is there a certain opcode in a file that i can find to tel me where the file will be loaded? where the base should be
example
org 1000h
executable bases
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pcmattman
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Re: executable bases
No. That's why there's executable file formats, like ELF.
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Troy Martin
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Re: executable bases
Nope. That's one the points of a relocatable executable file format. Even a simple 2^x byte executable header is perfect for this.
I wish I could add more texSolar wrote:It keeps stunning me how friendly we - as a community - are towards people who start programming "their first OS" who don't even have a solid understanding of pointers, their compiler, or how a OS is structured.
Re: executable bases
oh, alright, thanks
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Troy Martin
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Re: executable bases
What I would suggest is passing the base from the kernel to the program in a register such as DX (or EDX in pmode) so the program can then play with that.
I wish I could add more texSolar wrote:It keeps stunning me how friendly we - as a community - are towards people who start programming "their first OS" who don't even have a solid understanding of pointers, their compiler, or how a OS is structured.
Re: executable bases
I personally dont recommend that. It is hackish imho and creates an unnecessary dependency between the calling program and OS.What I would suggest is passing the base from the kernel to the program in a register such as DX (or EDX in pmode) so the program can then play with that.
If the program is needing to know where it is located at, there are nicer methods of obtaining that information. ie; like the program calling a API function to obtain it.
Just my 2 cents.
OS Development Series | Wiki | os | ncc
char c[2]={"\x90\xC3"};int main(){void(*f)()=(void(__cdecl*)(void))(void*)&c;f();}
char c[2]={"\x90\xC3"};int main(){void(*f)()=(void(__cdecl*)(void))(void*)&c;f();}
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salil_bhagurkar
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Re: executable bases
I think it should be possible (just to prove the concept) by locating an absolute jump/call within the first few instructions of the program. This would require some minimal disassembly of the program. By assuming an alignment of the program in the memory, it should be possible to inaccurately determine the load address..