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/* clone() implementation for ARC.
Copyright (C) 2020-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
#define _ERRNO_H 1
#include <bits/errno.h>
/* int clone(int (*fn)(void *), void *child_stack,
int flags, void *arg, ...
< pid_t *ptid, struct user_desc *tls, pid_t *ctid > );
NOTE: I'm assuming that the last 3 args are NOT var-args and in case all
3 are not relevant, caller will nevertheless pass those as NULL.
clone syscall in kernel (ABI: CONFIG_CLONE_BACKWARDS)
int sys_clone(unsigned long int clone_flags,
unsigned long int newsp,
int __user *parent_tidptr,
void *tls,
int __user *child_tidptr). */
ENTRY (__clone)
cmp r0, 0 /* @fn can't be NULL. */
and r1,r1,-4 /* @child_stack be 4 bytes aligned per ABI. */
cmp.ne r1, 0 /* @child_stack can't be NULL. */
bz L (__sys_err)
/* save some of the orig args
r0 containing @fn will be clobbered AFTER syscall (with ret val)
rest are clobbered BEFORE syscall due to different arg ordering. */
mov r10, r0 /* @fn. */
mov r11, r3 /* @args. */
mov r12, r2 /* @clone_flags. */
mov r9, r5 /* @tls. */
/* adjust libc args for syscall. */
mov r0, r2 /* libc @flags is 1st syscall arg. */
mov r2, r4 /* libc @ptid. */
mov r3, r5 /* libc @tls. */
mov r4, r6 /* libc @ctid. */
mov r8, __NR_clone
ARC_TRAP_INSN
cmp r0, 0 /* return code : 0 new process, !0 parent. */
beq thread_start_clone
blt L (__sys_err2) /* < 0 (signed) error. */
j [blink] /* Parent returns. */
L (__sys_err):
mov r0, -EINVAL
L (__sys_err2):
/* (1) No need to make -ve kernel error code as positive errno
__syscall_error expects the -ve error code returned by kernel
(2) r0 still had orig -ve kernel error code
(3) Tail call to __syscall_error so we dont have to come back
here hence instead of jmp-n-link (reg push/pop) we do jmp
(4) No need to route __syscall_error via PLT, B is inherently
position independent. */
b __syscall_error
PSEUDO_END (__clone)
.align 4
.type thread_start_clone, %function
thread_start_clone:
cfi_startproc
/* Terminate call stack by noting ra is undefined. */
cfi_undefined (blink)
/* Child jumps off to @fn with @arg as argument. */
jl.d [r10]
mov r0, r11
/* exit() with result from @fn (already in r0). */
mov r8, __NR_exit
ARC_TRAP_INSN
/* In case it ever came back. */
flag 1
cfi_endproc
.size thread_start_clone, .-thread_start_clone
libc_hidden_def (__clone)
weak_alias (__clone, clone)
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