li $t0, 0x10010000 li $t1, student id li $s3, 1 li $s5, 1 add $s0, $t0, $zero add $s1, $t1, $zero loop1 : sw $s1, 0($s0) srl $s2, $s1, 1 slt $s4, $s2, $s3 beq $s4, $s3, L2 addi $s0, $s0, 4 add $s1, $s2, $zero add $s5,$s5,$s3 j loop1 L2 : addi $s0, $s0, … Read more
The problem with creating shellcode from C programs is not that you cannot control the assembly generated, nor something related with the code generation. The problem with creating shellcode from C programs is symbols resolution or relocation, call it whatever you like. You approach, for what I have understand, is right, you are just using … Read more
sub $0x10,%rsp allocates space on the stack, it’s the same as doing pushq 0 twice except that the value in the allocated stack space will not necessarily be zero, but this is ok since the mov instructions used later replace the garbage with real data. As Michael rightly stated the mov $0x0,%eax is because printf … Read more
As @Peter Cordes said to me i read at https://stackoverflow.com/tags/x86/info about OFFSET keyword , and now it works. I knew the problem is i put in registry a data ,and not a address ,and looks like OFFSET keyword was what I was searching for . Wrorking one is : #include <stdio.h> char buff[] = “%d\n”; … Read more
No, implementing something like OpenGL is not possible. Since the time OpenGL has decended from the heavens complete, writing something like it was forbidden by all common religions. But really, what you’ll actually need is about 21 years of work, a few thousands of developers and broad support from all industry leaders, so yea, piece … Read more
To quote the gcc manual: If no init section is available, when GCC compiles any function called main (or more accurately, any function designated as a program entry point by the language front end calling expand_main_function), it inserts a procedure call to __main as the first executable code after the function prologue. The __main function … Read more
I think that for x86 assembly, you can write call getchar which will cause a trap. When the char is ready, it will be put in the eax register. You can then compare this value to the decimal value of char “0”, which is 48. solved How to convert this c++ code to assembly ? … Read more
From memory, the instruction has an opcode byte (“add”), an address mode byte, an offset for x (4 bytes) and the constant (4 bytes) ==> 10 bytes. I assume the 486 fetches 4 bytes at a time from memory with a bus address aligned to 4 byte DWORD boundaries. So 10 bytes arguably takes 3 … Read more
This is how you do it. Next code was made with Visual Studio 2010 C++ console project. First, the assembly part, pay attention to the comments, how to get the string’s address from stack, how the characters are visited, and the most important part, how the undesired chars are deleted: .386 .model flat, C .code … Read more
gas is primarily intended as a compiler backend, not for human use. As such, it’s lacking some features, among others this one. You can of course try to make a macro to do this, something along these lines: .intel_syntax noprefix .globl main .macro local head, tail:vararg # assume dwords for simplicity .set localsize, localsize + … Read more
I guess the thread will be soon on hold (“off topic”), so let me show quickly the corrected code: #include<stdio.h> int main (void) { char y = 10; char* format = “%d”; __asm { movzx eax, y add eax,1 push eax push format call printf add esp, 8 } return 0; } 1 solved error … Read more
There’s no single instruction that can do this. BMI1 blsi dst,src can isolate the lowest set bit, not the highest. i.e. x & -x. If x86 had a bit-reversed version of blsi, we could use that, but it doesn’t. But you can do much better than what you were suggesting. An all-zero input is always … Read more
att vs intel syntax has been covered many times, here and other places. Assembly language is a language defined by the assembler, the particular program used to convert the ASCII assembly language into machine code for the particular target you are interested in. Unlike say a C or C++ compiler where there is a standard … Read more
The compiler assigns offsets to all members, and includes these in all load/store operations on members: struct foo { uint32_t bar; uint32_t baz; uint32_t get_baz() { return baz; } }; uint32_t get_baz_from_foo(foo *f) { return f->baz; } becomes (ARM assembler code used for simplicity): foo__get_baz: ; calling convention: this pointer in r3 ; load 32 … Read more
Your code could be simplified a lot (and simpler code usually means that it’s simpler to find any mistakes). Here’s an outline of an easier way of doing this (I’ll leave it up to you to implement it in x86 assembly): void to_bin_string(unsigned input) { char output[33]; // The number of binary digits needed to … Read more