S16v3: add sp un-leak

docs/sbl-bringup.md

@@ -125,3 +125,5 @@
 - Poll-fn `0x8007748`: `cbz r6` (r6=2 константа caller'а, никогда 0) →
   вечный re-init (`movs r4,#0`, table loop) вместо poll#2-direct.
   Патч 2B→2B в `b`. Биты 0,1,2 `[0x73A100]` pref-set (scaffold).
+- S16v3: `add sp,#8` перед `bx ip` (снимает helper-фрейм, пропущенный
+  B66 — un-leak стека вниз).

qemu/saimaa.c

@@ -751,18 +751,20 @@ static void saimaa_machine_init(MachineState *machine)
                     cpu_physical_memory_write(0x08006964 + k, &word, 4);
                 }
             }
-            /* S16-stublet (b25, 44B @0x08006CC0): smart return for the
-             * B66 bx-ip chain. ip odd + top 8 (code) => bx ip (legit
-             * pushed-lr return); else default (restore r7, jump poll
+            /* S16-stublet (b27, 50B @0x08006CC0): smart return for the
+             * B66 bx-ip chain. ip odd + top 8 => add sp,#8 (pop the
+             * helper frame B66 skipped!) + bx ip (legit pushed-lr,
+             * un-leaks the stack); else default (restore r7, jump poll
              * resumption 0x8007779 via ip). */
             {
                 static const uint8_t s16[] = {
-                    0x1c, 0xf0, 0x01, 0x0f, 0x09, 0xd0, 0x5f, 0xea,
-                    0x1c, 0x63, 0x08, 0x2b, 0x00, 0xd1, 0x60, 0x47,
-                    0x5f, 0xea, 0x1c, 0x73, 0x08, 0x2b, 0x00, 0xd1,
-                    0x60, 0x47, 0x4a, 0xf2, 0x00, 0x07, 0xc0, 0xf2,
-                    0x73, 0x07, 0x47, 0xf2, 0x79, 0x7c, 0xc0, 0xf6,
-                    0x00, 0x08, 0xc0, 0x47,
+                    0xdd, 0xf8, 0x04, 0xc0, 0x1c, 0xf0, 0x01, 0x0f,
+                    0x0b, 0xd0, 0x5f, 0xea, 0x1c, 0x63, 0x08, 0x2b,
+                    0x00, 0xd1, 0x02, 0xb0, 0x60, 0x47, 0x5f, 0xea,
+                    0x1c, 0x73, 0x08, 0x2b, 0x00, 0xd1, 0x60, 0x47,
+                    0x4a, 0xf2, 0x00, 0x07, 0xc0, 0xf2, 0x73, 0x07,
+                    0x47, 0xf2, 0x79, 0x7c, 0xc0, 0xf6, 0x00, 0x0c,
+                    0x60, 0x47,
                 };
                 size_t k;
                 for (k = 0; k < sizeof(s16); k += 4) {

tools/sbl_uni.py

@@ -393,12 +393,14 @@ def main():
     mu.mem_write(0x08006964, bytes.fromhex(
         "04c09de50c309fe5002093e5022082e3002083e51eff2fe1"
         "00a17300"))
-    # S16-stublet (b25, 44B @0x08006CC0): smart return for B66 bx ip.
-    # ip odd + top 8 (DDRLOW/DDRHIGH code) => bx ip (legit pushed-lr
-    # return); else default (restore r7, jump poll resumption 0x8007779).
+    # S16-stublet (b27, 50B @0x08006CC0): smart return for B66 bx ip.
+    # ip odd + top 8 (code) => add sp,#8 (pop the helper frame it
+    # skipped!) + bx ip (legit pushed-lr return, un-leaks the stack);
+    # else default (restore r7, jump poll resumption 0x8007779).
     mu.mem_write(0x08006CC0, bytes.fromhex(
-        "1cf0010f09d05fea1c63082b00d160475fea1c73082b00d"
-        "160474af20007c0f2730747f2797cc0f6000c6047"))
+        "ddf804c01cf0010f0bd05fea1c63082b00d102b06047"
+        "5fea1c73082b00d160474af20007c0f2730747f2797c"
+        "c0f6000c6047"))
     # stack zone fill (STUBV odd)
     mu.mem_write(0x085F0000, struct.pack("<I", STUBV) * (0x10000 // 4))
     # pop-site slots (sp values from traces)