From 5fab4ba6c34c33e9d7026dbea12cbfd68beb2373 Mon Sep 17 00:00:00 2001
From: Thomas Oltmann <thomas.oltmann.hhg@gmail.com>
Date: Tue, 8 Jul 2025 15:59:52 +0200
Subject: [PATCH] Alloc'ing from the memory map

---
 lboot.S  |  9 +++------
 loader.c | 21 +++++++++++++++++----
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/lboot.S b/lboot.S
index 870d664..1759edf 100644
--- a/lboot.S
+++ b/lboot.S
@@ -108,7 +108,7 @@ _start:     cli
             call        print
             mov         $fn_initrd, %esi
             call        read_file
-            mov         %ebx, initrd_ptr
+            mov         %ebx, bb_ird_ptr
 
             mov         $msg_long, %si
             call        print
@@ -503,8 +503,6 @@ server_ip:  .space      4
 heap_ptr:   .long       0
 heap_end:   .long       0
 
-initrd_ptr: .long       0
-
             // Long mode initial page tables
 pd_ptr:     .long       0
 pdp_ptr:    .long       0
@@ -541,8 +539,8 @@ trampo64:
             mov         $2, %ebx
 2:          mov         type_table(%rbx), %bl
 
-            and         $-16, %rax
-            or          %rbx, %rax
+            and         $-16, %rcx
+            or          %rbx, %rcx
 
             mov         %rax, 0(%rdi)
             mov         %rcx, 8(%rdi)
@@ -568,7 +566,6 @@ type_table: .byte       0
             // ToDo List:
             // - Sorting the memmap
             // - Sanitizing the memmap
-            // - Translating the memmap to bootboot format
             // - Parsing a config file
 
 .section .data.bootboot
diff --git a/loader.c b/loader.c
index b482ccb..47a4771 100644
--- a/loader.c
+++ b/loader.c
@@ -185,13 +185,24 @@ load_elf(file_t file, uintptr_t *entry)
 	return 0;
 }
 
-/*
 static void *
-alloc(size_t size, size_t align)
+alloc(BOOTBOOT *bootboot_ptr, size_t size, size_t align)
 {
-
+	MMapEnt *mmap_end = (MMapEnt *)((char *)bootboot_ptr + bootboot_ptr->size);
+	for (MMapEnt *ent = &bootboot_ptr->mmap; ent < mmap_end; ent++) {
+		if (!MMapEnt_IsFree(ent)) continue;
+		int64_t mstart = MMapEnt_Ptr(ent);
+		int64_t msize  = MMapEnt_Size(ent);
+		int64_t mend   = mstart + msize;
+		mend -= size;
+		mend &= -align;
+		if (mend < mstart) continue;
+		ent->size = ((mend - mstart) & INT64_C(-16)) | MMAP_FREE;
+		return (void *)mend;
+	}
+	panic("panic: Could not allocate from memory map.");
+	return NULL;
 }
-*/
 
 void
 loader_main(BOOTBOOT *bootboot_ptr)
@@ -202,6 +213,8 @@ loader_main(BOOTBOOT *bootboot_ptr)
 		panic("panic: Malformed ELF64 executable");
 	}
 
+	alloc(bootboot_ptr, PAGES(1), PAGES(1));
+
 	uint64_t stack = 0;
 
 	__asm__ __volatile__ (