Add support for `qProcessInfo` and `qHostInfo` queries. by cfallin · Pull Request #190 · daniel5151/gdbstub

cfallin · 2026-03-05T00:35:39Z

Description

These are necessary in some cases to allow LLDB to use appropriate target-specific behaviors or modules. For example, when debugging a Wasm target, LLDB requires the stub to declare that it has a wasm32 architecture in order to actually use its Wasm module loader over the wire.

API Stability

This PR does not require a breaking API change

Checklist

Documentation
- Ensured any public-facing rustdoc formatting looks good (via cargo doc)
- (if appropriate) Added feature to "Debugging Features" in README.md
Validation
- Included output of running examples/armv4t with RUST_LOG=trace + any relevant GDB output under the "Validation" section below
- Included output of running ./example_no_std/check_size.sh before/after changes under the "Validation" section below
If implementing a new protocol extension IDET
- Included a basic sample implementation in examples/armv4t
- IDET can be optimized out (confirmed via ./example_no_std/check_size.sh)
- OR implementation requires introducing non-optional binary bloat (please elaborate under "Description")
If upstreaming an Arch implementation
- I have tested this code in my project, and to the best of my knowledge, it is working as intended.

Validation

Full validation requires the Wasmtime gdbstub server with bits I haven't upstreamed yet, along with #188 and #189.

These are necessary in some cases to allow LLDB to use appropriate target-specific behaviors or modules. For example, when debugging a Wasm target, LLDB requires the stub to declare that it has a wasm32 architecture in order to actually use its Wasm module loader over the wire.

daniel5151

Thank you for this (and other!) PRs!

I'll do my best to squeeze in reviews / offer feedback over the next few days

src/target/ext/process_info.rs

cfallin · 2026-03-05T17:25:51Z

Thanks for the review! I'll push updates to this and my other two later today hopefully. Happy to refine/make more user-friendly as needed -- these were the bare minimum to get my use-case working and I was planning to get a read on your API design philosophy, which I've got a better picture of, now :-)

cfallin · 2026-03-06T06:12:06Z

Updated based on feedback; thanks!

src/protocol/commands.rs

src/target/ext/process_info.rs

src/stub/core_impl/process_info.rs

cfallin · 2026-03-09T20:00:35Z

Updated based on all feedback; thanks!

cfallin · 2026-03-09T20:01:10Z

(This will likely merge-conflict with #188; I can rebase or merge-from-main as desired here once if that one merges first.)

daniel5151

Implementation looks great, so once we address some of these style / doc / organization comments, this should be good to go :)

src/target/ext/host_info.rs

src/target/ext/process_info.rs

src/target/ext/host_info.rs

src/target/ext/process_info.rs

src/target/mod.rs

src/stub/core_impl/info_response.rs

Co-authored-by: Daniel Prilik <danielprilik@gmail.com>

cfallin · 2026-03-09T21:17:49Z

Addressed all comments and merged from master to resolve merge-conflicts from #188 -- thanks!

daniel5151 · 2026-03-10T14:42:08Z

Awesome, this looks great! Thanks for sending this in and working with me on the iterations here.

Builds on daniel5151#188, daniel5151#189, daniel5151#190: add definitions for the WebAssembly architecture to `gdbstub_arch`. This includes all definitions needed for the `Arch` trait, as well as utility code for encoding/decoding the synthetic address space used by the gdbstub definitions for this architecture. Tested with Wasmtime using a (soon to be upstreamed) guest-debugging facility.

Builds on #188, #189, #190: add definitions for the WebAssembly architecture to `gdbstub_arch`. This includes all definitions needed for the `Arch` trait, as well as utility code for encoding/decoding the synthetic address space used by the gdbstub definitions for this architecture. Tested with Wasmtime using a (soon to be upstreamed) guest-debugging facility.

This adds a debug component that makes use of the debug-main world defined in bytecodealliance#12756 and serves the gdbstub protocol, with Wasm extensions, compatible with LLDB. This component is built and included inside the Wasmtime binary, and is loaded using the lower-level `-D debugger=...` debug-main option; the user doesn't need to specify the `.wasm` adapter component. Instead, the user simply runs `wasmtime run -g <PORT> program.wasm ...` and Wasmtime will load and prepare to run `program.wasm` as the debuggee, waiting for a gdbstub connection on the given TCP port before continuing. The workflow is: ``` $ wasmtime run -g 1234 program.wasm [ wasmtime starts and waits for connection ] $ /opt/wasi-sdk/bin/lldb # use LLDB from wasi-sdk release 32 or later (lldb) process connect --plugin wasm connect://localhost:1234 Process 1 stopped * thread #1, stop reason = signal SIGTRAP frame #0: 0x40000000000001cc -> 0x40000000000001cc: unreachable 0x40000000000001cd: end 0x40000000000001ce: local.get 0 0x40000000000001d0: call 13 (lldb) si Process 1 stopped * thread #1, stop reason = instruction step into frame #0: 0x4000000000000184 -> 0x4000000000000184: block 0x4000000000000186: block 0x4000000000000188: global.get 1 0x400000000000018e: i32.const 3664 [ ... ] ``` This makes use of the `gdbstub` third-party crate, into which I've upstreamed support for the Wasm extensions in daniel5151/gdbstub#188, daniel5151/gdbstub#189, daniel5151/gdbstub#190, and daniel5151/gdbstub#192. (I'll add vets as part of this PR.)

cfallin force-pushed the process-host-info branch from a180665 to 6fb1b3d Compare March 5, 2026 15:16

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cfallin force-pushed the process-host-info branch from 3025cf7 to dbd0887 Compare March 6, 2026 06:07

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daniel5151 mentioned this pull request Mar 9, 2026

Add support for Wasm-specific commands. #188

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daniel5151 requested changes Mar 9, 2026

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cfallin and others added 4 commits March 9, 2026 14:05

Update src/target/ext/host_info.rs

3f1a01d

Co-authored-by: Daniel Prilik <danielprilik@gmail.com>

Update src/target/ext/host_info.rs

f63c30d

Co-authored-by: Daniel Prilik <danielprilik@gmail.com>

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Merge remote-tracking branch 'origin/master' into process-host-info

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remove extra files from merge

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daniel5151 approved these changes Mar 10, 2026

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daniel5151 merged commit 8811bba into daniel5151:master Mar 10, 2026
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cfallin mentioned this pull request Mar 10, 2026

gdbstub_arch: add a WebAssembly architecture. #192

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cfallin mentioned this pull request Mar 12, 2026

Debugging: add builtin gdbstub component. bytecodealliance/wasmtime#12771

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cfallin commented Mar 5, 2026

Description

API Stability

Checklist

Validation

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