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
Clone this repository
For self-hosted knots, clone URLs may differ based on your setup.
Download tar.gz
Since the cpu_buffer->reader_page is updated if there are unwound
pages. After that update, we should skip the page if it is the
original reader_page, because the original reader_page is already
checked.
Cc: stable@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Ian Rogers <irogers@google.com>
Link: https://patch.msgid.link/177701353063.2223789.1471163147644103306.stgit@mhiramat.tok.corp.google.com
Fixes: ca296d32ece3 ("tracing: ring_buffer: Rewind persistent ring buffer on reboot")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Linus points out that dumping undefsyms_base.c form the Makefile
is rather ugly, and that a much better course of action would be
to have this file as a first-class citizen in the git tree.
This allows some extra cleanup in the Makefile, and the removal of
the .gitignore file in kernel/trace.
Cc: Marc Zyngier <maz@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/CAHk-=wieqGd_XKpu8UxDoyADZx8TDe8CF3RmkUXt5N_9t5Pf_w@mail.gmail.com
Link: https://lore.kernel.org/all/20260421095446.2951646-1-maz@kernel.org/
Link: https://patch.msgid.link/20260421100455.324333-1-pbonzini@redhat.com
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This odd file was added to automatically figure out tool-generated
symbols.
Honestly, it *should* have been just a real honest-to-goodness regular
file in git, instead of having strange code to generate it in the
Makefile, but that is not how that silly thing works. So now we need to
ignore it explicitly.
Fixes: 1211907ac0b5 ("tracing: Generate undef symbols allowlist for simple_ring_buffer")
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull kselftest fixes from Shuah Khan:
"Fix regressions in non-bash shells and busybox support, and revert a
commit that regressed in build and installation when one or more tests
fail to build.
Fix duplicated test number reporting introduced in ktap support patch"
* tag 'linux_kselftest-next-7.1-next-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
selftests: Fix duplicated test number reporting
selftests: Fix runner.sh for non-bash shells
selftests: Fix runner.sh busybox support
selftests: Deescalate error reporting
Pull more arm64 updates from Catalin Marinas:
"The main 'feature' is a workaround for C1-Pro erratum 4193714
requiring IPIs during TLB maintenance if a process is running in user
space with SME enabled.
The hardware acknowledges the DVMSync messages before completing
in-flight SME accesses, with security implications. The workaround
makes use of the mm_cpumask() to track the cores that need
interrupting (arm64 hasn't used this mask before).
The rest are fixes for MPAM, CCA and generated header that turned up
during the merging window or shortly before.
Summary:
Core features:
- Add workaround for C1-Pro erratum 4193714 - early CME (SME unit)
DVMSync acknowledgement. The fix consists of sending IPIs on TLB
maintenance to those CPUs running in user space with SME enabled
- Include kernel-hwcap.h in list of generated files (missed in a
recent commit generating the KERNEL_HWCAP_* macros)
CCA:
- Fix RSI_INCOMPLETE error check in arm-cca-guest
MPAM:
- Fix an unmount->remount problem with the CDP emulation,
uninitialised variable and checker warnings"
* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
arm_mpam: resctrl: Make resctrl_mon_ctx_waiters static
arm_mpam: resctrl: Fix the check for no monitor components found
arm_mpam: resctrl: Fix MBA CDP alloc_capable handling on unmount
virt: arm-cca-guest: fix error check for RSI_INCOMPLETE
arm64/hwcap: Include kernel-hwcap.h in list of generated files
arm64: errata: Work around early CME DVMSync acknowledgement
arm64: cputype: Add C1-Pro definitions
arm64: tlb: Pass the corresponding mm to __tlbi_sync_s1ish()
arm64: tlb: Introduce __tlbi_sync_s1ish_{kernel,batch}() for TLB maintenance
Commit 2964f6b816c2 ("selftests: Use ktap helpers for runner.sh") converted
the prints in runner.sh to use the relevant helpers from ktap_helpers.sh,
not modifying any of the strings printed in the process. This included
converting all the result reports to use the relevant ktap_test_ function.
Since the output was originally KTAP compliant the strings reported for
test names now include test numbers:
ok 59 59 selftests: arm64: syscall-abi
instead of the expected format:
ok 59 selftests: arm64: syscall-abi
which causes result parsers to interpret the second number as part of the
test name.
Given the use of the helpers the tracking of test numbers by runner.sh is
now redundant, remove it entirely to restore the expected output format.
Link: https://lore.kernel.org/r/20260417-selftests-fix-double-number-v1-1-1be5d7c36b94@kernel.org
Fixes: 2964f6b816c2 ("selftests: Use ktap helpers for runner.sh")
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Pull sh updates from John Paul Adrian Glaubitz:
"Two patches from Thomas Zimmermann, one by Tim Bird and one by Thomas
Weißschuh.
The first patch by Thomas Zimmermann adds a missing include in dac.h
for SH-3 which became necessary after 243ce64b2b37 ("backlight: Do not
include <linux/fb.h> in header file") which made __raw_readb() and
__raw_writeb() inaccessible in dac.h.
Thomas' second patch drops CONFIG_FIRMWARE_EDID for SH as it depends
on X86 or EFI_GENERIC_STUB which are not defined on SH for obvious
reasons.
The patch by Tim Bird fixes just a small typo in two SPDX ID lines
which he stumbled over by accident.
And, least but not last, the patch by Thomas Weißschuh removes the
CONFIG_VSYSCALL reference from UAPI. This was necessary as the
definition of AT_SYSINFO_EHDR was gated between CONFIG_VSYSCALL to
avoid a default gate VMA to be created. However that default gate VMA
was removed entirely in commit a6c19dfe3994 (arm64,ia64,ppc,s390,
sh,tile,um,x86,mm: remove default gate area)"
* tag 'sh-for-v7.1-tag1' of git://git.kernel.org/pub/scm/linux/kernel/git/glaubitz/sh-linux:
sh: Drop CONFIG_FIRMWARE_EDID from defconfig files
sh: Remove CONFIG_VSYSCALL reference from UAPI
sh: Fix typo in SPDX license ID lines
sh: Include <linux/io.h> in dac.h
* for-next/c1-pro-erratum-4193714:
: Work around C1-Pro erratum 4193714 (CVE-2026-0995)
arm64: errata: Work around early CME DVMSync acknowledgement
arm64: cputype: Add C1-Pro definitions
arm64: tlb: Pass the corresponding mm to __tlbi_sync_s1ish()
arm64: tlb: Introduce __tlbi_sync_s1ish_{kernel,batch}() for TLB maintenance
Commit 2964f6b816c2 ("selftests: Use ktap helpers for runner.sh") added a
number of bashisms and updated the interpreter specified for the script to
be /bin/bash to reflect this. Unfortunately this does not actually achieve
anything in production since the main way runner.sh is invoked is from the
top level run_kselftest.sh which sources it rather than running it as a
separate script and specifies the shell as /bin/sh. This means that on
systems where /bin/sh is not bash (such as Debian where /bin/sh defaults to
being dash) we see failures:
./run_kselftest.sh: 195: ./kselftest/runner.sh: Syntax error: "(" unexpected (expecting "}")
These bashisms come from this part of the change:
4. In runner.sh run_one(), get the return value and use ktap helpers for
all pass/fail reporting. This allows counting pass/fail numbers in the
main process.
which uses a bash array to track all the subtests being run. Convert this
to use a simple flat variable instead.
Link: https://lore.kernel.org/r/20260416-selftest-fix-readlink-e-v1-2-94e4cabbdec4@kernel.org
Fixes: 2964f6b816c2 ("selftests: Use ktap helpers for runner.sh")
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Pull uml updates from Johannes Berg:
"Mostly cleanups and small things, notably:
- musl libc compatibility
- vDSO installation fix
- TLB sync race fix for recent SMP support
- build fix for 32-bit with Clang 20/21"
* tag 'uml-for-7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux:
um: Disable GCOV_PROFILE_ALL on 32-bit UML with Clang 20/21
um: drivers: call kernel_strrchr() explicitly in cow_user.c
um: Replace strncpy() with strnlen()+memcpy_and_pad() in strncpy_chunk_from_user()
x86/um: fix vDSO installation
um: Remove CONFIG_FRAME_WARN from x86_64_defconfig
um: Fix pte_read() and pte_exec() for kernel mappings
um: Fix potential race condition in TLB sync
um: time-travel: clean up kernel-doc warnings
um: avoid struct sigcontext redefinition with musl
um: fix address-of CMSG_DATA() rvalue in stub
CONFIG_FIRMWARE_EDID=y depends on X86 or EFI_GENERIC_STUB. Neither
is true here, so drop the lines from the defconfig files.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
* for-next/misc:
: Miscellaneous cleanups/fixes
virt: arm-cca-guest: fix error check for RSI_INCOMPLETE
arm64/hwcap: Include kernel-hwcap.h in list of generated files
* for-next/mpam:
: Fix an unmount->remount problem with the CDP emulation, uninitialised
: variable and checker warnings
arm_mpam: resctrl: Make resctrl_mon_ctx_waiters static
arm_mpam: resctrl: Fix the check for no monitor components found
arm_mpam: resctrl: Fix MBA CDP alloc_capable handling on unmount
C1-Pro acknowledges DVMSync messages before completing the SME/CME
memory accesses. Work around this by issuing an IPI to the affected CPUs
if they are running in EL0 with SME enabled.
Note that we avoid the local DSB in the IPI handler as the kernel runs
with SCTLR_EL1.IESB=1. This is sufficient to complete SME memory
accesses at EL0 on taking an exception to EL1. On the return to user
path, no barrier is necessary either. See the comment in
sme_set_active() and the more detailed explanation in the link below.
To avoid a potential IPI flood from malicious applications (e.g.
madvise(MADV_PAGEOUT) in a tight loop), track where a process is active
via mm_cpumask() and only interrupt those CPUs.
Link: https://lore.kernel.org/r/ablEXwhfKyJW1i7l@J2N7QTR9R3
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Reviewed-by: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Commit 2964f6b816c2 ("selftests: Use ktap helpers for runner.sh") added an
import of ktap_helper.sh to runner.sh in order to standardise on these for
output formatting. Rather than build on the existing requirement for the
user to supply BASE_DIR to find the helpers it uses some magic which
features a use of "readlink -e". Unfortunately the -e option is a GNU
extension and is not available in at least busybox, meaning that runner.sh
starts failing:
./run_kselftest.sh: 5: ./kselftest/runner.sh: Bad substitution
./run_kselftest.sh: 5: .: cannot open ./ktap_helpers.sh: No such file
Fix this by using the already required BASE_DIR to locate the helper
library.
Link: https://lore.kernel.org/r/20260416-selftest-fix-readlink-e-v1-1-94e4cabbdec4@kernel.org
Fixes: 2964f6b816c2 ("selftests: Use ktap helpers for runner.sh")
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Pull printk updates from Petr Mladek:
- Fix printk ring buffer initialization and sanity checks
- Workaround printf kunit test compilation with gcc < 12.1
- Add IPv6 address printf format tests
- Misc code and documentation cleanup
* tag 'printk-for-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printf: Compile the kunit test with DISABLE_BRANCH_PROFILING DISABLE_BRANCH_PROFILING
lib/vsprintf: use bool for local decode variable
lib/hexdump: print_hex_dump_bytes() calls print_hex_dump_debug()
printk: ringbuffer: fix errors in comments
printk_ringbuffer: Add sanity check for 0-size data
printk_ringbuffer: Fix get_data() size sanity check
printf: add IPv6 address format tests
printk: Fix _DESCS_COUNT type for 64-bit systems
Clang 20 and 21 miscompute __builtin_object_size() when -fprofile-arcs
is active on 32-bit UML targets, which passes incorrect object size
calculations for local variables through always_inline copy_to_user()
and check_copy_size(), causing spurious compile-time errors:
include/linux/ucopysize.h:52:4: error: call to '__bad_copy_from' declared with 'error' attribute: copy source size is too small
The regression was introduced in LLVM commit 02b8ee281947 ("[llvm]
Improve llvm.objectsize computation by computing GEP, alloca and malloc
parameters bound"), which shipped in Clang 20. It was fixed in LLVM
by commit 45b697e610fd ("[MemoryBuiltins] Consider index type size
when aggregating gep offsets"), which was backported to the LLVM 22.x
release branch.
The bug requires 32-bit UML + GCOV_PROFILE_ALL (which uses -fprofile-arcs),
though the exact trigger depends on optimizer decisions influenced by other
enabled configs.
Prevent the bad combination by disabling UML's ARCH_HAS_GCOV_PROFILE_ALL
on 32-bit when using Clang 20.x or 21.x.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202604030531.O6FveVgn-lkp@intel.com/
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Assisted-by: Claude:claude-opus-4-6[1m]
Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20260409052038.make.995-kees@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>