Add test triggering cpu fault and check extended error info

To do this, we write an illegal instruction at the rom_entry
symbol in the rom binary.

rom/dev/tests/rom_integration_tests/main.rs

@@ -5,6 +5,7 @@ mod helpers;
 mod rv32_unit_tests;
 mod test_capabilities;
 mod test_cfi;
+mod test_cpu_fault;
 mod test_dice_derivations;
 mod test_fake_rom;
 mod test_fmcalias_derivation;

rom/dev/tests/rom_integration_tests/test_cpu_fault.rs

@@ -0,0 +1,59 @@
+// Licensed under the Apache-2.0 license
+
+use caliptra_builder::firmware;
+use caliptra_hw_model::{BootParams, HwModel, InitParams};
+use elf::{endian::LittleEndian, ElfBytes};
+
+#[test]
+fn test_cpu_fault() {
+    const GLOBAL_EXCEPTION: u32 = 0x01050002;
+
+    let rom_fwid = firmware::rom_from_env();
+
+    let elf_bytes = caliptra_builder::build_firmware_elf(rom_fwid).unwrap();
+    let mut rom = caliptra_builder::elf2rom(&elf_bytes).unwrap();
+    let elf = ElfBytes::<LittleEndian>::minimal_parse(&elf_bytes).unwrap();
+    let symbol_table = elf.symbol_table().unwrap().unwrap().0;
+    let string_table = elf.symbol_table().unwrap().unwrap().1;
+    let rom_entry_offset = symbol_table
+        .iter()
+        .find(|symbol| string_table.get(symbol.st_name as usize).unwrap() == "rom_entry")
+        .unwrap()
+        .st_value as usize;
+    println!("rom_entry_offset is {}", rom_entry_offset);
+
+    // Write an instruction that causes a cpu fault to the rom_entry offset
+    let illegal_instruction = [0xFF, 0xFF, 0xFF, 0xFF];
+    rom[rom_entry_offset..rom_entry_offset + illegal_instruction.len()]
+        .copy_from_slice(&illegal_instruction);
+
+    let mut hw = caliptra_hw_model::new(BootParams {
+        init_params: InitParams {
+            rom: &rom,
+            ..Default::default()
+        },
+        ..Default::default()
+    })
+    .unwrap();
+
+    hw.step_until(|m| m.soc_ifc().cptra_fw_error_fatal().read() == GLOBAL_EXCEPTION);
+
+    let mcause = hw.soc_ifc().cptra_fw_extended_error_info().at(0).read();
+    let mscause = hw.soc_ifc().cptra_fw_extended_error_info().at(1).read();
+    let mepc = hw.soc_ifc().cptra_fw_extended_error_info().at(2).read();
+    let ra = hw.soc_ifc().cptra_fw_extended_error_info().at(3).read();
+
+    println!(
+        "ROM Global Exception mcause=0x{:08X} mscause=0x{:08X} mepc=0x{:08X} ra=0x{:08X}",
+        mcause, mscause, mepc, ra,
+    );
+
+    // mcause must be illegal instruction
+    assert_eq!(mcause, 0x2);
+    // no mscause
+    assert_eq!(mscause, 0);
+    // mepc must be the value of the program counter at the failing instruction at rom_entry_offset
+    assert_eq!(mepc as usize, rom_entry_offset);
+    // return address won't be 0
+    assert_ne!(ra, 0);
+}