1 /* Copyright (C) 2001-2024 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 <https://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 /* The userland implementation is:
27 int clone (int (*fn)(void *arg), void *child_stack, int flags,
28 void *arg, pid_t *parent_tid, void *tls, pid_t *child_tid);
30 int clone (long flags, void *child_stack, pid_t *parent_tid,
31 pid_t *child_tid, void *tls);
33 The parameters are passed in register and on the stack from userland:
38 r8: TID field in parent
40 %rsp+8: TID field in child
43 rax: system call number
46 rdx: TID field in parent
47 r10: TID field in child
53 /* Sanity check arguments. */
55 testq %rdi,%rdi /* no NULL function pointers */
56 jz SYSCALL_ERROR_LABEL
58 /* Align stack to 16 bytes per the x86-64 psABI. */
60 jz SYSCALL_ERROR_LABEL /* no NULL stack pointers */
62 /* Insert the argument onto the new stack. */
67 /* Save the function pointer. It will be popped off in the
71 /* Do the system call. */
76 movl $SYS_ify(clone),%eax
78 /* End FDE now, because in the child the unwind info will be
84 jl SYSCALL_ERROR_LABEL
91 /* Clearing frame pointer is insufficient, use CFI. */
93 /* Clear the frame pointer. The ABI suggests this be done, to mark
94 the outermost frame obviously. */
97 /* Set up arguments for the function call. */
98 popq %rax /* Function to call. */
99 popq %rdi /* Argument. */
101 /* Call exit with return value from function call. */
103 movl $SYS_ify(exit), %eax
110 libc_hidden_def (__clone)
111 weak_alias (__clone, clone)