From 4be2c8dc7656aec5143fbda716de203205523f42 Mon Sep 17 00:00:00 2001
From: sasheg <sasheg@zern.cc>
Date: Sun, 13 Sep 2026 17:32:57 +0000
Subject: [PATCH] tools: add sled (zero-drift) detector + capstone disassembly
 history in trap handler

---
 tools/sbl_uni.py | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/tools/sbl_uni.py b/tools/sbl_uni.py
index 2a3fc00..d509864 100644
--- a/tools/sbl_uni.py
+++ b/tools/sbl_uni.py
@@ -101,6 +101,12 @@ def main():
     last = [0]
     from collections import deque
     hist = deque(maxlen=20000)
+    # sled detector: sequential runs (pc == prev+2/4) longer than THRESH
+    # are zero-drifts; log run start (the jump/fall that entered it).
+    _sled_start = [0]
+    _sled_n = [0]
+    _sled_log = []
+    _SLED_TH = 100
     calls = [] if "--calltrace" in sys.argv else None
     rets = [] if "--retrace" in sys.argv else None
     qlog = [] if "--querylog" in sys.argv else None
@@ -134,6 +140,16 @@ def main():
     def hook_code(mu, addr, size, data):
         count[0] += 1
         last[0] = addr
+        _pp = _prev[0]
+        _prev[0] = addr
+        if addr == _pp + 2 or addr == _pp + 4:
+            if _sled_n[0] == 0:
+                _sled_start[0] = _pp
+            _sled_n[0] += 1
+        else:
+            if _sled_n[0] >= _SLED_TH and len(_sled_log) < 20:
+                _sled_log.append((count[0], _sled_start[0], _pp, _sled_n[0]))
+            _sled_n[0] = 0
         if 0x08006B8C <= addr < 0x08006B9E:
             try:
                 _lr = mu.reg_read(_LR)
@@ -187,6 +203,21 @@ def main():
                 print(f"  [73A100]={bytes(mu.mem_read(0x073A100, 4)).hex()}")
             except Exception as e:
                 print(f"  [73A100] unreadable: {e}")
+            try:
+                from capstone import Cs, CS_ARCH_ARM, CS_MODE_THUMB, CS_MODE_ARM
+                md_t = Cs(CS_ARCH_ARM, CS_MODE_THUMB)
+                md_a = Cs(CS_ARCH_ARM, CS_MODE_ARM)
+                for _pc, _th in list(hist)[-60:]:
+                    try:
+                        _b = _pc & ~1
+                        _c = mu.mem_read(_b, 8 if _th else 12)
+                        for _ins in (md_t if _th else md_a).disasm(_c, _b):
+                            print(f"  hist {_b:#x}{'t' if _th else 'a'}: {_ins.mnemonic} {_ins.op_str}")
+                            break
+                    except Exception:
+                        print(f"  hist {_pc:#x}: <unreadable>")
+            except ImportError:
+                pass
             _trap_n[0] -= 1
             if _trap_n[0] <= 0 and "--trapn" in sys.argv:
                 mu.emu_stop()
@@ -216,7 +247,6 @@ def main():
                     if len(elog) < 20000:
                         elog.append((count[0], _prev[0], -addr, 2))
                 _inrng[_i] = inside
-            _prev[0] = addr
         if calls is not None and size in (2, 4):
             try:
                 if size == 2:
@@ -585,6 +615,12 @@ def main():
                 print(f"  {pc:#x}: <unreadable>")
     except ImportError:
         print("hist:", [hex(pc) for pc, _ in list(hist)[-12:]])
+    if _sled_log or _sled_n[0] >= _SLED_TH:
+        if _sled_n[0] >= _SLED_TH:
+            _sled_log.append((count[0], _sled_start[0], last[0], _sled_n[0]))
+        print(f"sleds: {len(_sled_log)}")
+        for n, s, e, c in _sled_log:
+            print(f"  insn#{n} [{s:#x}..{e:#x}] len={c}")
     if elog is not None:
         print(f"entries: {len(elog)}")
         for n, prev, cur, th in elog[:10]: