From 27c47ff74432279004746222f39802105f6246c0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B8rn=20Guldberg?= <jogul16@student.sdu.dk>
Date: Sun, 2 Jun 2019 22:26:08 +0200
Subject: [PATCH] first xex-file has now been executed and returned to safe
 kernel state

---
 filesystems/lsfs/test_lsfs.nasm |  2 +-
 lib/xex.nasm                    | 86 ++++++++++++++++++++++++++++++---
 2 files changed, 79 insertions(+), 9 deletions(-)

diff --git a/filesystems/lsfs/test_lsfs.nasm b/filesystems/lsfs/test_lsfs.nasm
index 6486ec2..a3ec188 100644
--- a/filesystems/lsfs/test_lsfs.nasm
+++ b/filesystems/lsfs/test_lsfs.nasm
@@ -13,7 +13,7 @@ lfsf_systemcall:
     int 0x16
 	
 	mov ah, 0x0e
-    mov al, 65 ; backspace
+    mov al, 66 ; backspace
     int 0x10 ; print char
     ret
 
diff --git a/lib/xex.nasm b/lib/xex.nasm
index 145fdff..600733e 100644
--- a/lib/xex.nasm
+++ b/lib/xex.nasm
@@ -2,8 +2,11 @@
 ; This is the "program" to execute a program 
 xex: 
 	pusha ; save state before program
-    sub sp, 2048
-    mov [.program_executable_buffer], sp
+    ;sub sp, 2048
+    ;mov [.program_executable_buffer], sp
+    
+    ;mov [.program_executable_buffer], sp
+
     call os_clear_screen
     call lsfs_list_files_command
     
@@ -72,24 +75,91 @@ xex:
     mov BYTE [bx], 0
     mov si, [.program_executable_buffer]
     call zstring_to_integer ; ax now contain the interger index for the file
+	mov ax, 3   
+    call dumpax
     mov [.fileindex_for_open_file], ax ; save the file index
 
     
     mov ax, [.fileindex_for_open_file]
     mov bx, [.program_executable_buffer]
-    call lsfs_read_file
+    
+	
+
+
+
+
+.xex_lsfs_read_file:
+    ; INPUT ax = file index
+    ; INPUT bx = filebuffer
+    pusha ; save all register state
+    ; We need to find the data pointers for the file. 
+
+    push bx
 
-    mov [.program_executable_buffer], ax
+	mov dx, 24 ; LSFS_magic_start_sector
+    add ax, dx  ; senctor number, into the master Table. 
+    call dumpax
+    mov WORD  [XEXPACK.db_addr_offset], xex_lsfs_loading_buffer
+    mov WORD  [XEXPACK.lba_addr_dw_low], ax
+    mov WORD  [XEXPACK.blkcnt], 0x1  ; Read to sectors, that is what the space is for the buffer in svim
+    mov WORD  [XEXPACK.db_addr_segment], 0x50
+    mov si, XEXPACK                          ; address of "disk address packet"
+    mov ah, 0x42                            ; READ
+    mov dl, [global_disk_identifier]        
+    int 0x13
+
+    pop bx
+
+    ; Save the buffer addr
+    mov bx, [xex_lsfs_loading_buffer + 288] ; this is the first data pointer
+    mov ax, bx
+    call dumpax
+    mov WORD [XEXPACK.lba_addr_dw_low], bx
+    mov WORD [XEXPACK.blkcnt], 0x4  ; Read to sectors, that is what the space is for the buffer in svim
+    mov WORD [XEXPACK.db_addr_segment], 0x2000
+    mov WORD [XEXPACK.db_addr_offset], 0x0
+    mov si, XEXPACK                          ; address of "disk address packet"
+    mov ah, 0x42                             ; READ
+    mov dl, [global_disk_identifier]        
+    int 0x13
+    
+    popa
+    
+    mov ax, [xex_lsfs_loading_buffer + 264]
 
     ; I guess we should have something like 
-    call ax ; here. We want to execute the file that we just have benn loaded in memory 
-    		  ; The executable should make use of the global systemcall table. 
-    		  ; That is what we are trying to get to work here. 
+    push cs 			; this gives us the correct code segment for the kernel
+    push .this_place	; this gives the correct adress to come back from the program. 
+    push 0x2000
+    push 0x0
+    
+    ;push 0x0050 
+    ;push 0x0512
+    retf
+
+    .this_place:
+    ;mov bx, ss
+    ;call bx:ax ; here. We want to execute the file that we just have benn loaded in memory 
+    		   ; The executable should make use of the global systemcall table. 
+    		   ; That is what we are trying to get to work here. 
 
+    ;add sp, 2048
     popa ; retore
     ret
 
 
 .welcome_xex_enter_fileindex db 'Enter program index to execute: ', 0
 .fileindex_for_open_file dw 0
-.program_executable_buffer db 0
\ No newline at end of file
+.program_executable_buffer dw 0
+
+align 2
+xex_lsfs_loading_buffer times 512 db 0
+
+XEXPACK:
+  .dap_Size:         db  0x10   ; This is always 16 bytes (0x10)
+  .rev_byte:         db  0x0    ; reserved byte, should always be zero
+  .blkcnt:           dw  0x0    ; int 13 resets this to # of blocks actually read/written
+  .db_addr_offset:   dw  0x0    ; memory buffer destination address (0:7c00)
+  .db_addr_segment:  dw  0x0    ; in memory page zero
+  .lba_addr_dw_low:  dd  0x0    ; put the lba to read in this spot
+  .lba_addr_dw_high: dd  0x0    ; more storage bytes only for big lba's ( > 4 bytes )
\ No newline at end of file