v0.5.5: crash reports go to a dedicated CRASHLOG USB stick

The fault handler now writes crash.log to the volume labeled CRASHLOG
(label-selected via fat::crash_vol), falling back to slot 0.  On real
hardware the boot USB may be unwritable, so a second stick labeled
CRASHLOG survives the write; the shell auto-prints the previous crash
report from it at next boot (read_crash_log resolves /disk/<uid>/crash.log
through the FAT path, since Disk nodes hold no cached children).

- fat.rs: volume_label() + crash_vol() (no allocation)
- fs.rs: write_crash_log targets crash_vol(); read_crash_log prefers the
  CRASHLOG disk node; drop now-unused first_disk()
- mkdisk.sh: --label option
- test-fault.sh: boots with a dedicated CRASHLOG stick (mkfs -F 32 -n
  CRASHLOG), verifies crash.log lands there and NOT on the ESP

1 files changed, 36 insertions, 1 deletions

diff --git a/rsdos/src/main.rs b/rsdos/src/main.rs
index 2717dff..4521a42 100644
--- a/rsdos/src/main.rs
+++ b/rsdos/src/main.rs
@@ -81,6 +81,9 @@ fn panic(info: &PanicInfo) -> ! {
         core::str::from_utf8(&stage_buf[..stage_n]).unwrap_or(""),
     ];
     rsnix::gop::dump_lines(&lines);
+    // Persist to the disk so the report survives the reboot on real
+    // hardware (no serial console).  Best-effort; heap-free lines.
+    rsnix::fs::write_crash_log(&lines);
     loop {
         unsafe {
             core::arch::asm!("cli; hlt");
@@ -107,6 +110,31 @@ pub unsafe extern "efiapi" fn efi_main(image_handle: Handle, system_table: *mut
     // Keep the runtime-services table for later (ResetSystem → poweroff).
     rsnix::power::init(st.runtime_services);
 
+    // Capture the kernel's own image range BEFORE ExitBootServices: the
+    // heap and page allocators must never hand out the running kernel's
+    // code/data/bss pages (a heap allocation landing on the .bss corrupts
+    // statics like the FAT ACTIVE_VOL — observed as a dead filesystem in
+    // the fault path).
+    unsafe {
+        let mut li: *mut core::ffi::c_void = core::ptr::null_mut();
+        let li_guid = rsnix::uefi::EFI_LOADED_IMAGE_PROTOCOL_GUID;
+        if (bs.handle_protocol)(image_handle, &li_guid as *const rsnix::uefi::Guid, &mut li)
+            == rsnix::uefi::EFI_SUCCESS
+            && !li.is_null()
+        {
+            let p = &*(li as *const rsnix::uefi::LoadedImageProtocol);
+            rsnix::memory::set_kernel_image_range(p.image_base as usize, p.image_size as usize);
+            rsnix::serial_println!(
+                "mem: kernel image 0x{:x}..0x{:x} ({} KiB) reserved",
+                p.image_base as usize,
+                p.image_base as usize + p.image_size as usize,
+                p.image_size as usize / 1024
+            );
+        } else {
+            rsnix::serial_println!("mem: WARNING — kernel image range unknown");
+        }
+    }
+
     // ---- Phase 1: UEFI boot services alive ----
 
     // Print banner via UEFI console
@@ -208,7 +236,14 @@ pub unsafe extern "efiapi" fn efi_main(image_handle: Handle, system_table: *mut
     dump_memory_summary();
 
     if rsnix::memory::self_test() {
-        rsnix::serial_println!("heap: self-test OK (alloc/free/coalesce)");
+        let hs = rsnix::memory::heap_stats();
+        rsnix::serial_println!(
+            "heap: self-test OK (0x{:x}..0x{:x} {} KiB free={} KiB)",
+            hs.heap_start,
+            hs.heap_end,
+            hs.heap_size / 1024,
+            hs.free_bytes / 1024
+        );
     } else {
         rsnix::serial_println!("heap: self-test FAILED");
     }