libc/arch-arm/bionic/__bionic_clone.S

/*
 * Copyright (C) 2008-2010 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)
    mov     ip, sp
    # save registers to parent stack
    stmfd   sp!, {r4, r5, r6, r7}
    .cfi_def_cfa_offset 16
    .cfi_rel_offset r4, 0
    .cfi_rel_offset r5, 4
    .cfi_rel_offset r6, 8
    .cfi_rel_offset r7, 12

    # load extra parameters
    ldmfd   ip, {r4, r5, r6}

    # Push 'fn' and 'arg' onto the child stack.
    stmdb   r1!, {r5, r6}

    # Make the system call.
    ldr     r7, =__NR_clone
    swi     #0

    # Are we the child?
    movs    r0, r0
    beq     1f

    # In the parent, reload saved registers then either return or set errno.
    ldmfd   sp!, {r4, r5, r6, r7}
    cmn     r0, #(MAX_ERRNO + 1)
    bxls    lr
    neg     r0, r0
    b       __set_errno_internal

1:  # The child.
    # Setting lr to 0 will make the unwinder stop at __start_thread
    mov    lr, #0
    # Call __start_thread with the 'fn' and 'arg' we stored on the child stack.
    pop    {r0, r1}
    b      __start_thread
END(__bionic_clone)
.hidden __bionic_clone