sysdeps/unix/sysv/linux/aarch64/clone.S

   1 /* Copyright (C) 1996-2019 Free Software Foundation, Inc.
   2
   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 <sysdep.h>
  23 #define _ERRNO_H        1
  24 #include <bits/errno.h>
  25
  26 /* int clone(int (*fn)(void *arg),            x0
  27              void *child_stack,               x1
  28              int flags,                       x2
  29              void *arg,                       x3
  30              pid_t *ptid,                     x4
  31              struct user_desc *tls,           x5
  32              pid_t *ctid);                    x6
  33  */
  34         .text
  35 ENTRY(__clone)
  36         DELOUSE (0)
  37         DELOUSE (1)
  38         DELOUSE (2)
  39         DELOUSE (3)
  40         DELOUSE (4)
  41         DELOUSE (5)
  42         DELOUSE (6)
  43         /* Save args for the child.  */
  44         mov     x10, x0
  45         mov     x11, x2
  46         mov     x12, x3
  47
  48         /* Sanity check args.  */
  49         mov     x0, #-EINVAL
  50         cbz     x10, .Lsyscall_error
  51         cbz     x1, .Lsyscall_error
  52
  53         /* Do the system call.  */
  54         /* X0:flags, x1:newsp, x2:parenttidptr, x3:newtls, x4:childtid.  */
  55         mov     x0, x2                  /* flags  */
  56         /* New sp is already in x1.  */
  57         mov     x2, x4                  /* ptid  */
  58         mov     x3, x5                  /* tls  */
  59         mov     x4, x6                  /* ctid  */
  60         mov     x8, #SYS_ify(clone)
  61         svc     0x0
  62
  63         cmp     x0, #0
  64         beq     thread_start
  65         blt     .Lsyscall_error
  66         RET
  67 PSEUDO_END (__clone)
  68
  69         .align 4
  70         .type thread_start, %function
  71 thread_start:
  72         cfi_startproc
  73         cfi_undefined (x30)
  74         mov     x29, 0
  75
  76         /* Pick the function arg and execute.  */
  77         mov     x0, x12
  78         blr     x10
  79
  80         /* We are done, pass the return value through x0.  */
  81         mov     x8, #SYS_ify(exit)
  82         svc     0x0
  83         cfi_endproc
  84         .size thread_start, .-thread_start
  85
  86 libc_hidden_def (__clone)
  87 weak_alias (__clone, clone)