Syscall to count files.

Author: cstack

Makefile

@@ -29,17 +29,18 @@ drivers/frame_buffer.o \
 drivers/keyboard.o \
 drivers/pic.o \
 drivers/serial_port.o \
-filesystem.o \
 interrupts.o \
+kernel_filesystem.o \
 kmain.o \
 multiboot_utils.o \
 process.o \
 stdio.o \
 stdlib.o \
-string.o
+string.o \
+syscalls.o
 
-STDLIB = stdlib/assembly_functions.o \
-stdlib/stdio.o
+STDLIB = stdlib/stdio.o \
+stdlib/syscalls.o
 
 all: os.iso
 

asm_interrupts.s

@@ -772,7 +772,7 @@ global interrupt_handler_128
 interrupt_handler_128:
   push    dword 0
   push    dword 128
-  jmp     common_interrupt_handler
+  jmp     interrupt_handler_with_return_value
 
 global interrupt_handler_129
 interrupt_handler_129:
@@ -1566,3 +1566,33 @@ common_interrupt_handler:               ; the common parts of the generic interr
 
   ; return to the code that got interrupted
   iret
+
+interrupt_handler_with_return_value:
+  push    eax
+  push    ebx
+  push    ecx
+  push    edx
+  push    esi
+  push    edi
+  push    ebp
+  mov     eax, cr2
+  push    eax
+
+  ; call the C function
+  call    interrupt_handler
+
+  ; restore the registers
+  add    esp, 4 ; cr2
+  pop    ebp
+  pop    edi
+  pop    esi
+  pop    edx
+  pop    ecx
+  pop    ebx
+  ; don't pop eax. It contains the return value
+
+  ; pop eax, error_code and interrupt_number off the stack
+  add     esp, 12
+
+  ; return to the code that got interrupted
+  iret

filesystem.h

@@ -8,6 +8,7 @@
 #include "loader.h"
 #include "memory.h"
 #include "stdio.h"
+#include "syscalls.h"
 
 void log_stack_trace_line(uint32_t eip) {
   char * symbol_name = address_to_symbol_name(eip);
@@ -36,29 +37,7 @@ void log_interrupt_details(char* int_name, uint32_t error_code, uint32_t eip, st
   fprintf(LOG, "--------------------\n");
 }
 
-void sys_write_to_screen(char* s) {
-  fprintf(LOG, "sys_write_to_screen(%s)\n", s);
-  printf(s);
-}
-
-void handle_syscall(struct cpu_state* cpu) {
-  uint32_t syscall_num = cpu->eax;
-
-  fprintf(LOG, "--------------------\nSYSCALL (%i)\n", syscall_num);
-
-  switch (syscall_num) {
-    case (1):
-      sys_write_to_screen((char*) cpu->ebx);
-      break;
-    default:
-      fprintf(LOG, "Unknown syscall: %x\n", syscall_num);
-      while(1){}
-  }
-
-  fprintf(LOG, "--------------------\n");
-}
-
-void interrupt_handler(struct cpu_state cpu, uint32_t interrupt_number, uint32_t error_code, uint32_t eip) {
+uint32_t interrupt_handler(struct cpu_state cpu, uint32_t interrupt_number, uint32_t error_code, uint32_t eip) {
   switch(interrupt_number) {
     case(INT_KEYBOARD):
       keyboard_interrupt_handler();
@@ -100,8 +79,7 @@ void interrupt_handler(struct cpu_state cpu, uint32_t interrupt_number, uint32_t
       break;
 
     case(INT_SYSCALL):
-      handle_syscall(&cpu);
-      break;
+      return handle_syscall(&cpu);
 
     case(INT_OUT_OF_MEMORY):
       log_interrupt_details("INT_OUT_OF_MEMORY", error_code, eip, &cpu);
@@ -116,4 +94,6 @@ void interrupt_handler(struct cpu_state cpu, uint32_t interrupt_number, uint32_t
   }
 
   pic_acknowledge();
+
+  return 0;
 }

interrupts.c

@@ -22,6 +22,6 @@ struct cpu_state {
 } __attribute__((packed));
 
 void enable_keyboard_interrupts();
-void interrupt_handler(struct cpu_state cpu, uint32_t interrupt_number, uint32_t error_code, uint32_t eip);
+uint32_t interrupt_handler(struct cpu_state cpu, uint32_t interrupt_number, uint32_t error_code, uint32_t eip);
 
 #endif /* INCLUDE_INTERRUPTS_H */

interrupts.h

@@ -1,4 +1,4 @@
-#include "filesystem.h"
+#include "kernel_filesystem.h"
 
 #include "memory.h"
 #include "stdio.h"
@@ -74,3 +74,7 @@ struct file_t* get_file(char* name) {
 
   return 0;
 }
+
+struct file_t* get_first_file() {
+  return first_file;
+}

filesystem.c renamed to kernel_filesystem.c

@@ -0,0 +1,12 @@
+#ifndef INCLUDE_KERNEL_FILESYSTEM_H
+#define INCLUDE_KERNEL_FILESYSTEM_H
+
+#include "types.h"
+#include "multiboot.h"
+#include "stdlib/filesystem.h"
+
+void initialize_filesystem(struct module* mbinfo);
+struct file_t* get_file(char* name);
+struct file_t* get_first_file();
+
+#endif /* INCLUDE_KERNEL_FILESYSTEM_H */

kernel_filesystem.h

@@ -0,0 +1,11 @@
+#ifndef INCLUDE_SYSCALLS_H
+#define INCLUDE_SYSCALLS_H
+
+#include "types.h"
+#include "filesystem.h"
+
+void write_to_screen(char* s);
+uint32_t count_files();
+void list_files(struct file_t buffer[]);
+
+#endif /* INCLUDE_SYSCALLS_H */

stdlib/assembly_functions.h

@@ -8,3 +8,12 @@ write_to_screen:
   mov ebx, [esp+4]
   int 0x80
   ret                  ; return to the calling function
+
+global count_files
+; count_files
+; stack: [esp    ] return address
+count_files:
+  mov eax, 2
+  int 0x80
+  ret                  ; return to the calling function
+