Fix: Consider config file when initializing frame allocator

We still considered the ramdisk file as the last used frame when initializing the frame allocator, so we overwrote the config file. This commit fixes this by setting the `last_used_addr` correctly when creating the `BiosInfo`.

Author: phil-opp

bios/common/src/lib.rs

@@ -9,6 +9,7 @@ pub struct BiosInfo {
     pub kernel: Region,
     pub ramdisk: Region,
     pub config_file: Region,
+    pub last_used_addr: u64,
     pub framebuffer: BiosFramebufferInfo,
     pub memory_map_addr: u32,
     pub memory_map_len: u16,

bios/stage-2/src/main.rs

@@ -161,6 +161,7 @@ fn start(disk_number: u16, partition_table_start: *const u8) -> ! {
             start: config_file_start as u64,
             len: config_file_len,
         },
+        last_used_addr: config_file_start as u64 + config_file_len - 1,
         memory_map_addr: memory_map.as_mut_ptr() as u32,
         memory_map_len: memory_map.len().try_into().unwrap(),
         framebuffer: BiosFramebufferInfo {

bios/stage-4/src/main.rs

@@ -54,14 +54,7 @@ pub extern "C" fn _start(info: &mut BiosInfo) -> ! {
         PhysAddr::new(info.kernel.start)
     };
     let kernel_size = info.kernel.len;
-    let next_free_frame = match info.ramdisk.len {
-        0 => PhysFrame::containing_address(kernel_start + kernel_size - 1u64) + 1,
-        _ => {
-            PhysFrame::containing_address(PhysAddr::new(
-                info.ramdisk.start + info.ramdisk.len - 1u64,
-            )) + 1
-        }
-    };
+    let next_free_frame = PhysFrame::containing_address(PhysAddr::new(info.last_used_addr)) + 1;
     let mut frame_allocator = LegacyFrameAllocator::new_starting_at(
         next_free_frame,
         memory_map.iter().copied().map(MemoryRegion),