IBM POWER10 Receives DEXCR Support In Linux 6.5, Big Endian Improvements

Written by Michael Larabel in Linux Kernel on 2 July 2023 at 06:17 AM EDT. 7 Comments
The IBM PowerPC feature updates were merged on Friday to the Linux 6.5 kernel.

Most notable with the IBM POWER updates for Linux 6.5 is adding initial support for DEXCR found with the POWER10 processors. DEXCR is short for the Dynamic Execution Control Register that allows for dynamically controlling execution behavior on a per-CPU basis. With the Dynamic Execution Control Register behavior around indirect branch target prediction and other speculation features can be changed, enabling of return-oriented-programming (ROP) protections, and other behavior can be modified via this special purpose register. With Linux 6.5 this DEXCR support allows for ROP protection instructions to be used on Power 10 hardware.


The POWER updates also include some big endian enhancements this round. The ELFv2 ABI is now the default for 64-bit big endian kernel builds and the -mprofile-kernel option for big endian ELFv2 kernels is now used.

The third notable portion of these Linux 6.5 updates are extending Kernel Concurrency Sanitizer (KCSAN) support for PowerPC 32-bit and BookE builds. Linux's Kernel Concurrency Sanitizer is a dynamic race detector that leverages compiler-based instrumentation.

More details on these updates for the Linux 6.5 kernel via this pull.
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