Refactor the MemFlags internal representation#8162
Merged
alexcrichton merged 3 commits intobytecodealliance:mainfrom Mar 18, 2024
Merged
Refactor the MemFlags internal representation#8162alexcrichton merged 3 commits intobytecodealliance:mainfrom
MemFlags internal representation#8162alexcrichton merged 3 commits intobytecodealliance:mainfrom
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This commit refactors the internal `MemFlags` bits to be not just flags. Instead some bits are now grouped together and interpreted as a unit. This enables two primary API changes: * First the `heap`/`table`/`vmctx` split is now represented as an "alias region" which is set as an enum. This means that all `MemFlags` carry an `Option<AliasRegion>` internally. * Second trapping state is now represented as an `Option<TrapCode>`. This means that `notrap` is no longer a flag and `tabletrap` is no longer a flag. This does enable storing arbitrary trap codes though so long as they aren't `TrapCode::User(_)`. The main purpose of this commit is to enable using more trap codes with `MemFlags` for when a segfault is detected. For example with bytecodealliance#5291 we want a segfault to indicate a call-to-null, which is not currently covered by `MemFlags`.
Instead use the `AliasRegion` enum instead to help emphasize that only one region is possible on a `MemFlags`, not multiple.
jameysharp
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Mar 18, 2024
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This looks great, after one minor doc-comment fix I think. Very clear and reviewable, thank you!
Co-authored-by: Jamey Sharp <jamey@minilop.net>
alexcrichton
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This commit uses the support from bytecodealliance#8162 to skip null function pointer checks when performing an indirect call. Instead of an explicit check the segfault from accessing the null function pointer is caught and annotated with the appropriate trap. Closes bytecodealliance#5291
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This commit refactors the internal
MemFlagsbits to be not just flags.Instead some bits are now grouped together and interpreted as a unit.
This enables two primary API changes:
First the
heap/table/vmctxsplit is now represented as an "aliasregion" which is set as an enum. This means that all
MemFlagscarryan
Option<AliasRegion>internally.Second trapping state is now represented as an
Option<TrapCode>.This means that
notrapis no longer a flag andtabletrapis nolonger a flag. This does enable storing arbitrary trap codes though so
long as they aren't
TrapCode::User(_).The main purpose of this commit is to enable using more trap codes with
MemFlagsfor when a segfault is detected. For example with #5291 wewant a segfault to indicate a call-to-null, which is not currently
covered by
MemFlags.