libc/arch-arm64/bionic/__bionic_clone.S

/*
 * Copyright (C) 2013 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <private/bionic_asm.h>

// pid_t __bionic_clone(int flags, void* child_stack, pid_t* parent_tid, void* tls, pid_t* child_tid, int (*fn)(void*), void* arg);

ENTRY(__bionic_clone)
    stp     x29, x30, [sp, #-16]!
    mov     x29,  sp
    str     x8,       [sp, #-16]!

    # Align 'child_stack' to 16 bytes.
    and     x1, x1, #~0xf

    # Copy 'fn' and 'arg' onto the child stack.
    stp     x5, x6, [x1, #-16]

    # Zero out the top 32 bits of 'flags'. (Is this necessary?)
    uxtw    x0, w0

    # Make the system call.
    mov     x8, __NR_clone
    svc     #0

    # Are we the child?
    cbz     x0, .L_bc_child

    ldr     x8,       [sp], #16
    ldp     x29, x30, [sp], #16

    # Set errno if something went wrong.
    cmn     x0, #(MAX_ERRNO + 1)
    cneg    x0, x0, hi
    b.hi    __set_errno

    ret

.L_bc_child:
    # We're in the child now. Set the end of the frame record chain...
    mov     x29, xzr
    # ...and call __bionic_clone_entry with the 'fn' and 'arg' we stored on the child stack.
    ldp     x0, x1, [sp, #-16]
    b       __bionic_clone_entry
END(__bionic_clone)
.hidden __bionic_clone