Stream: git-wasmtime

Topic: wasmtime / PR #4779 Wasmtime: fix stack walking across fr...

Wasmtime GitHub notifications bot (Aug 24 2022 at 23:50):

fitzgen opened PR #4779 from stack-trace-panic to main:

We were previously implicitly assuming that all Wasm frames in a stack used the same VMRuntimeLimits as the previous frame's CallThreadState, but this is not true when Wasm in store A calls into the host which then calls into Wasm in store B:

| ...             |
| Host            |  |
+-----------------+  | stack
| Wasm in store A |  | grows
+-----------------+  | down
| Host            |  |
+-----------------+  |
| Wasm in store B |  V
+-----------------+

Trying to walk this stack would previously result in a runtime panic.

The solution is to push the maintenance of our list of saved Wasm FP/SP/PC registers that allow us to identify contiguous regions of Wasm frames on the stack deeper into CallThreadState. The saved registers list is now maintained whenever updating the CallThreadState linked list by making the CallThreadState::prev field private and only accessible via a getter and setter, where the setter always maintains our invariants.

Thanks to @bnjbvr for reporting this bug!

@cfallin do you feel familiar enough with this stuff that you'd be comfortable reviewing it? If not, I can totally wait for Alex to come back from PTO.

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Wasmtime GitHub notifications bot (Aug 24 2022 at 23:50):

fitzgen requested cfallin for a review on PR #4779.

Wasmtime GitHub notifications bot (Aug 24 2022 at 23:50):

fitzgen requested alexcrichton for a review on PR #4779.

Wasmtime GitHub notifications bot (Aug 30 2022 at 14:15):

alexcrichton submitted PR review.

Wasmtime GitHub notifications bot (Aug 30 2022 at 14:15):

alexcrichton submitted PR review.

Wasmtime GitHub notifications bot (Aug 30 2022 at 14:15):

alexcrichton created PR review comment:

This may have gone a bit awry

Wasmtime GitHub notifications bot (Aug 30 2022 at 17:02):

fitzgen updated PR #4779 from stack-trace-panic to main.

Wasmtime GitHub notifications bot (Aug 30 2022 at 17:03):

fitzgen created PR review comment:

Whoops...

Wasmtime GitHub notifications bot (Aug 30 2022 at 17:03):

fitzgen submitted PR review.

Wasmtime GitHub notifications bot (Aug 30 2022 at 17:03):

fitzgen has enabled auto merge for PR #4779.

Wasmtime GitHub notifications bot (Aug 30 2022 at 18:28):

fitzgen merged PR #4779.

Last updated: Nov 22 2024 at 17:03 UTC