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Change stack walking to stop at a precise fp #9420

Merged
merged 2 commits into from
Oct 9, 2024
Merged

Change stack walking to stop at a precise fp #9420

merged 2 commits into from
Oct 9, 2024

Commits on Oct 9, 2024

  1. Change stack walking to stop at a precise fp 

    Prior to this commit entry trampolines into wasm would record their
stack pointer at the time of the function call to wasm and then this
stack pointer was used to halt the stack walking process. The problem
with this though is that due to the `tail` ABI it's possible that the
callee will update the caller's stack pointer temporarily. This means
that the recorded stack pointer at the time the trampoline called wasm
may differ from the callee's idea of what the stack pointer is when a
backtrace happens.

To handle this condition when stack walking the frame pointer instead of
the stack pointer is now recorded when wasm is invoked. This frame
pointer is a trusted value as it's managed by Cranelift itself. This
additionally enables the stop condition for frame walking to be a
precise "it must be this value" condition.

Put together this commit fixes an issue where when `return_call` is used
it's possible for the initial few frames of the stack to get lost in
stack traces. After this the frame pointer chain should always be
precisely walked in its entirety, even in the face of different numbers
of arguments and parameters as `return_call` instructions are executed.
    @alexcrichton
    alexcrichton committed Oct 9, 2024
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  2. Add tail-calls, params, and results to stacks fuzzer 

    This commit extends the preexisting `stacks` fuzzer with a few new
features:

* `return_call` instructions are now generated
* functions may have both params/results to exercise logic around stack
  adjustments and how that might affect a stack trace
    @alexcrichton
    alexcrichton committed Oct 9, 2024
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