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Paul Chaignon d945a3c339 bpf: Use tnums for JEQ/JNE is_branch_taken logic 
[ Upstream commit f41345f47f ]

In the following toy program (reg states minimized for readability), R0
and R1 always have different values at instruction 6. This is obvious
when reading the program but cannot be guessed from ranges alone as
they overlap (R0 in [0; 0xc0000000], R1 in [1024; 0xc0000400]).

  0: call bpf_get_prandom_u32#7  ; R0_w=scalar()
  1: w0 = w0                     ; R0_w=scalar(var_off=(0x0; 0xffffffff))
  2: r0 >>= 30                   ; R0_w=scalar(var_off=(0x0; 0x3))
  3: r0 <<= 30                   ; R0_w=scalar(var_off=(0x0; 0xc0000000))
  4: r1 = r0                     ; R1_w=scalar(var_off=(0x0; 0xc0000000))
  5: r1 += 1024                  ; R1_w=scalar(var_off=(0x400; 0xc0000000))
  6: if r1 != r0 goto pc+1

Looking at tnums however, we can deduce that R1 is always different from
R0 because their tnums don't agree on known bits. This patch uses this
logic to improve is_scalar_branch_taken in case of BPF_JEQ and BPF_JNE.

This change has a tiny impact on complexity, which was measured with
the Cilium complexity CI test. That test covers 72 programs with
various build and load time configurations for a total of 970 test
cases. For 80% of test cases, the patch has no impact. On the other
test cases, the patch decreases complexity by only 0.08% on average. In
the best case, the verifier needs to walk 3% less instructions and, in
the worst case, 1.5% more. Overall, the patch has a small positive
impact, especially for our largest programs.

Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/be3ee70b6e489c49881cb1646114b1d861b5c334.1755694147.git.paul.chaignon@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-11-13 15:36:46 -05:00
arch s390/mm: Fix memory leak in add_marker() when kvrealloc() fails 2025-11-13 15:36:44 -05:00
block block: require LBA dma_alignment when using PI 2025-10-29 14:10:28 +01:00
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 dpll: spec: add missing module-name and clock-id to pin-get reply 2025-11-13 15:36:42 -05:00
drivers cpufreq: ti: Add support for AM62D2 2025-11-13 15:36:46 -05:00
fs smb: client: fix potential cfid UAF in smb2_query_info_compound 2025-11-13 15:36:38 -05:00
include bpf: Use tnums for JEQ/JNE is_branch_taken logic 2025-11-13 15:36:46 -05:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:37:27 +02:00
io_uring io_uring: correct __must_hold annotation in io_install_fixed_file 2025-10-29 14:10:28 +01:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel bpf: Use tnums for JEQ/JNE is_branch_taken logic 2025-11-13 15:36:46 -05:00
lib kunit: test_dev_action: Correctly cast 'priv' pointer to long* 2025-11-13 15:36:39 -05:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm treewide: remove MIGRATEPAGE_SUCCESS 2025-10-29 14:10:32 +01:00
net mptcp: fix MSG_PEEK stream corruption 2025-11-13 15:36:45 -05:00
rust rust: device: fix device context of Device::parent() 2025-10-29 14:10:22 +01:00
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: soc_sdw_utils: remove cs42l43 component_name 2025-11-13 15:36:42 -05:00
tools tools: ynl: avoid print_field when there is no reply 2025-11-13 15:36:42 -05:00
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 Linux 6.17.7 2025-11-02 22:18:05 +09:00
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.