wiggle: copy guest strings from shared memory #5475
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alexcrichton merged 2 commits intobytecodealliance:mainfrom Jan 4, 2023
Merged
wiggle: copy guest strings from shared memory #5475alexcrichton merged 2 commits intobytecodealliance:mainfrom
alexcrichton merged 2 commits intobytecodealliance:mainfrom
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Depends on #5471; review that PR first! |
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alexcrichton
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Along the same lines as bytecodealliance#5471, this change adds a new smart pointer, `GuestStrCow`, to copy the string bytes over from Wasm memory to the host when the string is found in shared memory. This is necessary to maintain Rust guarantees: with shared memory, the bytes backing a `GuestStr` could be altered by another thread and this would invalidate the assumption that we can dereference at any point to `&str`. `GuestStrCow` is essentially a wrapper around `GuestStr` when the memory is not shared but copies the memory region into a `String` when the memory is shared. This change updates the uses of Wiggle strings in both wasi-common and wasi-crypto.
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alexcrichton
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Along the same lines as #5471, this change adds a new smart pointer,
GuestStrCow, to copy the string bytes over from Wasm memory to thehost when the string is found in shared memory. This is necessary to
maintain Rust guarantees: with shared memory, the bytes backing a
GuestStrcould be altered by another thread and this would invalidatethe assumption that we can dereference at any point to
&str.GuestStrCowis essentially a wrapper aroundGuestStrwhen the memoryis not shared but copies the memory region into a
Stringwhen thememory is shared.