diff --git a/doc/building.9 b/doc/building.9
index 583b981..d19b224 100644
--- a/doc/building.9
+++ b/doc/building.9
@@ -1,6 +1,8 @@
-.TH building 9 "18 February 2021" "1" "Building the kernel"
+.TH building 9 "13 March 2021" "1" "Building the kernel"
 .SH SYNOPSIS
-Use the Makefile in /src to build the kernel.
+Bluejay uses the JMK build system, a simple M4 script that generates Makefiles.
+Use the jmk binary in bin/ to generate Makefiles, then build the kernel with the
+Makefile in src/kernel/.
 .SH DESCRIPTION
 The included Makefile provides several targets useful for building and
 debugging the kernel.  Here are the useful targets:
@@ -16,3 +18,5 @@
 qemu-iso:    boot the iso file
 
 clean:       delete build artifacts
+.SH SEE ALSO
+jmk(1)
diff --git a/doc/jmk.1 b/doc/jmk.1
new file mode 100644
index 0000000..b33bd89
--- /dev/null
+++ b/doc/jmk.1
@@ -0,0 +1,6 @@
+.TH jmk 1 "13 March 2021" "1" "JMK build system"
+.SH SYNOPSIS
+JMK -- Build system for Bluejay
+.SH DESCRIPTION
+When run, JMK will search all subdirectories for files named "Jmk" and will
+process them to create a Makefile in the same directory.
diff --git a/doc/jmk.5 b/doc/jmk.5
new file mode 100644
index 0000000..0262ba0
--- /dev/null
+++ b/doc/jmk.5
@@ -0,0 +1,174 @@
+.TH jmk 5 "13 March 2021" "1" "JMK format"
+.SH SYNOPSIS
+The JMK format is processed by jmk(1) to generate a Makefile.
+.SH DESCRIPTION
+jmk(1) is a simple M4 script which provides a handful of macros.
+These macros can be used to automate many tedious parts of creating
+makefiles.
+.SH OVERVIEW
+The following macros are provided by JMK:
+
+.B
+init(project, [target])
+.NB
+.RS
+Initialize the project named <project> to build the target <target>.
+If <target> is not provided, it defaults to <project>.
+.B
+Example:
+.NB
+
+.EX
+init(kernel, kernel.elf)
+# or
+init(my_lib, my_lib.a)
+.EE
+.RE
+
+.B
+preset(preset_name)
+.NB
+.RS
+Apply a preset to the project.
+Currently the following presets are available:
+
+freestanding: Applies CFLAGS suitable for freestanding targets.
+
+optimize: Applies -O2 optimization level
+
+debug: Applies -g
+
+32: Sets target architecture to 32 bit
+
+warn: Enables all warnings except unused-function and unused-variable.
+
+nasm: Forces the assembler to be nasm.
+
+.B
+Example:
+.NB
+
+.EX
+preset(32)
+preset(debug)
+CFLAGS += -my-flag
+.EE
+.RE
+
+.B
+archetype(archetype_name)
+.NB
+.RS
+Applies a given archetype to the project.
+An archetype provides support to compile a certain language or type of program.
+The two archetypes available by default are
+.B
+c
+.NB
+and
+.B
+asm,
+.NB
+whose meanings are self explanatory.
+.B
+Example:
+.NB
+
+.EX
+archetype(c)
+archetype(asm)
+.EE
+.RE
+
+.B
+depends(name, directory, [target])
+.NB
+.RS
+Register the target called <target> located in <directory> as a dependency named <name>.
+By default, <target> is set to the last segment of the directory path plus .a.
+E.g.: for foo/bar <target> would be bar.a by default.
+This is usually used in conjunction with lib().
+
+Internally this will generate a target for this library that will call make on the
+other project in order to build the target.
+See lib() for examples.
+.RE
+
+.B
+lib(dependency_name)
+.NB
+.RS
+Lib expands to the path to the dependency called <dependency_name> as defined by depends().
+This can, for example, be used in OBJECTS to specify the project's dependency on another
+(sub)project, or it can be used anywhere you would need to refer to the path of the
+target generated by that project.
+Despite the name, lib can be used for any type of dependency, not just for libraries.
+.B
+Example:
+.NB
+
+.EX
+depends(libc, $(ROOT)/src/libc, libc.a)
+OBJECTS = main.o lib(libc)
+.EE
+.RE
+
+.B
+phony(target)
+.NB
+.RS
+Adds <target> to the list of .PHONY targets.
+.RE
+
+.B
+type(type)
+.NB
+.RS
+Sets the project type and generates the actual target for the project.
+If you need to build your final target in a way unsupported by default, feel free to omit
+this and write the target by hand. <type> can be one of executable, static_lib or
+custom_link.
+The first two cases will build an executable and library respectively, using $(CC) and ar.
+custom_link will invoke $(LD), passing LDFLAGS.
+
+Note that the objects to include in the target are to be specified in OBJECTS,
+and should be built either automatically by an included archetype, or manually.
+.RE
+
+.B
+finish
+.NB
+.RS
+Include this at the end of every Jmk file, this generates some targets like .PHONY
+and clean, as well as setting up automatic Makefile regeneration.
+.RE
+
+.SH EXAMPLE
+Here is a full example of a JMK project:
+
+.EX
+init(kernel, kernel.elf)
+
+preset(freestanding)
+preset(optimize)
+preset(32)
+preset(nasm)
+
+LDFLAGS += -Tlink.ld
+
+archetype(c)
+archetype(asm)
+
+depends(some_driver, dri/some/driver/, driver.a)
+
+OBJECTS = boot.o main.o other.o something.o lib(some_driver)
+
+type(custom_link)
+
+qemu: kernel.elf
+    qemu-system-i386 $<
+
+finish
+.EE
+.SH SEE ALSO
+jmk(1), building(9)