Use enum for syscalls.

Author: cstack

kernel_syscalls.c

@@ -6,7 +6,6 @@
 #include "stdlib/syscalls.h"
 
 uint32_t sys_write_to_screen(char* s) {
-  fprintf(LOG, "sys_write_to_screen(%s)\n", s);
   fprintf(SCREEN, s);
   return 0;
 }
@@ -38,22 +37,35 @@ uint32_t sys_register_input_handler(InputHandler handler) {
   return 0;
 }
 
+char* syscall_name(Syscall syscall) {
+  switch (syscall) {
+    case (WRITE_TO_SCREEN):
+      return "WRITE_TO_SCREEN";
+    case (COUNT_FILES):
+      return "COUNT_FILES";
+    case (LIST_FILES):
+      return "LIST_FILES";
+    case (REGISTER_INPUT_HANDLER):
+      return "REGISTER_INPUT_HANDLER";
+  }
+}
+
 uint32_t handle_syscall(struct cpu_state* cpu) {
-  uint32_t syscall_num = cpu->eax;
+  Syscall syscall = (Syscall) cpu->eax;
 
-  fprintf(LOG, "--------------------\nSYSCALL (%i)\n", syscall_num);
+  fprintf(LOG, "--------------------\nSYSCALL (%i - %s)\n", syscall, syscall_name(syscall));
 
-  switch (syscall_num) {
-    case (1):
+  switch (syscall) {
+    case (WRITE_TO_SCREEN):
       return sys_write_to_screen((char*) cpu->ebx);
-    case (2):
+    case (COUNT_FILES):
       return sys_count_files();
-    case (3):
+    case (LIST_FILES):
       return sys_list_files((struct file_t *) cpu->ebx);
-    case (4):
+    case (REGISTER_INPUT_HANDLER):
       return sys_register_input_handler((InputHandler) cpu->ebx);
     default:
-      fprintf(LOG, "Unknown syscall: %x\n", syscall_num);
+      fprintf(LOG, "Unknown syscall: %x\n", syscall);
       while(1){}
   }
 

stdlib/syscalls.h

@@ -4,6 +4,14 @@
 #include "types.h"
 #include "filesystem.h"
 
+enum _Syscall {
+  WRITE_TO_SCREEN,
+  COUNT_FILES,
+  LIST_FILES,
+  REGISTER_INPUT_HANDLER
+};
+typedef enum _Syscall Syscall;
+
 void write_to_screen(char* s);
 uint32_t count_files();
 void list_files(struct file_t buffer[]);

stdlib/syscalls.s

@@ -4,7 +4,7 @@ global write_to_screen
 ; stack: [esp + 4] string
 ;        [esp    ] return address
 write_to_screen:
-  mov eax, 1
+  mov eax, 0
   mov ebx, [esp+4]
   int 0x80
   ret                  ; return to the calling function
@@ -13,7 +13,7 @@ global count_files
 ; count_files
 ; stack: [esp    ] return address
 count_files:
-  mov eax, 2
+  mov eax, 1
   int 0x80
   ret                  ; return to the calling function
 
@@ -22,7 +22,7 @@ global list_files
 ; stack: [esp + 4] address of buffer
 ;        [esp    ] return address
 list_files:
-  mov eax, 3
+  mov eax, 2
   mov ebx, [esp+4]
   int 0x80
   ret                  ; return to the calling function
@@ -32,7 +32,7 @@ global register_input_handler
 ; stack: [esp + 4] address of handler
 ;        [esp    ] return address
 register_input_handler:
-  mov eax, 4
+  mov eax, 3
   mov ebx, [esp+4]
   int 0x80
   ret                  ; return to the calling function