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IMEM tripwire (poison broke stack)

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lumia-emu
2026-09-14 00:15:36 +00:00
parent 2a3bdcd72d
commit 503c334b2e
3 changed files with 12 additions and 8 deletions
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docs/sbl-bringup.md
+3
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@@ -171,3 +171,6 @@
- Assert-hang `0x8018458` (`b .`) достигается напрямую через - Assert-hang `0x8018458` (`b .`) достигается напрямую через
maze-stale-lr (мимо патченного wrap-check). `b .` → `b success` maze-stale-lr (мимо патченного wrap-check). `b .` → `b success`
(2B, в success-путь). (2B, в success-путь).
- Урок: полный IMEM-poison ломает IMEM-стек (счётчики читают
0xFFFFFFFF вместо свежих нулей → underflow → wild-pop). Только
tripwire 16B на входе дрейфа `[0x8600000,0x8600010)`.
qemu/saimaa.c
+3 -3
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@@ -822,12 +822,12 @@ static void saimaa_machine_init(MachineState *machine)
cpu_physical_memory_write(a, &fill, 4); cpu_physical_memory_write(a, &fill, 4);
} }
} }
/* IMEM poison [0x8600000,0x8600F00): drift-sink trap (UDF in /* IMEM tripwire [0x8600000,0x8600010): drift-sink trap.
* both modes). IMEM stack [0x8600F00,0x8610000) intact. */ * Rest of IMEM stays zeros (SBL stack reads data there). */
{ {
uint32_t p = 0xFFFFFFFF; uint32_t p = 0xFFFFFFFF;
uint32_t a; uint32_t a;
for (a = 0x08600000; a < 0x08600F00; a += 4) { for (a = 0x08600000; a < 0x08600010; a += 4) {
cpu_physical_memory_write(a, &p, 4); cpu_physical_memory_write(a, &p, 4);
} }
} }
tools/sbl_uni.py
+6 -5
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@@ -474,11 +474,12 @@ def main():
"60474af20007c0f2730747f2797cc0f6000c6047")) "60474af20007c0f2730747f2797cc0f6000c6047"))
# stack zone fill (STUBV odd) # stack zone fill (STUBV odd)
mu.mem_write(0x085F0000, struct.pack("<I", STUBV) * (0x10000 // 4)) mu.mem_write(0x085F0000, struct.pack("<I", STUBV) * (0x10000 // 4))
# IMEM poison [0x8600000,0x8600F00): drift-sink trap. Fill/IMEM-zero # IMEM tripwire [0x8600000,0x8600010): drift-sink trap (UDF).
# sleds (fall-through ldr/movs/andeq) drift silently to IMEM-top # Fill-drift falls through here sequentially; faults LOUDLY at
# fault; poison faults LOUDLY at drift-entry (UDF in both modes). # entry instead of sledding silently to IMEM-top. Rest of IMEM
# IMEM stack [0x8600F00,0x8610000) left intact. # stays zeros (SBL IMEM-stack reads data there; full poison
mu.mem_write(0x08600000, b"\xff\xff\xff\xff" * (0xF00 // 4)) # corrupts counters (0xFFFFFFFF vs fresh 0)!).
mu.mem_write(0x08600000, b"\xff\xff\xff\xff" * 4)
# pop-site slots (sp values from traces) # pop-site slots (sp values from traces)
for a, v in [(0x085FFF14, 0x802f65d), (0x085FFF1C, 0x802f665), for a, v in [(0x085FFF14, 0x802f65d), (0x085FFF1C, 0x802f665),
(0x085FFF44, 0x8013ba5), (0x085FFF5C, 0x802f681), (0x085FFF44, 0x8013ba5), (0x085FFF5C, 0x802f681),