Re: [9fans] assembly syntax in plan 9

[Alexander Kapshuk <alexander.kapshuk@gmail.com>]

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i have a question about putting things on the stack for x86 arch under plan
9...

under unix/linux, when defining a function, i would:
(1). push the address the base pointer is pointing to prior to this
function being called, onto the stack; e.g. pushl %ebp
(2). then i would have the base pointer point to the current stack pointer;
e.g. movl %esp, %ebp
(3). then i would allocate space on the stack for local variables, if any;
e.g. subl $n, %esp;
(4). then follows the function body;
to return from the function i would:
(1). restore the stack pointer; e.g. movl %ebp, %esp;
(2). restore the base pointer, e.g. popl %ebp;
(3). then return to the calling function;

i searched the 9fans archives for posts on assembly programming under plan
9; found some bits and pieces; e.g. in one of the posts it was mentioned
that BP is a general purpose register, not the base pointer; and that FP is
what ebp is under unix/linux;

in the paper for the plan 9 assembler, it says that there are three
registers available to manipulate the stack, FP, SP, and TOS; would the
following comparison stand true then?
plan9    unix/linux
-------     -------------
FP        EBP
SP        -4(%EBP)...-n(%EBP) /* local variables */
TOS     ESP

thanks;

sasha kapshuk

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