Linux 3.17 Lands Memfd, A KDBUS Prerequisite
Written by Michael Larabel in Linux Kernel on 19 August 2014 at 04:54 PM EDT. 16 Comments
There's many new features to Linux 3.17 that were covered over the past two weeks on Phoronix. One of the merged Linux 3.17 features that went under our radar at the time was the new memfd syscall was merged, which is a requirement of the forthcoming KDBUS, the kernel-based D-Bus implementation sought after by the systemd crew.

Memfd is a mechanism similar to Android's Ashmem that allows zero-copy message passing in KDBUS. Memfd effectively comes down to just a chunk of memory with a file descriptor attached that can be passed to mmap(). The memfd_create() function returns a raw shmem file and there's optional support for sealing.

Memfd is needed by KDBUS for message passing and now the code -- after being public but out-of-tree for several months -- is finally mainline. As a result, the KDBUS code has been updated to take advantage of the mainline Linux 3.17 state.

While KDBUS wasn't merged for Linux 3.17, it seems to be getting closer to being in shape for merging. At the start of the year the developers expressed a goal of mainlining KDBUS in 2014 and now their next opportunity would be Linux 3.18 otherwise Linux 3.19 would be cutting it close to the end of the year.

Those wishing to checkout the latest KDBUS code can find it via Greg KH's GitHub.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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