It turns out the issue comes from the wrong SP register value getting restored by python script.
TLDR, If you happen to met that GDB cannot unwind correctly, try set $sp=$sp+4 The issue is that when an exception happened, armv7-m could push 4 bytes to stack, to make sure SP is 8bytes aligned. See https://developer.arm.com/documentation/ddi0403/d/System-Level-Architecture/System-Level-Programmers--Model/ARMv7-M-exception-model/Stack-alignment-on-exception-entry It happens that NuttX release 12.6.0 generates code that has SP not aligned to 4 bytes as shown below, right before triggering SVC. [image: img_v3_02is_bcd2a515-ec2b-4432-a86a-cbd232cb736l.jpeg] According to the documentation, we can distinguish this situation from xPSR[9] bit. xPSR is pushed to stack automatically. [image: img_v3_02is_e29e799d-75c4-4520-b145-a2369b4b5ael.jpeg] In this case, the real SP after restore should be `SP + 4`. After adjusting it manually, now GDB can unwind correctly. [image: a8GxTXm0aT.jpeg] NuttX release 12.8.0 changes the sys_call to macro, which saves 4 bytes on stack, avoiding this issue (coincidently?). The latest master branch does not have this issue too, and I’m not sure if it’s guaranteed or not. Regards, Neo
