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Diffstat (limited to 'FutureFeatures.md')
| -rw-r--r-- | FutureFeatures.md | 25 |
1 files changed, 21 insertions, 4 deletions
diff --git a/FutureFeatures.md b/FutureFeatures.md index f2320b1..f8a8397 100644 --- a/FutureFeatures.md +++ b/FutureFeatures.md @@ -40,10 +40,27 @@ possible to use a non-standard ABI for specialized purposes. ## Finer-grained control over memory -* `mmap` of files. -* `madvise(MADV_DONTNEED)`. -* Shared memory, where a physical address range is mapped to multiple physical - pages in a single WebAssembly module as well as across modules. +Provide access to safe OS-provided functionality including: +* `map_file(addr, length, Blob, file-offset)`: semantically, this operation + copies the specified range from `Blob` into the range `[addr, addr+length)` + (where `addr+length <= memory_size`) but implementations are encouraged + to `mmap(addr, length, MAP_FIXED | MAP_PRIVATE, fd)` +* `dont_need(addr, length)`: semantically, this operation zeroes the given range + but the implementation is encouraged to `madvise(addr, length, MADV_DONTNEED)` +* `shmem_create(length)`: create a memory object that can be simultaneously + shared between multiple linear memories +* `map_shmem(addr, length, shmem, shmem-offset)`: like `map_file` except + `MAP_SHARED`, which isn't otherwise valid on read-only Blobs +* `mprotect(addr, length, prot-flags)`: change protection on the range + `[addr, addr+length)` (where `addr+length <= memory_size`) + +The `addr` and `length` parameters above would be required to be multiples of +the [`page_size`](AstSemantics.md#resizing) global constant. + +The above list of functionality mostly covers the set of functionality +provided by the `mmap` OS primitive. One significant exception is that `mmap` +can allocate noncontiguous virtual address ranges. See the +[FAQ](FAQ.md#what-about-mmap) for rationale. ## More expressive control flow |