1/* Copyright (C) 2000-2022 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
19#include <sysdep.h>
20#include <asm/errno.h>
21
22
23/* int __clone2(int (*fn) (void *arg), void *child_stack_base, */
24/* size_t child_stack_size, int flags, void *arg, */
25/* pid_t *parent_tid, void *tls, pid_t *child_tid) */
26
27#define CHILD p8
28#define PARENT p9
29
30ENTRY(__clone2)
31 .prologue
32 alloc r2=ar.pfs,8,1,6,0
33 cmp.eq p6,p0=0,in0
34 cmp.eq p7,p0=0,in1
35 mov r8=EINVAL
36 mov out0=in3 /* Flags are first syscall argument. */
37 mov out1=in1 /* Stack address. */
38(p6) br.cond.spnt.many __syscall_error /* no NULL function pointers */
39(p7) br.cond.spnt.many __syscall_error /* no NULL stack pointers */
40 ;;
41 mov out2=in2 /* Stack size. */
42 mov out3=in5 /* Parent TID Pointer */
43 mov out4=in7 /* Child TID Pointer */
44 mov out5=in6 /* TLS pointer */
45 /*
46 * clone2() is special: the child cannot execute br.ret right
47 * after the system call returns, because it starts out
48 * executing on an empty stack. Because of this, we can't use
49 * the new (lightweight) syscall convention here. Instead, we
50 * just fall back on always using "break".
51 *
52 * Furthermore, since the child starts with an empty stack, we
53 * need to avoid unwinding past invalid memory. To that end,
54 * we'll pretend now that __clone2() is the end of the
55 * call-chain. This is wrong for the parent, but only until
56 * it returns from clone2() but it's better than the
57 * alternative.
58 */
59 mov r15=SYS_ify (clone2)
60 .save rp, r0
61 break __IA64_BREAK_SYSCALL
62 .body
63 cmp.eq p6,p0=-1,r10
64 cmp.eq CHILD,PARENT=0,r8 /* Are we the child? */
65(p6) br.cond.spnt.many __syscall_error
66 ;;
67(CHILD) mov loc0=gp
68(PARENT) ret
69 ;;
70 ld8 out1=[in0],8 /* Retrieve code pointer. */
71 mov out0=in4 /* Pass proper argument to fn */
72 ;;
73 ld8 gp=[in0] /* Load function gp. */
74 mov b6=out1
75 br.call.dptk.many rp=b6 /* Call fn(arg) in the child */
76 ;;
77 mov out0=r8 /* Argument to exit */
78 mov gp=loc0
79 mov r15=SYS_ify (exit)
80 .save rp, r0
81 break __IA64_BREAK_SYSCALL
82 ret /* Not reached. */
83PSEUDO_END(__clone2)
84
85libc_hidden_def (__clone2)
86
87/* For now we leave __clone undefined. This is unlikely to be a */
88/* problem, since at least the i386 __clone in glibc always failed */
89/* with a 0 sp (eventhough the kernel explicitly handled it). */
90/* Thus all such calls needed to pass an explicit sp, and as a result, */
91/* would be unlikely to work on ia64. */
92

source code of glibc/sysdeps/unix/sysv/linux/ia64/clone2.S