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
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1444589
3
929
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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
...
Pull coccinelle updates from Julia Lawall:
"This simplifies and clarifies the handling of output generated by
Coccinelle that is sent to standard error.
By default, this goes to /dev/null. Remind the user of that and
encourage them to provide another file name (Benjamin Philip)"
* tag 'cocci-7.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlawall/linux:
Documentation: Coccinelle: document debug log handling
scripts: coccicheck: warn on unset debug file
scripts: coccicheck: simplify debug file handling
Basic coverage of python script support from `perf script`.
Committer testing:
$ perf test 'perf script python'
107: perf script python tests : Ok
$ perf test -vv 'perf script python'
107: perf script python tests:
--- start ---
test child forked, pid 595537
Testing event: sched:sched_switch
perf script python test [Skipped: failed to record sched:sched_switch]
Testing event: task-clock
Generating python script...
generated Python script: /tmp/__perf_test_script.J4rWj.py
Executing python script...
perf script python test [Success: task-clock triggered param_dict]
---- end(0) ----
107: perf script python tests : Ok
$
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Yujie Liu <yujie.liu@intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Pull NTB (PCIe non-transparent bridge) updates from Jon Mason:
"NTB updates include debugfs improvements, correctness fixes, cleanups,
and new hardware support:
ntb_transport QP stats are converted to seq_file, a tx_memcpy_offload
module parameter is introduced with associated ordering fixes, and a
debugfs queue name truncation bug is corrected.
Additional fixes address format specifier mismatches in ntb_tool and
boundary conditions in the Switchtec driver, while unused MSI helpers
are removed and the codebase migrates to dma_map_phys().
Intel Gen6 (Diamond Rapids) NTB support is also added"
* tag 'ntb-7.0' of https://github.com/jonmason/ntb:
NTB: ntb_transport: Use seq_file for QP stats debugfs
NTB: ntb_transport: Fix too small buffer for debugfs_name
ntb/ntb_tool: correct sscanf format for u64 and size_t in tool_peer_mw_trans_write
ntb: intel: Add Intel Gen6 NTB support for DiamondRapids
NTB/msi: Remove unused functions
ntb: ntb_hw_switchtec: Increase MAX_MWS limit to 256
ntb: ntb_hw_switchtec: Fix array-index-out-of-bounds access
ntb: ntb_hw_switchtec: Fix shift-out-of-bounds for 0 mw lut
NTB: epf: allow built-in build
ntb: migrate to dma_map_phys instead of map_page
NTB: ntb_transport: Add 'tx_memcpy_offload' module option
NTB: ntb_transport: Remove unused 'retries' field from ntb_queue_entry
The current debug documentation does not mention that logs are printed
to stdout unless DEBUG_FILE is set. It also doesn't mention that
Coccinelle cannot overwrite debug files.
Document this behaviour in the examples and reference it in the
debugging section.
Signed-off-by: Benjamin Philip <benjamin.philip495@gmail.com>
Signed-off-by: Julia Lawall <julia.lawall@inria.fr>
Basic coverage of perl script support from `perf script`. This is
disabled by default and so the test will most normally skip.
Committer testing:
$ perf test 'perf script perl'
106: perf script perl tests : Skip
$ perf test -vv 'perf script perl'
106: perf script perl tests:
--- start ---
test child forked, pid 578323
perf script perl test [Skipped: no libperl support]
---- end(-2) ----
106: perf script perl tests : Skip
$ perf check feature libperl
libperl: [ OFF ] # HAVE_LIBPERL_SUPPORT ( tip: Deprecated, use LIBPERL=1 and install perl-ExtUtils-Embed/libperl-dev to build with it )
$
Install perl-ExtUtils-Embed, build with LIBPERL=1, rebuild:
$ perf check feature libperl
libperl: [ on ] # HAVE_LIBPERL_SUPPORT
$ perf test 'perf script perl'
106: perf script perl tests : Ok
$ perf test -vv 'perf script perl'
106: perf script perl tests:
--- start ---
test child forked, pid 588206
Testing event: sched:sched_switch
perf script perl test [Skipped: failed to record sched:sched_switch]
Testing event: task-clock
Generating perl script...
generated Perl script: /tmp/__perf_test_script.RpMn5.pl
Executing perl script...
perf script perl test [Success: task-clock triggered $VAR1]
---- end(0) ----
106: perf script perl tests : Ok
$
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Yujie Liu <yujie.liu@intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Pull io_uring fixes from Jens Axboe:
- A fix for a missing URING_CMD128 opcode check, fixing an issue with
the SQE mixed mode support introduced in 6.19. Merged late due to
having multiple dependencies
- Add sqe->cmd size checking for big SQEs, similar to what we have for
normal sized SQEs
- Fix a race condition in zcrx, that leads to a double free
* tag 'io_uring-20260221' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux:
io_uring: Add size check for sqe->cmd
io_uring: add IORING_OP_URING_CMD128 to opcode checks
io_uring/zcrx: fix user_ref race between scrub and refill paths
The ./qp*/stats debugfs file for each NTB transport QP is currently
implemented with a hand-crafted kmalloc() buffer and a series of
scnprintf() calls. This is a pre-seq_file style pattern and makes future
extensions easy to truncate.
Convert the stats file to use the seq_file helpers via
DEFINE_SHOW_ATTRIBUTE(), which simplifies the code and lets the seq_file
core handle buffering and partial reads.
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
coccicheck prints debug logs to stdout unless a debug file has been set.
This makes it hard to read coccinelle's suggested changes, especially
for someone new to coccicheck.
From this commit, we warn about this behaviour from within the script on
an unset debug file. Explicitly setting the debug file to /dev/null
suppresses the warning while keeping the default.
Signed-off-by: Benjamin Philip <benjamin.philip495@gmail.com>
Signed-off-by: Julia Lawall <julia.lawall@inria.fr>
Allow the script generated by "perf script -g <language>" to be a file
path and the language determined by the file extension.
This is useful in testing so that the generated script file can be
written to a test directory.
Committer testing:
$ perf record ls a.a
ls: cannot access 'a.a': No such file or directory
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.003 MB perf.data (7 samples) ]
$ perf script -g python
generated Python script: perf-script.py
$ perf script -g myscript.py
generated Python script: myscript.py
$ diff -u perf-script.py myscript.py
$ tail myscript.py
def trace_unhandled(event_name, context, event_fields_dict, perf_sample_dict):
print(get_dict_as_string(event_fields_dict))
print('Sample: {'+get_dict_as_string(perf_sample_dict['sample'], ', ')+'}')
def print_header(event_name, cpu, secs, nsecs, pid, comm):
print("%-20s %5u %05u.%09u %8u %-20s " % \
(event_name, cpu, secs, nsecs, pid, comm), end="")
def get_dict_as_string(a_dict, delimiter=' '):
return delimiter.join(['%s=%s'%(k,str(v))for k,v in sorted(a_dict.items())])
$
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Yujie Liu <yujie.liu@intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Pull memblock fix from Mike Rapoport:
"Fix detection of NUMA node for CXL windows
phys_to_target_node() may assign a CXL Fixed Memory Window to the
wrong NUMA node when a CXL node resides in the gap of discontinuous
System RAM node.
Fix this by checking both numa_meminfo and numa_reserved_meminfo,
preferring the reserved NID when the address appears in both"
* tag 'fixes-2026-02-21' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock:
mm: numa_memblks: Identify the accurate NUMA ID of CFMW
For SQE128, sqe->cmd provides 80 bytes for uring_cmd. Add macro to
check if size of user struct does not exceed 80 bytes at compile time.
User doesn't have to track this manually during development.
Replace io_uring_sqe_cmd() inline func with macro and add
io_uring_sqe128_cmd() which checks struct
size for 16 bytes cmd and 80 bytes cmd respectively.
Signed-off-by: Govindarajulu Varadarajan <govind.varadar@gmail.com>
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The buffer used for "qp%d" was only 4 bytes, which truncates names like
"qp10" to "qp1" and causes multiple queues to share the same directory.
Enlarge the buffer and use sizeof() to avoid truncation.
Fixes: fce8a7bb5b4b ("PCI-Express Non-Transparent Bridge Support")
Cc: <stable@vger.kernel.org> # v3.9+
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
This commit separates handling unset files and pre-existing files. It
also eliminates a duplicated check for unset files in run_cmd_parmap().
Signed-off-by: Benjamin Philip <benjamin.philip495@gmail.com>
Signed-off-by: Julia Lawall <julia.lawall@inria.fr>
If babeltrace is detected check that --to-ctf functions with a data
file and in pipe mode.
Committer testing:
$ perf test 'perf data convert --to-ctf'
124: 'perf data convert --to-ctf' command test : Ok
$ perf test -vv 'perf data convert --to-ctf'
124: 'perf data convert --to-ctf' command test:
--- start ---
test child forked, pid 556008
libbabeltrace: [ on ] # HAVE_LIBBABELTRACE_SUPPORT
Testing Perf Data Conversion Command to CTF (File input)
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.021 MB /tmp/__perf_test.perf.data.9TxzZ (115 samples) ]
[ perf data convert: Converted '/tmp/__perf_test.perf.data.9TxzZ' into CTF data '/tmp/__perf_test.ctf.f5EkS' ]
[ perf data convert: Converted and wrote 0.012 MB (115 samples) ]
Perf Data Converter Command to CTF (File input) [SUCCESS]
Testing Perf Data Conversion Command to CTF (Pipe mode)
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.047 MB - ]
Failed to setup all events.
[ perf data convert: Converted '/tmp/__perf_test.perf.data.9TxzZ' into CTF data '/tmp/__perf_test.ctf.f5EkS' ]
[ perf data convert: Converted and wrote 0.000 MB (0 samples) ]
Perf Data Converter Command to CTF (Pipe mode) [SUCCESS]
Unexpected signal in main
---- end(0) ----
124: 'perf data convert --to-ctf' command test : Ok
$
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Derek Foreman <derek.foreman@collabora.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Pull sched_ext fixes from Tejun Heo:
- Various bug fixes for the example schedulers and selftests
* tag 'sched_ext-for-7.0-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
tools/sched_ext: fix getopt not re-parsed on restart
tools/sched_ext: scx_userland: fix data races on shared counters
tools/sched_ext: scx_pair: fix stride == 0 crash on single-CPU systems
tools/sched_ext: scx_central: fix CPU_SET and skeleton leak on early exit
tools/sched_ext: scx_userland: fix stale data on restart
tools/sched_ext: scx_flatcg: fix potential stack overflow from VLA in fcg_read_stats
selftests/sched_ext: Fix rt_stall flaky failure
tools/sched_ext: scx_userland: fix restart and stats thread lifecycle bugs
tools/sched_ext: scx_central: fix sched_setaffinity() call with the set size
tools/sched_ext: scx_flatcg: zero-initialize stats counter array
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