kernel panic and trapping :)

src/boot/entry.S

@@ -2,11 +2,15 @@
 .global _start
 _start:
     la sp, stack_top      # Set up the stack pointer
+    la t0, trap_entry     # Set up the trap handler
+    csrw mtvec, t0        # Set the trap vector to our trap handler
     call kmain            # Jump to our C code
 loop:
     wfi                   # Wait for Interrupt (saves CPU)
     j loop                # Infinite loop if C returns
-
+.align 4
+trap_entry:
+    j handle_trap
 .section .bss
 .align 16
 stack_low:

src/kernel/kernel.c

@@ -2,8 +2,10 @@
 #include <stddef.h>
 #include <drivers/uart.h>
 #include <syscon/syscon.h>
+#include <kernel/panic.h>
 
 void kmain() {
     kprint("Hello, OS World!\n");
+    kpanic_force();
     poweroff();
 }

src/kernel/panic.c

@@ -0,0 +1,27 @@
+#include <stddef.h>
+#include <stdint.h>
+#include <drivers/uart.h>
+#include <syscon/syscon.h>
+
+void kpanic(const char *reason){
+	kprint(reason);
+	poweroff();
+}
+
+void kpanic_force() {
+    // 1. Immediate Output
+    kprint("\n!!! FORCE PANIC !!!\n");
+
+    // 2. Trigger a hardware breakpoint or illegal instruction
+    // This allows a debugger (GDB) to stop exactly here.
+    // 'ebreak' is the standard RISC-V way to trigger a debug trap.
+    __asm__ volatile("ebreak");
+
+    // 3. If no debugger is attached or we continue, kill the VM
+    poweroff();
+
+    // 4. Final halt
+    while(1) {
+        __asm__ volatile("wfi");
+    }
+}

src/kernel/panic.h

@@ -0,0 +1,16 @@
+#ifndef PANIC_H
+#define PANIC_H
+
+void kpanic(const char *reason);
+void kpanic_force();
+
+#define KASSERT(cond, msg) \
+    if (!(cond)) { \
+        kprint("ASSERTION FAILED: "); \
+        kprint(__FILE__); \
+        kprint(":"); \
+        /* Note: Printing line numbers requires a custom itoa/printf */ \
+        kpanic(msg); \
+    }
+
+#endif

src/kernel/trap.c

@@ -0,0 +1,20 @@
+#include <stdint.h>
+#include <stddef.h>
+#include <drivers/uart.h>
+#include <syscon/syscon.h>
+
+void handle_trap() {
+    kprint("\n!!! HARDWARE EXCEPTION DETECTED !!!\n");
+    
+    // Read the 'mcause' register to see WHY we trapped
+    unsigned long cause;
+    __asm__ volatile("csrr %0, mcause" : "=r"(cause));
+
+    if (cause == 3) { // 3 is the code for 'breakpoint' (ebreak)
+        kprint("Reason: ebreak (Breakpoint)\n");
+    } else {
+        kprint("Reason: Other Exception\n");
+    }
+
+    poweroff();
+}