Emerald: Implement panic unwind using unwinding crate

This is simliar to what xous target does, we just copies and changed how we get the `eh_frame` to use the new
feature we added in `emerald_std`

Author: Amjad50

Cargo.lock

@@ -1212,15 +1212,15 @@ dependencies = [
 
 [[package]]
 name = "emerald_kernel_user_link"
-version = "0.2.7"
+version = "0.2.8"
 dependencies = [
  "compiler_builtins",
  "rustc-std-workspace-core",
 ]
 
 [[package]]
 name = "emerald_std"
-version = "0.2.8"
+version = "0.2.9"
 dependencies = [
  "compiler_builtins",
  "emerald_kernel_user_link",

compiler/rustc_target/src/spec/base/emerald.rs

@@ -9,7 +9,7 @@ pub fn opts() -> TargetOptions {
         // position_independent_executables: false,
         // static_position_independent_executables: false,
         // has_thread_local: false,
-        panic_strategy: PanicStrategy::Abort,
+        panic_strategy: PanicStrategy::Unwind,
         ..Default::default()
     }
 }

library/panic_unwind/src/lib.rs

@@ -50,6 +50,7 @@ cfg_if::cfg_if! {
         all(target_family = "windows", target_env = "gnu"),
         target_os = "psp",
         target_os = "xous",
+        target_os = "emerald",
         target_os = "solid_asp3",
         all(target_family = "unix", not(target_os = "espidf")),
         all(target_vendor = "fortanix", target_env = "sgx"),

library/std/Cargo.toml

@@ -61,7 +61,7 @@ r-efi-alloc = { version = "1.0.0", features = ['rustc-dep-of-std'] }
 # This is from `https://github.com/Amjad50/Emerald`, i.e. it must be run from that context
 # TODO: for now we are using relative path, as we are using `libm` from `git` and we can't publish
 #       that. Fix it later
-emerald_std = { version = "0.2.8", features = ['rustc-dep-of-std'], path = "../../../../libraries/emerald_std" }
+emerald_std = { version = "0.2.9", features = ['rustc-dep-of-std'], path = "../../../../libraries/emerald_std" }
 
 [features]
 backtrace = [

library/std/src/sys/pal/emerald/os.rs

@@ -7,9 +7,30 @@ use crate::io;
 use crate::marker::PhantomData;
 use crate::os::emerald::prelude::OsStringExt;
 use crate::path::{self, PathBuf};
+use crate::ptr::addr_of;
 use crate::sys::common::small_c_string::run_path_with_cstr;
 use crate::sys::pal::emerald::syscall_to_io_error;
 
+#[cfg(not(test))]
+#[cfg(feature = "panic_unwind")]
+mod eh_unwinding {
+    pub(crate) struct EhFrameFinder(usize /* eh_frame */);
+    pub(crate) static mut EH_FRAME_SETTINGS: EhFrameFinder = EhFrameFinder(0);
+    impl EhFrameFinder {
+        pub(crate) fn init(&mut self, eh_frame: usize) {
+            self.0 = eh_frame;
+        }
+    }
+    unsafe impl unwind::EhFrameFinder for EhFrameFinder {
+        fn find(&self, _pc: usize) -> Option<unwind::FrameInfo> {
+            Some(unwind::FrameInfo {
+                text_base: None,
+                kind: unwind::FrameInfoKind::EhFrame(self.0),
+            })
+        }
+    }
+}
+
 // This function is needed by the panic runtime. The symbol is named in
 // pre-link args for the target specification, so keep that in sync.
 #[no_mangle]
@@ -22,6 +43,13 @@ extern "C" {
 
 #[no_mangle]
 pub extern "C" fn _start(argc: isize, argv: *const *const u8) -> ! {
+    #[cfg(not(test))]
+    #[cfg(feature = "panic_unwind")]
+    unsafe {
+        eh_unwinding::EH_FRAME_SETTINGS
+            .init(emerald_std::process::process_metadata().eh_frame_adress);
+        unwind::set_custom_eh_frame_finder(&*addr_of!(eh_unwinding::EH_FRAME_SETTINGS)).ok();
+    }
     exit(unsafe { main(argc, argv) });
 }
 

library/std/src/sys/personality/mod.rs

@@ -30,6 +30,7 @@ cfg_if::cfg_if! {
         target_os = "psp",
         target_os = "xous",
         target_os = "solid_asp3",
+        target_os = "emerald",
         all(target_family = "unix", not(target_os = "espidf"), not(target_os = "l4re")),
         all(target_vendor = "fortanix", target_env = "sgx"),
     ))] {

library/unwind/Cargo.toml

@@ -19,7 +19,7 @@ libc = { version = "0.2.140", features = ['rustc-dep-of-std'], default-features
 compiler_builtins = "0.1.0"
 cfg-if = "1.0"
 
-[target.'cfg(target_os = "xous")'.dependencies]
+[target.'cfg(any(target_os = "xous", target_os = "emerald"))'.dependencies]
 unwinding = { version = "0.2.1", features = ['rustc-dep-of-std', 'unwinder', 'fde-custom'], default-features = false }
 
 [features]

library/unwind/src/lib.rs

@@ -26,7 +26,7 @@ cfg_if::cfg_if! {
     ))] {
         mod libunwind;
         pub use libunwind::*;
-    } else if #[cfg(target_os = "xous")] {
+    } else if #[cfg(any(target_os = "xous", target_os = "emerald"))] {
         mod unwinding;
         pub use unwinding::*;
     } else {

library/unwind/src/unwinding.rs

@@ -1,6 +1,6 @@
 #![allow(nonstandard_style)]
 
-use libc::{c_int, c_void};
+use core::ffi::{c_int, c_void};
 
 #[repr(C)]
 #[derive(Copy, Clone, PartialEq)]