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, 10 insertions, 8 deletions

diff --git a/rsnix/src/ahci.rs b/rsnix/src/ahci.rs
index 72da07d..a77b341 100644
--- a/rsnix/src/ahci.rs
+++ b/rsnix/src/ahci.rs
@@ -510,22 +510,24 @@ fn active() -> Option<&'static Disk> {
     disks().get(unsafe { ACTIVE }).and_then(|d| d.as_ref())
 }
 
-/// DMA `count` sectors starting at `lba` into the selected disk's buffer.
-pub fn read_sectors(lba: u64, count: u32) -> Result<(), ()> {
+/// Bounds-checked DMA of `count` sectors starting at `lba` into/out of the
+/// selected disk's buffer (single code path for both directions).
+fn dma_sectors(lba: u64, count: u32, cmd: u8, write: bool) -> Result<(), ()> {
     let d = active().ok_or(())?;
     if lba + count as u64 > d.sectors {
         return Err(());
     }
-    issue(d, ATA_READ_DMA_EXT, lba, count, false)
+    issue(d, cmd, lba, count, write)
+}
+
+/// DMA `count` sectors starting at `lba` into the selected disk's buffer.
+pub fn read_sectors(lba: u64, count: u32) -> Result<(), ()> {
+    dma_sectors(lba, count, ATA_READ_DMA_EXT, false)
 }
 
 /// DMA `count` sectors starting at `lba` out of the selected disk's buffer.
 pub fn write_sectors(lba: u64, count: u32) -> Result<(), ()> {
-    let d = active().ok_or(())?;
-    if lba + count as u64 > d.sectors {
-        return Err(());
-    }
-    issue(d, ATA_WRITE_DMA_EXT, lba, count, true)
+    dma_sectors(lba, count, ATA_WRITE_DMA_EXT, true)
 }
 
 /// Pointer to the selected disk's 4 KiB DMA buffer.