Add a test to verify that ramdisk is marked as used in memory map

tests/ramdisk.rs

@@ -18,3 +18,11 @@ fn check_ramdisk() {
         Some(Path::new(RAMDISK_PATH)),
     );
 }
+
+#[test]
+fn memory_map() {
+    run_test_kernel_with_ramdisk(
+        env!("CARGO_BIN_FILE_TEST_KERNEL_RAMDISK_memory_map"),
+        Some(Path::new(RAMDISK_PATH)),
+    );
+}

tests/test_kernels/ramdisk/src/bin/memory_map.rs

@@ -0,0 +1,88 @@
+#![no_std] // don't link the Rust standard library
+#![no_main] // disable all Rust-level entry points
+
+use bootloader_api::{
+    config::Mapping, entry_point, info::MemoryRegionKind, BootInfo, BootloaderConfig,
+};
+use core::{fmt::Write, ptr::slice_from_raw_parts};
+use test_kernel_ramdisk::{exit_qemu, serial, QemuExitCode, RAMDISK_CONTENTS};
+use x86_64::{
+    structures::paging::{OffsetPageTable, PageTable, PageTableFlags, Translate},
+    VirtAddr,
+};
+
+pub const BOOTLOADER_CONFIG: BootloaderConfig = {
+    let mut config = BootloaderConfig::new_default();
+    config.mappings.physical_memory = Some(Mapping::FixedAddress(0x0000_6000_0000_0000));
+    config
+};
+
+entry_point!(kernel_main, config = &BOOTLOADER_CONFIG);
+
+fn kernel_main(boot_info: &'static mut BootInfo) -> ! {
+    writeln!(serial(), "Boot info: {boot_info:?}").unwrap();
+
+    let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset.into_option().unwrap());
+    let level_4_table = unsafe { active_level_4_table(phys_mem_offset) };
+    let page_table = unsafe { OffsetPageTable::new(level_4_table, phys_mem_offset) };
+
+    let ramdisk_start_addr = VirtAddr::new(boot_info.ramdisk_addr.into_option().unwrap());
+    assert_eq!(boot_info.ramdisk_len as usize, RAMDISK_CONTENTS.len());
+    let ramdisk_end_addr = ramdisk_start_addr + boot_info.ramdisk_len;
+
+    let mut next_addr = ramdisk_start_addr;
+    while next_addr < ramdisk_end_addr {
+        let phys_addr = match page_table.translate(next_addr) {
+            x86_64::structures::paging::mapper::TranslateResult::Mapped {
+                frame,
+                offset: _,
+                flags,
+            } => {
+                assert!(flags.contains(PageTableFlags::PRESENT));
+                assert!(flags.contains(PageTableFlags::WRITABLE));
+
+                next_addr += frame.size();
+
+                frame.start_address()
+            }
+            other => panic!("invalid result: {other:?}"),
+        };
+        let region = boot_info
+            .memory_regions
+            .iter()
+            .find(|r| r.start <= phys_addr.as_u64() && r.end > phys_addr.as_u64())
+            .unwrap();
+        assert_eq!(region.kind, MemoryRegionKind::Bootloader);
+    }
+
+    let actual_ramdisk = unsafe {
+        &*slice_from_raw_parts(
+            boot_info.ramdisk_addr.into_option().unwrap() as *const u8,
+            boot_info.ramdisk_len as usize,
+        )
+    };
+    writeln!(serial(), "Actual contents: {actual_ramdisk:?}").unwrap();
+    assert_eq!(RAMDISK_CONTENTS, actual_ramdisk);
+
+    exit_qemu(QemuExitCode::Success);
+}
+
+/// This function is called on panic.
+#[cfg(not(test))]
+#[panic_handler]
+fn panic(info: &core::panic::PanicInfo) -> ! {
+    let _ = writeln!(test_kernel_ramdisk::serial(), "PANIC: {info}");
+    exit_qemu(QemuExitCode::Failed);
+}
+
+pub unsafe 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();
+
+    &mut *page_table_ptr // unsafe
+}