Detect If File Exists

[ChupaChu]

I was trying to detect if syser is runing or not, idea is if it is running read access to its driver file will be denied.. balah blah.. but strange thing happens when i execute this code:

function isitthere:boolean;
var s:pAnsiChar;
s1,s3:string;
begin
GetSystemDirectory(s,255);  //s is Pchar of system folder (e.g. c:\win\system32)
s1:=String(s)+'\drivers';  //s1=drivers path of windows - where sysboot usualy is..
SetCurrentDir(s1);  //change to s1 dir
s3:='SysBoot.sys';
Result := FileAge(s3) <> -1; //look for file s3 (true if its there false if not there)
end;

When i run this code it throwas an exception - access violation of some kind, then i terminate the process and my winlogon.exe process freeks out and go to 100% cpu usage until next reboot!? What is happening here?!

Interesting thing it does not happen if i look for lets say .txt file :?)

How to go around this?

Any ideas?

[4e4en]

try this one

function isitthere:boolean;
var s:pAnsiChar;
begin
GetSystemDirectory(s,255);
Result := FileExists( String(s) + '\drivers\SysBoot.sys' );
end;

[ChupaChu]

It shud work but it does not.

I get in olly: Access violation when reading [65747385] and then it crashes. Last thing i get is:

EAX 65747379
ECX 7C97C0D8 ntdll.7C97C0D8
EDX 65747385
EBX 0019F500
ESP 000A117C
EBP 000A119C
ESI 00000000
EDI 7C90EE18 ntdll.7C90EE18
EIP 7C937969 ntdll.7C937969
C 0  ES 0023 32bit 0(FFFFFFFF)
P 0  CS 001B 32bit 0(FFFFFFFF)
A 0  SS 0023 32bit 0(FFFFFFFF)
Z 0  DS 0023 32bit 0(FFFFFFFF)
S 0  FS 003B 32bit 7FFDF000(FFF)
T 0  GS 0000 NULL
D 0
O 0  LastErr ERROR_SUCCESS (00000000)
EFL 00000202 (NO,NB,NE,A,NS,PO,GE,G)

I really dont know why is this happening. Any clues?

[4e4en]

function isitthere:boolean;
var s: string;  len: cardinal;
begin
SetLength(s, MAX_PATH);
len := GetTempPath(MAX_PATH, PChar(s));
SetLength(TempDir, s);
Result := FileExists( s + '\drivers\SysBoot.sys' );
end;

[ChupaChu]

Excelent idea to use MAX_PATH, as i looked in olly after crashing it always dies on address of [000000xx]=??? and you will guess i had (xx-1) bytes of data successfully read (full path) and it just did not stop - i really cant imagine why!?..

I have found also that in one function the same code work in another not, so i guess it is some bug in place but i dont want to waste my time on that just now.

4e4en - Thanks once again for support - You have been extremely helpful its apreciated!!!

Edited October 6, 2007 by ChupaChu