1 /* Copyright (C) 2001-2014 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <http://www.gnu.org/licenses/>. */
18 /* clone() is even more special than fork() as it mucks with stacks
19 and invokes a function in the right context after its all over. */
23 #include <bits/errno.h>
24 #include <asm-syntax.h>
26 #define CLONE_VM 0x00000100
27 #define CLONE_THREAD 0x00010000
29 /* The userland implementation is:
30 int clone (int (*fn)(void *arg), void *child_stack, int flags, void *arg),
32 int clone (long flags, void *child_stack).
34 The parameters are passed in register and on the stack from userland:
39 r8d: TID field in parent
41 %esp+8: TID field in child
44 rax: system call number
47 rdx: TID field in parent
48 r10: TID field in child
54 /* Sanity check arguments. */
56 testq %rdi,%rdi /* no NULL function pointers */
57 jz SYSCALL_ERROR_LABEL
58 testq %rsi,%rsi /* no NULL stack pointers */
59 jz SYSCALL_ERROR_LABEL
61 /* Insert the argument onto the new stack. */
65 /* Save the function pointer. It will be popped off in the
66 child in the ebx frobbing below. */
69 /* Do the system call. */
74 movl $SYS_ify(clone),%eax
76 /* End FDE now, because in the child the unwind info will be
82 jl SYSCALL_ERROR_LABEL
89 /* Clearing frame pointer is insufficient, use CFI. */
91 /* Clear the frame pointer. The ABI suggests this be done, to mark
92 the outermost frame obviously. */
95 testq $CLONE_THREAD, %rdi
100 movl $SYS_ify(getpid), %eax
102 2: movl %eax, %fs:PID
106 /* Set up arguments for the function call. */
107 popq %rax /* Function to call. */
108 popq %rdi /* Argument. */
110 /* Call exit with return value from function call. */
112 call HIDDEN_JUMPTARGET (_exit)
118 weak_alias (__clone, clone)