[exceptions] Print all registers state before crash

Author: scopeInfinity

src/kernel/core.asm

@@ -17,6 +17,7 @@ global kernel_core_entry_asm
         mov fs, ax
         mov gs, ax
 
+        xor ebp, ebp    ; origin of stack trace
         mov esp, STACKINIT_KERNEL_CORE  ; init stack pointer
         jmp kernel_core_entry
 

src/kernel/interrupts/exceptions.asm

@@ -43,16 +43,23 @@ global _interrupt_handler_0x1F_exception
     _interrupt_handler_%1_exception:
         ; As we are HLT at end of exception there
         ; is no need to save context for now.
+        pushad         ; execution all general purpose registers
+
         xor eax, eax
+        mov eax, gs    ; execution gs
+        push eax
+        mov eax, fs    ; execution fs
+        push eax
+        mov eax, es    ; execution es
+        push eax
         mov eax, ds    ; execution ds
         push eax
-        xor eax, eax
-        mov eax, ss    ; execution ss (current also)
+        mov eax, ss    ; execution ss
+        push eax
+        mov eax, %1    ; exception id
         push eax
         mov eax, GDT_KERNEL_DS  ; kernel ds
         mov ds, eax
-        mov eax, %1
-        push eax
         call interrupt_handler_0x00_0x1F_exception
         HLT
 %endmacro

src/kernel/interrupts/exceptions.c

@@ -37,41 +37,58 @@ extern void _interrupt_handler_0x1D_exception();
 extern void _interrupt_handler_0x1E_exception();
 extern void _interrupt_handler_0x1F_exception();
 
-void interrupt_handler_0x00_0x1F_exception(int id, int err_code, int ds, int ss, int ip, int cs, int eflag) {
+#define gdt_address_from_segment(s, gdte_size) (((s)%(gdte_size)==0)?get_gdt_baseaddress(gdt_table, GDT_TABLE_SIZE, (s)/(gdte_size)):-1)
+
+struct exceptionContext {
+    int id;  // exception id
+
+    int ss, ds, es, fs, gs;
+    int edi, esi, ebp, esp, ebx, edx, ecx, eax;
+
+    // at end
+    int err_code;  // can be optional for some interrupts.
+    int ip, cs, eflag;
+};
+
+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);
     panic_screen_init();
-    print_log("Hardware exception %d (0x%x) triggered", id, id);
-    print_log("  Error Code: %x", err_code);
-    print_log("  CS    : %x (GDT entry)", cs);
-    print_log("  DS    : %x (GDT entry)", ds);
-    print_log("  SS    : %x (GDT entry)", ss);
-    print_log("  IP    : %x", ip);
-    print_log("  FLAG  : %x", eflag);
-    if(cs%sizeof(struct GDTEntry)==0) {
-        print_log("  PID   : %d", get_idt_reverse_pid_lookup_cs(cs));
-        unsigned int abs_cs = get_gdt_baseaddress(gdt_table, GDT_TABLE_SIZE, cs/sizeof(struct GDTEntry));
-        print_log("  abs IP: %x", abs_cs+ip);
-        print_log("  abs CS: %x", abs_cs);
-    } else {
-        print_log("  PID   : invalid");
-        print_log("  abs IP: invalid");
-        print_log("  abs CS: invalid");
-    }
-    if(ds%sizeof(struct GDTEntry)==0) {
-        print_log("  abs DS: %x", get_gdt_baseaddress(gdt_table, GDT_TABLE_SIZE, ds/sizeof(struct GDTEntry)));
-    } else {
-        print_log("  abs DS: invalid");
+
+    print_log("Hardware exception %d (0x%x) triggered", context.id, context.id);
+    print_log("  Error Code: %x", context.err_code);
+    if(context.cs%gdte_size==0) {
+        print_log("  PID   : %d", get_idt_reverse_pid_lookup_cs(context.cs));
     }
-    if(ss%sizeof(struct GDTEntry)==0) {
-        print_log("  abs SS: %x", get_gdt_baseaddress(gdt_table, GDT_TABLE_SIZE, ss/sizeof(struct GDTEntry)));
-    } else {
-        print_log("  abs SS: invalid");
+    print_log("  FLAG  : %x", context.eflag);
+    print_log("  IP    : %x", context.ip);
+    print_log("  CS    : %x => %x", context.cs, gdt_address_from_segment(context.cs, gdte_size));
+    print_log("  DS    : %x => %x", context.ds, gdt_address_from_segment(context.ds, gdte_size));
+    print_log("  SS    : %x => %x", context.ss, gdt_address_from_segment(context.ss, gdte_size));
+    print_log("  ES    : %x => %x", context.es, gdt_address_from_segment(context.es, gdte_size));
+    print_log("  FS    : %x => %x", context.fs, gdt_address_from_segment(context.fs, gdte_size));
+    print_log("  GS    : %x => %x", context.gs, gdt_address_from_segment(context.gs, gdte_size));
+    print_log("  EAX: %x EBX: %x ECX: %x EDX: %x", context.eax, context.ebx, context.ecx, context.edx);
+    print_log("  ESP: %x EBP: %x ESI: %x EDI: %x", context.esp, context.ebp, context.esi, context.edi);
+
+    // stack trace
+    {
+        const int stack_trace_max_depth = 5;
+        int last_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;
+        }
+
     }
 
-    switch (id) {
+
+    switch (context.id) {
         case 0x0D:
-            PANIC(id, "[hw_exception] general_protection_fault");
+            PANIC(context.id, "[hw_exception] general_protection_fault");
     }
-    PANIC(id, "[hw_exception] triggered: no handler");
+    PANIC(context.id, "[hw_exception] triggered: no handler");
 }
 
 void interrupt_handler_0x0D_general_protection_fault(int id, int ip, int cs) {

src/kernel/interrupts/timer.asm

@@ -118,11 +118,19 @@ global create_infant_process_irq0_stack
         ; do_not_care: next two cs, ip
         ; CS and IP doesn't matter, as they are controlled by _int_irq0_end
 
-        ; do_not_care: next four are eax, ebx, ecx, edx
+        ; user: pushad
         mov ecx, eax
         sub ecx, 8
-        mov [eax-12-24], ecx ; pushad esp
-        ; do_not_care: next three are ebp, esi, edi
+        mov [eax-28], ecx
+        mov ecx, 0
+        mov [eax-12], ecx  ; user: eax
+        mov [eax-16], ecx  ; user: ecx
+        mov [eax-20], ecx  ; user: edx
+        mov [eax-24], ecx  ; user: ebx
+        ; missing esp, pushed on top.
+        mov [eax-32], ecx  ; user: ebp==0, origin of stack trace.
+        mov [eax-36], ecx  ; user: esi
+        mov [eax-40], ecx  ; user: edi
 
         mov ecx, [ebp+0x08]     ; arg0
         mov [eax-44], ecx       ; user: ds

src/usr/local/src/cat.c

@@ -9,7 +9,7 @@ void process(char filename[]) {
         return;
     }
     char buffer[80];
-    for (size_t i = 0; i < 20; i++) {
+    while(1) {
         if (!fgets(buffer, sizeof(buffer), handler)) {
             break;
         }

tests/app/cat_test.sh

@@ -7,5 +7,4 @@ QEMU_SCREENSHOT_NAME="cat_test.ppm"
 python3 -m tests.qemu.monitor -p ${MONITOR_PORT:?} -sc cat readme.md
 
 test_create_screen_dump
-test_screen_content $LINENO "FuzzyOS"
-test_screen_content $LINENO "32-bit x86"
+test_screen_content $LINENO "Use make to build binaries and image files"