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  • Assembly stack persistency

    - by user246100
    Hello. I would like to know if after calling functions the data I have in the stack is persistent. Like, I would like to know if (assuming cdecl convention) can I do this (independently of function X and independently of optimizations): push 1 push 2 push 3 call X call X call X add 12 esp ? Also, let's say that before the calls I save the address of where the pushed values are in a global variable. Can I, inside X, alter the values it contain by acessing the global variable? Like, for some reason I want that in X I'm able to alter the values in stack so that the second and third call to X receive different values.

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  • For Loops in MIPS assembly

    - by John Moffitt
    I'm having problems getting my processor to simulate correctly and I think I've narrowed it down to the program I'm giving it. 1. li $R1, 0 2. li $R2, 0x100 3. li $R6, 1 4. li $R8, 0 5. li $R9, 20 6. lw $R3, 0($R1) 7. lw $R4, 4($R1) 8. add $R5, $R3, $R4 9. srlv $R5, $R5, $R6 10. sw $R5, 0($R2) 11. addi $R1, $R1, 4 12. addi $R2, $R2, 4 13. addi $R8, $R8, 1 14. slt $R7, $R8, $R9 15. bnq $R7, $zero, -9 It should iterate through the bottom portion 20 times and then exit. I'm particularly unsure about the branch instruction but I can't find anything wrong with it so : /

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  • x86 Assembly Question about outputting

    - by jdea
    My code looks like this _declspec(naked) void f(unsigned int input,unsigned int *output) { __asm{ push dword ptr[esp+4] call factorial pop ecx mov [output], eax //copy result ret } } __declspec(naked) unsigned int factorial(unsigned int n) { __asm{ push esi mov esi, dword ptr [esp+8] cmp esi, 1 jg RECURSE mov eax, 1 jmp END RECURSE: dec esi push esi call factorial pop esi inc esi mul esi END: pop esi ret } } Its a factorial function and I'm trying to output the answer after it recursively calculates the number that was passed in But what I get returned as an output is the same large number I keep getting Not sure about what is wrong with my output, by I also see this error CXX0030: Error: expression cannot be evaluated Thanks!

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  • Intel Assembly Programming

    - by Kay
    class MyString{ char buf[100]; int len; boolean append(MyString str){ int k; if(this.len + str.len>100){ for(k=0; k<str.len; k++){ this.buf[this.len] = str.buf[k]; this.len ++; } return false; } return true; } } Does the above translate to: start: push ebp ; save calling ebp mov ebp, esp ; setup new ebp push esi ; push ebx ; mov esi, [ebp + 8] ; esi = 'this' mov ebx, [ebp + 14] ; ebx = str mov ecx, 0 ; k=0 mov edx, [esi + 200] ; edx = this.len append: cmp edx + [ebx + 200], 100 jle ret_true ; if (this.len + str.len)<= 100 then ret_true cmp ecx, edx jge ret_false ; if k >= str.len then ret_false mov [esi + edx], [ebx + 2*ecx] ; this.buf[this.len] = str.buf[k] inc edx ; this.len++ aux: inc ecx ; k++ jmp append ret_true: pop ebx ; restore ebx pop esi ; restore esi pop ebp ; restore ebp ret true ret_false: pop ebx ; restore ebx pop esi ; restore esi pop ebp ; restore ebp ret false My greatest difficulty here is figuring out what to push onto the stack and the math for pointers. NOTE: I'm not allowed to use global variables and i must assume 32-bit ints, 16-bit chars and 8-bit booleans.

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  • assembly language programming (prime number)

    - by chris
    Prompt the user for a positive three digit number, then read it. Let's call it N. Divide into N all integer values from 2 to (N/2)+1 and test to see if the division was even, in which case N is instantly shown to be non-prime. Output a message printing N and saying that it is not prime. If none of those integer values divide evenly (remainder never is zero), then N is shown to be prime. Output a message printing N and saying that it is prime. Ask the user if he or she wants to test another number; if the user types "n" or "N", quit. If "y" or "Y", jump back and repeat. Comments in your code are essential. Hi. I am kinda in rush to do this.. please help me doing it. I'll be much appreciated. thank you

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  • Using different versions of the same assembly in the same folder

    - by Hemanshu Bhojak
    I have the following situation Project A - Uses Castle Windsor v2.2 - Uses Project B via WindsorContainer Project B - Uses NHibernate - Uses Castle Windsor v2.1 In the bin folder of Project A I have the dll Castle.DynamicProxy2.dll v2.2 and NHibernate dlls. Now the problem is that NHibernate is dependent on Castle.DynamicProxy2.dll v2.1 which is not there. How do I resolve this situation.

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  • how to push a string address to stack with assembly, machine code

    - by Yigit
    Hi all, I am changing minesweeper.exe in order to have an understanding of how code injection works. Simply, I want the minesweeper to show a message box before starting. So, I find a "cave" in the executable and then define the string to show in messagebox and call the messagebox. Additionally of course, I have to change the value at module entry point of the executable and first direct it to my additional code, then continue its own code. So at the cave what I do; "hello starbuck",0 push 0 //arg4 of MessageBoxW function push the address of my string //arg3, must be title push the address of my string //arg2, must be the message push 0 //arg1 call MessageBoxW ... Now since the memory addresses of codes in the executable change everytime it is loaded in the memory, for calling the MessageBoxW function, I give the offset of the address where MessageBoxW is defined in Import Address Table. For instance, if MessageBoxW is defined at address1 in the IAT and the instruction just after call MessageBoxW is at address2 instead of writing call MessageBoxW, I write call address2 - address1. So my question is, how do I do it for pushing the string's address to the stack? For example, if I do these changes via ollydbg, I give the immediate address of "hello starbuck" for pushing and it works. But after reloading the executable or starting it outside of ollydbg, it naturally fails, since the immediate addresses change. Thanks in advance, Yigit.

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  • Assembly - Read next sector of a virtual disk

    - by ali
    As any programmer in the world at least once in his/her life, I am trying to create my "revolutionary", the new and only one operating system. :D Well, I am using a virtual emulator (Oracle VM Virtual Box), for which I create a new unknwon operating system, with a vmdk disk. I like vmdk because they are just plain files, so I can paste my boot-loader over the first 512 bytes of the virtual hard disk. Now, I am trying to read the next sector of this virtual disk, on which I would paste a simple kernel that would display a message. I have two questions: Am I reading the second segment (the first -512 bytes- is occupied by the bootloader) correctly? CODE: CitesteDisc: mov bx, 0x8000 ; segment mov es, bx mov bx, 0x0000 ; offset mov ah, 0x02 ; read function mov al, 0x01 ; sectors - this might be wrong, trying to read from hd mov ch, 0x00 ; cylinder mov cl, 0x02 ; sector mov dh, 0x00 ; head mov dl, 0x80 ; drive - trying to read from hd int 0x13 ; disk int mov si, ErrorMessage ; - This will display an error message jc ShowMessage jmp [es:bx] ; buffer Here, I get the error message, after checking CF. However, if I use INT 13, 1 to get last status message, AL is 0 - so no error is saved. Am I pasting my simple kernel in the correct place inside the vmdk? What I do is pasting it after the 512th byte of the file, the first 512 bytes, as I said, are the boot-loader. The file would look like this: BE 45 7C E8 16 00 EB FE B4 0E B7 00 B3 07 CD 10 <- First sector C3 AC 08 C0 74 05 E8 EF FF EB F6 C3 B4 00 B2 80 CD 13 BE 5D 7C 72 F5 BB 00 80 8E C3 BB 00 00 B4 02 B0 06 B5 00 B1 01 B6 00 B2 07 CD 13 BE 4E 7C 72 CF 26 FF 27 57 65 6C 63 6F 6D 65 21 00 52 65 61 64 69 6E 67 20 65 72 72 6F 72 21 00 52 65 73 65 74 74 69 6E 67 20 65 72 72 6F 72 21 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 AA <- Boot-loader signature B4 0E B0 2E CD 10 EB FE 00 00 00 00 00 00 00 00 <- Start of the second sector 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 So, this is the way I am trying to add the kernel to the second sector. What do you think is wrong with this? Thanks!

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  • ARM assembly puzzle

    - by ivant
    First of all, I'm not sure if solution even exists. I spent more than a couple of hours trying to come up with one, so beware. The problem: r1 contains an arbitrary integer, flags are not set according to its value. Set r0 to 1 if r1 is 0x80000000, to 0 otherwise, using only two instructions. It's easy to do that in 3 instructions (there are many ways), however doing it in 2 seems very hard, and may very well be impossible.

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  • assembly of pdp-11(simulator)

    - by lego69
    I have this code on pdp-11 tks = 177560 tkb = 177562 tps = 177564 tpb = 177566 lcs = 177546 . = torg + 2000 main: mov #main, sp mov #kb_int, @#60 mov #200, @#62 mov #101, @#tks mov #clock, @#100 mov #300, @#102 mov #100, @#lcs loop: mov @#tks,r2 aslb r2 bmi loop halt clock: tst bufferg beq clk_end mov #msg,-(sp) jsr pc, print_str tst (sp)+ clr bufferg bic #100,@#tks clr @#lcs clk_end:rti kb_int: mov r1,-(sp) jsr pc, read_char movb r1,@buff_ptr inc buff_ptr bis #1,@#tks cmpb r1,#'q bne next_if mov #0, @#tks next_if:cmpb r1,#32. bne end_kb_int clrb @buff_ptr mov #buffer,-(sp) jsr pc, print_str tst (sp)+ mov #buffer,buff_ptr end_kb_int: mov (sp)+,r1 rti ;############################# read_char: tstb @#tks bpl read_char movb @#tkb, r1 rts pc ;############################# print_char: tstb @#tps bpl print_char movb r1, @#tpb rts pc ;############################# print_str: mov r1,-(sp) mov r2,-(sp) mov 6(sp),r2 str_loop: movb (r2)+,r1 beq pr_str_end jsr pc, print_char br str_loop pr_str_end: mov (sp)+,r2 mov (sp)+,r1 rts pc . = torg + 3000 msg:.ascii<Something is wrong!> .byte 0 .even buff_ptr: .word buffer buffer: .blkw 3 bufferg: .word 0 Can somebody please explain how this part is working, thanks in advance movb r1,@buff_ptr inc buff_ptr bis #1,@#tks cmpb r1,#'q bne next_if mov #0, @#tks next_if:cmpb r1,#32. bne end_kb_int clrb @buff_ptr mov #buffer,-(sp) jsr pc, print_str tst (sp)+ mov #buffer,buff_ptr

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  • Output character in assembly

    - by lolopolosko
    Please help me! How i can output character that moves around the perimeter of a rectangle (10*5 or 15*7) in console with TASM? .MODEL small .STACK 100h .CODE start: mov ah,03 int 10h mov cx,10 A: push cx mov ah,03 int 10h mov ah,02h inc dl int 10h mov al,42 int 29h pop cx LOOP A mov ah,4ch int 21h end start I do not know how to solve the problem...

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  • What am I doing wrong? (Simple Assembly Loop)

    - by sunnyohno
    It won't let me post the picture. Btw, Someone from Reddit.programming sent me over here. So thanks! TITLE MASM Template ; Description ; ; Revision date: INCLUDE Irvine32.inc .data myArray BYTE 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 .code main PROC call Clrscr mov esi, OFFSET myArray mov ecx, LENGTHOF myArray mov eax, 0 L1: add eax, [esi] inc esi loop L1 call WriteInt exit main ENDP END main Results in: -334881242

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  • Help with optimizing C# function via C and/or Assembly

    - by MusiGenesis
    I have this C# method which I'm trying to optimize: // assume arrays are same dimensions private void DoSomething(int[] bigArray1, int[] bigArray2) { int data1; byte A1; byte B1; byte C1; byte D1; int data2; byte A2; byte B2; byte C2; byte D2; for (int i = 0; i < bigArray1.Length; i++) { data1 = bigArray1[i]; data2 = bigArray2[i]; A1 = (byte)(data1 >> 0); B1 = (byte)(data1 >> 8); C1 = (byte)(data1 >> 16); D1 = (byte)(data1 >> 24); A2 = (byte)(data2 >> 0); B2 = (byte)(data2 >> 8); C2 = (byte)(data2 >> 16); D2 = (byte)(data2 >> 24); A1 = A1 > A2 ? A1 : A2; B1 = B1 > B2 ? B1 : B2; C1 = C1 > C2 ? C1 : C2; D1 = D1 > D2 ? D1 : D2; bigArray1[i] = (A1 << 0) | (B1 << 8) | (C1 << 16) | (D1 << 24); } } The function basically compares two int arrays. For each pair of matching elements, the method compares each individual byte value and takes the larger of the two. The element in the first array is then assigned a new int value constructed from the 4 largest byte values (irrespective of source). I think I have optimized this method as much as possible in C# (probably I haven't, of course - suggestions on that score are welcome as well). My question is, is it worth it for me to move this method to an unmanaged C DLL? Would the resulting method execute faster (and how much faster), taking into account the overhead of marshalling my managed int arrays so they can be passed to the method? If doing this would get me, say, a 10% speed improvement, then it would not be worth my time for sure. If it was 2 or 3 times faster, then I would probably have to do it. Note: please, no "premature optimization" comments, thanks in advance. This is simply "optimization".

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  • Call/Ret in x86 assembly embedded in C++

    - by SP658
    This is probably trivial, but for some reason I can't it to work. Its supposed to be a simple function that changes the last byte of a dword to 'AA' (10101010), but nothing happens when I call the function. It just returns my original dword __declspec(naked) long function(unsigned long inputDWord, unsigned long *outputDWord) { _asm{ mov ebx, dword ptr[esp+4] push ebx call SET_AA pop ebx mov eax, dword ptr[esp+8] mov dword ptr[eax], ebx } } __declspec(naked) unsigned long SET_AA( unsigned long inputDWord ) { __asm{ mov eax, [esp+4] mov al, 0xAA ret } }

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  • Scan for first zero bit (Assembly)?

    - by cthulhu
    I have some numbers in AH, AL, BL, BH registers. I need to check whether there is 0 bit in each of the registers in left half of the number. If yes, then put into check variable value 10 else -10. How can I do this? I tried something like that: org 100h check dw 0 mov ah, 11111111b mov al, 11111111b mov bl, 11111111b mov bh, 11111111b mov check, -10 shr ah, 4 shr al, 4 shr bl, 4 shr bh, 4 cmp ah, 0Fh jz first first: cmp al, 0Fh jz second second: cmp bl, 0Fh jz third third: cmp bh, 0Fh jz final final: mov check, 10 ret

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  • C#: Custom assembly directory

    - by Svish
    Say we have an application which consists of one executable and 5 libraries. Regularly all of these will be contained in one directory and the libraries will be loaded from there. Is it possible to do so that I can have for example some of the libraries in one directory called Lib, and the rest in one called Lib2? So that the application directory would only contain the executable itself and the other assemblies would be contained in various logical directories. How can I do this? And I would like to know how to do the loading of the assemblies, but also how to make the building of the application put the assemblies in the right directory.

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  • Question about inserting assembly code in C++

    - by Bruce
    I am working on VC++ compiler. I want to accomplish the following The variables s.AddrFrame.Offset and s.AddrStack.Offset contain the value of EBP and ESP respectively. I want to extract the value of old EBP and the return address. Assuming the address EBP + 1 contains the old 32 bit EBP value and EBP + 5 the return address I wrote the following code: unsigned int old_ebp = 0; unsigned int ret_addr = 0; __asm{ mov old_ebp, DWORD PTR [s.AddrFrame.Offset + 1] mov ret_addr, DWORD PTR [s.AddrStack.Offset + 5] } But this is not compiling xxxx.cpp(1130) : error C2415: improper operand type Please Help

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  • About using assembly with c

    - by kristus
    Hi. I've sort of just finished a mandatory task at school, and I'm about to deliver it. But then I came across something that was unfamiliar, header files. :( What I've got: test-program.c task_header.h function1.s function2.s function3.s function4.s test-program.c: #include <stdio.h> #include <stdlib.h> #include <string.h> #include "task_header.h" . .. ... task_header.h: extern void function1(...); extern void function2(...); extern int function3(...); extern void function4(...); And then I use the command: gcc -m32 -o runtest test-program.c function1.s function2.s function3.s function4.s Is this a proper way to do it, or is it possible to modify it? So I can type: gcc -m32 -o runtest test-program.c ?

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