fix memory issues and add basic device discovery

discuss: pci/dtb device discovery? now that the x0 issue is fixed it is
entirely possible.

1 files changed, 20 insertions, 8 deletions

diff --git a/src/core.rs b/src/core.rs
index 60d720b..6317c9e 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -168,7 +168,7 @@ pub fn lh(state: &mut CpuState, rd: usize, rs1: usize, imm: u32) {
 }
 
 pub fn lw(state: &mut CpuState, rd: usize, rs1: usize, imm: u32) {
-    let addr = (state.registers[rs1] + imm) as usize;
+    let addr = (state.registers[rs1].wrapping_add(imm)) as usize;
     let slice = state.memory.read_multiple_bytes(addr, 4, 99).unwrap();
     let number = u32::from_le_bytes(slice[0..4].try_into().unwrap());
 
@@ -224,42 +224,54 @@ pub fn sw(state: &mut CpuState, rs1: usize, rs2: usize, imm: u32) {
 
 pub fn beq(state: &mut CpuState, rs1: usize, rs2: usize, imm: u32) {
     if state.registers[rs1] == state.registers[rs2] {
-        state.pc += imm;
+        state.pc = state.pc.wrapping_add(imm);
+    } else {
+        state.pc += 4;
     }
 }
 
 pub fn bne(state: &mut CpuState, rs1: usize, rs2: usize, imm: u32) {
     if state.registers[rs1] != state.registers[rs2] {
-        state.pc += imm;
+        state.pc = state.pc.wrapping_add(imm);
+    } else {
+        state.pc += 4;
     }
 }
 
 pub fn blt(state: &mut CpuState, rs1: usize, rs2: usize, imm: u32) {
     if (state.registers[rs1] as i32) < (state.registers[rs2] as i32) {
-        state.pc += imm;
+        state.pc = state.pc.wrapping_add(imm);
+    } else {
+        state.pc += 4;
     }
 }
 
 pub fn bge(state: &mut CpuState, rs1: usize, rs2: usize, imm: u32) {
     if (state.registers[rs1] as i32) >= (state.registers[rs2] as i32) {
-        state.pc += imm;
+        state.pc = state.pc.wrapping_add(imm);
+    } else {
+        state.pc += 4;
     }
 }
 
 pub fn bltu(state: &mut CpuState, rs1: usize, rs2: usize, imm: u32) {
     if state.registers[rs1] < state.registers[rs2] {
-        state.pc += imm;
+        state.pc = state.pc.wrapping_add(imm);
+    } else {
+        state.pc += 4;
     }
 }
 
 pub fn bgeu(state: &mut CpuState, rs1: usize, rs2: usize, imm: u32) {
     if state.registers[rs1] >= state.registers[rs2] {
-        state.pc += imm;
+        state.pc = state.pc.wrapping_add(imm);
+    } else {
+        state.pc += 4;
     }
 }
 pub fn jal(state: &mut CpuState, rd: usize, imm: u32) {
     state.registers[rd] = state.pc + 4;
-    state.pc += imm;
+    state.pc = state.pc.wrapping_add(imm);
 }
 
 pub fn jalr(state: &mut CpuState, rd: usize, rs1: usize, imm: u32) {