diff --git a/api/src/info.rs b/api/src/info.rs
index 771948de..cdb48722 100644
--- a/api/src/info.rs
+++ b/api/src/info.rs
@@ -56,6 +56,9 @@ pub struct BootInfo {
     pub ramdisk_addr: Optional<u64>,
     /// Ramdisk image size, set to 0 if addr is None
     pub ramdisk_len: u64,
+
+    #[doc(hidden)]
+    pub _test_sentinel: u64,
 }
 
 impl BootInfo {
@@ -73,6 +76,7 @@ impl BootInfo {
             tls_template: Optional::None,
             ramdisk_addr: Optional::None,
             ramdisk_len: 0,
+            _test_sentinel: 0,
         }
     }
 }
diff --git a/bios/common/src/lib.rs b/bios/common/src/lib.rs
index 6d34e559..166e12df 100644
--- a/bios/common/src/lib.rs
+++ b/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,
diff --git a/bios/stage-2/src/main.rs b/bios/stage-2/src/main.rs
index d07957c8..b5b07d65 100644
--- a/bios/stage-2/src/main.rs
+++ b/bios/stage-2/src/main.rs
@@ -115,7 +115,7 @@ fn start(disk_number: u16, partition_table_start: *const u8) -> ! {
     }
     let config_file_start = ramdisk_start.wrapping_add(ramdisk_len.try_into().unwrap());
     let config_file_len = try_load_file(
-        "config.json",
+        "boot.json",
         config_file_start,
         &mut fs,
         &mut disk,
@@ -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 {
diff --git a/bios/stage-4/src/main.rs b/bios/stage-4/src/main.rs
index f51f2252..260dd622 100644
--- a/bios/stage-4/src/main.rs
+++ b/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),
@@ -173,7 +166,7 @@ pub extern "C" fn _start(info: &mut BiosInfo) -> ! {
         ramdisk_len: info.ramdisk.len,
     };
 
-    load_and_switch_to_kernel(kernel, frame_allocator, page_tables, system_info);
+    load_and_switch_to_kernel(kernel, config, frame_allocator, page_tables, system_info);
 }
 
 fn init_logger(
diff --git a/common/config/src/lib.rs b/common/config/src/lib.rs
index 2286ad16..267cb64f 100644
--- a/common/config/src/lib.rs
+++ b/common/config/src/lib.rs
@@ -22,6 +22,8 @@ pub struct BootConfig {
     ///
     /// Enabled by default.
     pub serial_logging: bool,
+
+    pub _test_sentinel: u64,
 }
 
 impl Default for BootConfig {
@@ -31,6 +33,7 @@ impl Default for BootConfig {
             log_level: Default::default(),
             frame_buffer_logging: true,
             serial_logging: true,
+            _test_sentinel: 0,
         }
     }
 }
diff --git a/common/src/lib.rs b/common/src/lib.rs
index 97778db1..3a0e3163 100644
--- a/common/src/lib.rs
+++ b/common/src/lib.rs
@@ -8,7 +8,7 @@ use bootloader_api::{
     info::{FrameBuffer, FrameBufferInfo, MemoryRegion, TlsTemplate},
     BootInfo, BootloaderConfig,
 };
-use bootloader_boot_config::LevelFilter;
+use bootloader_boot_config::{BootConfig, LevelFilter};
 use core::{alloc::Layout, arch::asm, mem::MaybeUninit, slice};
 use level_4_entries::UsedLevel4Entries;
 use usize_conversions::FromUsize;
@@ -125,6 +125,7 @@ impl<'a> Kernel<'a> {
 /// directly to these functions, so see their docs for more info.
 pub fn load_and_switch_to_kernel<I, D>(
     kernel: Kernel,
+    boot_config: BootConfig,
     mut frame_allocator: LegacyFrameAllocator<I, D>,
     mut page_tables: PageTables,
     system_info: SystemInfo,
@@ -144,6 +145,7 @@ where
     );
     let boot_info = create_boot_info(
         &config,
+        &boot_config,
         frame_allocator,
         &mut page_tables,
         &mut mappings,
@@ -435,6 +437,7 @@ pub struct Mappings {
 /// are taken from the given `frame_allocator`.
 pub fn create_boot_info<I, D>(
     config: &BootloaderConfig,
+    boot_config: &BootConfig,
     mut frame_allocator: LegacyFrameAllocator<I, D>,
     page_tables: &mut PageTables,
     mappings: &mut Mappings,
@@ -539,6 +542,7 @@ where
             .map(|addr| addr.as_u64())
             .into();
         info.ramdisk_len = mappings.ramdisk_slice_len;
+        info._test_sentinel = boot_config._test_sentinel;
         info
     });
 
diff --git a/src/uefi/mod.rs b/src/uefi/mod.rs
index 69024718..030ea9bb 100644
--- a/src/uefi/mod.rs
+++ b/src/uefi/mod.rs
@@ -68,6 +68,7 @@ impl UefiBoot {
             bootloader_path,
             self.kernel.as_path(),
             self.ramdisk.as_deref(),
+            self.config.as_deref(),
             out_path,
         )
         .context("failed to create UEFI PXE tftp folder")?;
diff --git a/src/uefi/pxe.rs b/src/uefi/pxe.rs
index 84c7b0d6..4eac7f8c 100644
--- a/src/uefi/pxe.rs
+++ b/src/uefi/pxe.rs
@@ -1,11 +1,13 @@
 use std::path::Path;
 
 use anyhow::Context;
+use bootloader_boot_config::BootConfig;
 
 pub fn create_uefi_tftp_folder(
     bootloader_path: &Path,
     kernel_binary: &Path,
     ramdisk_path: Option<&Path>,
+    boot_config: Option<&str>,
     out_path: &Path,
 ) -> anyhow::Result<()> {
     std::fs::create_dir_all(out_path)
@@ -39,5 +41,10 @@ pub fn create_uefi_tftp_folder(
         })?;
     }
 
+    if let Some(config) = boot_config {
+        let to = out_path.join("boot.json");
+        std::fs::write(to, config).context("failed to write boot.json")?;
+    }
+
     Ok(())
 }
diff --git a/tests/config_file.rs b/tests/config_file.rs
index af5c0f31..69f805dc 100644
--- a/tests/config_file.rs
+++ b/tests/config_file.rs
@@ -3,25 +3,25 @@ use bootloader_test_runner::run_test_kernel_internal;
 use bootloader::BootConfig;
 
 #[test]
-fn basic_boot() {
-    let config: BootConfig = Default::default();
+fn default_config() {
     run_test_kernel_internal(
-        env!("CARGO_BIN_FILE_TEST_KERNEL_CONFIG_FILE_basic_boot"),
+        env!("CARGO_BIN_FILE_TEST_KERNEL_CONFIG_FILE_no_config"),
+        None,
         None,
-        Some(&config),
     );
 }
 
 #[test]
-fn custom_options_boot() {
+fn custom_boot_config() {
     let config = BootConfig {
         frame_buffer: Default::default(),
         log_level: Default::default(),
         frame_buffer_logging: false,
         serial_logging: true,
+        _test_sentinel: 0xb001b001b001,
     };
     run_test_kernel_internal(
-        env!("CARGO_BIN_FILE_TEST_KERNEL_CONFIG_FILE_basic_boot_broken_config_file"),
+        env!("CARGO_BIN_FILE_TEST_KERNEL_CONFIG_FILE_custom_config"),
         None,
         Some(&config),
     );
diff --git a/tests/test_kernels/config_file/src/bin/basic_boot_broken_config_file.rs b/tests/test_kernels/config_file/src/bin/custom_config.rs
similarity index 91%
rename from tests/test_kernels/config_file/src/bin/basic_boot_broken_config_file.rs
rename to tests/test_kernels/config_file/src/bin/custom_config.rs
index 5232aa80..425e268a 100644
--- a/tests/test_kernels/config_file/src/bin/basic_boot_broken_config_file.rs
+++ b/tests/test_kernels/config_file/src/bin/custom_config.rs
@@ -9,6 +9,7 @@ entry_point!(kernel_main);
 
 fn kernel_main(boot_info: &'static mut BootInfo) -> ! {
     writeln!(serial(), "Entered kernel with boot info: {boot_info:?}").unwrap();
+    assert_eq!(boot_info._test_sentinel, 0xb001b001b001);
     exit_qemu(QemuExitCode::Success);
 }
 
diff --git a/tests/test_kernels/config_file/src/bin/basic_boot.rs b/tests/test_kernels/config_file/src/bin/no_config.rs
similarity index 93%
rename from tests/test_kernels/config_file/src/bin/basic_boot.rs
rename to tests/test_kernels/config_file/src/bin/no_config.rs
index 5232aa80..d0898bde 100644
--- a/tests/test_kernels/config_file/src/bin/basic_boot.rs
+++ b/tests/test_kernels/config_file/src/bin/no_config.rs
@@ -9,6 +9,7 @@ entry_point!(kernel_main);
 
 fn kernel_main(boot_info: &'static mut BootInfo) -> ! {
     writeln!(serial(), "Entered kernel with boot info: {boot_info:?}").unwrap();
+    assert_eq!(boot_info._test_sentinel, 0);
     exit_qemu(QemuExitCode::Success);
 }
 
diff --git a/uefi/src/main.rs b/uefi/src/main.rs
index 56aea62c..d0cee33b 100644
--- a/uefi/src/main.rs
+++ b/uefi/src/main.rs
@@ -73,6 +73,15 @@ fn main_inner(image: Handle, mut st: SystemTable<Boot>) -> Status {
     }
 
     let mut boot_mode = BootMode::Disk;
+
+    let mut kernel = load_kernel(image, &mut st, boot_mode);
+    if kernel.is_none() {
+        // Try TFTP boot
+        boot_mode = BootMode::Tftp;
+        kernel = load_kernel(image, &mut st, boot_mode);
+    }
+    let kernel = kernel.expect("Failed to load kernel");
+
     let config_file = load_config_file(image, &mut st, boot_mode);
     let mut error_loading_config: Option<serde_json_core::de::Error> = None;
     let mut config: BootConfig = match config_file
@@ -87,14 +96,6 @@ fn main_inner(image: Handle, mut st: SystemTable<Boot>) -> Status {
         }
     };
 
-    let mut kernel = load_kernel(image, &mut st, boot_mode);
-    if kernel.is_none() {
-        // Try TFTP boot
-        boot_mode = BootMode::Tftp;
-        kernel = load_kernel(image, &mut st, boot_mode);
-    }
-    let kernel = kernel.expect("Failed to load kernel");
-
     #[allow(deprecated)]
     if config.frame_buffer.minimum_framebuffer_height.is_none() {
         config.frame_buffer.minimum_framebuffer_height =
@@ -105,7 +106,7 @@ fn main_inner(image: Handle, mut st: SystemTable<Boot>) -> Status {
         config.frame_buffer.minimum_framebuffer_width =
             kernel.config.frame_buffer.minimum_framebuffer_width;
     }
-    let framebuffer = init_logger(image, &st, config);
+    let framebuffer = init_logger(image, &st, &config);
 
     unsafe {
         *SYSTEM_TABLE.get() = None;
@@ -193,6 +194,7 @@ fn main_inner(image: Handle, mut st: SystemTable<Boot>) -> Status {
 
     bootloader_x86_64_common::load_and_switch_to_kernel(
         kernel,
+        config,
         frame_allocator,
         page_tables,
         system_info,
@@ -218,7 +220,7 @@ fn load_config_file(
     st: &mut SystemTable<Boot>,
     boot_mode: BootMode,
 ) -> Option<&'static mut [u8]> {
-    load_file_from_boot_method(image, st, "config.json\0", boot_mode)
+    load_file_from_boot_method(image, st, "boot.json\0", boot_mode)
 }
 
 fn load_kernel(
@@ -473,7 +475,7 @@ fn create_page_tables(
 fn init_logger(
     image_handle: Handle,
     st: &SystemTable<Boot>,
-    config: BootConfig,
+    config: &BootConfig,
 ) -> Option<RawFrameBufferInfo> {
     let gop_handle = st
         .boot_services()