b18: S7 exit router + dstub trap + docs

2026-09-12 10:30:18 +00:00
parent 67539f7351
commit 049f98122b
6 changed files with 1097 additions and 50 deletions
@@ -1,22 +1,16 @@
    .syntax unified
    .cpu cortex-a7
    .thumb
-    @ maze entry logger: ring buffer of 8 (lr,sp) at MAILBOX, return 0.
-    @ Preserves all regs except r0 (return value) and r12 (IP, clobber-ok).
+    @ maze entry: return 0. Guard: bad lr (high byte != 0x08) spins
+    @ with IRQs off instead of jumping into the void.
    .text
    .global maze_stub
 maze_stub:
-    push {r0-r3}
-    movw r12, #:lower16:0x08006890
-    movt r12, #:upper16:0x08006890
-    ldr r0, [r12, #32]
-    add r0, #1
-    and r0, #7
-    str r0, [r12, #32]
-    lsl r0, #3
-    add r0, r12
-    str lr, [r0]
-    str sp, [r0, #4]
-    pop {r0-r3}
    movs r0, #0
+    lsr r12, lr, #24
+    cmp r12, #8
+    bne maze_hang
    bx lr
+maze_hang:
+    cpsid i
+    b maze_hang