add -Zmiri-strict-provenance
This implements [strict provenance](https://github.com/rust-lang/rust/issues/95228) in Miri. The only change is that casting an integer to a pointer does not even attempt to produce a good provenance for the given address; instead, it always uses the invalid provenance. This stricter than even `-Zmiri-tag-raw-pointers` in that it also rejects the following example (which does not even involve Stacked Borrows):
```rust
fn main() {
let x = 22;
let ptr = &x as *const _ as *const u8;
let roundtrip = ptr as usize as *const u8;
let _ = unsafe { roundtrip.offset(1) };
}
```
The new flag also implies `-Zmiri-tag-raw-pointers` since the only reason one would *not* want to tag raw pointers is to support ptr-int-ptr roundtrips.
Note that the flag does *not* check against ptr-to-int *transmutes*; that still requires `-Zmiri-check-number-validity`. You can also check for strict provenance *without* Stacked Borrows by adding `-Zmiri-disable-stacked-borrows`.
The new "Miri hard mode" flags for maximal checking are `-Zmiri-strict-provenance -Zmiri-check-number-validity`. (Add `-Zmiri-symbolic-alignment-check` if you feel extra spicy today.)
Make backtraces work with #[global_allocator]
Currently, backtraces break when the global allocator is overridden because the allocator will attempt to deallocate memory allocated directly by Miri.
~~This PR fixes that by using a new memory kind and providing a function to deallocate it. We can't call the custom allocator to allocate because it's not possible to call a function in the middle of a shim.~~
This PR fixes that by adding a new version of the backtrace API accessible by setting `flags` to 1. Existing code still functions.
backtrace-rs PR: rust-lang/backtrace-rs#462
Fixes https://github.com/rust-lang/miri/issues/1996
This tries to clarify exactly why an access is not valid by printing
what memory range the access was over, which in combination with
tag-tracking may help a user figure out the source of the problem.
Allow varargs for libc::open when it is allowed by the second argument
This PR allows `libc::open` to be called using two or three arguments as defined in https://man7.org/linux/man-pages/man2/open.2.html
The presence of the third argument depends on the value of the second argument. If the second argument dictates that the third argument is *required* miri will emit an error if the argument is missing. If the second argument does *not* require a third argument, then the argument is ignored and passed as 0 internally (it would be ignored by libc anyway)
also ignore 'thread leaks' with -Zmiri-ignore-leaks
This is a step towards https://github.com/rust-lang/miri/issues/1371. The remaining hard part would be supporting checking for memory leaks when there are threads still running. For now we elegantly avoid this problem by using the same flag to control both of these checks. :)
Report an error if a `#[no_mangle]`/`#[export_name = ...]` function has the same symbol name as a built-in shim
Implements https://github.com/rust-lang/miri/pull/1776#issuecomment-821322605.
The error looks like this:
```
error: found `malloc` symbol definition that clashes with a built-in shim
--> tests/compile-fail/function_calls/exported_symbol_shim_clashing.rs:12:9
|
12 | malloc(0);
| ^^^^^^^^^ found `malloc` symbol definition that clashes with a built-in shim
|
help: the `malloc` symbol is defined here
--> tests/compile-fail/function_calls/exported_symbol_shim_clashing.rs:2:1
|
2 | / extern "C" fn malloc(_: usize) -> *mut std::ffi::c_void {
3 | | //~^ HELP the `malloc` symbol is defined here
4 | | unreachable!()
5 | | }
| |_^
= note: inside `main` at tests/compile-fail/function_calls/exported_symbol_shim_clashing.rs:12:9
```
This does not implement "better error messages than we do currently for arg/ABI mismatches" in https://github.com/rust-lang/miri/pull/1776#issuecomment-821343175 -- I failed to remove all `check_arg_count()` and `check_abi()` (they are still used in `src/shims/intrinsics.rs` and `call_dlsym()`) and they don't receive the name of the shim.
