/* Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */ /* clone() is even more special than fork() as it mucks with stacks and invokes a function in the right context after its all over. */ #include <features.h> #define _ERRNO_H 1 #include <bits/errno.h> #include <sys/syscall.h> #define CLONE_VM 0x00000100 #define CLONE_THREAD 0x00010000 /* The userland implementation is: int clone (int (*fn)(void *arg), void *child_stack, int flags, void *arg), the kernel entry is: int clone (long flags, void *child_stack). The parameters are passed in register and on the stack from userland: rdi: fn rsi: child_stack rdx: flags rcx: arg r8d: TID field in parent r9d: thread pointer %esp+8: TID field in child The kernel expects: rax: system call number rdi: flags rsi: child_stack rdx: TID field in parent r10: TID field in child r8: thread pointer */ .text .global clone .type clone,%function clone: /* Sanity check arguments. */ movq $-EINVAL,%rax testq %rdi,%rdi /* no NULL function pointers */ jz __syscall_error testq %rsi,%rsi /* no NULL stack pointers */ jz __syscall_error /* Insert the argument onto the new stack. */ subq $16,%rsi movq %rcx,8(%rsi) /* Save the function pointer. It will be popped off in the child in the ebx frobbing below. */ movq %rdi,0(%rsi) /* Do the system call. */ movq %rdx, %rdi movq %r8, %rdx movq %r9, %r8 movq 8(%rsp), %r10 movl $__NR_clone,%eax syscall testq %rax,%rax jl __syscall_error jz .Lthread_start .Lpseudo_end: ret .Lthread_start: /* Clear the frame pointer. The ABI suggests this be done, to mark the outermost frame obviously. */ xorl %ebp, %ebp #ifdef RESET_PID testq $CLONE_THREAD, %rdi jne 1f testq $CLONE_VM, %rdi movl $-1, %eax jne 2f movl $__NR_getpid, %eax syscall 2: movl %eax, %fs:PID movl %eax, %fs:TID 1: #endif /* Set up arguments for the function call. */ popq %rax /* Function to call. */ popq %rdi /* Argument. */ call *%rax /* Call exit with return value from function call. */ movq %rax, %rdi movl $__NR_exit, %eax syscall .size clone,.-clone weak_alias(clone, __clone)