Linux Plumbers Conference 2019

Big systems are becoming more common these days. Having thousands of CPUs is
no more a dream and some applications are attempting to spread over all
these CPUs by creating threads.
This leads to contention on the mm->mmap_sem which is protecting the memory
layout shared by these threads.
There were multiple attempts to get rid of the mmap_sem's contention or the
mmap_sem itself, Speculative...

The ABI between Linux and user software mostly sits at the user/privileged boundary, although many architectures extend this with a small amount of special-case code that sits in userspace, such as in special pages or shared libraries (vDSOs) mapped into each user process [1] that user code can call into.

The reasons for this are a bit arbitrary: system interface libraries such as glibc and...

Execute only memory can protect from attacks that involve reading executable code. This feature already exists on some CPUs and is enabled for userspace.

This talk will explain how we are working on creating a virtualized “not-readable” permission bit for guest page tables for x86 and the impact to the kernel. This bit can be used to create execute-only memory for userspace programs as done...