page table something idk i'm tired

Makefile

@@ -22,7 +22,7 @@ clean:
 run: $(final) $(iso)
 	@qemu-system-$(arch) -bios $(efi_bios) -cdrom $(iso) \
 -chardev stdio,id=char0,mux=on,logfile=serial.log,signal=off \
-  -serial chardev:char0 -mon chardev=char0
+  -serial chardev:char0 -mon chardev=char0 -m 512M
 
 quick_invalidate:
 	@echo "quick invalidation"

arch/x86_64/linker.ld

@@ -11,6 +11,16 @@ SECTIONS {
 
     .text :
     {
-        *(.text)
+        *(.text .text.*)
+    }
+
+    .rodata :
+    {
+        *(.rodata .rodata.*)
+    }
+
+    .data.rel.ro :
+    {
+        *(.data.rel.ro.local*) *(.data.rel.ro .data.rel.ro.*)
     }
 }

serial.log

@@ -6,19 +6,11 @@ BdsDxe: starting Boot0001 "UEFI QEMU DVD-ROM QM00003 " from PciRoot(0x0)/Pci(0x1
 
 
WARNING: no console will be available to OS
 
error: no suitable video mode found.
-
hello from wukkOS!
+
using serial port 0 as console
+
 
 
 welcome to wukkOS!
 (c) 2022 Real Microsoft, LLC
 initialising memory maps...[OK]
-memory map:
-0 - a0000 : available
-100000 - 800000 : available
-800000 - 808000 : reserved for hibernation
-808000 - 80b000 : available
-80b000 - 80c000 : reserved for hibernation
-80c000 - 810000 : available
-810000 - 900000 : reserved for hibernation
-900000 - 78ef000 : available
-78ef000 - 79ef000 : reserved
+L4 entry 0: PageTableEntry { addr: PhysAddr(0x128000), flags: PRESENT | WRITABLE | ACCESSED }

src/boot/mod.rs

@@ -5,17 +5,31 @@ use crate::KernelArgs;
 use multiboot2::{load, MemoryMapTag, BootInformation};
 
 pub struct KernelInfo {
+    kernel_start: u64,
+    kernel_end: u64,
+    safe_mem_start: u64,
     #[cfg(feature = "f_multiboot2")]
     boot_info: BootInformation,
 }
 
 impl KernelInfo {
     pub fn init_from_kernel_args(args: KernelArgs) -> Self {
-        let mut kernel_info = KernelInfo {
-            #[cfg(feature = "f_multiboot2")]
-            boot_info: unsafe { load(args.multiboot_information_address).expect("ERR ARGS BAD!") },
-        };
-        kernel_info
+        #[cfg(feature = "f_multiboot2")]
+        {
+            let boot_info = unsafe { load(args.multiboot_information_address) }.expect("failed to load multiboot2 information");
+            let elf_sections = boot_info.elf_sections_tag().expect("no elf sections tag");
+            let kernel_start = elf_sections.sections().map(|s| s.start_address()).min().unwrap();
+            let kernel_end = elf_sections.sections().map(|s| s.end_address()).max().unwrap();
+            // get end of multiboot for safe memory
+            let safe_mem_start = boot_info.start_address() + boot_info.total_size();
+            let kernel_info = KernelInfo {
+                kernel_start,
+                kernel_end,
+                safe_mem_start: safe_mem_start as u64,
+                boot_info,
+            };
+            kernel_info
+        }
     }
 
     #[cfg(feature = "f_multiboot2")]
@@ -23,4 +37,8 @@ impl KernelInfo {
         let mm_tag = self.boot_info.memory_map_tag().expect("ERR NO MEM MAP TAG!");
         mm_tag.all_memory_areas()
     }
+
+    pub fn is_safe_memory(&self, addr: u64) -> bool {
+        addr >= self.safe_mem_start && addr >= self.kernel_end
+    }
 }

src/lib.rs

@@ -11,8 +11,10 @@ use lazy_static::lazy_static;
 use core::panic::PanicInfo;
 use multiboot2::MemoryAreaType;
 use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
+use x86_64::VirtAddr;
 use crate::boot::KernelInfo;
 use crate::internals::WhyDoTheyCallItOvenWhenYouOfInTheColdFoodOfOutHotEatTheFood::*;
+use crate::memory::active_level_4_table;
 use crate::serial::terminal::ST;
 
 mod font;
@@ -78,6 +80,7 @@ pub extern fn kernel_main(args: KernelArgs) -> ! {
     if let Some(i) = console_port {
         let port = &serial_ports.ports[i];
         ST.init_from_port(*port);
+        println!("using serial port {} as console", i);
     }
 
 
@@ -90,15 +93,12 @@ pub extern fn kernel_main(args: KernelArgs) -> ! {
     let kern_info = KernelInfo::init_from_kernel_args(args);
     let mut mem_areas = kern_info.memory_areas();
     println!("[OK]");
-    println!("memory map:");
-    while let Some(area) = mem_areas.next() {
-        println!("{:x} - {:x} : {}", area.start_address(), area.end_address(), match area.typ() {
-            MemoryAreaType::Available => "available",
-            MemoryAreaType::Reserved => "reserved",
-            MemoryAreaType::AcpiAvailable => "ACPI available",
-            MemoryAreaType::ReservedHibernate => "reserved for hibernation",
-            MemoryAreaType::Defective => "defective",
-        });
+    let l4_table = active_level_4_table(VirtAddr::new(0));
+
+    for (i, entry) in l4_table.iter().enumerate() {
+        if !entry.is_unused() {
+            println!("L4 entry {}: {:?}", i, entry);
+        }
     }
 
     loop {}

src/memory/mod.rs

@@ -0,0 +1,15 @@
+use x86_64::registers::control::Cr3;
+use x86_64::structures::paging::PageTable;
+use x86_64::VirtAddr;
+
+pub fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut PageTable {
+    use x86_64::registers::control::Cr3;
+
+    let (level_4_table_frame, _) = Cr3::read();
+
+    let phys = level_4_table_frame.start_address();
+    let virt = physical_memory_offset + phys.as_u64();
+    let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
+
+    unsafe { &mut  *page_table_ptr } // unsafe
+}