From 43a0d9017c380bf3320ae5cb2d62a792422b0736 Mon Sep 17 00:00:00 2001
From: Thomas Oltmann <thomas.oltmann.hhg@gmail.com>
Date: Tue, 8 Jul 2025 17:22:00 +0200
Subject: [PATCH] We have liftoff!

---
 Makefile |  2 +-
 lboot.S  | 13 ++++++++++++-
 loader.c | 24 +++++++++++++++++++-----
 3 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/Makefile b/Makefile
index e689cd0..edd51a3 100644
--- a/Makefile
+++ b/Makefile
@@ -20,4 +20,4 @@ lboot.o: lboot.S
 	$(CC) $(CFLAGS) -c -o $@ $(@:.o=.S)
 
 loader.o: loader.c bootboot.h fs.h
-	$(CC) $(CFLAGS) -m64 -Os -c -o $@ $(@:.o=.c)
+	$(CC) $(CFLAGS) -m64 -O0 -c -o $@ $(@:.o=.c)
diff --git a/lboot.S b/lboot.S
index 1759edf..5bc8a75 100644
--- a/lboot.S
+++ b/lboot.S
@@ -237,7 +237,7 @@ _pgnext:    mov         %ecx, %eax
             ret
 
             // make_heap: find a memory range suitable for heap usage
-make_heap:  mov         $bb_memmap-24, %si
+make_heap:  mov         $bb_memmap-24, %esi
 _mhnext:    add         $24, %si
             mov         $bootboot, %eax
             add         bb_size,   %eax
@@ -282,6 +282,7 @@ _mhnext:    add         $24, %si
             // If so, switch to it.
             mov         %eax, heap_ptr
             mov         %ecx, heap_end
+            mov         %esi, heap_mment
             jmp         _mhnext
 
 _mhdone:    ret
@@ -502,6 +503,7 @@ server_ip:  .space      4
 
 heap_ptr:   .long       0
 heap_end:   .long       0
+heap_mment: .long       tx_buf
 
             // Long mode initial page tables
 pd_ptr:     .long       0
@@ -524,6 +526,15 @@ trampo64:
             mov         %eax, %gs
             mov         %eax, %ss
 
+            // Remove our heap from the memory map so it doesn't get overwritten
+            mov         heap_mment, %esi
+            mov         8(%rsi), %rcx
+            add         0(%rsi), %rcx
+            mov         heap_ptr, %eax
+            sub         %rax, %rcx
+            mov         %rax, 0(%rsi)
+            mov         %rcx, 8(%rsi)
+
             // Mangle e820 memmap into bootboot's format
             mov         $bb_memmap, %rsi
             mov         $bb_memmap, %rdi
diff --git a/loader.c b/loader.c
index 47a4771..f9479e3 100644
--- a/loader.c
+++ b/loader.c
@@ -172,10 +172,9 @@ load_elf(file_t file, uintptr_t *entry)
 			if (file.size < phdr->p_offset + phdr->p_filesz) {
 				return -1;
 			}
-			panic("Loading segment");
-			memcpy((void *)ADDR_LOAD, file.ptr + phdr->p_offset, phdr->p_filesz);
+			memcpy((void *)phdr->p_vaddr, file.ptr + phdr->p_offset, phdr->p_filesz);
 			if (phdr->p_filesz < phdr->p_memsz) {
-				memset((void *)(ADDR_LOAD + phdr->p_filesz), 0, phdr->p_memsz - phdr->p_filesz);
+				memset((void *)(phdr->p_vaddr + phdr->p_filesz), 0, phdr->p_memsz - phdr->p_filesz);
 			}
 		}
 	}
@@ -207,14 +206,29 @@ alloc(BOOTBOOT *bootboot_ptr, size_t size, size_t align)
 void
 loader_main(BOOTBOOT *bootboot_ptr)
 {
+	void *backing = alloc(bootboot_ptr, MEG(2), MEG(2));
+	memset(backing, 0xAE, MEG(2));
+	uint64_t *pd  = alloc(bootboot_ptr, PAGES(1), PAGES(1));
+	memset(pd, 0, PAGES(1));
+	uint64_t *pdp = alloc(bootboot_ptr, PAGES(1), PAGES(1));
+	memset(pdp, 0, PAGES(1));
+
+	uint64_t cr3;
+	__asm__ ("mov\t%%cr3, %%rax" : "=a"(cr3));
+	uint64_t *pml4 = (uint64_t *)(cr3 & UINT64_C(-0x1000));
+
+	pml4[0x1FF] = (uint64_t)pdp | 0x3;
+	pdp [0x1FF] = (uint64_t)pd  | 0x3;
+	pd  [0x1FF] = (uint64_t)backing | 0x3 | 0x180;
+
+	memcpy((void *)ADDR_BOOTBOOT, bootboot_ptr, PAGES(1));
+
 	uint64_t entry = 0;
 	file_t elf = { (void *)bootboot_ptr->initrd_ptr, MEG(2) };
 	if (load_elf(elf, &entry) < 0) {
 		panic("panic: Malformed ELF64 executable");
 	}
 
-	alloc(bootboot_ptr, PAGES(1), PAGES(1));
-
 	uint64_t stack = 0;
 
 	__asm__ __volatile__ (