This is done without using Microsoft's internal APIs. MAP_PRIVATE
mappings are copied to the subprocess via a pipe, since Microsoft
doesn't want us to have proper COW pages. MAP_SHARED mappings are
remapped without needing to do any copying. Global variables need
copying along with the stack and the whole heap of anonymous mem.
This actually improves the reliability of the redbean http server
although one shouldn't expect 10k+ connections on a home computer
that isn't running software built to serve like Linux or FreeBSD.
This is a recently introduced Linux Kernel feature that gives people
like Debian package mantainers the power to arbitrarily redefine how
executables are interpreted by the kernel. If your system gets tuned
this way and you're not able to disable it, then you need to restore
default behavior for the APE MZqFpD prefix as follows:
sudo sh -c "echo ':APE:M::MZqFpD::/bin/sh:' >/proc/sys/fs/binfmt_misc/register"
This prefix will cover all .com executables built with this tooling.
Please don't run the above command unless you're certain you need it.
See #2 for additional context.
I wanted a tiny scriptable meltdown proof way to run userspace programs
and visualize how program execution impacts memory. It helps to explain
how things like Actually Portable Executable works. It can show you how
the GCC generated code is going about manipulating matrices and more. I
didn't feel fully comfortable with Qemu and Bochs because I'm not smart
enough to understand them. I wanted something like gVisor but with much
stronger levels of assurances. I wanted a single binary that'll run, on
all major operating systems with an embedded GPL barrier ZIP filesystem
that is tiny enough to transpile to JavaScript and run in browsers too.
https://justine.storage.googleapis.com/emulator625.mp4
Justine Tunney