fix buffer overflow in exec

exec.inc

@@ -9,6 +9,7 @@
 ;PSP is a Program Segment Prefix
 PSP_ERR_MODE    equ  002h   ;4 is sizeof.term_instr
 PSP_CMD_LINE    equ  080h
+PSP_CMD_LINE_LEN equ 020h
 PSP_CODE_START  equ  100h
 
 term_instr:
@@ -32,9 +33,12 @@ exec:
     ;allocate segment for the program
     call    malloc
 
+    push    cx
     ;copy command line into PSP
     mov     di, PSP_CMD_LINE
-    call    strcpy
+    mov     cx, PSP_CMD_LINE_LEN
+    call    strncpy
+    pop     cx
 
     mov     word[es:PSP_ERR_MODE], DEF_ERR_MODE
     

stdlib/string.inc

@@ -8,6 +8,7 @@
 
 include 'memset.inc'
 include 'string\strcpy.inc'
+include 'string\strncpy.inc'
 include 'string\strcmp.inc'
 include 'string\strlen.inc'
 include 'string\strtok.inc'

stdlib/string/strncpy.inc

@@ -0,0 +1,27 @@
+; VictoriaOS: strcpy function
+; Copyright Ilya Strukov, 2008
+
+; This program is free software; you can redistribute it and/or modify
+; it under the terms of the GNU General Public License as published by
+; the Free Software Foundation; either version 2 of the License, or
+; (at your option) any later version.
+
+;================================================
+; #proc string copy
+; #input: ds:si - source, es:di - destination, cx - dest. buffer size
+strncpy:
+    push    ax cx si di
+    dec     cx
+    cld 
+  strncpy_loop:
+    lodsb
+    stosb
+    test    al, al
+    jz      strncpy_exit
+    loop    strncpy_loop
+    xor     al, al  ;add \0 at the end
+    stosb
+  strncpy_exit:
+    pop     di si cx ax
+    ret
+;-- vim: set filetype=fasm: