libnbd VS safeclib

Below is the small framework we use to fuzz a network client. It works by creating a Unix socket, forking, then having the client (under test) on one side of the socket and a small loop which reads the input file into the socket on the other side.

https://gitlab.com/nbdkit/libnbd/-/tree/master/fuzzing

We did a bunch of benchmarking around this when writing nbdcopy (https://gitlab.com/nbdkit/libnbd/-/tree/master/copy) which can copy file to file as well as between local files and NBD servers. There was also the goal to avoid polluting the page cache, which depending on if you're going to use the file content immediately afterwards or not matters.

Anyway long story short, the best thing we found (for Linux) was Linus's own advice linked from here: https://stackoverflow.com/a/3756466

Of course assembler spezializations are an anti-pattern, because the optimizer should be fixed to do it much better. Better C code is often 2x faster than hand optimized assembler.

Eg my C memcpy with inlined and vectorized clang beats glibc or gcc memcpy in assembler easily. https://github.com/rurban/safeclib/blob/master/tests/perf_me...

+1 This along with https://github.com/rurban/safeclib (and its forks/derivatives).

I have yet to look into Annex K. It didn't seem to gain much traction. Some people at Red Hat wrote a field experience report about it. I recently discovered an implementation of Annex K functions that claims to be pretty portable, safeclib.

See my testsuite and remarks at https://github.com/rurban/safeclib/blob/master/doc/libc-overview.md , esp. towards the windows implementation

I do it because nobody else implemented a secure memset. What they call secure is just avoiding that the compiler ignores it. A secure memset also cleans the caches with a memory barrier, so that meltdown cannot read it.

explicit_bzero and it's numerous variants are not only insecure, but also slow. (byte wise!)

Only safelibc has a secure memset_s. https://github.com/rurban/safeclib/blob/master/tests/perf_me...