Hello guys, I would like know how to do a exception detect, for example:
pointer dd 20
.code
start:
mov eax,pointer
mov edx,50
mov [eax],edx
this code would give a error, in C/C++ is very simple ( with __try statement ) but in assembler?
thanks :D
In assembler, it is also very simple:
include \masm32\MasmBasic\MasmBasic.inc ; download (http://masm32.com/board/index.php?topic=94.0)
.data
pointer dd 20
Init tc ; Init with Try/Catch
mov eax, pointer
mov edx, 50
Try
mov [eax], edx
Catch only ; pass here only if there was an exception
Print "That was illegal, my friend - "
Finally
Inkey "ok?"
Exit
TryCatchEnd ; last instruction
end start
Ah, yes, but how does one do it if one doesn't want to use MASM Basic? (No offense, you understand, JJ: I know it's a marvelous creation, I just have no interest in learning it.)
wow
I it disassemble and is much code lol also it's detected as virus :P
any alternative , mate? :P
Looks simple, but I never tried it.
ASSUME FS:NOTHING;MASM assumes the use of this register to be ERROR by default
PUSH OFFSET YourExceptionHandler
PUSH FS:[0]
MOV FS:[0], ESP
; Guarded code here.
;Here is how to uninstall it
;------------------------------------------------------------------------------
;UNINSTALL PER-THREAD EH
;------------------------------------------------------------------------------
POP FS:[0]
ADD ESP,4
http://www.winasm.net/forum/index.php?showtopic=2082
Quote from: RHL on June 20, 2012, 06:13:07 PM
wow
I it disassemble and is much code lol also it's detected as virus :P
any alternative , mate? :P
The alternative is to study EXCEPTION_POINTERS and EXCEPTION_RECORD and SetUnhandledException and the like.
Re virus: submit the exe to virusscan.jotti.org/
IMHO any decent self-rolled assembly proggie should trigger at least one false positive there, but I am afraid Jotti found nothing for my executable (http://virusscan.jotti.org/en-gb/scanresult/ebc992f72fa73af6c750ca0cde43767aec40933d) :redface:
Quote from: NoCforMe on June 20, 2012, 06:03:50 PM
Ah, yes, but how does one do it if one doesn't want to use MASM Basic? (No offense, you understand, JJ: I know it's a marvelous creation, I just have no interest in learning it.)
Strange ::)
Y'know, MasmBasic is made explicitly for people whose credo is "no C for me" :greensml:
Farabi left out an important part of that code - the handler, itself :P
.CODE
;------------------------------------------------------------------------------
;INSTALL PER-THREAD EH
;------------------------------------------------------------------------------
ASSUME FS:NOTHING;MASM assumes the use of this register to be ERROR by default
PUSH OFFSET PTExceptionHandler
PUSH FS:[0]
MOV FS:[0], ESP
;------------------------------------------------------------------------------
;THE CODE BETWEEN INSTALLATION & DE-INSTALLATION IS GUARDED BY THE PER-THREAD EH
;------------------------------------------------------------------------------
;MORE GUARDED CODE HERE
;Generate an exception inside the guarded area
INT 3;EXCEPTION BREAKPOINT
SafeOffset:
;MORE GUARDED CODE HERE
;------------------------------------------------------------------------------
;UNINSTALL PER-THREAD EH
;------------------------------------------------------------------------------
POP FS:[0]
ADD ESP,4
;------------------------------------------------------------------------------
;THE CODE HERE IS NOT GUARDED BY THE PER-THREAD EH
;------------------------------------------------------------------------------
;MORE UNGUARDED CODE HERE
INVOKE ExitProcess, NULL
;------------------------------------------------------------------------------
PTExceptionHandler PROC C pExcept:DWORD, pFrame:DWORD, pContext:DWORD, pDispatch:DWORD
MOV EAX, pContext
MOV [EAX].CONTEXT.regEip, OFFSET SafeOffset
MOV EAX,ExceptionContinueExecution
RET
PTExceptionHandler ENDP
;------------------------------------------------------------------------------
thank you very much, guys is very simple - also :biggrin:
ed:
I can't: :( lol
start:
ASSUME FS:NOTHING
PUSH OFFSET SafeOffset
PUSH FS:[0]
MOV FS:[0], ESP
mov eax,0
mov edx,5
mov [eax],edx <--- no jump
mov eax,1
SafeOffset:
POP FS:[0]
ADD ESP,4
INVOKE ExitProcess, NULL
end start
Quote from: jj2007 on June 21, 2012, 01:10:26 AM
Quote from: NoCforMe on June 20, 2012, 06:03:50 PM
Ah, yes, but how does one do it if one doesn't want to use MASM Basic? (No offense, you understand, JJ: I know it's a marvelous creation, I just have no interest in learning it.)
Strange ::)
Y'know, MasmBasic is made explicitly for people whose credo is "no C for me" :greensml:
Well, since you brought it up, no, not strange at all: I don't like using C, and I don't like using BASIC either. (Funny, BASIC was the first programming language I learned, followed by COBOL.) My preference is (more or less) "pure" '86 assembly language. (I don't like using macros either, although I used to use them back in the good old 16-bit DOS days.)
As I said, I don't mean to take anything away from your marvelous creation, and I'm glad it's there for folks who want to use it. It's just not for me (different strokes for different folks and all that). Which is why I'd like to know the underlying lower-level implementation of "catch" and "try", etc.
[If anyone wants to continue this tangential discussion, what forum here would be the appropriate one for discussing such "religious" topics?]
To return back on-topic, I'm guessing that some answers to the OP's question lie beneath
this MSDN page on structured exception handling (http://msdn.microsoft.com/en-us/library/ms680657%28v=vs.85%29.aspx).
MasmBasic is very fast - Jochen is a good coder, and has done a lot of work on it
i don't use it much at the moment, because i am trying to learn the win32 API
MasmBasic is a layer of abstraction from that goal
but - i intend to use it more in the future, after i have learned what i want
Getting back to the original question, it looks as if handing exceptions can be easily done using WinAPI functions. (I haven't actually used them, so if someone knows that I'm wrong about this, please let us know.)
It looks as if you need simply to use AddVectoredExceptionHandler (http://msdn.microsoft.com/en-us/library/ms679274%28v=vs.85%29.aspx) to add your own exception handler (defined as a callback function (http://msdn.microsoft.com/en-us/library/ms681419%28v=vs.85%29.aspx)). This function will then be called in the event of an exception (hardware or software).
Is it really that simple?
Quote from: NoCforMe on June 21, 2012, 05:55:19 AM
Is it really that simple?
Well, yes and no. You might have a look at \masm32\MasmBasic\MasmBasic.inc - search for TryCatchEnd MACRO and Init MACRO.
The handler itself is not that difficult, it's more the decisions what to do in case of an exception, where to jump etc etc - all that is "under the hood" of that simple Try/Catch sequence. Which, by the way, looks like C but came to my knowledge with GfaBasic around 1987.
Re MasmBasic: I am just teasing you a little bit ;)
Although one useful bit to know is that most proggies that start with
include \masm32\include\masm32rt.inc
work just fine if you replace that line with
include \masm32\MasmBasic\MasmBasic.inc
... with the difference that you have the deb macro (http://www.webalice.it/jj2006/MasmBasicQuickReference.htm#Mb1017) at your fingertips ;-)
Jeremy Gordon has a very impressive write-up with examples on his GoTools site :t
Quote from: jj2007 on June 21, 2012, 06:25:02 AM
Quote from: NoCforMe on June 21, 2012, 05:55:19 AM
Is it really that simple?
Well, yes and no. You might have a look at \masm32\MasmBasic\MasmBasic.inc - search for TryCatchEnd MACRO and Init MACRO.
Which raises an interesting question: why don't I have masm32\MasmBasic\* on my computah? I just recently upgraded my MASM32 installation: how come I didn't get your Basic stuff? Is that an option I didn't check or something?
Quote from: NoCforMe on June 21, 2012, 11:13:03 AMwhy don't I have masm32\MasmBasic\* on my computah? I just recently upgraded my MASM32...
It's a shame, really :eusa_boohoo:
Masm32 v17 will come with Masmbasic (http://masm32.com/board/index.php?topic=94.0) and Windows RG (http://www.deanliou.com/WinRG/WinRG2.htm) preinstalled. Right, Hutch?
MASM512 will probably come with Windows COSMOS with MasmBasicUniverse as an optional extra but absolutely do not hold your breath waiting. :P
Windows cosmos can't be any better than Windows RG (http://www.deanliou.com/WinRG/WinRG2.htm) ("really good edition") :biggrin:
Quote from: hutch-- on June 25, 2012, 08:01:43 PM
MASM512 will probably come with Windows COSMOS with MasmBasicUniverse as an optional extra but absolutely do not hold your breath waiting. :P
MASM512 ? No, it will come with MasmBasicGalaxy iam sure Hutch ! :badgrin:
Quote from: jj2007 on June 25, 2012, 08:24:45 PM
Windows cosmos can't be any better than Windows RG (http://www.deanliou.com/WinRG/WinRG2.htm) ("really good edition") :biggrin:
Windows RG :lol:
Remind me on the old days of P2 400 Mhz. Its a bad bad bad bad days.