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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *  * Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *  * Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in
     12  *    the documentation and/or other materials provided with the
     13  *    distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
     22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include <private/bionic_asm.h>
     30 
     31 // pid_t __bionic_clone(int flags, void* child_stack, pid_t* parent_tid, void* tls, pid_t* child_tid, int (*fn)(void*), void* arg);
     32 ENTRY_PRIVATE(__bionic_clone)
     33     mov     ip, sp
     34     # save registers to parent stack
     35     stmfd   sp!, {r4, r5, r6, r7}
     36     .cfi_def_cfa_offset 16
     37     .cfi_rel_offset r4, 0
     38     .cfi_rel_offset r5, 4
     39     .cfi_rel_offset r6, 8
     40     .cfi_rel_offset r7, 12
     41 
     42     # load extra parameters
     43     ldmfd   ip, {r4, r5, r6}
     44 
     45     # Push 'fn' and 'arg' onto the child stack.
     46     stmdb   r1!, {r5, r6}
     47 
     48     # Make the system call.
     49     ldr     r7, =__NR_clone
     50     swi     #0
     51 
     52     # Are we the child?
     53     movs    r0, r0
     54     beq     .L_bc_child
     55 
     56     # In the parent, reload saved registers then either return or set errno.
     57     ldmfd   sp!, {r4, r5, r6, r7}
     58     cmn     r0, #(MAX_ERRNO + 1)
     59     bxls    lr
     60     neg     r0, r0
     61     b       __set_errno_internal
     62 
     63 .L_bc_child:
     64     # Setting lr to 0 will make the unwinder stop at __start_thread.
     65     mov    lr, #0
     66     # Call __start_thread with the 'fn' and 'arg' we stored on the child stack.
     67     pop    {r0, r1}
     68     b      __start_thread
     69 END(__bionic_clone)
     70