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wiggle: copy guest strings from shared memory (#5475)

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* wiggle: copy guest strings from shared memory

Along the same lines as #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.

* review: perform UTF-8 check on `GuestStr` construction
This commit is contained in:
Andrew Brown
2023-01-04 08:10:00 -08:00
committed by GitHub
parent 52ba72f341
commit 7c67378ab6
6 changed files with 96 additions and 54 deletions
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25
crates/wasi-common/src/snapshots/preview_1.rs
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@@ -663,7 +663,7 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
self.table()
.get_dir(u32::from(dirfd))?
.get_cap(DirCaps::CREATE_DIRECTORY)?
.create_dir(path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref())
.create_dir(path.as_cow()?.deref())
.await
}
@@ -678,7 +678,7 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
.get_dir(u32::from(dirfd))?
.get_cap(DirCaps::PATH_FILESTAT_GET)?
.get_path_filestat(
path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref(),
path.as_cow()?.deref(),
flags.contains(types::Lookupflags::SYMLINK_FOLLOW),
)
.await?;
@@ -705,7 +705,7 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
.get_dir(u32::from(dirfd))?
.get_cap(DirCaps::PATH_FILESTAT_SET_TIMES)?
.set_times(
path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref(),
path.as_cow()?.deref(),
atim,
mtim,
flags.contains(types::Lookupflags::SYMLINK_FOLLOW),
@@ -736,9 +736,9 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
src_dir
.hard_link(
src_path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref(),
src_path.as_cow()?.deref(),
target_dir.deref(),
target_path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref(),
target_path.as_cow()?.deref(),
)
.await
}
@@ -764,7 +764,7 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
let oflags = OFlags::from(&oflags);
let fdflags = FdFlags::from(fdflags);
let path = path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)");
let path = path.as_cow()?;
if oflags.contains(OFlags::DIRECTORY) {
if oflags.contains(OFlags::CREATE)
|| oflags.contains(OFlags::EXCLUSIVE)
@@ -813,7 +813,7 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
.table()
.get_dir(u32::from(dirfd))?
.get_cap(DirCaps::READLINK)?
.read_link(path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref())
.read_link(path.as_cow()?.deref())
.await?
.into_os_string()
.into_string()
@@ -835,7 +835,7 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
self.table()
.get_dir(u32::from(dirfd))?
.get_cap(DirCaps::REMOVE_DIRECTORY)?
.remove_dir(path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref())
.remove_dir(path.as_cow()?.deref())
.await
}
@@ -855,9 +855,9 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
.get_cap(DirCaps::RENAME_TARGET)?;
src_dir
.rename(
src_path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref(),
src_path.as_cow()?.deref(),
dest_dir.deref(),
dest_path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref(),
dest_path.as_cow()?.deref(),
)
.await
}
@@ -871,7 +871,7 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
self.table()
.get_dir(u32::from(dirfd))?
.get_cap(DirCaps::SYMLINK)?
.symlink(src_path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref(), dest_path.as_str()?.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref())
.symlink(src_path.as_cow()?.deref(), dest_path.as_cow()?.deref())
.await
}
@@ -883,8 +883,7 @@ impl wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
self.table()
.get_dir(u32::from(dirfd))?
.get_cap(DirCaps::UNLINK_FILE)?
.unlink_file(path.as_str()?
.expect("cannot use with shared memories; see https://github.com/bytecodealliance/wasmtime/issues/5235 (TODO)").deref())
.unlink_file(path.as_cow()?.deref())
.await
}