From 517fcba43bf6f6527f4bbddd0cdc278607f18d75 Mon Sep 17 00:00:00 2001
From: Thomas Oltmann <thomas.oltmann.hhg@gmail.com>
Date: Sat, 5 Jul 2025 19:34:54 +0200
Subject: [PATCH] Alloc'ing from heap we set up.

---
 lboot.S | 30 ++++++++++++------------------
 1 file changed, 12 insertions(+), 18 deletions(-)

diff --git a/lboot.S b/lboot.S
index ce723ce..13e8255 100644
--- a/lboot.S
+++ b/lboot.S
@@ -40,8 +40,6 @@ _start:     cli
             mov         $msg_fin, %si
             call        print
 
-            // hang: sleep indefinitely
-hang:       hlt
             jmp         hang
 
 .set        COM1,       0x3F8
@@ -179,22 +177,14 @@ _mhnext:    add         $24, %si
 
 _mhdone:    ret
 
-            // alloc: take ECX bytes from usable space in memmap
+            // alloc: take ECX bytes from heap, return ptr in EAX
+            // The allocation does not get marked in the memmap.
             // No realignment is performed, so only alloc aligned sizes.
-alloc:      mov         $memmap-24, %si
-_anext:     add         $24, %si
-            cmp         memmap_end, %si // ran over end of memmap?
-            jae         _aerr
-            cmpl        $1, 16(%si)
-            jne         _anext
-            // TODO check that entry has enough space
-            cmpl        $0, 4(%si) // memory is above 4Gb?
-            jne         _aerr
-            mov         0(%si), %eax
-            addl        %ecx, 0(%si)
-            adcl        $0, 4(%si)
-            subl        %ecx, 8(%si)
-            sbbl        $0, 12(%si)
+alloc:      cmp         heap_size, %ecx
+            ja          _aerr
+            mov         heap_start, %eax
+            add         %ecx, heap_start
+            sub         %ecx, heap_size
             ret
 _aerr:      mov         $msg_aerr, %si
             call        print
@@ -247,6 +237,10 @@ gdt:        // entry 0: null descriptor
 gdt_ptr:    .word       gdt_size-1
             .long       gdt
 
+            // hang: sleep indefinitely
+hang:       hlt
+            jmp         hang
+
             // Messages to print
 msg_start:  .asciz      "Netboot via fernlader v1 ...\r\n"
 msg_a20:    .asciz      " * Enabling A20\r\n"
@@ -255,7 +249,7 @@ msg_getmap: .asciz      " * Memory Map\r\n"
 msg_mkheap: .asciz      " * Making Space\r\n"
 msg_paging: .asciz      " * Paging\r\n"
 msg_fin:    .asciz      "Finished.\r\n"
-msg_aerr:   .asciz      "panic: Unable to allocate memory.\r\n"
+msg_aerr:   .asciz      "panic: Out of heap space.\r\n"
 
 heap_start: .long       0
 heap_size:  .long       0