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Nathan Chancellor 2bb70ae4c9 net/mlx5e: Return 1 instead of 0 in invalid case in mlx5e_mpwrq_umr_entry_size() 
[ Upstream commit aaf043a568 ]

When building with Clang 20 or newer, there are some objtool warnings
from unexpected fallthroughs to other functions:

  vmlinux.o: warning: objtool: mlx5e_mpwrq_mtts_per_wqe() falls through to next function mlx5e_mpwrq_max_num_entries()
  vmlinux.o: warning: objtool: mlx5e_mpwrq_max_log_rq_size() falls through to next function mlx5e_get_linear_rq_headroom()

LLVM 20 contains an (admittedly problematic [1]) optimization [2] to
convert divide by zero into the equivalent of __builtin_unreachable(),
which invokes undefined behavior and destroys code generation when it is
encountered in a control flow graph.

mlx5e_mpwrq_umr_entry_size() returns 0 in the default case of an
unrecognized mlx5e_mpwrq_umr_mode value. mlx5e_mpwrq_mtts_per_wqe(),
which is inlined into mlx5e_mpwrq_max_log_rq_size(), uses the result of
mlx5e_mpwrq_umr_entry_size() in a divide operation without checking for
zero, so LLVM is able to infer there will be a divide by zero in this
case and invokes undefined behavior. While there is some proposed work
to isolate this undefined behavior and avoid the destructive code
generation that results in these objtool warnings, code should still be
defensive against divide by zero.

As the WARN_ONCE() implies that an invalid value should be handled
gracefully, return 1 instead of 0 in the default case so that the
results of this division operation is always valid.

Fixes: 168723c1f8 ("net/mlx5e: xsk: Use umr_mode to calculate striding RQ parameters")
Link: https://lore.kernel.org/CAGG=3QUk8-Ak7YKnRziO4=0z=1C_7+4jF+6ZeDQ9yF+kuTOHOQ@mail.gmail.com/ [1]
Link: 37932643ab [2]
Closes: https://github.com/ClangBuiltLinux/linux/issues/2131
Closes: https://github.com/ClangBuiltLinux/linux/issues/2132
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20251014-mlx5e-avoid-zero-div-from-mlx5e_mpwrq_umr_entry_size-v1-1-dc186b8819ef@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-10-29 14:10:18 +01:00
arch s390/mm: Use __GFP_ACCOUNT for user page table allocations 2025-10-29 14:10:17 +01:00
block block: Remove elevator_lock usage from blkg_conf frozen operations 2025-10-23 16:24:37 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-19 16:37:14 +02:00
Documentation arm64: errata: Apply workarounds for Neoverse-V3AE 2025-10-23 16:24:38 +02:00
drivers net/mlx5e: Return 1 instead of 0 in invalid case in mlx5e_mpwrq_umr_entry_size() 2025-10-29 14:10:18 +01:00
fs smb: server: let smb_direct_flush_send_list() invalidate a remote key first 2025-10-29 14:10:17 +01:00
include cgroup/misc: fix misc_res_type kernel-doc warning 2025-10-29 14:10:15 +01:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:37:27 +02:00
io_uring io_uring: protect mem region deregistration 2025-10-23 16:24:22 +02:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel sched/fair: Block delayed tasks on throttled hierarchy during dequeue 2025-10-29 14:10:15 +01:00
lib lib/genalloc: fix device leak in of_gen_pool_get() 2025-10-19 16:37:28 +02:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm slab: reset slab->obj_ext when freeing and it is OBJEXTS_ALLOC_FAIL 2025-10-23 16:24:21 +02:00
net tls: don't rely on tx_work during send() 2025-10-23 16:24:31 +02:00
rust rust: cpufreq: fix formatting 2025-10-23 16:24:38 +02:00
samples 15 hotfixes. 11 are cc:stable and the remainder address post-6.16 issues 2025-09-17 21:34:26 -07:00
scripts kbuild: Add '.rel.*' strip pattern for vmlinux 2025-10-19 16:37:15 +02:00
security KEYS: trusted_tpm1: Compare HMAC values in constant time 2025-10-19 16:37:28 +02:00
sound ASoC: amd/sdw_utils: avoid NULL deref when devm_kasprintf() fails 2025-10-23 16:24:37 +02:00
tools selftests: arg_parsing: Ensure data is flushed to disk before reading. 2025-10-23 16:24:37 +02:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.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 MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore gitignore: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap 7 hotfixes. 4 are cc:stable and the remainder address post-6.16 issues or 2025-09-28 09:32:00 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.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: retire Boris from TLS maintainers 2025-08-26 17:36:01 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS i2c-for-6.17-rc8 2025-09-28 13:19:23 -07:00
Makefile Unbreak 'make tools/*' for user-space targets 2025-10-29 14:10:18 +01:00
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.