text: /* Native-dependent code for OpenBSD/i386.
  
     Copyright (C) 2002-2021 Free Software Foundation, Inc.
  
     This file is part of GDB.
  
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 3 of the License, or
     (at your option) any later version.
  
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
  
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  
  #include "defs.h"
  #include "gdbcore.h"
  #include "regcache.h"
  #include "target.h"
  
  #include <sys/sysctl.h>
  #include <machine/frame.h>
  #include <machine/pcb.h>
  
  #include "i386-tdep.h"
  #include "i386-bsd-nat.h"
  #include "obsd-nat.h"
  #include "bsd-kvm.h"
  
  static int
  i386obsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  {
    struct gdbarch *gdbarch = regcache->arch ();
    enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
    struct switchframe sf;
  
    /* The following is true for OpenBSD 3.6:
  
       The pcb contains %esp and %ebp at the point of the context switch
       in cpu_switch().  At that point we have a stack frame as
       described by `struct switchframe', which for OpenBSD 3.6 has the
       following layout:
  
       interrupt level
       %edi
       %esi
       %ebx
       %eip
  
       we reconstruct the register state as it would look when we just
       returned from cpu_switch().  */
  
    /* The stack pointer shouldn't be zero.  */
    if (pcb->pcb_esp == 0)
      return 0;
  
    /* Read the stack frame, and check its validity.  We do this by
       checking if the saved interrupt priority level in the stack frame
       looks reasonable..  */
  #ifdef PCB_SAVECTX
    if ((pcb->pcb_flags & PCB_SAVECTX) == 0)
      {
        /* Yes, we have a frame that matches cpu_switch().  */
        read_memory (pcb->pcb_esp, (gdb_byte *) &sf, sizeof sf);
        pcb->pcb_esp += sizeof (struct switchframe);
        regcache->raw_supply (I386_EDI_REGNUM, &sf.sf_edi);
        regcache->raw_supply (I386_ESI_REGNUM, &sf.sf_esi);
        regcache->raw_supply (I386_EBX_REGNUM, &sf.sf_ebx);
        regcache->raw_supply (I386_EIP_REGNUM, &sf.sf_eip);
      }
    else
  #endif
      {
        /* No, the pcb must have been last updated by savectx().  */
        pcb->pcb_esp = pcb->pcb_ebp;
        pcb->pcb_ebp = read_memory_integer(pcb->pcb_esp, 4, byte_order);
        sf.sf_eip = read_memory_integer(pcb->pcb_esp + 4, 4, byte_order);
        regcache->raw_supply (I386_EIP_REGNUM, &sf.sf_eip);
      }
  
    regcache->raw_supply (I386_EBP_REGNUM, &pcb->pcb_ebp);
    regcache->raw_supply (I386_ESP_REGNUM, &pcb->pcb_esp);
  
    return 1;
  }
  
  static i386_bsd_nat_target<obsd_nat_target> the_i386_obsd_nat_target;
  
  void _initialize_i386obsd_nat ();
  void
  _initialize_i386obsd_nat ()
  {
    add_inf_child_target (&i386_obsd_nat_target);
  
    /* Support debugging kernel virtual memory images.  */
    bsd_kvm_add_target (i386obsd_supply_pcb);
  
    /* OpenBSD provides a vm.psstrings sysctl that we can use to locate
       the sigtramp.  That way we can still recognize a sigtramp if its
       location is changed in a new kernel.  This is especially
       important for OpenBSD, since it uses a different memory layout
       than NetBSD, yet we cannot distinguish between the two.
  
       Of course this is still based on the assumption that the sigtramp
       is placed directly under the location where the program arguments
       and environment can be found.  */
  #ifdef VM_PSSTRINGS
    {
      struct _ps_strings _ps;
      int mib[2];
      size_t len;
  
      mib[0] = CTL_VM;
      mib[1] = VM_PSSTRINGS;
      len = sizeof (_ps);
      if (sysctl (mib, 2, &_ps, &len, NULL, 0) == 0)
        {
  	i386obsd_sigtramp_start_addr = (u_long) _ps.val - 128;
  	i386obsd_sigtramp_end_addr = (u_long) _ps.val;
        }
    }
  #endif
  }
  