syscalls: implement read syscall

grubshit/aaa.asm

@@ -1,33 +1,45 @@
 section .data
-    file_path db '/ebalo/huy.txt', 0        ; Specific file path, null-terminated
-    message   db 'Hello, World from KatauOS!', 10, 0    ; Message to write, with newline
-    message_len equ $ - message - 1        ; Length of message (14 bytes, excluding null)
+    file_path db '/ebalo/huy.txt', 0        ; File path
+    message   db 'Hello, World from KatauOS!', 10, 0  ; Message with newline
+    message_len equ $ - message - 1         ; Length excluding null terminator
+
+section .bss
+    buffer resb 256           ; Buffer for reading file content
+    read_count resd 1         ; Store bytes read count
 
 section .text
     global _start
 
 _start:
-    ; Open the file
-    mov eax, 5              ; System call number for sys_open
-    mov ebx, file_path      ; Pointer to file path
-    mov ecx, 65             ; Flags: O_WRONLY (1) | O_CREAT (64)
-    mov edx, 0x1A4          ; Mode: 0644 (rw-r--r--)
-    int 0x80                ; Invoke system call
-    mov edi, eax            ; Save file descriptor in edi
+    ; Reopen file for reading
+    mov eax, 5                ; sys_open
+    mov ebx, file_path
+    mov ecx, 0                ; O_RDONLY
+    mov edx, 0                ; Mode (unused)
+    int 0x80
+    mov edi, eax              ; Save new descriptor
 
-    ; Write to the file
-    mov eax, 4              ; System call number for sys_write
-    mov ebx, edi            ; File descriptor
-    mov ecx, message        ; Pointer to message
-    mov edx, message_len    ; Number of bytes to write
-    int 0x80                ; Invoke system call
+    ; Read file content
+    mov eax, 3                ; sys_read
+    mov ebx, edi
+    mov ecx, buffer
+    mov edx, 256
+    int 0x80
+    mov [read_count], eax     ; Save bytes read count
 
-    ; Close the file
-    mov eax, 6              ; System call number for sys_close
-    mov ebx, edi            ; File descriptor
-    int 0x80                ; Invoke system call
+    ; Write to stdout
+    mov eax, 4                ; sys_write
+    mov ebx, 1                ; stdout
+    mov ecx, buffer
+    mov edx, [read_count]     ; Use actual bytes read
+    int 0x80
 
-    ; Exit the program
-    mov eax, 1              ; System call number for sys_exit
-    xor ebx, ebx            ; Return status 0
-    int 0x80                ; Invoke system call
+    ; Close file
+    mov eax, 6                ; sys_close
+    mov ebx, edi
+    int 0x80
+
+    ; Exit
+    mov eax, 1                ; sys_exit
+    xor ebx, ebx              ; Return 0
+    int 0x80

src/kernel/kernel.c

@@ -218,7 +218,7 @@ void kmain(unsigned int magic, unsigned int info)
 	printf("huy1 points to: 0x%X huy2 points to:0x%X\n", huy, huy2);
 	printf("huy1: %s\nhuy2: %s", huy, huy2);
 
-	exec_from_file("/boot/katauos.bin");
+	exec_from_file("/ebalo/aaa");
 
 	while(1)
 	{

src/tasking/exec_from_file.c

@@ -68,7 +68,7 @@ void exec_from_file(const char* filename)
 
     uint8_t* file;
 
-    int result = read_file("/ebalo/aaa", &file);
+    int result = read_file(filename, &file);
     debug_log("result: %X\n", result);
     debug_log("buffer: %s\n", file);
 

src/tasking/syscalls.c

@@ -46,6 +46,22 @@ const char* flags_to_mode_str(int flags) {
     return mode;
 }
 
+int sys_read(TrapFrame *tf)
+{
+    if(tf->ebx < 3)
+    {
+        //TODO: implement stdin handling here
+    }
+    else
+    {
+        if(current->file_descriptors[tf->ebx] == NULL)
+        {
+            return -EBADF;
+        }
+        return fat_fread(current->file_descriptors[tf->ebx], (void*)tf->ecx, tf->edx);
+    }
+}
+
 int sys_write(TrapFrame *tf)
 {
     if(tf->ebx < 3)
@@ -53,7 +69,9 @@ int sys_write(TrapFrame *tf)
         //stdin, stdout or stderr
         if(tf->ebx == STDOUT_FILENO)
         {
+            debug_log("\n=================SYS_WRITE output to stdout=====================\n");
             print((char*)tf->ecx, tf->edx);
+            debug_log("\n=================END OF THAT SHIT=====================\n");
             tf->ecx++;
         }
     }
@@ -102,9 +120,12 @@ int sys_open(TrapFrame *tf)
 int sys_close(TrapFrame *tf)
 {
     int fd = tf->ebx;
+    debug_log("SYS_CLOSE: fd = 0x%X", fd);
     if(current->file_descriptors[fd] != NULL)
     {
+        debug_log("SYS_CLOSE: current->file_descriptors[fd] != NULL");
         int result = fat_fclose(current->file_descriptors[fd]);
+        debug_log("SYS_CLOSE: fat_fclose result: 0x%X", result);
         free(current->file_descriptors[fd]);
         current->file_descriptors[fd] = NULL;
         return result;
@@ -120,6 +141,12 @@ void handle_syscall(TrapFrame *tf)
     debug_log("ECX: %s ", tf->ecx);
     debug_log("EDX: %X\n", tf->edx);
     
+    if(tf->eax == 3)//read
+    {
+        int r = sys_read(tf);
+        tf->eax = r;
+    }
+
     if(tf->eax == 4)//write
     {
         int r = sys_write(tf);