1 files changed, 34 insertions, 0 deletions
diff --git a/boot/heap.zig b/boot/heap.zig
new file mode 100644
index 0000000..2f4e74b
--- /dev/null
+++ b/boot/heap.zig
@@ -0,0 +1,34 @@
+// this just grabs a contiguous chunk of frams from the PMM and then
+// hands out a bump allocator, this just gives std.mem.Allocator which
+// we'll pass to the revo VM later. FixedBufferAllocator never reclaims
+// freed space unless you free in reverse order which is ehhhhh, fine ig
+// for bootstrapping.
+//
+// TODO: swap fixed buffer allocator for a free list allocator
+
+const std = @import("std");
+const pmm = @import("pmm.zig");
+const serial = @import("serial.zig");
+
+// 4 MiB. 
+// NOTE: bump if the VM needs more
+const HEAP_PAGES: usize = 1024;
+
+var fba: std.heap.FixedBufferAllocator = undefined;
+
+pub fn init() void {
+    const phys = pmm.allocContig(HEAP_PAGES) orelse @panic("heap: no contiguous frames for the heap");
+    const virt = pmm.physToVirt(phys);
+    const buf: [*]u8 = @ptrFromInt(virt);
+    fba = std.heap.FixedBufferAllocator.init(buf[0 .. HEAP_PAGES * pmm.PAGE_SIZE]);
+
+    serial.write("heap: ");
+    serial.writeDec((HEAP_PAGES * pmm.PAGE_SIZE) / (1024 * 1024));
+    serial.write(" MiB at ");
+    serial.writeHex(virt);
+    serial.write("\r\n");
+}
+
+pub fn allocator() std.mem.Allocator {
+    return fba.allocator();
+}