add libbabeltrace to the listed features
perf build: Allow passing extra Clang flags via EXTRA_BPF_FLAGS
perf test data_type_profiling.sh: Skip just the Rust tests if code_with_type workload is missing
tools build: Fix feature test for rust compiler
perf libunwind: Fix calls to thread__e_machine()
perf stat: Add no-affinity flag
perf evlist: Reduce affinity use and move into iterator, fix no affinity
perf evlist: Missing TPEBS close in evlist__close()
perf evlist: Special map propagation for tool events that read on 1 CPU
perf stat-shadow: In prepare_metric fix guard on reading NULL perf_stat_evsel
Revert "perf tool_pmu: More accurately set the cpus for tool events"
tools build: Emit dependencies file for test-rust.bin
tools build: Make test-rust.bin be removed by the 'clean' target
...
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