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Nathan Chancellor bbedfced93 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 14:04:36 +01:00
arch powerpc/32: Remove PAGE_KERNEL_TEXT to fix startup failure 2025-10-29 14:04:36 +01:00
block blk-crypto: fix missing blktrace bio split events 2025-10-19 16:23:12 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2025-04-25 10:44:04 +02:00
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-19 16:23:10 +02:00
Documentation doc: fix seg6_flowlabel path 2025-10-29 14:04:33 +01:00
drivers net/mlx5e: Return 1 instead of 0 in invalid case in mlx5e_mpwrq_umr_entry_size() 2025-10-29 14:04:36 +01:00
fs smb: server: let smb_direct_flush_send_list() invalidate a remote key first 2025-10-29 14:04:36 +01:00
include net/ip6_tunnel: Prevent perpetual tunnel growth 2025-10-29 14:04:33 +01:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:23:13 +02:00
io_uring io_uring: include dying ring in task_work "should cancel" state 2025-09-25 10:58:53 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:07:30 +01:00
kernel sched/fair: Fix pelt lost idle time detection 2025-10-29 14:04:35 +01:00
lib asm-generic/io: Add _RET_IP_ to MMIO trace for more accurate debug info 2025-10-19 16:23:22 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm/hugetlb: early exit from hugetlb_pages_alloc_boot() when max_huge_pages=0 2025-10-19 16:23:18 +02:00
net tls: don't rely on tx_work during send() 2025-10-29 14:04:34 +01:00
rust rust: module: place cleanup_module() in .exit.text section 2025-07-06 10:57:54 +02:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:29:56 +02:00
scripts gcc-plugins: Remove TODO_verify_il for GCC >= 16 2025-10-15 11:56:20 +02:00
security KEYS: trusted_tpm1: Compare HMAC values in constant time 2025-10-19 16:23:14 +02:00
sound ALSA: usb-audio: Fix NULL pointer deference in try_to_register_card 2025-10-29 14:04:35 +01:00
tools selftests/mm: skip soft-dirty tests when CONFIG_MEM_SOFT_DIRTY is disabled 2025-10-19 16:23:21 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:07:25 +01:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:46:21 +02:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:21:15 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -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 Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
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 sign-file,extract-cert: move common SSL helper functions to a header 2025-04-25 10:44:04 +02:00
Makefile Linux 6.1.157 2025-10-19 16:23:23 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 Restructured Text 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.