uplink: add panic extern

piecrust-uplink/CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add call to `panic` in panic handler [#271]
+- Add `panic` extern [#271]
+
 ### Removed
 
 - Remove call to `hdebug` on panic [#271]

piecrust-uplink/src/abi.rs

@@ -4,6 +4,8 @@
 //
 // Copyright (c) DUSK NETWORK. All rights reserved.
 
+use core::fmt::{self, Write};
+
 mod allocator;
 
 mod handlers;
@@ -19,3 +21,37 @@ pub use state::*;
 mod debug;
 #[cfg(feature = "debug")]
 pub use debug::*;
+
+/// A small struct that can `fmt::Write` to the argument buffer.
+///
+/// It is just an offset to the argument buffer, representing how much has been
+/// written to it.
+#[derive(Default)]
+pub struct ArgbufWriter(usize);
+
+impl ArgbufWriter {
+    pub fn ofs(&self) -> usize {
+        self.0
+    }
+}
+
+impl Write for ArgbufWriter {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        let bytes = s.as_bytes();
+        let bytes_len = bytes.len();
+
+        let new_ofs = self.0 + bytes_len;
+
+        if new_ofs > crate::ARGBUF_LEN {
+            return Err(fmt::Error);
+        }
+
+        state::with_arg_buf(|buf| {
+            buf[self.0..new_ofs].copy_from_slice(bytes);
+        });
+
+        self.0 = new_ofs;
+
+        Ok(())
+    }
+}

piecrust-uplink/src/abi/debug.rs

@@ -4,49 +4,10 @@
 //
 // Copyright (c) DUSK NETWORK. All rights reserved.
 
-use core::fmt::{self, Write};
-
-use crate::abi::state;
-use crate::ARGBUF_LEN;
-
 extern "C" {
     pub fn hdebug(arg_len: u32);
 }
 
-/// A small struct that can `fmt::Write` to the argument buffer.
-///
-/// It is just an offset to the argument buffer, representing how much has been
-/// written to it.
-#[derive(Default)]
-pub struct ArgbufWriter(usize);
-
-impl ArgbufWriter {
-    pub fn ofs(&self) -> usize {
-        self.0
-    }
-}
-
-impl Write for ArgbufWriter {
-    fn write_str(&mut self, s: &str) -> fmt::Result {
-        let bytes = s.as_bytes();
-        let bytes_len = bytes.len();
-
-        let new_ofs = self.0 + bytes_len;
-
-        if new_ofs > ARGBUF_LEN {
-            return Err(fmt::Error);
-        }
-
-        state::with_arg_buf(|buf| {
-            buf[self.0..new_ofs].copy_from_slice(bytes);
-        });
-
-        self.0 = new_ofs;
-
-        Ok(())
-    }
-}
-
 /// Macro to format and send debug output to the host
 #[macro_export]
 macro_rules! debug {

piecrust-uplink/src/abi/handlers.rs

@@ -4,10 +4,27 @@
 //
 // Copyright (c) DUSK NETWORK. All rights reserved.
 
+use core::fmt::Write;
 use core::panic::PanicInfo;
 
+extern "C" {
+    pub fn panic(arg_len: u32);
+}
+
 #[panic_handler]
-fn panic(_info: &PanicInfo) -> ! {
+unsafe fn handle_panic(info: &PanicInfo) -> ! {
+    let mut w = crate::ArgbufWriter::default();
+
+    // If we fail in writing to the argument buffer, we just call `panic` after
+    // writing a standard message instead.
+    if let Some(args) = info.message() {
+        if w.write_fmt(*args).is_err() {
+            w = crate::ArgbufWriter::default();
+            let _ = write!(w, "PANIC INFO TOO LONG");
+        }
+    }
+
+    panic(w.ofs() as u32);
     unreachable!()
 }