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Message
From: Matjaz Breskvar<phoenix@o...>
Date: Mon Apr 25 02:14:28 CEST 2005
Subject: [openrisc] Syscall Argument Passing
* Balaji V. Iyer (bviyer@n...) wrote:
> Hello Everyone,
>
> I have a question about how syscalls are handled in OpenRISC 1200. Ok
> let's say we have to use the _read function, and "read" generally has 3
> arguements taken in, they are:
>
> int read (int fd, char *buffer, int nbyte)
>
>
> How are the values for fd, *buffer and nbyte passed into the function? Are
> they passed through the parameter registers (r3, r4, r5 respectively,)
> and the sys function will automatically know these registers to sample? Or
> are they pushed into the stack with the stack base address stored at a
> certain place (like the stack pointer, r1)?
this is defined as part of ABI and implemented
in linux/include/asm-or32/unistd.h
loking into that file you'll notice that syscall that takes 3 arguments
puts them into r3, r4, r5 (just like function call).
best regards,
p.
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