[docs] Update the README with roadmap info

README.md

@@ -1,10 +1,10 @@
 ![jsix](assets/jsix.svg)
 
-# jsix: A hobby operating system
+# The jsix operating system
 
-**jsix** is the hobby operating system that I am currently building. It's far
-from finished, or even being usable. Instead, it's a sandbox for me to play
-with kernel-level code and explore architectures.
+**jsix** is a custom multi-core x64 operating system that I am building from
+scratch. It's far from finished, or even being usable - see the *Status and
+Roadmap* section, below.
 
 The design goals of the project are:
 
@@ -23,9 +23,8 @@ The design goals of the project are:
   by the traditional microkernel problems.
 
 * Exploration - I'm really mostly doing this to have fun learning and exploring
-  modern OS development. Modular design may be tossed out (hopefully
-  temporarily) in some places to allow me to play around with the related
-  hardware.
+  modern OS development. Initial feature implementations may temporarily throw
+  away modular design to allow for exploration of the related hardware.
 
 A note on the name: This kernel was originally named Popcorn, but I have since
 discovered that the Popcorn Linux project is also developing a kernel with that
@@ -35,6 +34,67 @@ and my wonderful wife.
 
 [cpu_features]: https://github.com/justinian/jsix/blob/master/src/libraries/cpu/include/cpu/features.inc
 
+## Status and Roadmap
+
+The following major feature areas are targets for jsix development:
+
+#### UEFI boot loader
+
+_Done._ The bootloader loads the kernel and initial userspace programs, and
+sets up necessary kernel arguments about the memory map and EFI GOP
+framebuffer. Possible future ideas:
+
+- take over more init-time functions from the kernel
+- rewrite it in Zig
+
+#### Memory
+
+_Virtual memory: Sufficient._ The kernel manages virtual memory with a number
+of kinds of `vm_area` objects representing mapped areas, which can belong to
+one or more `vm_space` objects which represent a whole virtual memory space.
+(Each process has a `vm_space`, and so does the kernel itself.)
+
+Remaining to do:
+
+- TLB shootdowns
+- Page swapping
+
+_Physical page allocation: Sufficient._ The current physical page allocator
+implementation suses a group of block representing up-to-1GiB areas of usable
+memory as defined by the bootloader. Each block has a three-level bitmap
+denoting free/used pages.
+
+#### Multitasking
+
+_Sufficient._ The global scheduler object keeps separate ready/blocked lists
+per core. Cores periodically attempt to balance load via work stealing.
+
+User-space tasks are able to create threads as well as other processes.
+
+Several kernel-only tasks exist, though I'm trying to reduce that. Eventually
+only the timekeeping task should be a separate kernel-only thread.
+
+#### API
+
+_In progress._ User-space tasks are able to make syscalls to the kernel via
+fast SYSCALL/SYSRET instructions.
+
+Major tasks still to do:
+
+- The process initialization protocol needs to be re-built entirely.
+- Processes' handles to kernel objects need the ability to check capabilities
+
+#### Hardware Support
+
+  * Framebuffer driver: _In progress._ Currently on machines with a video
+	device accessible by UEFI, jsix starts a user-space framebuffer driver that
+	only prints out kernel logs.
+  * Serial driver: _To do._ Machines without a video device should have a
+	user-space log output task like the framebuffer driver, but currently this
+	is done inside the kernel.
+  * USB driver: _To do_
+  * AHCI (SATA) driver: _To do_
+
 ## Building
 
 jsix uses the [Ninja][] build tool, and generates the build files for it with a