tjh.dev
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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The reproducer:
echo | ./usr/gen_init_cpio /dev/stdin > /dev/null
fsync() on a pipe fd returns -EINVAL, which makes gen_init_cpio fail.
Ignore -EINVAL from fsync().
Fixes: ae18b94099b0 ("gen_init_cpio: support -o <output_file> parameter")
Cc: David Disseldorp <ddiss@suse.de>
Cc: Nicolas Schier <nsc@kernel.org>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Reviewed-by: David Disseldorp <ddiss@suse.de>
Link: https://patch.msgid.link/20251007-gen_init_cpio-pipe-v2-1-b098ab94b58a@arista.com
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Commit 27758d8c2583 ("kbuild: enable -Werror for hostprogs")
unconditionally enabled -Werror for the compiler, assembler, and linker
when building the host programs, as the build footprint of the host
programs is small (thus risk of build failures from warnings are low)
and that stage of the build may not have Kconfig values (thus
CONFIG_WERROR could not be used as a precondition).
While turning warnings into errors unconditionally happens in a few
places within the kernel, it can be disruptive to people who may be
building with newer compilers, such as while doing a bisect. While it is
possible to avoid this behavior by passing HOSTCFLAGS=-w or
HOSTCFLAGS=-Wno-error, it may not be the most intuitive for regular
users not intimately familiar with Kbuild.
Avoid being disruptive to the entire build by depending on the explicit
opt-in of CONFIG_WERROR or W=e to enable -Werror and the like while
building the host programs. While this means there is a small portion of
the build that does not have -Werror enabled (namely scripts/kconfig/*
and scripts/basic/fixdep), it is better than not having it altogether.
Fixes: 27758d8c2583 ("kbuild: enable -Werror for hostprogs")
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reported-by: Askar Safin <safinaskar@gmail.com>
Closes: https://lore.kernel.org/20251005011100.1035272-1-safinaskar@gmail.com/
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Tested-by: Miguel Ojeda <ojeda@kernel.org> # Rust
Link: https://patch.msgid.link/20251006-kbuild-hostprogs-werror-fix-v1-1-23cf1ffced5c@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
On m68k, check_sizetypes in headers_check reports:
./usr/include/asm/bootinfo-amiga.h:17: found __[us]{8,16,32,64} type without #include <linux/types.h>
This header file does not use any of the Linux-specific integer types,
but merely refers to them from comments, so this is a false positive.
As of commit c3a9d74ee413bdb3 ("kbuild: uapi: upgrade check_sizetypes()
warning to error"), this check was promoted to an error, breaking m68k
all{mod,yes}config builds.
Fix this by stripping simple comments before looking for Linux-specific
integer types.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://patch.msgid.link/949f096337e28d50510e970ae3ba3ec9c1342ec0.1759753998.git.geert@linux-m68k.org
[nathan: Adjust comment and remove unnecessary escaping from slashes in
regex]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Segmentation fault ./scripts/mod/modpost -o vmlinux.symvers vmlinux.o
stops the kernel build. It comes when write_vmlinux_export_c_file()
tries to buf_printf alias->builtin_modname. malloc'ed memory is not
necessarily zeroed. NULL new->builtin_modname before adding to aliases.
Fixes: 5ab23c7923a1 ("modpost: Create modalias for builtin modules")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/4590a243-0a7e-b7e6-e2d3-cd1b41a12237@google.com
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
CONFIG_EFI_DEBUG embeds absolute file paths into object files, which
makes the resulting vmlinux specific to the build environment.
Add a note about this in reproducible-builds.rst
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nicolas Schier <nsc@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20250924-kbuild-doc-config-debug-efi-in-reproducible-builds-v2-1-d2d6b9dcdb7d@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Alexey Gladkov says:
The modules.builtin.modinfo file is used by userspace (kmod to be specific) to
get information about builtin modules. Among other information about the module,
information about module aliases is stored. This is very important to determine
that a particular modalias will be handled by a module that is inside the
kernel.
There are several mechanisms for creating modalias for modules:
The first is to explicitly specify the MODULE_ALIAS of the macro. In this case,
the aliases go into the '.modinfo' section of the module if it is compiled
separately or into vmlinux.o if it is builtin into the kernel.
The second is the use of MODULE_DEVICE_TABLE followed by the use of the
modpost utility. In this case, vmlinux.o no longer has this information and
does not get it into modules.builtin.modinfo.
For example:
$ modinfo pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30
modinfo: ERROR: Module pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30 not found.
$ modinfo xhci_pci
name: xhci_pci
filename: (builtin)
license: GPL
file: drivers/usb/host/xhci-pci
description: xHCI PCI Host Controller Driver
The builtin module is missing alias "pci:v*d*sv*sd*bc0Csc03i30*" which will be
generated by modpost if the module is built separately.
To fix this it is necessary to add the generated by modpost modalias to
modules.builtin.modinfo. Fortunately modpost already generates .vmlinux.export.c
for exported symbols. It is possible to add `.modinfo` for builtin modules and
modify the build system so that `.modinfo` section is extracted from the
intermediate vmlinux after modpost is executed.
Link: https://patch.msgid.link/cover.1758182101.git.legion@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Commit bd7c2312128e ("pinctrl: meson: Fix typo in device table macro")
is needed in kbuild-next to avoid a build error with a future change.
While at it, address the conflict between commit 41f9049cff32 ("riscv:
Only allow LTO with CMODEL_MEDANY") and commit 6578a1ff6aa4 ("riscv:
Remove version check for LTO_CLANG selects"), as reported by Stephen
Rothwell [1].
Link: https://lore.kernel.org/20250908134913.68778b7b@canb.auug.org.au/ [1]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Since .vmlinux.export.c is used to add generated by modpost modaliases
for builtin modules the .vmlinux.export.o is no longer optional and
should always be created. The generation of this file is not dependent
on CONFIG_MODULES.
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/0e63a9c7741fe8217e4fd7c60afcf057ffa2ef5a.1758182101.git.legion@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
s390 and x86 have required LLVM 15 since
30d17fac6aae ("scripts/min-tool-version.sh: raise minimum clang version to 15.0.0 for s390")
7861640aac52 ("x86/build: Raise the minimum LLVM version to 15.0.0")
respectively. This series bumps the rest of the kernel to 15.0.0 to
match, which allows for a decent number of clean ups.
On the distros front, we will only leave behind Debian Bookworm and
Ubuntu Jammy. In both of those cases, builders / developers can either
use the kernel.org toolchains or https://apt.llvm.org to get newer
versions that will run on those distributions, if they cannot upgrade.
archlinux:latest clang version 20.1.8
debian:oldoldstable-slim Debian clang version 11.0.1-2
debian:oldstable-slim Debian clang version 14.0.6
debian:stable-slim Debian clang version 19.1.7 (3+b1)
debian:testing-slim Debian clang version 19.1.7 (3+b1)
debian:unstable-slim Debian clang version 19.1.7 (3+b2)
fedora:41 clang version 19.1.7 (Fedora 19.1.7-4.fc41)
fedora:latest clang version 20.1.8 (Fedora 20.1.8-3.fc42)
fedora:rawhide clang version 20.1.8 (Fedora 20.1.8-3.fc43)
opensuse/leap:latest clang version 17.0.6
opensuse/tumbleweed:latest clang version 20.1.8
ubuntu:focal clang version 10.0.0-4ubuntu1
ubuntu:jammy Ubuntu clang version 14.0.0-1ubuntu1.1
ubuntu:noble Ubuntu clang version 18.1.3 (1ubuntu1)
ubuntu:latest Ubuntu clang version 18.1.3 (1ubuntu1)
ubuntu:rolling Ubuntu clang version 20.1.2 (0ubuntu1)
ubuntu:devel Ubuntu clang version 20.1.8 (0ubuntu1)
Link: https://lore.kernel.org/r/20250821-bump-min-llvm-ver-15-v2-0-635f3294e5f0@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
For some modules, modalias is generated using the modpost utility and
the section is added to the module file.
When a module is added inside vmlinux, modpost does not generate
modalias for such modules and the information is lost.
As a result kmod (which uses modules.builtin.modinfo in userspace)
cannot determine that modalias is handled by a builtin kernel module.
$ cat /sys/devices/pci0000:00/0000:00:14.0/modalias
pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30
$ modinfo xhci_pci
name: xhci_pci
filename: (builtin)
license: GPL
file: drivers/usb/host/xhci-pci
description: xHCI PCI Host Controller Driver
Missing modalias "pci:v*d*sv*sd*bc0Csc03i30*" which will be generated by
modpost if the module is built separately.
To fix this it is necessary to generate the same modalias for vmlinux as
for the individual modules. Fortunately '.vmlinux.export.o' is already
generated from which '.modinfo' can be extracted in the same way as for
vmlinux.o.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/28d4da3b0e3fc8474142746bcf469e03752c3208.1758182101.git.legion@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
When extract-vmlinux succeeds, it doesn't output which decompression method
was found at which offset. Adding this additional output in check_vmlinux()
helps troubleshooting and reverse-engineering images.
The last check_vmlinux() call was also quoted to accept spaces.
Signed-off-by: Maxime Thiebaut <maxime+kernel@thiebaut.dev>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://lore.kernel.org/r/X6OQ4pHdpreJtlTnf0tFEb4Uxz8T8gFv_7Yw6tpBK4ZBgHYjJr_URwUwCVynpkb-H8Yjk7DdBF01zY-sfqu_7N5trZQfcd6s_4PtdGlHtlA=@thiebaut.dev
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Now that the minimum supported version of LLVM for building the kernel
has been bumped to 15.0.0, two KMSAN checks can be cleaned up.
CONFIG_HAVE_KMSAN_COMPILER will always be true when using clang so
remove the cc-option test and use a simple check for CONFIG_CC_IS_CLANG.
CONFIG_HAVE_KMSAN_PARAM_RETVAL will always be true so it can be removed
outright.
Acked-by: Marco Elver <elver@google.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20250821-bump-min-llvm-ver-15-v2-12-635f3294e5f0@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Pull generic phy driver fixes from Vinod Koul:
- Qualcomm repeater override properties, qmp pcie bindings fix for
clocks and initialization sequence for firmware power down case
- Marvell comphy bindings clock and child node constraints
- Tegra xusb device reference leaks fix
- TI omap usb device ref leak on unbind and RGMII IS settings fix
* tag 'phy-fix-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/phy/linux-phy:
phy: qcom: qmp-pcie: Fix PHY initialization when powered down by firmware
phy: ti: gmii-sel: Always write the RGMII ID setting
dt-bindings: phy: qcom,sc8280xp-qmp-pcie-phy: Update pcie phy bindings
phy: ti-pipe3: fix device leak at unbind
phy: ti: omap-usb2: fix device leak at unbind
phy: tegra: xusb: fix device and OF node leak at probe
dt-bindings: phy: marvell,comphy-cp110: Fix clock and child node constraints
phy: qualcomm: phy-qcom-eusb2-repeater: fix override properties
At this point, if a symbol is compiled as part of the kernel,
information about which module the symbol belongs to is lost.
To save this it is possible to add the module name to the alias name.
It's not very pretty, but it's possible for now.
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Andreas Hindborg <a.hindborg@kernel.org>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: rust-for-linux@vger.kernel.org
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/1a0d0bd87a4981d465b9ed21e14f4e78eaa03ded.1758182101.git.legion@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
The module export checks are looking for EXPORT_SYMBOL_GPL_FOR_MODULES()
which was renamed to EXPORT_SYMBOL_FOR_MODULES(). Update the checks.
Fixes: 6d3c3ca4c77e ("module: Rename EXPORT_SYMBOL_GPL_FOR_MODULES to EXPORT_SYMBOL_FOR_MODULES")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Daniel Gomez <da.gomez@samsung.com>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://lore.kernel.org/r/20250825-export_modules_fix-v1-1-5c331e949538@suse.cz
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
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