Attempt to capture panics with GDB

bittide-instances/data/gdb/smoltcp-hitl-prog.gdb

@@ -1,9 +1,24 @@
 # SPDX-FileCopyrightText: 2024 Google LLC
 #
 # SPDX-License-Identifier: Apache-2.0
+set logging file ./_build/hitl/gdb-out.log
+set logging overwrite on
+set logging enabled on
 file "./_build/cargo/firmware-binaries/riscv32imc-unknown-none-elf/release/smoltcp_client"
-target extended-remote :3333
 
-# Load binary on CPU and start execution
+break core::panicking::panic
+break ExceptionHandler
+break rust_begin_unwind
+break smoltcp_client::gdb_panic
+
+target extended-remote :3333
 load
-start
+
+define hook-stop
+printf "!!! program stopped executing !!!"
+i r
+bt
+quit 1
+end
+
+continue

firmware-binaries/.cargo/config.toml

@@ -4,7 +4,12 @@
 
 [build]
 target = "riscv32imc-unknown-none-elf"
-rustflags = ["-C", "target-feature=+f"]
+rustflags = [
+  "-C", "target-feature=+f",
+  # XXX: These two seem to be ignored
+  "-C", "force-frame-pointers=yes",
+  "-C", "force-unwind-tables=yes"
+]
 target-dir = "../_build/cargo/firmware-binaries"
 
 [unstable]

firmware-binaries/examples/smoltcp_client/Cargo.toml

@@ -12,10 +12,26 @@ authors = ["Google LLC"]
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-bittide-sys = { path = "../../../firmware-support/bittide-sys" }
-riscv-rt = "0.11.0"
 riscv = "^0.10"
-heapless = { version = "0.8", default-features = false}
-smoltcp = { git = "https://github.com/smoltcp-rs/smoltcp.git", rev = "dc08e0b42e668c331bb2b6f8d80016301d0efe03", default-features = false, features = ["medium-ethernet", "proto-ipv4", "socket-tcp", "socket-dhcpv4"] }
+riscv-rt = "0.11.0"
 ufmt = "0.2.0"
-log = {version = "0.4.21", features = ["max_level_off", "release_max_level_info"]}
+
+[dependencies.bittide-sys]
+path = "../../../firmware-support/bittide-sys"
+
+[dependencies.gdb-trace]
+path = "../../../firmware-support/gdb-trace"
+
+[dependencies.heapless]
+version = "0.8"
+default-features = false
+
+[dependencies.log]
+version = "0.4.21"
+features = ["max_level_off", "release_max_level_info"]
+
+[dependencies.smoltcp]
+git = "https://github.com/smoltcp-rs/smoltcp.git"
+rev = "dc08e0b42e668c331bb2b6f8d80016301d0efe03"
+default-features = false
+features = ["medium-ethernet", "proto-ipv4", "socket-tcp", "socket-dhcpv4"]

firmware-binaries/examples/smoltcp_client/src/main.rs

@@ -42,6 +42,10 @@ const CHUNK_SIZE: usize = 4096;
 const SERVER_IP: IpAddress = IpAddress::v4(10, 0, 0, 1);
 const SERVER_PORT: u16 = 1234;
 
+gdb_trace::gdb_panic! {
+    unsafe { Uart::new(UART_ADDR) }
+}
+
 // See https://github.com/bittide/bittide-hardware/issues/681
 #[allow(static_mut_refs)]
 #[cfg_attr(not(test), entry)]
@@ -178,18 +182,6 @@ fn exception_handler(_trap_frame: &riscv_rt::TrapFrame) -> ! {
     }
 }
 
-#[panic_handler]
-fn panic_handler(info: &core::panic::PanicInfo) -> ! {
-    let mut uart = unsafe { Uart::new(UART_ADDR) };
-
-    uwriteln!(uart, "Panicked!").unwrap();
-    info!("error: {}\n", info);
-    uwriteln!(uart, "Looping forever now").unwrap();
-    loop {
-        continue;
-    }
-}
-
 fn update_dhcp(iface: &mut Interface, socket: &mut dhcpv4::Socket) {
     let event = socket.poll();
     match event {

firmware-support/Cargo.toml

@@ -4,6 +4,6 @@
 
 [workspace]
 members = [
-  "bittide-sys",
+  "bittide-sys", "gdb-trace",
 ]
 resolver = "2"

firmware-support/gdb-trace/Cargo.toml

@@ -0,0 +1,13 @@
+# SPDX-FileCopyrightText: 2022 Google LLC
+#
+# SPDX-License-Identifier: CC0-1.0
+
+[package]
+name = "gdb-trace"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+riscv = "0.12.1"

firmware-support/gdb-trace/src/lib.rs

@@ -0,0 +1,29 @@
+// SPDX-FileCopyrightText: 2022 Google LLC
+//
+// SPDX-License-Identifier: Apache-2.0
+
+#![no_std]
+
+use core::{fmt::Write, panic::PanicInfo};
+
+/// Internal function for a GDB panic handler. It disables interrupts and attemps to write
+/// the panic info to the provided write-able interface. It's expected that the user will
+/// be running a GDB process and set a breakpoint to the panic handler so that the output
+/// can be read.
+#[allow(clippy::empty_loop)]
+pub fn gdb_panic_internal<W: Write>(writer: &mut W, info: &PanicInfo) -> ! {
+    riscv::interrupt::machine::disable();
+    writeln!(writer, "{:?}", info).unwrap();
+    loop {}
+}
+
+#[macro_export]
+macro_rules! gdb_panic {
+    ($writer:expr) => {
+        #[panic_handler]
+        fn gdb_panic(info: &::core::panic::PanicInfo) -> ! {
+            let mut writer = $writer;
+            $crate::gdb_panic_internal(&mut writer, info);
+        }
+    };
+}