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
Configure Feed
Select the types of activity you want to include in your feed.
Clone this repository
For self-hosted knots, clone URLs may differ based on your setup.
Download tar.gz
When compiling with CONFIG_LTO_CLANG_THIN, vmlinux.o has
__irf_[start|end] before the first FILE entry:
$ readelf -sW vmlinux.o
Symbol table '.symtab' contains 597706 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 NOTYPE LOCAL DEFAULT 18 __irf_start
2: 0000000000000200 0 NOTYPE LOCAL DEFAULT 18 __irf_end
3: 0000000000000000 0 SECTION LOCAL DEFAULT 17 .text
4: 0000000000000000 0 SECTION LOCAL DEFAULT 18 .init.ramfs
This causes klp-build warnings like:
vmlinux.o: warning: objtool: no correlation: __irf_start
vmlinux.o: warning: objtool: no correlation: __irf_end
The problem is that Clang LTO is stripping the initramfs_data.o FILE
symbol, causing those two symbols to be orphaned and not noticed by
klp-diff's correlation logic. Add a loop to correlate any symbols found
before the first FILE symbol.
Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Reported-by: Song Liu <song@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/e21ec1141fc749b5f538d7329b531c1ab63a6d1a.1770055235.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
The klp_object_ext and klp_func_ext data, which are stored in the
__klp_objects and __klp_funcs sections, respectively, are not needed
after they are used to create the actual klp_object and klp_func
instances. This operation is implemented by the init function in
scripts/livepatch/init.c.
Prefix the two sections with ".init" so they are freed after the module
is initializated.
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Aaron Tomlin <atomlin@atomlin.com>
Link: https://patch.msgid.link/20260123102825.3521961-3-petr.pavlu@suse.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
The linker script scripts/module.lds.S specifies that all input
__klp_objects sections should be consolidated into an output section of
the same name, and start/stop symbols should be created to enable
scripts/livepatch/init.c to locate this data.
This start/stop pattern is not ideal for modules because the symbols are
created even if no __klp_objects input sections are present.
Consequently, a dummy __klp_objects section also appears in the
resulting module. This unnecessarily pollutes non-livepatch modules.
Instead, since modules are relocatable files, the usual method for
locating consolidated data in a module is to read its section table.
This approach avoids the aforementioned problem.
The klp_modinfo already stores a copy of the entire section table with
the final addresses. Introduce a helper function that
scripts/livepatch/init.c can call to obtain the location of the
__klp_objects section from this data.
Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Aaron Tomlin <atomlin@atomlin.com>
Link: https://patch.msgid.link/20260123102825.3521961-2-petr.pavlu@suse.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Some special sections specify their ELF section entsize, for example:
.pushsection section, "M", @progbits, 8
The entsize (8 in this example) is needed by objtool klp-diff for
extracting individual entries.
Clang assembler versions older than 20 silently ignore the above
construct and set entsize to 0, resulting in the following error:
.discard.annotate_data: missing special section entsize or annotations
Add a klp-build check to prevent the use of Clang assembler versions
prior to 20.
Fixes: 24ebfcd65a87 ("livepatch/klp-build: Introduce klp-build script for generating livepatch modules")
Reported-by: Song Liu <song@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/957fd52e375d0e2cfa3ac729160da995084a7f5e.1769562556.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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>
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>
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>
When objtool is cross-compiled in ia32 container for x86_64 target it
fails with the following errors:
> disas.c: In function 'disas_print_addr_sym':
> disas.c:173:38: error: format '%lx' expects argument of type 'long unsigned int', but argument 3 has type 'bfd_vma' {aka 'long long unsigned int'} [-Werror=format=]
> 173 | DINFO_FPRINTF(dinfo, "0x%lx <%s>", addr, symstr);
> | ^~~~~~~~~~~~ ~~~~
> | |
> | bfd_vma {aka long long unsigned int}
Provide a correct printf-fmt depending on sizeof(bfd_vma).
Fixes: 5d859dff266f ("objtool: Print symbol during disassembly")
Signed-off-by: Dmitry Safonov <dima@arista.com>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Link: https://patch.msgid.link/20260126-objtool-ia32-v1-1-bb6feaf17566@arista.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Commit 436326bc525d ("objtool: fix build failure due to missing libopcodes
check") tests for libopcodes using an empty main(), which passes even when
static libraries lack their dependencies. This causes undefined reference
errors (xmalloc, bfd_get_bits, etc.) when linking against static libopcodes
without its required libbfd and libiberty.
Fix by testing with an actual libopcodes symbol and trying increasingly
complete library combinations until one succeeds.
Fixes: 436326bc525d ("objtool: fix build failure due to missing libopcodes check")
Reported-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Link: https://patch.msgid.link/20260121162532.1596238-1-sashal@kernel.org
Pull landlock fixes from Mickaël Salaün:
"This fixes TCP handling, tests, documentation, non-audit elided code,
and minor cosmetic changes"
* tag 'landlock-6.19-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
landlock: Clarify documentation for the IOCTL access right
selftests/landlock: Properly close a file descriptor
landlock: Improve the comment for domain_is_scoped
selftests/landlock: Use scoped_base_variants.h for ptrace_test
selftests/landlock: Fix missing semicolon
selftests/landlock: Fix typo in fs_test
landlock: Optimize stack usage when !CONFIG_AUDIT
landlock: Fix spelling
landlock: Clean up hook_ptrace_access_check()
landlock: Improve erratum documentation
landlock: Remove useless include
landlock: Fix wrong type usage
selftests/landlock: NULL-terminate unix pathname addresses
selftests/landlock: Remove invalid unix socket bind()
selftests/landlock: Add missing connect(minimal AF_UNSPEC) test
selftests/landlock: Fix TCP bind(AF_UNSPEC) test case
landlock: Fix TCP handling of short AF_UNSPEC addresses
landlock: Fix formatting
Pull cgroup fixes from Tejun Heo:
- Add Chen Ridong as cpuset reviewer
- Add SPDX license identifiers to cgroup files that were missing them
* tag 'cgroup-for-6.19-rc5-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
kernel: cgroup: Add LGPL-2.1 SPDX license ID to legacy_freezer.c
kernel: cgroup: Add SPDX-License-Identifier lines
MAINTAINERS: Add Chen Ridong as cpuset reviewer
Move the description of the LANDLOCK_ACCESS_FS_IOCTL_DEV access right
together with the file access rights.
This group of access rights applies to files (in this case device
files), and they can be added to file or directory inodes using
landlock_add_rule(2). The check for that works the same for all file
access rights, including LANDLOCK_ACCESS_FS_IOCTL_DEV.
Invoking ioctl(2) on directory FDs can not currently be restricted
with Landlock. Having it grouped separately in the documentation is a
remnant from earlier revisions of the LANDLOCK_ACCESS_FS_IOCTL_DEV
patch set.
Link: https://lore.kernel.org/all/20260108.Thaex5ruach2@digikod.net/
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20260111175203.6545-2-gnoack3000@gmail.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Pull ext4 fixes from Ted Ts'o:
- Fix an inconsistency in structure size on 32-bit platforms caused by
padding differences for the new EXT4_IOC_[GS]ET_TUNE_SB_PARAM ioctls
- Fix a buffer leak on the error path when dropping the refcount an
xattr value stored in an inode
- Fix missing locking on the error path for the file defragmentation
ioctl leading to a BUG
* tag 'ext4_for_linus-6.19-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
ext4: fix iloc.bh leak in ext4_xattr_inode_update_ref
ext4: add missing down_write_data_sem in mext_move_extent().
ext4: fix ext4_tune_sb_params padding
Add an appropriate SPDX-License-Identifier line to the file,
and remove the GNU boilerplate text.
Signed-off-by: Tim Bird <tim.bird@sony.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Add a missing close(srv_fd) call, and use EXPECT_EQ() to check the
result.
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Fixes: f83d51a5bdfe ("selftests/landlock: Check IOCTL restrictions for named UNIX domain sockets")
Link: https://lore.kernel.org/r/20260101134102.25938-2-gnoack3000@gmail.com
[mic: Use EXPECT_EQ() and update commit message]
Signed-off-by: Mickaël Salaün <mic@digikod.net>