Linux 6.3 comes loaded with many changes and new features

After two months of development, Linus Torvalds announced the release of the new version of the Linux 6.3 kernel, in which among the most notable changes is the cleaning of ARM platforms and obsolete graphics drivers, continuous integration of Rust language support, hwnoise utility, among other things.

The new version accepted 15637 fixes from 2055 developers; patch size: 76 MB (changes affected 14296 files, added 1023183 lines of code, removed 883103 lines). For comparison, in the previous version, 16843 fixes were proposed by 2178 developers; patch size – 62 MB.

Main news in Linux 6.3

In this new version that is presented, a major code cleanup related to older ARM boards and unused , which has reduced the size of the kernel fonts by 150 thousand lines. Removed over 40 old ARM platforms

It is also highlighted that migrating from the Rust-for-Linux branch continues of additional functionality related to the use of Rust as a second language for developing drivers and kernel modules. Rust support is not enabled by default and does not cause Rust to be included as a required kernel build dependency. The functionality offered in previous versions has been extended with support for the types Arc (an implementation of pointers with a reference count), ScopeGuard (cleanup is performed when going out of scope), and ForeignOwnable (provides pointer movement between code C and Rust).

Besides that, Linux in user mode (which runs the kernel as a user process) on x86-64 systems supports code written in Rust and added support for compiling user-mode Linux using clang with link-time optimizations (LTO) enabled.

We can also find in this new version of Linux 6.3 the hwnoise utility to trace delays caused by hardware behavior. Deviations in the execution time of operations (jitter) are determined when interrupt processing is disabled, exceeding one microsecond in 10 minutes of calculations.

Added a kernel module with a Dhrystone reference implementation que can be used to assess CPU performance in setups without userspace components (for example, migrating to newer SoCs that only boot the kernel).

for systems based on the instruction set architectures LongArch (used in Loongson 3 5000 processors and implementing a new RISC ISA similar to MIPS and RISC-V), added support for randomization of the kernel address space (KASLR), relocation of the kernel in memory (relocation), hardware point capping, and kprobe mechanism.

The mechanism memfd, which allows an area of ​​memory to be identified via a file descriptor passed between processes, added the ability to create areas where code execution is prohibited (memfd not executable) and it is impossible to set execute rights in the future.

On the other hand, it is noted that in Linux 6.3 Addresses a vulnerability that could bypass Specter v2 attack protection when using Simultaneous Multi-Threading (SMT or Hyper-Threading) technology and caused by disabling the STIBP (Single-Threaded Indirect Branch Predictors) mechanism when selecting the IBRS protection mode.

For IPv4, it is possible to use the BIG TCP extension, which allows you to increase the size TCP packet maximum up to 4 GB to optimize the operation of the high-speed internal networks of data centers. This increase in packet size with a 16-bit header field is achieved by implementing "jumbo" packets that have the IP header size set to 0 and the actual size is transmitted in a separate 32-bit field in a separate attached header.

Of the other changes that stand out:

• A DRM driver has been added for the VPU (Versatile Processing Unit) embedded in Intel Meteor Lake (14th Generation) CPUs, designed to speed up machine learning and computer vision operations.
• The driver is implemented by the "accel" subsystem, which aims to provide support for compute accelerators that can be shipped as stand-alone ASICs or as IP blocks within SoCs and GPUs.
• The i915 (Intel) driver extends support for Intel Arc (DG2/Alchemist) discrete graphics cards, provides preliminary support for Meteor Lake GPUs, and includes support for Intel Xe HP 4tile GPUs.
• The amdgpu driver adds support for AdaptiveSync technology and the ability to use Secure Display with multiple displays. Updated support for DCN 3.2 (Display Core Next), SR-IOV RAS, VCN RAS, SMU 13.x and DP 2.1.
• Added support for the SM8350, SM8450 SM8550, SDM845, and SC8280XP platforms to the msm (Qualcomm Adreno GPU) driver. The Nouveau driver has dropped support for legacy ioctl calls.
• Improved ext4 FS performance by allowing multiple processes to simultaneously perform direct I/O operations on preallocated blocks using shared inode locks instead of exclusive locks.
• Experimental support for VerSilicon NPU (VeriSilicon Neural Network Processor) has been added to the etnaviv driver.
• Added driver ath12k for wireless cards based on Qualcomm chips with Wi-Fi 7 support.
• Added support for wireless cards based on RealTek RTL8188EU chips.
• Added support for RISC-V boards based on Allwinner D1 and D1s SoCs.

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