kernel/linux.git/init/version.c, branch v6.6.131

init/version.c: remove #include

2022-12-10T01:33:20+00:00

Commit 2df8220cc511 ("kbuild: build init/built-in.a just once") moved the usage of the define UTS_RELEASE to the file version-timestamp.c. version-timestamp.c in turn is included from version.c but already includes utsrelease.h itself properly. The unneeded include of utsrelease.h from version.c can be dropped. Fixes: 2df8220cc511 ("kbuild: build init/built-in.a just once") Signed-off-by: Thomas Weißschuh Signed-off-by: Masahiro Yamada

kbuild: build init/built-in.a just once

2022-09-28T19:40:15+00:00

Kbuild builds init/built-in.a twice; first during the ordinary directory descending, second from scripts/link-vmlinux.sh. We do this because UTS_VERSION contains the build version and the timestamp. We cannot update it during the normal directory traversal since we do not yet know if we need to update vmlinux. UTS_VERSION is temporarily calculated, but omitted from the update check. Otherwise, vmlinux would be rebuilt every time. When Kbuild results in running link-vmlinux.sh, it increments the version number in the .version file and takes the timestamp at that time to really fix UTS_VERSION. However, updating the same file twice is a footgun. To avoid nasty timestamp issues, all build artifacts that depend on init/built-in.a are atomically generated in link-vmlinux.sh, where some of them do not need rebuilding. To fix this issue, this commit changes as follows: [1] Split UTS_VERSION out to include/generated/utsversion.h from include/generated/compile.h include/generated/utsversion.h is generated just before the vmlinux link. It is generated under include/generated/ because some decompressors (s390, x86) use UTS_VERSION. [2] Split init_uts_ns and linux_banner out to init/version-timestamp.c from init/version.c init_uts_ns and linux_banner contain UTS_VERSION. During the ordinary directory descending, they are compiled with __weak and used to determine if vmlinux needs relinking. Just before the vmlinux link, they are compiled without __weak to embed the real version and timestamp. Signed-off-by: Masahiro Yamada

init/version.c: remove #include

2022-09-28T19:40:15+00:00

This is unneeded since commit 073a9ecb3a73 ("init/version.c: remove Version_ symbol"). Signed-off-by: Masahiro Yamada

init: add "hostname" kernel parameter

2022-07-18T00:31:37+00:00

The gethostname system call returns the hostname for the current machine. However, the kernel has no mechanism to initially set the current machine's name in such a way as to guarantee that the first userspace process to call gethostname will receive a meaningful result. It relies on some unspecified userspace process to first call sethostname before gethostname can produce a meaningful name. Traditionally the machine's hostname is set from userspace by the init system. The init system, in turn, often relies on a configuration file (say, /etc/hostname) to provide the value that it will supply in the call to sethostname. Consequently, the file system containing /etc/hostname usually must be available before the hostname will be set. There may, however, be earlier userspace processes that could call gethostname before the file system containing /etc/hostname is mounted. Such a process will get some other, likely meaningless, name from gethostname (such as "(none)", "localhost", or "darkstar"). A real-world example where this can happen, and lead to undesirable results, is with mdadm. When assembling arrays, mdadm distinguishes between "local" arrays and "foreign" arrays. A local array is one that properly belongs to the current machine, and a foreign array is one that is (possibly temporarily) attached to the current machine, but properly belongs to some other machine. To determine if an array is local or foreign, mdadm may compare the "homehost" recorded on the array with the current hostname. If mdadm is run before the root file system is mounted, perhaps because the root file system itself resides on an md-raid array, then /etc/hostname isn't yet available and the init system will not yet have called sethostname, causing mdadm to incorrectly conclude that all of the local arrays are foreign. Solving this problem *could* be delegated to the init system. It could be left up to the init system (including any init system that starts within an initramfs, if one is in use) to ensure that sethostname is called before any other userspace process could possibly call gethostname. However, it may not always be obvious which processes could call gethostname (for example, udev itself might not call gethostname, but it could via udev rules invoke processes that do). Additionally, the init system has to ensure that the hostname configuration value is stored in some place where it will be readily accessible during early boot. Unfortunately, every init system will attempt to (or has already attempted to) solve this problem in a different, possibly incorrect, way. This makes getting consistently working configurations harder for users. I believe it is better for the kernel to provide the means by which the hostname may be set early, rather than making this a problem for the init system to solve. The option to set the hostname during early startup, via a kernel parameter, provides a simple, reliable way to solve this problem. It also could make system configuration easier for some embedded systems. [dmoulding@me.com: v2] Link: https://lkml.kernel.org/r/20220506060310.7495-2-dmoulding@me.com Link: https://lkml.kernel.org/r/20220505180651.22849-2-dmoulding@me.com Signed-off-by: Dan Moulding Cc: Thomas Gleixner Cc: Jonathan Corbet Signed-off-by: Andrew Morton

kbuild: add an elfnote for whether vmlinux is built with lto

2021-04-24T20:25:42+00:00

Currently, clang LTO built vmlinux won't work with pahole. LTO introduced cross-cu dwarf tag references and broke current pahole model which handles one cu as a time. The solution is to merge all cu's as one pahole cu as in [1]. We would like to do this merging only if cross-cu dwarf references happens. The LTO build mode is a pretty good indication for that. In earlier version of this patch ([2]), clang flag -grecord-gcc-switches is proposed to add to compilation flags so pahole could detect "-flto" and then merging cu's. This will increate the binary size of 1% without LTO though. Arnaldo suggested to use a note to indicate the vmlinux is built with LTO. Such a cheap way to get whether the vmlinux is built with LTO or not helps pahole but is also useful for tracing as LTO may inline/delete/demote global functions, promote static functions, etc. So this patch added an elfnote with a new type LINUX_ELFNOTE_LTO_INFO. The owner of the note is "Linux". With gcc 8.4.1 and clang trunk, without LTO, I got $ readelf -n vmlinux Displaying notes found in: .notes Owner Data size Description ... Linux 0x00000004 func description data: 00 00 00 00 ... With "readelf -x ".notes" vmlinux", I can verify the above "func" with type code 0x101. With clang thin-LTO, I got the same as above except the following: description data: 01 00 00 00 which indicates the vmlinux is built with LTO. [1] https://lore.kernel.org/bpf/20210325065316.3121287-1-yhs@fb.com/ [2] https://lore.kernel.org/bpf/20210331001623.2778934-1-yhs@fb.com/ Suggested-by: Arnaldo Carvalho de Melo Signed-off-by: Yonghong Song Reviewed-by: Nick Desaulniers Tested-by: Sedat Dilek # LLVM/Clang v12.0.0-rc4 (x86-64) Tested-by: Arnaldo Carvalho de Melo Signed-off-by: Masahiro Yamada

init/version.c: remove Version_ symbol

2021-02-26T17:41:04+00:00

This code hunk creates a Version_ symbol if CONFIG_KALLSYMS is disabled. For example, building the kernel v5.10 for allnoconfig creates the following symbol: $ nm vmlinux | grep Version_ c116b028 B Version_330240 There is no in-tree user of this symbol. Commit 197dcffc8ba0 ("init/version.c: define version_string only if CONFIG_KALLSYMS is not defined") mentions that Version_* is only used with ksymoops. However, a commit in the pre-git era [1] had added the statement, "ksymoops is useless on 2.6. Please use the Oops in its original format". That statement existed until commit 4eb9241127a0 ("Documentation: admin-guide: update bug-hunting.rst") finally removed the stale ksymoops information. This symbol is no longer needed. [1] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=ad68b2f085f5c79e4759ca2d13947b3c885ee831 Link: https://lkml.kernel.org/r/20210120033452.2895170-1-masahiroy@kernel.org Signed-off-by: Masahiro Yamada Cc: Mauro Carvalho Chehab Cc: Randy Dunlap Cc: Daniel Guilak Cc: Lee Revell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

uts: Use generic ns_common::count

2020-08-19T12:13:20+00:00

Switch over uts namespaces to use the newly introduced common lifetime counter. Currently every namespace type has its own lifetime counter which is stored in the specific namespace struct. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This introduces a common lifetime counter into struct ns_common. The ns_common struct encompasses information that all namespaces share. That should include the lifetime counter since its common for all of them. It also allows us to unify the type of the counters across all namespaces. Most of them use refcount_t but one uses atomic_t and at least one uses kref. Especially the last one doesn't make much sense since it's just a wrapper around refcount_t since 2016 and actually complicates cleanup operations by having to use container_of() to cast the correct namespace struct out of struct ns_common. Having the lifetime counter for the namespaces in one place reduces maintenance cost. Not just because after switching all namespaces over we will have removed more code than we added but also because the logic is more easily understandable and we indicate to the user that the basic lifetime requirements for all namespaces are currently identical. Signed-off-by: Kirill Tkhai Reviewed-by: Kees Cook Acked-by: Christian Brauner Link: https://lore.kernel.org/r/159644978167.604812.1773586504374412107.stgit@localhost.localdomain Signed-off-by: Christian Brauner

treewide: Add SPDX license identifier for missed files

2019-05-21T08:50:45+00:00

Add SPDX license identifiers to all files which: - Have no license information of any form - Have EXPORT_.*_SYMBOL_GPL inside which was used in the initial scan/conversion to ignore the file These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

kbuild: Add build salt to the kernel and modules

2018-07-17T16:18:05+00:00

In Fedora, the debug information is packaged separately (foo-debuginfo) and can be installed separately. There's been a long standing issue where only one version of a debuginfo info package can be installed at a time. There's been an effort for Fedora for parallel debuginfo to rectify this problem. Part of the requirement to allow parallel debuginfo to work is that build ids are unique between builds. The existing upstream rpm implementation ensures this by re-calculating the build-id using the version and release as a seed. This doesn't work 100% for the kernel because of the vDSO which is its own binary and doesn't get updated when embedded. Fix this by adding some data in an ELF note for both the kernel and modules. The data is controlled via a Kconfig option so distributions can set it to an appropriate value to ensure uniqueness between builds. Suggested-by: Masahiro Yamada Signed-off-by: Laura Abbott Signed-off-by: Masahiro Yamada

init/version.c: include instead of

2017-11-18T00:10:02+00:00

init/version.c has nothing to do with modules, so remove the . Instead, include for EXPORT_SYMBOL_GPL. This cuts off a lot of unnecessary header parsing. Link: http://lkml.kernel.org/r/1505920984-8523-1-git-send-email-yamada.masahiro@socionext.com Signed-off-by: Masahiro Yamada Cc: Paul Gortmaker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds