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

   1 /* Copyright (C) 1996-2018 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by David Huggins-Daines <dhd@debian.org>, 2000.
   4    Based on the Alpha version by Richard Henderson <rth@tamu.edu>, 1996.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library.  If not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 /* clone() is even more special than fork() as it mucks with stacks
  21    and invokes a function in the right context after its all over.  */
  22
  23 #include <asm/unistd.h>
  24 #include <sysdep.h>
  25 #define _ERRNO_H        1
  26 #include <bits/errno.h>
  27 #include <tcb-offsets.h>
  28
  29 /* Non-thread code calls __clone with the following parameters:
  30    int clone(int (*fn)(void *arg),
  31              void *child_stack,
  32              int flags,
  33              void *arg)
  34
  35    NPTL Code will call __clone with the following parameters:
  36    int clone(int (*fn)(void *arg),
  37              void *child_stack,
  38              int flags,
  39              void *arg,
  40              int *parent_tidptr,
  41              struct user_desc *newtls,
  42              int *child_pidptr)
  43
  44    The code should not mangle the extra input registers.
  45    Syscall expects:                             Input to __clone:
  46         4(r25) - function pointer               (r26, arg0)
  47         0(r25) - argument                       (r23, arg3)
  48         r26 - clone flags.                      (r24, arg2)
  49         r25+64 - user stack pointer.            (r25, arg1)
  50         r24 - parent tid pointer.               (stack - 52)
  51         r23 - struct user_desc newtls pointer.  (stack - 56)
  52         r22 - child tid pointer.                (stack - 60)
  53         r20 - clone syscall number              (constant)
  54
  55    Return:
  56
  57         On success the thread ID of the child process is returend in
  58         the callers context.
  59         On error return -1, and set errno to the value returned by
  60         the syscall.
  61  */
  62
  63         .text
  64 ENTRY(__clone)
  65         /* Prologue */
  66         stwm    %r4, 64(%sp)
  67         .cfi_def_cfa_offset -64
  68         .cfi_offset 4, 0
  69         stw     %sp, -4(%sp)
  70 #ifdef PIC
  71         stw     %r19, -32(%sp)
  72         .cfi_offset 19, 32
  73 #endif
  74
  75         /* Sanity check arguments.  */
  76         comib,=,n  0, %arg0, .LerrorSanity        /* no NULL function pointers */
  77         comib,=,n  0, %arg1, .LerrorSanity        /* no NULL stack pointers */
  78
  79         /* Save the function pointer, arg, and flags on the new stack.  */
  80         stwm    %r26, 64(%r25)
  81         stw     %r23, -60(%r25)
  82         stw     %r24, -56(%r25)
  83         /* Clone arguments are (int flags, void * child_stack) */
  84         copy    %r24, %r26              /* flags are first */
  85         /* User stack pointer is in the correct register already */
  86
  87         /* Load args from stack... */
  88         ldw     -116(%sp), %r24         /* Load parent_tidptr */
  89         ldw     -120(%sp), %r23         /* Load newtls */
  90         ldw     -124(%sp), %r22         /* Load child_tidptr */
  91
  92         /* Save the PIC register. */
  93 #ifdef PIC
  94         copy    %r19, %r4               /* parent */
  95 #endif
  96
  97         /* Do the system call */
  98         ble     0x100(%sr2, %r0)
  99         ldi     __NR_clone, %r20
 100
 101         ldi     -4096, %r1
 102         comclr,>>= %r1, %ret0, %r0      /* Note: unsigned compare. */
 103         b,n     .LerrorRest
 104
 105         /* Restore the PIC register.  */
 106 #ifdef PIC
 107         copy    %r4, %r19               /* parent */
 108 #endif
 109
 110         comib,=,n 0, %ret0, .LthreadStart
 111
 112         /* Successful return from the parent
 113            No need to restore the PIC register,
 114            since we return immediately. */
 115
 116         ldw     -84(%sp), %rp
 117         bv      %r0(%rp)
 118         ldwm    -64(%sp), %r4
 119
 120 .LerrorRest:
 121         /* Something bad happened -- no child created */
 122         bl      __syscall_error, %rp
 123         sub     %r0, %ret0, %arg0
 124         ldw     -84(%sp), %rp
 125         /* Return after setting errno, ret0 is set to -1 by __syscall_error. */
 126         bv      %r0(%rp)
 127         ldwm    -64(%sp), %r4
 128
 129 .LerrorSanity:
 130         /* Sanity checks failed, return -1, and set errno to EINVAL. */
 131         bl      __syscall_error, %rp
 132         ldi     EINVAL, %arg0
 133         ldw     -84(%sp), %rp
 134         bv      %r0(%rp)
 135         ldwm    -64(%sp), %r4
 136
 137 .LthreadStart:
 138         /* Load up the arguments.  */
 139         ldw     -60(%sp), %arg0
 140         ldw     -64(%sp), %r22
 141
 142         /* $$dyncall fixes child's PIC register */
 143
 144         /* Call the user's function */
 145 #ifdef PIC
 146         copy    %r19, %r4
 147 #endif
 148         bl      $$dyncall, %r31
 149         copy    %r31, %rp
 150 #ifdef PIC
 151         copy    %r4, %r19
 152 #endif
 153         copy    %r28, %r26
 154         ble     0x100(%sr2, %r0)
 155         ldi     __NR_exit, %r20
 156
 157         /* We should not return from exit.
 158            We do not restore r4, or the stack state.  */
 159         iitlbp  %r0, (%sr0, %r0)
 160
 161 PSEUDO_END(__clone)
 162
 163 libc_hidden_def (__clone)
 164 weak_alias (__clone, clone)