Exec

[System123]

I have finally gotten my multitasking to work, and I have now implemented an Exec function that allows me to execute bin and com files. This will later be upgraded to run ELF files. At the moment I just need some advice.

When the exec function is called, I load the file to memory, then I create a new user task for the program. I now need to implement a way to kill the task and free the memory used by it when the program is finished running. My problem is how would I implement this. Would adding a system call in the program at the end be the easiest way? ie:

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...Program Code...

mov eax, 0x00 //System call to kill task
int 0x80

Or is there a better way to do this?

[Hangin10]

AFAIK, it's usually (always?) done like that, with that code probably ending the routine that called main.

[JamesM]

Almost - under UNIX that call is executed when main returns, or when exit() is called. It's a function called _exit() - exit() calls all functions registered with atexit(), then falls through to _exit() which calls your OS cleanup code.

so in your crt0.c you'd normally have:

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_exit(main(argc, argv, env));