Created vondehi (markdown)

explain/vondehi.md

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+## vondehi
+
+Vondehi is an in-memory unpacker for data compressed with `gzip` or `xz` (or
+`xz` in LZMA1-mode). It basically performs these steps:
+
+1. Set up a memfd using the `memfd_create` syscall. This file descriptor works
+   like a regular file, except the backing storage is RAM.
+2. Fork, pipe the payload data to `zcat` or `xzcat`, which outputs everything
+   to teh memfd from step 1.
+3. Run `execveat` on the memfd.
+
+Of course, the code itself is hand-optimized x86 assembly, and is very crazy.