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#include "kernel/prelude/kernel_prelude.hats"
#define ATS_DYNLOADFLAG 0
staload BOOT = "kernel/bootinfo/multiboot.sats"
staload "./frame.sats"
staload "lib/SATS/init.sats"
staload "lib/DATS/init.dats"
staload UN = "prelude/SATS/unsafe.sats"
implement containing_address(address) =
@{
counter = $UN.cast{size_t}(address) / i2sz(PAGE_SIZE)
}
fn containing_area(area : $BOOT.memory_area_t) :<> frame_t = containing_address(ptr_add<uint8>(area.base_addr,area.length - i2sz(1)))
//FIX: function doesn't handle no frames left
fn choose_next_area(allocator : &frame_allocator_t) :<!wrt,!ref> void = let
val length = g1ofg0($BOOT.get_memory_mappings_n())
val next_free_frame = allocator.next_free_frame
fun loop {n,i : nat | i < n} .<n-i>. ( i : size_t i, n : size_t n) :<!ref> $BOOT.memory_area_t = let
val entry = $BOOT.get_memory_mapping(i)
val fr = containing_area(entry)
in
if (entry.type = 1 && fr.num >= next_free_frame.num) then
entry
else if (i < n-1) then
loop (succ(i),n)
else
entry //TODO: fix
end
in
if (length > 0) then //TODO: fix
allocator.current_area := loop(i2sz(0), length);
if (allocator.current_area.length > 1) then
let
val start_frame = containing_address(allocator.current_area.base_addr)
in
if (allocator.next_free_frame.num < start_frame.num) then
allocator.next_free_frame := start_frame
end
end
local
// Private function
extern fn _allocate_frame(allocator: &frame_allocator_t):<!wrt,!ref> frame_t
in
local
// Static variable
var _v : frame_allocator_t?
prval () = opt_none _v
var v = uninitialized<frame_allocator_t>(_v)
// Reference to allocator
val allocator_ref = ref_make_viewptr{initializable frame_allocator_t} (view@v | addr@v)
in
implement init(kernel_start, kernel_end, multiboot_start, multiboot_end) = let
val allocator = @{
next_free_frame = containing_address(the_null_ptr),
current_area = $BOOT.invalid_area,
kernel_start = containing_address(kernel_start),
kernel_end = containing_address(kernel_end),
multiboot_start = containing_address(multiboot_start),
multiboot_end = containing_address(multiboot_end)
} : frame_allocator_t
implement initialize$fwork<frame_allocator_t>(v) = (
v := allocator;
$effmask_ref(choose_next_area(v));
let prval () = opt_some v in true end
)
in
initialize<frame_allocator_t>(allocator_ref)
end
implement allocate_frame(): frame_t = let
implement exec$fwork<frame_allocator_t><frame_t>(v) = $effmask_ref(_allocate_frame(v))
in
exec<frame_allocator_t><frame_t>(allocator_ref)
end
end
implement _allocate_frame(allocator) : frame_t =
if (allocator.current_area.type != 0u) then
let
val area = allocator.current_area
val frame = @{ num = allocator.next_free_frame.num }
// last frame of current area
val last_frame_area = containing_area(area)
in
if (frame.num > last_frame_area.num) then (
// all frames of current area are used, switch to next area
choose_next_area(allocator);
_allocate_frame(allocator)
) else if (frame.num >= allocator.kernel_start.num && frame.num <= allocator.kernel_end.num) then (
// frame is used by kernel
allocator.next_free_frame := @{num = allocator.kernel_end.num + 1};
_allocate_frame(allocator)
) else if (frame.num >= allocator.multiboot_start.num && frame.num <= allocator.multiboot_end.num) then (
// frame is used by multiboot info structure
allocator.next_free_frame := @{num = allocator.multiboot_end.num + 1};
_allocate_frame(allocator)
) else (
// frame is unused, increment `next_free_frame` and return it
allocator.next_free_frame.num := succ(allocator.next_free_frame.num);
frame
);
end
else
@{num = i2sz(0)} // No free frames left
end
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