semihosting on the "blue pill" board

[ldericher]

Hello knurling-rs,

I can't seem to get semihosting to work with the app-template and my STM32F103C8T6 "blue pill" board. I'm using VSCode and the "Debugger for probe-rs" behind an STLink V2:

$ probe-rs list
The following debug probes were found:
[0]: STLink V2 (VID: 0483, PID: 3748, Serial: [...], StLink)

$ probe-rs info
Probing target via JTAG

ARM Chip:
Debug Port: Version 1, DP Designer: ARM Ltd
└── 0 MemoryAP
    └── ROM Table (Class 1)
        ├── Cortex-M3 SCS   (Generic IP component)
        │   └── CPUID
        │       ├── IMPLEMENTER: ARM Ltd
        │       ├── VARIANT: 1
        │       ├── PARTNO: 3107
        │       └── REVISION: 1
        ├── Cortex-M3 DWT   (Generic IP component)
        ├── Cortex-M3 FBP   (Generic IP component)
        ├── Cortex-M3 ITM   (Generic IP component)
        └── Cortex-M3 TPIU  (Coresight Component)

[...]

Now, whenever I start debugging anything, I end up in line 212 of cortex-m-semihosting/src/lib.rs, indicative of a failed semihosting attempt.

In a more "bare" setup (without knurling-rs, using the "Cortex-Debug" VSC extension and a manually setup "cargo build" prelaunch task) I was able to resolve the same issue leveraging "preLaunchCommands" for the gdb process, i.e. "monitor arm semihosting enable". I can't seem to find a similar setting with the arguably better approach using probe-rs and knurling.

I've selfhosted both experimental projects in my gitea instance and added a containers.dev config for convenience.

• With knurling + probe-rs (failed semihosting): https://code.yavook.de/jmm/bluepill-knurling-rs
• With manual setup + Cortex-Debug: https://code.yavook.de/jmm/bluepill-rust-blinky/src/commit/4132b45631b65d326b8f4ad85acfbc752b64c18a

Any ideas forward?

Crossposted at probe-rs/vscode/issues/89

[jonathanpallant]

The Knurling project generally recommends defmt over RTT as the logging mechanism instead of semihosting. We typically only suggest semihosting for causing probe-rs to quit, e.g. after running a short example. You could ask the probe-rs team on Matrix to see if they support whichever semihosting operation you are attempting to use.