1/* Copyright (C) 1996-2024 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 <https://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
25/* int clone(int (*fn)(void *arg), void *child_stack, int flags,
26 void *arg, pid_t *ptid, void *tls, pid_t *ctid);
27
28 Note that everything past ARG is technically optional, based
29 on FLAGS, and that CTID is arg 7, and thus is on the stack.
30 However, since a load from top-of-stack better be legal always,
31 we don't bother checking FLAGS. */
32
33 .text
34 .align 4
35 .globl __clone
36 .ent __clone
37 .usepv __clone, USEPV_PROF
38
39 cfi_startproc
40__clone:
41#ifdef PROF
42 .set noat
43 ldgp gp,0(pv)
44 lda AT, _mcount
45 jsr AT, (AT), _mcount
46 .set at
47#endif
48
49 /* Sanity check arguments. */
50 ldiq v0, EINVAL
51 beq a0, SYSCALL_ERROR_LABEL /* no NULL function pointers */
52 beq a1, SYSCALL_ERROR_LABEL /* no NULL stack pointers */
53
54 /* Save the fn ptr and arg on the new stack. */
55 subq a1, 32, a1
56 stq a0, 0(a1)
57 stq a3, 8(a1)
58 stq a2, 16(a1)
59
60 /* The syscall is of the form clone(flags, usp, ptid, ctid, tls).
61 Shift the flags, ptid, ctid, tls arguments into place; the
62 child_stack argument is already correct. */
63 mov a2, a0
64 mov a4, a2
65 ldq a3, 0(sp)
66 mov a5, a4
67
68 /* Do the system call. */
69 ldiq v0, __NR_clone
70 call_pal PAL_callsys
71
72 bne a3, SYSCALL_ERROR_LABEL
73 beq v0, thread_start
74
75 /* Successful return from the parent. */
76 ret
77
78PSEUDO_END(__clone)
79 cfi_endproc
80
81/* Load up the arguments to the function. Put this block of code in
82 its own function so that we can terminate the stack trace with our
83 debug info. */
84
85 .align 4
86 .ent thread_start
87 cfi_startproc
88thread_start:
89 mov 0, fp
90 cfi_def_cfa_register(fp)
91 cfi_undefined(ra)
92
93 /* Load up the arguments. */
94 ldq pv, 0(sp)
95 ldq a0, 8(sp)
96 addq sp, 32, sp
97
98 /* Call the user's function. */
99 jsr ra, (pv)
100 ldgp gp, 0(ra)
101
102 mov v0, a0
103 ldiq v0, __NR_exit
104 call_pal PAL_callsys
105
106 /* Die horribly. */
107 .align 4
108 halt
109
110 .align 4
111 cfi_endproc
112 .end thread_start
113
114libc_hidden_def (__clone)
115weak_alias (__clone, clone)
116

source code of glibc/sysdeps/unix/sysv/linux/alpha/clone.S