From f3c3bd738413cd201ea58ac9834b261399037be6 Mon Sep 17 00:00:00 2001
From: pca006132 <john.lck40@gmail.com>
Date: Thu, 2 Jul 2020 13:10:11 +0800
Subject: [PATCH] Backtrace: panic handler with proper backtrace.

---
 src/libunwind/build.rs   |  1 +
 src/runtime/src/main.rs  |  3 +++
 src/runtime/src/panic.rs | 26 ++++++++++++++++++++++++++
 3 files changed, 30 insertions(+)
 create mode 100644 src/runtime/src/panic.rs

diff --git a/src/libunwind/build.rs b/src/libunwind/build.rs
index d38a8854..d7f6645d 100644
--- a/src/libunwind/build.rs
+++ b/src/libunwind/build.rs
@@ -39,6 +39,7 @@ mod llvm_libunwind {
         let cfg = &mut cc::Build::new();
         setup_options(cfg);
         cfg.compiler("clang");
+        cfg.flag("-funwind-tables");
 
         let unwind_sources = vec![
             "Unwind-sjlj.c",
diff --git a/src/runtime/src/main.rs b/src/runtime/src/main.rs
index 21402a9e..2ec3e577 100644
--- a/src/runtime/src/main.rs
+++ b/src/runtime/src/main.rs
@@ -2,6 +2,8 @@
 #![no_main]
 #![recursion_limit="1024"]  // for futures_util::select!
 #![feature(llvm_asm)]
+#![feature(alloc_error_handler)]
+#![feature(panic_info_message)]
 
 extern crate alloc;
 
@@ -24,6 +26,7 @@ mod kernel;
 mod moninj;
 mod load_pl;
 mod eh_artiq;
+mod panic;
 
 fn identifier_read(buf: &mut [u8]) -> &str {
     unsafe {
diff --git a/src/runtime/src/panic.rs b/src/runtime/src/panic.rs
new file mode 100644
index 00000000..b49ba562
--- /dev/null
+++ b/src/runtime/src/panic.rs
@@ -0,0 +1,26 @@
+use libboard_zynq::{slcr, print, println};
+use unwind::backtrace;
+
+#[panic_handler]
+fn panic(info: &core::panic::PanicInfo) -> ! {
+    print!("panic at ");
+    if let Some(location) = info.location() {
+        print!("{}:{}:{}", location.file(), location.line(), location.column());
+    } else {
+        print!("unknown location");
+    }
+    if let Some(message) = info.message() {
+        println!(": {}", message);
+    } else {
+        println!("");
+    }
+    println!("Backtrace: ");
+    let _ = backtrace(|ip| {
+        // Backtrace gives us the return address, i.e. the address after the delay slot,
+        // but we're interested in the call instruction.
+        println!("{:#08x}", ip - 2 * 4);
+    });
+    println!("End backtrace");
+    slcr::RegisterBlock::unlocked(|slcr| slcr.soft_reset());
+    loop {}
+}