Convert the StableVec class to use virtual addressing #3608
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The Firedancer team maintains a line-for-line reimplementation of the |
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@alessandrod @Lichtso 32-bit build fixes (PR 2 of 2, so far) |
| pub ptr: NonNull<T>, | ||
| pub cap: usize, | ||
| pub len: usize, | ||
| pub addr: u64, |
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ptr was renamed to addr here but forgotten to change it in test_memory_layout() as well.
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This PR also needs a rebase for CI to pass. |
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| @@ -56,13 +55,13 @@ impl<T> StableVec<T> { | |||
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| impl<T> AsRef<[T]> for StableVec<T> { | |||
| fn as_ref(&self) -> &[T] { | |||
| self | |||
| self.deref() | |||
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.. At this point, I honestly don't recall other than that's what makes the types correct. Maybe previously it was constructing a true slice directly from the data (evilly), and now it's using deref to do the from_raw_parts thing..?
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Well, it is a bit more explicit now, so that probably won't hurt. Was just curious if there was another reason behind it.
Problem
When doing a 32-bit build of Agave, pointers are of course 32 bits. The StableVec class is used to store vectors within the interpreter's 64-bit address space, but uses a Rust pointer to point to its data (and usize for both cap and len fields).
Summary of Changes
This PR updates the StableVec to use u64s for virtual addresses and sizes, rather than the compilers pointer and usize type, which are 32 bits in a 32-bit build, even though they contain 64-bit virtual addresses.
This could lead to an issue if this class were used to copy vectors between physical and virtual space (e.g. a StableVec that points to data in virtual memory, but is copied out into a Rust vector that now stuffs everything into 32-bit pointers and usizes), but at worst that would only be an issue for 32-bit builds, not the usual 64-bit ones, and that also does not appear to be something that actually happens. StableVec is used to store vectors in situations where the exact memory layout cannot change, i.e. inside the vm space, not as an kind of enhanced version of Rust's usual Vector class.
Fixes #