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Please help me in adding new system call in SCO
Please also explain me how the system calls actually work on SCO.
I think Call gates are used for implementing system call in SCO.
I am trying to understand the assembly language code of a binary file which makes a system call 'open'.

I am attaching asm file of the above program.

Thanks in advance.

Hi,

aashish wrote: Please help me in adding new system call in SCO
Please also explain me how the system calls actually work on SCO.
I think Call gates are used for implementing system call in SCO.
I am trying to understand the assembly language code of a binary file which makes a system call 'open'.

I am attaching asm file of the above program.

Thanks in advance.

Ok, I've converted the asm file into NASM, as it's what I'm most familiar with..

You've got standard C calling conventions:
Which calls this:
I assume that [0x80495a0] contains the address of a function in a DLL. When the DLL is loaded the OS would set each address in the jump table to addresses corresponding to the DLL's functions (which depend on where the DLL was loaded). The code in the DLL would do the actually system call (if necessary).

This approach is like trying to see what an elephants face looks like by looking under it's tail. Do you have the source code for SCO?

Cheers,

Brendan

First off, this board is primarily about developing new OSes, most of which are open source; while there are some hard-core Unix experts here, most are primarily familiar with Linux or one or more of the *BSD branches, not OpenServer (the 'official' System V descendant that SCO owns the rights to, or at least claims to - Novell has since challenged this,s tating that they only liscensed it from them, or something). A forum specific to SCO Unix might be more apppropriate; The comp.unix.sco.programmer FAQ might be a good place to start.

Second, it would help to know what the purpose is, esp. since you probably don't need to add an actual new system call. Certainly, it isn't needed for writing a new device driver; details on driver programming for SCO OpenServer can be easily googled for.

Third, if yu are intending some kind of 'turnabout' hack against SCO, forget it. Source code control is very different with commercial software developers than it is with open source developers; there really is no way of 'sneaking' your code into their code base without breaking a dozen laws, and if you get caught it would only give the Linux community a black eye. Don't even think about trying.