August 19-21 - Co-Located Events
August 21-23 - Conference
Hilton San Diego Bayfront - San Diego, CA
More information for Open Source Summit + Embedded Linux Conference North America 2019
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Wednesday, August 21 • 11:30am - 12:05pm
The Problems Emulating a Call via Breakpoint in the Kernel - Steven Rostedt, VMware*

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The Linux kernel is the lowest layer of software (above BIOS) and that requires it to be as efficient as possible. Recent hardware issues have arisen (Spectre and Meltdown) that caused the Linux kernel to have to take measures to protect itself, but these measures have also had significant impact to performance. One solution was the addition of retpolines, but these slow down indirect calls, which is highly used by trace events. Work has been started to create dynamic call sites in the kernel to handle these cases. But to make these modifications, breakpoints must be used, and emulating calls from breakpoints has various issues. This talk will describe retpolines, why dynamic call sites help, and explain the issues as well as various solutions (spoiler, they all suck) to emulating calls with breakpoints. The same issue has recently come up with handling function tracing and live kernel patching, and those will also be explained. Come to this talk to get a good idea of why most kernel developers have gray hair.

avatar for Steven Rostedt

Steven Rostedt

Open Source Engineer, VMWare, Inc.
Steven has been working on the Linux kernel since 1998 (started while working on his masters). He has been working on the Linux kernel professionally since 2001. Steven is one of the original developers of the PREEMPT_RT patch which turns Linux into a true real-time operating system... Read More →

Wednesday August 21, 2019 11:30am - 12:05pm PDT
Indigo H
  Linux Systems
  • Session Slides Included Yes