10d949aa3e
Adding unwinding support for x86_64_fortanix_unknown_sgx target. Unwinding support is provided by our port of LLVM's libunwind which is available from https://github.com/fortanix/libunwind/tree/release_50. libunwind requires support for rwlock and printing to stderr, which is only provided by `std` for this target. This poses two problems: 1) how to expose the `std` functionality to C and 2) dependency inversion. ### Exposing `std` For exposing the functionality we chose to expose the following symbols: * __rust_rwlock_rdlock * __rust_rwlock_wrlock * __rust_rwlock_unlock * __rust_print_err * __rust_abort Also, the following are needed from `alloc`: * __rust_alloc * __rust_dealloc #### Rust RWLock in C In `libunwind`, RWLock is initialized as a templated static variable: ```c pthread_rwlock_t DwarfFDECache<A>::_lock = PTHREAD_RWLOCK_INITIALIZER; ``` I don't know of a good way to use the Rust sys::rwlock::RWLock type and initializer there. We could have a static global variable in Rust, but that doesn't work with the templating. The variable needs to be initialized statically, since this target doesn't support the .init section. Currently, I just used a byte array and standard C array initialization. The mapping between this C type and the Rust type needs to be manually maintained. There is a compile-time check and a unit test to make sure the Rust versions of these C definitions match the actual Rust type. If any reviewer knows of a better solution, please do tell. ### Dependency inversion issue `std` depends on `panic_unwind` which depends on `libunwind`, and `libunwind` depends on `std`. This is not normally supported by Rust's linking system. Therefore we use raw C exports from `std` *and* `libunwind.a` is linked last in the target `post_link_objects` instead of being built as part of the Rust `libunwind`. Currently, all C exports are defined in `src/libstd/sys/sgx/rwlock.rs` to overcome LTO issues. Only the `__rust_rwlock_*` definitions *need* to live there for privacy reasons. Once again, if any reviewer knows of a better solution, please do tell. r? @alexcrichton |
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| abi | ||
| spec | ||
| build.rs | ||
| Cargo.toml | ||
| lib.rs | ||
| README.md | ||
librustc_target contains some very low-level details that are
specific to different compilation targets and so forth.
For more information about how rustc works, see the rustc guide.