From 4e8de774ef76caed41dffa19de0e90f1ec356534 Mon Sep 17 00:00:00 2001
From: slinky55 <lbmason55@gmail.com>
Date: Sat, 13 Jun 2026 20:43:09 -0400
Subject: [PATCH] started work on pmm

---
 kernel/common_stubs.S | 17 ++++++++++++++++-
 kernel/interrupts.c   |  2 +-
 kernel/kmain.c        |  4 ++++
 kernel/memory/mm.c    | 37 +++++++++++++++++++++++++++++++++++++
 kernel/multiboot.h    | 29 +++++++++++++++++++++++++++++
 5 files changed, 87 insertions(+), 2 deletions(-)
 create mode 100644 kernel/memory/mm.c
 create mode 100644 kernel/multiboot.h

diff --git a/kernel/common_stubs.S b/kernel/common_stubs.S
index 5370460..ace90d6 100644
--- a/kernel/common_stubs.S
+++ b/kernel/common_stubs.S
@@ -1,4 +1,9 @@
 .code32 
+.section .text 
+.global disable_interrupts
+disable_interrupts:
+    cli 
+    ret
 
 .global enable_interrupts
 enable_interrupts:
@@ -8,4 +13,14 @@ enable_interrupts:
 .global io_wait 
 io_wait:
     outb %al, $0x80
-    ret
\ No newline at end of file
+    ret
+
+.global load_grub_boot_struct
+load_grub_boot_struct:
+    mov %ebx, grub_boot_struct_ptr
+
+.section .bss
+.align 4
+.global grub_boot_struct_ptr 
+grub_boot_struct_ptr:
+    .int 0
\ No newline at end of file
diff --git a/kernel/interrupts.c b/kernel/interrupts.c
index 58a508f..d3310ca 100644
--- a/kernel/interrupts.c
+++ b/kernel/interrupts.c
@@ -21,7 +21,7 @@ const char* err_messages[32] = {
     [0] = "Divide by 0",
     [1] = "",
     [8] = "",
-    [13] = "General Protection Fault",a->i
+    [13] = "General Protection Fault",
     [14] = "Page Fault",
 };
 
diff --git a/kernel/kmain.c b/kernel/kmain.c
index 3259920..681ed39 100644
--- a/kernel/kmain.c
+++ b/kernel/kmain.c
@@ -12,6 +12,10 @@ extern void init_pit();
 extern int init_ps2();
 extern void enable_interrupts();
 
+extern void load_grub_boot_struct(void);
+
+extern void* grub_boot_struct_ptr;
+
 void kmain(void) 
 {
   extern print_stream_t vga_print_stream;
diff --git a/kernel/memory/mm.c b/kernel/memory/mm.c
new file mode 100644
index 0000000..6b2114b
--- /dev/null
+++ b/kernel/memory/mm.c
@@ -0,0 +1,37 @@
+#include "multiboot.h"
+
+static uint32_t max_address = 0;
+static uint32_t total_available_memory = 0;
+
+void parse_mmap(void* base, uint32_t limit) {
+    multiboot_mmap_entry* entry = (multiboot_mmap_entry*)base;
+    void* end = (void*)((uint32_t)base + limit);
+
+    while ((void*)entry < end) {
+        if (entry->type == 1) {
+            uint32_t region_start = (uint32_t)(entry->addr);
+            uint32_t region_end = (uint32_t)(entry->addr + entry->len);
+            if (region_end > max_address) {
+                max_address = region_end;
+            }
+
+            total_available_memory += entry->len;
+
+            // start breaking up the address range
+            // if it's safe (not kernel, not BIOS structures, etc..), find the corresponding page in our PMM, mark it free
+            // need to align start and end to 4kb
+            if (entry->len < 4096) {
+                continue;
+            }
+
+            for (uint32_t addr = region_start; addr < region_end; addr += 4096) {
+                // check for physical kernel address range 
+
+                // check if this address range contains our multiboot structure
+
+                // don't allow pages under 1MB
+            }
+        }
+        entry = (multiboot_mmap_entry*)((uint32_t)entry + entry->size + sizeof(entry->size));
+    }
+}
\ No newline at end of file
diff --git a/kernel/multiboot.h b/kernel/multiboot.h
new file mode 100644
index 0000000..3d39f3d
--- /dev/null
+++ b/kernel/multiboot.h
@@ -0,0 +1,29 @@
+#ifndef KMULTIBOOT_H
+#define KMULTIBOOT_H
+
+#include <stdint.h>
+
+typedef struct  {
+    uint32_t flags;
+    uint32_t mem_lower;
+    uint32_t mem_upper;
+    uint32_t boot_device;
+    uint32_t cmdline;
+    uint32_t mods_count;
+    uint32_t mods_addr;
+    uint32_t num;
+    uint32_t size;
+    uint32_t addr;
+    uint32_t shndx;
+    uint32_t mmap_length;
+    uint32_t mmap_addr; 
+} multiboot_info;
+
+typedef struct __attribute__((packed)) {
+    uint32_t size;
+    uint64_t addr;  
+    uint64_t len;    
+    uint32_t type;
+} multiboot_mmap_entry;
+
+#endif
\ No newline at end of file