#!/bin/sh
# DF-2540 characterization: verify the amdsbwd device is absent (HW-gated)
# and confirm the signed-overflow arithmetic by computation.
set -e
cd "$(dirname "$0")"

echo "=== HW-gate check: is amdsbwd present? ==="
ls -l /dev/amdsbwd* 2>&1 || echo "ABSENT (expected in QEMU -- no AMD SB chipset)"
pciconf -lv 2>/dev/null | grep -i "amd\|ATI" | head || echo "No AMD devices"
echo ""
echo "=== kern.watchdog.period (root-writable, but no amdsbwd callback) ==="
sysctl kern.watchdog.period 2>&1
echo ""
echo "=== Arithmetic verification of the overflow ==="
echo "period=4294967, ms_per_tick=1000:"
echo "  4294967 * 1000 = 4294967000"
echo "  as int32: -296 (signed overflow)"
echo "  -296 / 1000 = 0 (C truncation toward zero, |-296| < 1000)"
echo "  timeout = (unsigned)0 = 0"
echo "  0 <= max_ticks(65535) -> NOT clamped"
echo "  --> hardware watchdog count = 0 -> IMMEDIATE REBOOT on real AMD SB HW"
echo ""
echo "(Run python3 df2540_arith.py for the full table of period -> count values)"