fix pi-lens warnings: unwraps, shell SC2046, dup code (fmtbuf/scripts/hexdump/cat/ahci/pci)

- memory.rs: self-test Layout::from_size_align no longer panics — the
  test fails cleanly on an invalid layout
- fat.rs: v() no longer unwraps the active-volume slot — invariant
  violation logs + halts instead of panicking mid-disk-io
- strbuf: shared FmtBuf replaces the duplicated PanicBuf/FmtBuf
  (main.rs + sched.rs)
- test-disk.sh: SC2046 — conditional --fresh arg no longer relies on
  word splitting
- scripts: boot.sh/boot-image.sh share lib-boot-args.sh (dup args loop)
- shell: cat/hexdump stdin pairs unified with Option<&str> marker;
  hexdump format_row folded into format_partial
- ahci: read/write_sectors unified behind dma_sectors
- pci: config_read/write share config_addr

1 files changed, 11 insertions, 1 deletions

diff --git a/rsnix/src/fat.rs b/rsnix/src/fat.rs
index bad01cd..eda81ed 100644
--- a/rsnix/src/fat.rs
+++ b/rsnix/src/fat.rs
@@ -167,8 +167,18 @@ fn write_sector(lba: u64, data: &[u8; SECTOR]) -> Result<(), ()> {
 
 // --- cluster math ----------------------------------------------------------
 
+/// Current volume's metadata — only ever reached with a selected volume
+/// (the fs layer calls `select_vol` first), so a missing slot is a kernel
+/// invariant violation, not a recoverable error.
 fn v() -> &'static mut Volume {
-    vols().get_mut(*active_vol()).unwrap()
+    let i = *active_vol();
+    match vols().get_mut(i) {
+        Some(v) => v,
+        None => {
+            crate::serial_println!("fat: internal error — no volume at slot {}", i);
+            crate::interrupts::halt();
+        }
+    }
 }
 
 fn spc() -> usize {