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Nathan Chancellor 9c03f6194e kbuild: Add '-fno-builtin-wcslen' 
commit 84ffc79bfb upstream.

A recent optimization change in LLVM [1] aims to transform certain loop
idioms into calls to strlen() or wcslen(). This change transforms the
first while loop in UniStrcat() into a call to wcslen(), breaking the
build when UniStrcat() gets inlined into alloc_path_with_tree_prefix():

  ld.lld: error: undefined symbol: wcslen
  >>> referenced by nls_ucs2_utils.h:54 (fs/smb/client/../../nls/nls_ucs2_utils.h:54)
  >>>               vmlinux.o:(alloc_path_with_tree_prefix)
  >>> referenced by nls_ucs2_utils.h:54 (fs/smb/client/../../nls/nls_ucs2_utils.h:54)
  >>>               vmlinux.o:(alloc_path_with_tree_prefix)

Disable this optimization with '-fno-builtin-wcslen', which prevents the
compiler from assuming that wcslen() is available in the kernel's C
library.

[ More to the point - it's not that we couldn't implement wcslen(), it's
  that this isn't an optimization at all in the context of the kernel.

  Replacing a simple inlined loop with a function call to the same loop
  is just stupid and pointless if you don't have long strings and fancy
  libraries with vectorization support etc.

  For the regular 'strlen()' cases, we want the compiler to do this in
  order to handle the trivial case of constant strings. And we do have
  optimized versions of 'strlen()' on some architectures. But for
  wcslen? Just no.    - Linus ]

Cc: stable@vger.kernel.org
Link: 9694844d7e [1]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[nathan: Resolve small conflict in older trees]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-04-20 10:16:01 +02:00
arch x86/e820: Fix handling of subpage regions when calculating nosave ranges in e820__register_nosave_regions() 2025-04-20 10:16:01 +02:00
block block: fix 'kmem_cache of name 'bio-108' already exists' 2025-03-22 12:54:21 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: api - Fix larval relookup type and mask 2025-04-10 14:39:20 +02:00
Documentation dt-bindings: coresight: qcom,coresight-tpdm: Fix too many 'reg' 2025-04-20 10:15:53 +02:00
drivers ACPI: platform-profile: Fix CFI violation when accessing sysfs files 2025-04-20 10:16:00 +02:00
fs nfsd: don't ignore the return code of svc_proc_register() 2025-04-20 10:16:01 +02:00
include landlock: Add the errata interface 2025-04-20 10:15:55 +02:00
init ARM: 9443/1: Require linker to support KEEP within OVERLAY for DCE 2025-04-10 14:39:40 +02:00
io_uring io_uring/kbuf: reject zero sized provided buffers 2025-04-20 10:15:40 +02:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel sched_ext: create_dsq: Return -EEXIST on duplicate request 2025-04-20 10:15:59 +02:00
lib lib: scatterlist: fix sg_split_phys to preserve original scatterlist offsets 2025-04-20 10:15:45 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/hwpoison: introduce folio_contain_hwpoisoned_page() helper 2025-04-20 10:15:50 +02:00
net sctp: detect and prevent references to a freed transport in sendmsg 2025-04-20 10:15:50 +02:00
rust rust: Fix enabling Rust and building with GCC for LoongArch 2025-04-10 14:39:36 +02:00
samples rust: treewide: switch to the kernel Vec type 2025-03-13 13:01:46 +01:00
scripts kbuild: exclude .rodata.(cst|str)* when building ranges 2025-04-20 10:15:44 +02:00
security landlock: Prepare to add second errata 2025-04-20 10:15:56 +02:00
sound ALSA: hda/realtek: Enable Mute LED on HP OMEN 16 Laptop xd000xx 2025-04-20 10:15:42 +02:00
tools libbpf: Prevent compiler warnings/errors 2025-04-20 10:16:01 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow building irqbypass.ko as as module when kvm.ko is a module 2025-04-20 10:15:54 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: enable Clippy's check-private-items 2025-03-13 13:01:42 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: add entry for the Rust alloc module 2025-03-13 13:01:47 +01:00
Makefile kbuild: Add '-fno-builtin-wcslen' 2025-04-20 10:16:01 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

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.