[exception] Print stack trace instruction pointer on crash

Author: scopeInfinity

src/kernel/interrupts/exceptions.asm

@@ -4,6 +4,7 @@
 
 extern interrupt_handler_0x00_0x1F_exception
 
+global at_stack
 global _interrupt_handler_0x00_exception
 global _interrupt_handler_0x01_exception
 global _interrupt_handler_0x02_exception
@@ -69,6 +70,22 @@ global _interrupt_handler_0x1F_exception
         iret
 %endmacro
 
+  at_stack:
+    push ebp
+    mov ebp, esp
+
+    push ds
+    mov eax, ss
+    mov ds, eax
+
+    mov esi, [ebp+8]  ; stack pointer
+    mov eax, [esi]
+
+    pop ds
+
+    pop ebp
+    ret
+
     create_low__interrupt_handler_xy_exception_nohup 0x00  ; divide-by-zero
     create_low__interrupt_handler_xy_exception 0x01
     create_low__interrupt_handler_xy_exception 0x02

src/kernel/interrupts/exceptions.c

@@ -50,6 +50,8 @@ struct exceptionContext {
     int ip, cs, eflag;
 };
 
+int at_stack(int esp);
+
 void interrupt_handler_0x00_0x1F_exception(struct exceptionContext context) {
     // written for handler with error code otherwise ip, cs and eflag will skew.
     const int gdte_size = sizeof(struct GDTEntry);
@@ -74,13 +76,14 @@ void interrupt_handler_0x00_0x1F_exception(struct exceptionContext context) {
     // stack trace
     {
         const int stack_trace_max_depth = 5;
-        int last_ebp = context.ebp;
+        int ebp = context.ebp;
         // stack[ebp] => previous_ebp, if previous_ebp == 0 then break;
-        for(int i=0; i<stack_trace_max_depth; i++) {
-            // to be implemented
-            break;
+        print_log("stack trace: \n - %x", context.ip);
+        for(int i=0; ebp>0 && i<stack_trace_max_depth; i++) {
+            int return_address = at_stack(ebp+4);
+            print_log(" - %x (ni)", return_address);
+            ebp = at_stack(ebp);
         }
-
     }