1/* Copyright (C) 2001-2016 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
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.
8
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.
13
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/>. */
17
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. */
20
21#include <sysdep.h>
22#define _ERRNO_H 1
23#include <bits/errno.h>
24#include <asm-syntax.h>
25
26#define CLONE_VM 0x00000100
27#define CLONE_THREAD 0x00010000
28
29/* The userland implementation is:
30 int clone (int (*fn)(void *arg), void *child_stack, int flags, void *arg),
31 the kernel entry is:
32 int clone (long flags, void *child_stack).
33
34 The parameters are passed in register and on the stack from userland:
35 rdi: fn
36 rsi: child_stack
37 rdx: flags
38 rcx: arg
39 r8d: TID field in parent
40 r9d: thread pointer
41%esp+8: TID field in child
42
43 The kernel expects:
44 rax: system call number
45 rdi: flags
46 rsi: child_stack
47 rdx: TID field in parent
48 r10: TID field in child
49 r8: thread pointer */
50
51
52 .text
53ENTRY (__clone)
54 /* Sanity check arguments. */
55 movq $-EINVAL,%rax
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
60
61 /* Insert the argument onto the new stack. */
62 subq $16,%rsi
63 movq %rcx,8(%rsi)
64
65 /* Save the function pointer. It will be popped off in the
66 child in the ebx frobbing below. */
67 movq %rdi,0(%rsi)
68
69 /* Do the system call. */
70 movq %rdx, %rdi
71 movq %r8, %rdx
72 movq %r9, %r8
73 mov 8(%rsp), %R10_LP
74 movl $SYS_ify(clone),%eax
75
76 /* End FDE now, because in the child the unwind info will be
77 wrong. */
78 cfi_endproc;
79 syscall
80
81 testq %rax,%rax
82 jl SYSCALL_ERROR_LABEL
83 jz L(thread_start)
84
85 ret
86
87L(thread_start):
88 cfi_startproc;
89 /* Clearing frame pointer is insufficient, use CFI. */
90 cfi_undefined (rip);
91 /* Clear the frame pointer. The ABI suggests this be done, to mark
92 the outermost frame obviously. */
93 xorl %ebp, %ebp
94
95 testq $CLONE_THREAD, %rdi
96 jne 1f
97 testq $CLONE_VM, %rdi
98 movl $-1, %eax
99 jne 2f
100 movl $SYS_ify(getpid), %eax
101 syscall
1022: movl %eax, %fs:PID
103 movl %eax, %fs:TID
1041:
105
106 /* Set up arguments for the function call. */
107 popq %rax /* Function to call. */
108 popq %rdi /* Argument. */
109 call *%rax
110 /* Call exit with return value from function call. */
111 movq %rax, %rdi
112 call HIDDEN_JUMPTARGET (_exit)
113 cfi_endproc;
114
115 cfi_startproc;
116PSEUDO_END (__clone)
117
118weak_alias (__clone, clone)
119