From bfd7592c10befe0ba086f15bf169ab85a311a75e Mon Sep 17 00:00:00 2001
From: Nathan Lee <me@nwlee.tech>
Date: Mon, 24 Aug 2026 20:23:16 -0500
Subject: add floating point error CSR

---
 src/core.rs        | 8 ++++++--
 src/main.rs        | 3 ++-
 wrv32em-common.dts | 2 ++
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/core.rs b/src/core.rs
index 2746d1b..24c6a8f 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -388,8 +388,12 @@ pub fn fdiv_s(state: &mut CpuState, rd: usize, rs1: usize, rs2: usize) {
     let b = state.f_registers[rs2];
 
     state.f_registers[rd] = if b == 0.0 {
-        f32::NAN
-        // todo: raise division by zero in csr
+        state.csr[0x001 /*fflags*/] |= 0b100;
+        if a.is_sign_positive() {
+            f32::INFINITY
+        } else {
+            f32::NEG_INFINITY
+        }
     } else {
         a / b
     }
diff --git a/src/main.rs b/src/main.rs
index 74515b1..814dfeb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -420,7 +420,8 @@ fn return_to_userspace(state: &mut CpuState) {
 }
 
 fn exit(state: &mut CpuState) {
-    let data = read_all(&state.memory, RINGBUF_ADDR as u32, RINGBUF_SIZE as u32);
+    let mut data = read_all(&state.memory, RINGBUF_ADDR as u32, RINGBUF_SIZE as u32);
+    data.retain(|&x| x != 0);
     std::fs::write("core_dump.txt", data).unwrap();
     std::process::exit(0);
 }
diff --git a/wrv32em-common.dts b/wrv32em-common.dts
index 7ba1946..969821c 100644
--- a/wrv32em-common.dts
+++ b/wrv32em-common.dts
@@ -4,6 +4,8 @@
     #address-cells = <1>;
     #size-cells = <1>;
 
+    initrd = <0x50000000 0x50000000>;
+
     memory@80000000 {
         device_type = "memory";
         status = "okay";
-- 
cgit v1.2.3