1/* Wrapper around clone system call.  RISC-V version.
2   Copyright (C) 1996-2021 Free Software Foundation, Inc.
3   This file is part of the GNU C Library.
4
5   The GNU C Library is free software; you can redistribute it and/or
6   modify it under the terms of the GNU Lesser General Public
7   License as published by the Free Software Foundation; either
8   version 2.1 of the License, or (at your option) any later version.
9
10   The GNU C Library is distributed in the hope that it will be useful,
11   but WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   Lesser General Public License for more details.
14
15   You should have received a copy of the GNU Lesser General Public
16   License along with the GNU C Library.  If not, see
17   <https://www.gnu.org/licenses/>.  */
18
19/* clone() is even more special than fork() as it mucks with stacks
20   and invokes a function in the right context after its all over.  */
21
22#include <sys/asm.h>
23#include <sysdep.h>
24#define _ERRNO_H	1
25#include <bits/errno.h>
26#include <tls.h>
27#include "tcb-offsets.h"
28
29/* int clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg,
30	     void *parent_tidptr, void *tls, void *child_tidptr) */
31
32	.text
33LEAF (__clone)
34
35	/* Align stack to a 128-bit boundary as per RISC-V ABI.  */
36	andi		a1,a1,ALMASK
37
38	/* Sanity check arguments.  */
39	beqz		a0,L (invalid)	/* No NULL function pointers.  */
40	beqz		a1,L (invalid)	/* No NULL stack pointers.  */
41
42	addi		a1,a1,-16	/* Reserve argument save space.  */
43	REG_S		a0,0(a1)	/* Save function pointer.  */
44	REG_S		a3,SZREG(a1)	/* Save argument pointer.  */
45
46	/* The syscall expects the args to be in different slots.  */
47	mv		a0,a2
48	mv		a2,a4
49	mv		a3,a5
50	mv		a4,a6
51
52	/* Do the system call.  */
53	li		a7,__NR_clone
54	scall
55
56	bltz		a0,L (error)
57	beqz		a0,L (thread_start)
58
59	/* Successful return from the parent.  */
60	ret
61
62L (invalid):
63	li		a0, -EINVAL
64	/* Something bad happened -- no child created.  */
65L (error):
66	j		__syscall_error
67	END (__clone)
68
69/* Load up the arguments to the function.  Put this block of code in
70   its own function so that we can terminate the stack trace with our
71   debug info.  */
72
73ENTRY (__thread_start)
74L (thread_start):
75	/* Terminate call stack by noting ra is undefined.  Use a dummy
76	   .cfi_label to force starting the FDE.  */
77	.cfi_label .Ldummy
78	cfi_undefined (ra)
79
80	/* Restore the arg for user's function.  */
81	REG_L		a1,0(sp)	/* Function pointer.  */
82	REG_L		a0,SZREG(sp)	/* Argument pointer.  */
83
84	/* Call the user's function.  */
85	jalr		a1
86
87	/* Call exit with the function's return value.  */
88	li		a7, __NR_exit
89	scall
90
91	END (__thread_start)
92
93libc_hidden_def (__clone)
94weak_alias (__clone, clone)
95