Hi to all. I am new at the forum and exuse me if i make something wrong!!
I would to learn how could i calculate the offset of simple c program?
Lets say tha i have that simple program:
Code:#include <stdio.h> int main() { int x=1; printf("x = %d", x); return 0; }
Did you want the offset of main or the offset of x? To get the offset of main(), declare a pointer to function and set it to main(), but note this could be a pointer to a jump to main, if in debugger mode on some compilers. If it's a jump, you'd need to check for that and adjust the offset to point to the actual instance of main(). It could also be an jump via an index to an array of pointers to functions, which will require additional logic to determine where main() is actually located.
For the offset of x, you use &x.
Last edited by rcgldr; 09-28-2013 at 12:36 PM.
Could i get the whole programs offset??
You might try objdump -f or something like that.
Adding
may show you the address of main, although note what rcgldr said.Code:printf("main: 0x%p\n", main);
What OS are you on?
Why do you want to do this?
The cost of software maintenance increases with the square of the programmer's creativity. - Robert D. Bliss
You'd have to use OS specific functions to obtain the memory map for a process. Windows Vista and later version of Windows randomize the offsets of program and static data somewhat, in an effort to make it more difficult to use buffer overflow hacks on programs.Originally Posted by PrimeSec
I am using linux. I want to know how many bytes will cost me in memory!!
Try objdump -p yourprog.
The cost of software maintenance increases with the square of the programmer's creativity. - Robert D. Bliss
Offset from what?!
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I'm sorry, but this is a silly question.
The layout of a program (and data it uses) in memory is system dependent. Some systems go out of their way to randomise the layout somewhat (in the sense that some elements of layout differ each time the program runs) for security reasons (make it difficult to exploit knowledge of memory layout for nefarious means). With a lot of systems, the layout is further adapted based on available memory resources.
You can estimate the minimum memory usage of a variable using sizeof(). That gives the amount of memory used by your program, in the sense that it can be detected by standard-conformant code. However, the compiler and host system can do things to change memory usage (for example, optimise away the existence of a variable, organise variables into pages, etc etc). There is also a certain amount of memory usage of real world programs based on executable instructions since - after all - a variable is rarely of any use unless things are done with it, its value is accessed, etc etc.
That was great!!! It showed me my programs start address in memory
Is there a way to get the memory where the program ends?
