shell - Gnu Assembler - using Fork() -

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i want spawn shell e.g. /bin/sh.

so looked here: http://docs.cs.up.ac.za/programming/asm/derick_tut/syscalls.html fork syscall number 2.

so code like:

.globl  _start  .text _start:     movl    **wtf-here?!?!** (how use pt_regs?), %ebx     movl    $2, %eax     int $0x80      movl    $0, %ebx     movl    $1, %eax     int $0x80 .data

anybody idea?

afaik table state of registers on entry in kernel, not how call it

simply put syscall preserve ebx , ecx, , process syscall result follows:

    pushl  ebx          # registers preserve     pushl  ecx     movl    $2, %eax    # system call number fork.     int    $0x80        # call int     popl   ecx          # restore preserved regs.     popl   ebx     cmpl  $-4095,%eax   # int returning values between-4095..-1 -> error.     jb    .lsyscok     negl  %eax          # error. negate value.     call  seterrno      # call procedure sets errno in pic safe way.     movl  $-1,%eax      # set return value in case of error (exactly -1)  .lsyscok:

read manpages how determine if in child or in parent. pay attention allowed in parent afterwards. note on bsd systems might want call rfork spawn processes.


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