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Auto merge of #99420 - RalfJung:vtable, r=oli-obk

make vtable pointers entirely opaque

This implements the scheme discussed in https://github.com/rust-lang/unsafe-code-guidelines/issues/338: vtable pointers should be considered entirely opaque and not even readable by Rust code, similar to function pointers.

- We have a new kind of `GlobalAlloc` that symbolically refers to a vtable.
- Miri uses that kind of allocation when generating a vtable.
- The codegen backends, upon encountering such an allocation, call `vtable_allocation` to obtain an actually dataful allocation for this vtable.
- We need new intrinsics to obtain the size and align from a vtable (for some `ptr::metadata` APIs), since direct accesses are UB now.

I had to touch quite a bit of code that I am not very familiar with, so some of this might not make much sense...
r? `@oli-obk`
This commit is contained in:
bors 2022-07-22 01:33:49 +00:00
commit aa01891700
69 changed files with 673 additions and 527 deletions

View file

@ -1565,6 +1565,8 @@ symbols! {
volatile_store,
vreg,
vreg_low16,
vtable_align,
vtable_size,
warn,
wasm_abi,
wasm_import_module,