unwind: add support for using `unwinding` crate

The `unwinding` crate supports processing unwinding data, and is written
entirely in Rust. This allows it to be ported to new platforms more
easily than using the llvm-based `libunwind`.

While `libunwind` is very well supported on major targets, it is
difficult to use on other targets. SGX is an example of this where Rust
carries custom patches in order to enable backtrace support.

This adds an alternative for supported architectures. Rather than
providing a custom target, `unwinding` allows for a solution that is
completely written in Rust.

This adds `xous` as the first consumer, and forthcoming patches will
modify libstd to take advantage of this.

Signed-off-by: Sean Cross <sean@xobs.io>

1 files changed, 3 insertions, 0 deletions

diff --git a/library/unwind/src/lib.rs b/library/unwind/src/lib.rs
index 335bded71c1..eeee98f754e 100644
--- a/library/unwind/src/lib.rs
+++ b/library/unwind/src/lib.rs
@@ -26,6 +26,9 @@ cfg_if::cfg_if! {
     ))] {
         mod libunwind;
         pub use libunwind::*;
+    } else if #[cfg(target_os = "xous")] {
+        mod unwinding;
+        pub use unwinding::*;
     } else {
         // no unwinder on the system!
         // - wasm32 (not emscripten, which is "unix" family)