ports/sysdeps/unix/sysv/linux/hppa/nptl/pt-vfork.S

   1 /* Copyright (C) 2005, 2010 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library.  If not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <sysdep.h>
  19 #define _ERRNO_H        1
  20 #include <bits/errno.h>
  21 #include <tcb-offsets.h>
  22
  23 /* Clone the calling process, but without copying the whole address space.
  24    The calling process is suspended until the new process exits or is
  25    replaced by a call to `execve'.  Return -1 for errors, 0 to the new process,
  26    and the process ID of the new process to the old process.  */
  27
  28 /* Load the thread register.
  29    Load the saved PID value.
  30    Negate the value.
  31    Store the temporary PID. */
  32 #define SAVE_PID                                                        \
  33         mfctl %cr27, %r26                               ASM_LINE_SEP    \
  34         ldw PID_THREAD_OFFSET(%r26),%r1                 ASM_LINE_SEP    \
  35         sub %r0,%r1,%r1                                 ASM_LINE_SEP    \
  36         stw %r1,PID_THREAD_OFFSET(%r26)                 ASM_LINE_SEP
  37 /* If we are the parent...
  38    Get the thread pointer.
  39    Load the saved PID.
  40    Negate the value (got back original)
  41    Restore the PID. */
  42 #define RESTORE_PID                                                     \
  43         cmpb,=,n %r0,%ret0,.Lthread_start               ASM_LINE_SEP    \
  44         mfctl %cr27, %r26                               ASM_LINE_SEP    \
  45         ldw PID_THREAD_OFFSET(%r26),%r1                 ASM_LINE_SEP    \
  46         sub %r0,%r1,%r1                                 ASM_LINE_SEP    \
  47         stw %r1,PID_THREAD_OFFSET(%r26)                 ASM_LINE_SEP    \
  48 .Lthread_start:                                         ASM_LINE_SEP
  49
  50         /* r26, r25, r24, r23 are free since vfork has no arguments */
  51 ENTRY(__vfork)
  52         /* We must not create a frame. When the child unwinds to call
  53            exec it will clobber the same frame that the parent
  54            needs to unwind.  */
  55
  56         /* Save the PIC register. */
  57 #ifdef PIC
  58         copy    %r19, %r25      /* parent */
  59 #endif
  60
  61         /* Save the process PID */
  62         SAVE_PID
  63
  64         /* Syscall saves and restores all register states */
  65         ble     0x100(%sr2,%r0)
  66         ldi     __NR_vfork,%r20
  67
  68         /* Conditionally restore the PID */
  69         RESTORE_PID
  70
  71         /* Check for error */
  72         ldi     -4096,%r1
  73         comclr,>>= %r1,%ret0,%r0        /* Note: unsigned compare. */
  74         b,n     .Lerror
  75
  76         /* Return, and DO NOT restore rp. The child may have called
  77            functions that updated the frame's rp. This works because
  78            the kernel ensures rp is preserved across the vfork
  79            syscall.  */
  80         bv,n    %r0(%rp)
  81
  82 .Lerror:
  83         /* Now we need a stack to call a function. We are assured
  84            that there is no child now, so it's safe to create
  85            a frame.  */
  86         stw     %rp, -20(%sp)
  87         stwm    %r3, 64(%sp)
  88         stw     %sp, -4(%sp)
  89
  90         sub     %r0,%ret0,%r3
  91         SYSCALL_ERROR_HANDLER
  92         /* Restore the PIC register (in delay slot) on error */
  93 #ifdef PIC
  94         copy    %r25, %r19    /* parent */
  95 #else
  96         nop
  97 #endif
  98         /* Write syscall return into errno location */
  99         stw     %r3, 0(%ret0)
 100         ldw     -84(%sp), %rp
 101         bv      %r0(%rp)
 102         ldwm    -64(%sp), %r3
 103 PSEUDO_END (__vfork)
 104 libc_hidden_def (__vfork)
 105 weak_alias (__vfork, vfork)
 106