On Wed, 16 Apr 2003 12:58:15 -0400 (EDT)
"Richard B. Johnson" <root@chaos.analogic.com> wrote:
>
> How does the kernel get more than five parameters?
>
> Currently...
> eax = function code
> ebx = first parameter
> ecx = second parameter
> edx = third parameter
> esi = fourth parameter
> edi = fifth parameter
>
> Some functions like mmap() take 6 parameters!
> Does anybody know how these parameters get passed?
> I have an "ultra-light" 'C' runtime library I have
> been working on and, so-far, I've got everything up
> to mmap() (in syscall.h) (89 functions) working.
> I thought, maybe ebp was being used, but it doesn't
> seem to be the case.
>
> Maybe after 5 functions, there is a parameter list
> passed by pointer???? I don't have a clue and I
> can figure out the code, it's really obscure...
Certain Linux 2.4 calls pass a sixth parameter in EBP. Calls compatible with earlier versions of the kernel pass six or
more parameters in a parameter block and pass the address of the parameter block in EBX (this change was probably
made in kernel 2.4 because someone noticed that an extra copy between kernel and user space was slowing down
those functions with exactly six parameters; who knows the real reason, though).
Relevant? No idea.
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This archive was generated by hypermail 2b29 : Wed Apr 23 2003 - 22:00:19 EST