SoylentNews

The Mighty Buzzard writes:

So, it appears Microsoft is serious about this whole running Linux binaries on Windows. They've been shy on the details up until now but that's apparently ending [microsoft.com]:

We recently announced Bash on Ubuntu on Windows which enables native Linux ELF64 binaries to run on Windows via the Windows Subsystem for Linux (WSL). This subsystem was created by the Microsoft Windows Kernel team and has generated a lot of excitement. One of the most frequent question we get asked is how is this approach different from a traditional virtual machine. In this first of a series of blog posts, we will provide an overview of WSL that will answer that and other common questions. In future posts we will dive deep into the component areas introduced.

Since its inception, Microsoft Windows NT was designed to allow environment subsystems like Win32 to present a programmatic interface to applications without being tied to implementation details inside the kernel. This allowed the NT kernel to support POSIX, OS/2 and Win32 subsystems at its initial release.

Early subsystems were implemented as user mode modules that issued appropriate NT system calls based on the API they presented to applications for that subsystem. All applications were PE/COFF executables, a set of libraries and services to implement the subsystem API and NTDLL to perform the NT system call. When a user mode application got launched the loader invoked the right subsystem to satisfy the application dependencies based on the executable header.

Later versions of subsystems replaced the POSIX layer to provide the Subsystem for Unix-based Applications (SUA). This composed of user mode components to satisfy:

1. Process and signal management
2. Terminal management
3. System service requests and inter process communication

The primary role of SUA was to encourage applications to get ported to Windows without significant rewrites. This was achieved by implementing the POSIX user mode APIs using NT constructs. Given that these components were constructed in user mode, it was difficult to have semantic and performance parity for kernel mode system calls like fork(). Because this model relied on the need for programs to be recompiled it required ongoing feature porting and was a maintenance burden.

Over time these initial subsystems were retired. However, since the Windows NT Kernel was architected to allow new subsystem environments, we were able to use the initial investments made in this area and broaden them to develop the Windows Subsystem for Linux.

They go on into a little bit more depth in TFA if your employer hasn't blocked microsoft.com subdomains on principle.

Original Submission