gdb/bsd-kvm.c - third_party/binutils-gdb - Git at Google

 /* BSD Kernel Data Access Library (libkvm) interface.

    Copyright (C) 2004-2016 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 "cli/cli-cmds.h"
 #include "command.h"
 #include "frame.h"
 #include "regcache.h"
 #include "target.h"
 #include "value.h"
 #include "gdbcore.h"		/* for get_exec_file */
 #include "gdbthread.h"

 #include <fcntl.h>
 #include <kvm.h>
 #ifdef HAVE_NLIST_H
 #include <nlist.h>
 #endif
 #include <paths.h>
 #include "readline/readline.h"
 #include <sys/param.h>
 #include <sys/proc.h>
 #include <sys/user.h>

 #include "bsd-kvm.h"

 /* Kernel memory device file.  */
 static const char *bsd_kvm_corefile;

 /* Kernel memory interface descriptor.  */
 static kvm_t *core_kd;

 /* Address of process control block.  */
 static struct pcb *bsd_kvm_paddr;

 /* Pointer to architecture-specific function that reconstructs the
    register state from PCB and supplies it to REGCACHE.  */
 static int (*bsd_kvm_supply_pcb)(struct regcache *regcache, struct pcb *pcb);

 /* Target ops for libkvm interface.  */
 static struct target_ops bsd_kvm_ops;

 /* This is the ptid we use while we're connected to kvm.  The kvm
    target currently doesn't export any view of the running processes,
    so this represents the kernel task.  */
 static ptid_t bsd_kvm_ptid;

 static void
 bsd_kvm_open (const char *arg, int from_tty)
 {
   char errbuf[_POSIX2_LINE_MAX];
   char *execfile = NULL;
   kvm_t *temp_kd;
   char *filename = NULL;

   target_preopen (from_tty);

   if (arg)
     {
       char *temp;

       filename = tilde_expand (arg);
       if (filename[0] != '/')
 	{
 	  temp = concat (current_directory, "/", filename, (char *)NULL);
 	  xfree (filename);
 	  filename = temp;
 	}
     }

   execfile = get_exec_file (0);
   temp_kd = kvm_openfiles (execfile, filename, NULL,
 			   write_files ? O_RDWR : O_RDONLY, errbuf);
   if (temp_kd == NULL)
     error (("%s"), errbuf);

   bsd_kvm_corefile = filename;
   unpush_target (&bsd_kvm_ops);
   core_kd = temp_kd;
   push_target (&bsd_kvm_ops);

   add_thread_silent (bsd_kvm_ptid);
   inferior_ptid = bsd_kvm_ptid;

   target_fetch_registers (get_current_regcache (), -1);

   reinit_frame_cache ();
   print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
 }

 static void
 bsd_kvm_close (struct target_ops *self)
 {
   if (core_kd)
     {
       if (kvm_close (core_kd) == -1)
 	warning (("%s"), kvm_geterr(core_kd));
       core_kd = NULL;
     }

   inferior_ptid = null_ptid;
   delete_thread_silent (bsd_kvm_ptid);
 }

 static LONGEST
 bsd_kvm_xfer_memory (CORE_ADDR addr, ULONGEST len,
 		     gdb_byte *readbuf, const gdb_byte *writebuf)
 {
   ssize_t nbytes = len;

   if (readbuf)
     nbytes = kvm_read (core_kd, addr, readbuf, nbytes);
   if (writebuf && nbytes > 0)
     nbytes = kvm_write (core_kd, addr, writebuf, nbytes);
   return nbytes;
 }

 static enum target_xfer_status
 bsd_kvm_xfer_partial (struct target_ops *ops, enum target_object object,
 		      const char *annex, gdb_byte *readbuf,
 		      const gdb_byte *writebuf,
 		      ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
 {
   switch (object)
     {
     case TARGET_OBJECT_MEMORY:
       {
 	LONGEST ret = bsd_kvm_xfer_memory (offset, len, readbuf, writebuf);

 	if (ret < 0)
 	  return TARGET_XFER_E_IO;
 	else if (ret == 0)
 	  return TARGET_XFER_EOF;
 	else
 	  {
 	    *xfered_len = (ULONGEST) ret;
 	    return TARGET_XFER_OK;
 	  }
       }

     default:
       return TARGET_XFER_E_IO;
     }
 }

 static void
 bsd_kvm_files_info (struct target_ops *ops)
 {
   if (bsd_kvm_corefile && strcmp (bsd_kvm_corefile, _PATH_MEM) != 0)
     printf_filtered (_("\tUsing the kernel crash dump %s.\n"),
 		     bsd_kvm_corefile);
   else
     printf_filtered (_("\tUsing the currently running kernel.\n"));
 }

 /* Fetch process control block at address PADDR.  */

 static int
 bsd_kvm_fetch_pcb (struct regcache *regcache, struct pcb *paddr)
 {
   struct pcb pcb;

   if (kvm_read (core_kd, (unsigned long) paddr, &pcb, sizeof pcb) == -1)
     error (("%s"), kvm_geterr (core_kd));

   gdb_assert (bsd_kvm_supply_pcb);
   return bsd_kvm_supply_pcb (regcache, &pcb);
 }

 static void
 bsd_kvm_fetch_registers (struct target_ops *ops,
 			 struct regcache *regcache, int regnum)
 {
   struct nlist nl[2];

   if (bsd_kvm_paddr)
     {
       bsd_kvm_fetch_pcb (regcache, bsd_kvm_paddr);
       return;
     }

   /* On dumping core, BSD kernels store the faulting context (PCB)
      in the variable "dumppcb".  */
   memset (nl, 0, sizeof nl);
   nl[0].n_name = "_dumppcb";

   if (kvm_nlist (core_kd, nl) == -1)
     error (("%s"), kvm_geterr (core_kd));

   if (nl[0].n_value != 0)
     {
       /* Found dumppcb.  If it contains a valid context, return
 	 immediately.  */
       if (bsd_kvm_fetch_pcb (regcache, (struct pcb *) nl[0].n_value))
 	return;
     }

   /* Traditional BSD kernels have a process proc0 that should always
      be present.  The address of proc0's PCB is stored in the variable
      "proc0paddr".  */

   memset (nl, 0, sizeof nl);
   nl[0].n_name = "_proc0paddr";

   if (kvm_nlist (core_kd, nl) == -1)
     error (("%s"), kvm_geterr (core_kd));

   if (nl[0].n_value != 0)
     {
       struct pcb *paddr;

       /* Found proc0paddr.  */
       if (kvm_read (core_kd, nl[0].n_value, &paddr, sizeof paddr) == -1)
 	error (("%s"), kvm_geterr (core_kd));

       bsd_kvm_fetch_pcb (regcache, paddr);
       return;
     }

 #ifdef HAVE_STRUCT_THREAD_TD_PCB
   /* In FreeBSD kernels for 5.0-RELEASE and later, the PCB no longer
      lives in `struct proc' but in `struct thread'.  The `struct
      thread' for the initial thread for proc0 can be found in the
      variable "thread0".  */

   memset (nl, 0, sizeof nl);
   nl[0].n_name = "_thread0";

   if (kvm_nlist (core_kd, nl) == -1)
     error (("%s"), kvm_geterr (core_kd));

   if (nl[0].n_value != 0)
     {
       struct pcb *paddr;

       /* Found thread0.  */
       nl[0].n_value += offsetof (struct thread, td_pcb);
       if (kvm_read (core_kd, nl[0].n_value, &paddr, sizeof paddr) == -1)
 	error (("%s"), kvm_geterr (core_kd));

       bsd_kvm_fetch_pcb (regcache, paddr);
       return;
     }
 #endif

   /* i18n: PCB == "Process Control Block".  */
   error (_("Cannot find a valid PCB"));
 }


 /* Kernel memory interface commands.  */
 struct cmd_list_element *bsd_kvm_cmdlist;

 static void
 bsd_kvm_cmd (char *arg, int fromtty)
 {
   /* ??? Should this become an alias for "target kvm"?  */
 }

 #ifndef HAVE_STRUCT_THREAD_TD_PCB

 static void
 bsd_kvm_proc_cmd (char *arg, int fromtty)
 {
   CORE_ADDR addr;

   if (arg == NULL)
     error_no_arg (_("proc address"));

   if (core_kd == NULL)
     error (_("No kernel memory image."));

   addr = parse_and_eval_address (arg);
 #ifdef HAVE_STRUCT_LWP
   addr += offsetof (struct lwp, l_addr);
 #else
   addr += offsetof (struct proc, p_addr);
 #endif

   if (kvm_read (core_kd, addr, &bsd_kvm_paddr, sizeof bsd_kvm_paddr) == -1)
     error (("%s"), kvm_geterr (core_kd));

   target_fetch_registers (get_current_regcache (), -1);

   reinit_frame_cache ();
   print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
 }

 #endif

 static void
 bsd_kvm_pcb_cmd (char *arg, int fromtty)
 {
   if (arg == NULL)
     /* i18n: PCB == "Process Control Block".  */
     error_no_arg (_("pcb address"));

   if (core_kd == NULL)
     error (_("No kernel memory image."));

   bsd_kvm_paddr = (struct pcb *)(u_long) parse_and_eval_address (arg);

   target_fetch_registers (get_current_regcache (), -1);

   reinit_frame_cache ();
   print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
 }

 static int
 bsd_kvm_thread_alive (struct target_ops *ops,
 		      ptid_t ptid)
 {
   return 1;
 }

 static char *
 bsd_kvm_pid_to_str (struct target_ops *ops, ptid_t ptid)
 {
   static char buf[64];
   xsnprintf (buf, sizeof buf, "<kvm>");
   return buf;
 }

 static int
 bsd_kvm_return_one (struct target_ops *ops)
 {
   return 1;
 }

 /* Add the libkvm interface to the list of all possible targets and
    register CUPPLY_PCB as the architecture-specific process control
    block interpreter.  */

 void
 bsd_kvm_add_target (int (*supply_pcb)(struct regcache *, struct pcb *))
 {
   gdb_assert (bsd_kvm_supply_pcb == NULL);
   bsd_kvm_supply_pcb = supply_pcb;

   bsd_kvm_ops.to_shortname = "kvm";
   bsd_kvm_ops.to_longname = _("Kernel memory interface");
   bsd_kvm_ops.to_doc = _("Use a kernel virtual memory image as a target.\n\
 Optionally specify the filename of a core dump.");
   bsd_kvm_ops.to_open = bsd_kvm_open;
   bsd_kvm_ops.to_close = bsd_kvm_close;
   bsd_kvm_ops.to_fetch_registers = bsd_kvm_fetch_registers;
   bsd_kvm_ops.to_xfer_partial = bsd_kvm_xfer_partial;
   bsd_kvm_ops.to_files_info = bsd_kvm_files_info;
   bsd_kvm_ops.to_thread_alive = bsd_kvm_thread_alive;
   bsd_kvm_ops.to_pid_to_str = bsd_kvm_pid_to_str;
   bsd_kvm_ops.to_stratum = process_stratum;
   bsd_kvm_ops.to_has_memory = bsd_kvm_return_one;
   bsd_kvm_ops.to_has_stack = bsd_kvm_return_one;
   bsd_kvm_ops.to_has_registers = bsd_kvm_return_one;
   bsd_kvm_ops.to_magic = OPS_MAGIC;

   add_target (&bsd_kvm_ops);

   add_prefix_cmd ("kvm", class_obscure, bsd_kvm_cmd, _("\
 Generic command for manipulating the kernel memory interface."),
 		  &bsd_kvm_cmdlist, "kvm ", 0, &cmdlist);

 #ifndef HAVE_STRUCT_THREAD_TD_PCB
   add_cmd ("proc", class_obscure, bsd_kvm_proc_cmd,
 	   _("Set current context from proc address"), &bsd_kvm_cmdlist);
 #endif
   add_cmd ("pcb", class_obscure, bsd_kvm_pcb_cmd,
 	   /* i18n: PCB == "Process Control Block".  */
 	   _("Set current context from pcb address"), &bsd_kvm_cmdlist);

   /* Some notes on the ptid usage on this target.

      The pid field represents the kvm inferior instance.  Currently,
      we don't support multiple kvm inferiors, but we start at 1
      anyway.  The lwp field is set to != 0, in case the core wants to
      refer to the whole kvm inferior with ptid(1,0,0).

      If kvm is made to export running processes as gdb threads,
      the following form can be used:
      ptid (1, 1, 0) -> kvm inferior 1, in kernel
      ptid (1, 1, 1) -> kvm inferior 1, process 1
      ptid (1, 1, 2) -> kvm inferior 1, process 2
      ptid (1, 1, n) -> kvm inferior 1, process n  */

   bsd_kvm_ptid = ptid_build (1, 1, 0);
 }
	/* BSD Kernel Data Access Library (libkvm) interface.

	Copyright (C) 2004-2016 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 "cli/cli-cmds.h"
	#include "command.h"
	#include "frame.h"
	#include "regcache.h"
	#include "target.h"
	#include "value.h"
	#include "gdbcore.h" /* for get_exec_file */
	#include "gdbthread.h"

	#include <fcntl.h>
	#include <kvm.h>
	#ifdef HAVE_NLIST_H
	#include <nlist.h>
	#endif
	#include <paths.h>
	#include "readline/readline.h"
	#include <sys/param.h>
	#include <sys/proc.h>
	#include <sys/user.h>

	#include "bsd-kvm.h"

	/* Kernel memory device file. */
	static const char *bsd_kvm_corefile;

	/* Kernel memory interface descriptor. */
	static kvm_t *core_kd;

	/* Address of process control block. */
	static struct pcb *bsd_kvm_paddr;

	/* Pointer to architecture-specific function that reconstructs the
	register state from PCB and supplies it to REGCACHE. */
	static int (bsd_kvm_supply_pcb)(struct regcache regcache, struct pcb *pcb);

	/* Target ops for libkvm interface. */
	static struct target_ops bsd_kvm_ops;

	/* This is the ptid we use while we're connected to kvm. The kvm
	target currently doesn't export any view of the running processes,
	so this represents the kernel task. */
	static ptid_t bsd_kvm_ptid;

	static void
	bsd_kvm_open (const char *arg, int from_tty)
	{
	char errbuf[_POSIX2_LINE_MAX];
	char *execfile = NULL;
	kvm_t *temp_kd;
	char *filename = NULL;

	target_preopen (from_tty);

	if (arg)
	{
	char *temp;

	filename = tilde_expand (arg);
	if (filename[0] != '/')
	{
	temp = concat (current_directory, "/", filename, (char *)NULL);
	xfree (filename);
	filename = temp;
	}
	}

	execfile = get_exec_file (0);
	temp_kd = kvm_openfiles (execfile, filename, NULL,
	write_files ? O_RDWR : O_RDONLY, errbuf);
	if (temp_kd == NULL)
	error (("%s"), errbuf);

	bsd_kvm_corefile = filename;
	unpush_target (&bsd_kvm_ops);
	core_kd = temp_kd;
	push_target (&bsd_kvm_ops);

	add_thread_silent (bsd_kvm_ptid);
	inferior_ptid = bsd_kvm_ptid;

	target_fetch_registers (get_current_regcache (), -1);

	reinit_frame_cache ();
	print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
	}

	static void
	bsd_kvm_close (struct target_ops *self)
	{
	if (core_kd)
	{
	if (kvm_close (core_kd) == -1)
	warning (("%s"), kvm_geterr(core_kd));
	core_kd = NULL;
	}

	inferior_ptid = null_ptid;
	delete_thread_silent (bsd_kvm_ptid);
	}

	static LONGEST
	bsd_kvm_xfer_memory (CORE_ADDR addr, ULONGEST len,
	gdb_byte readbuf, const gdb_byte writebuf)
	{
	ssize_t nbytes = len;

	if (readbuf)
	nbytes = kvm_read (core_kd, addr, readbuf, nbytes);
	if (writebuf && nbytes > 0)
	nbytes = kvm_write (core_kd, addr, writebuf, nbytes);
	return nbytes;
	}

	static enum target_xfer_status
	bsd_kvm_xfer_partial (struct target_ops *ops, enum target_object object,
	const char annex, gdb_byte readbuf,
	const gdb_byte *writebuf,
	ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
	{
	switch (object)
	{
	case TARGET_OBJECT_MEMORY:
	{
	LONGEST ret = bsd_kvm_xfer_memory (offset, len, readbuf, writebuf);

	if (ret < 0)
	return TARGET_XFER_E_IO;
	else if (ret == 0)
	return TARGET_XFER_EOF;
	else
	{
	*xfered_len = (ULONGEST) ret;
	return TARGET_XFER_OK;
	}
	}

	default:
	return TARGET_XFER_E_IO;
	}
	}

	static void
	bsd_kvm_files_info (struct target_ops *ops)
	{
	if (bsd_kvm_corefile && strcmp (bsd_kvm_corefile, _PATH_MEM) != 0)
	printf_filtered (_("\tUsing the kernel crash dump %s.\n"),
	bsd_kvm_corefile);
	else
	printf_filtered (_("\tUsing the currently running kernel.\n"));
	}

	/* Fetch process control block at address PADDR. */

	static int
	bsd_kvm_fetch_pcb (struct regcache regcache, struct pcb paddr)
	{
	struct pcb pcb;

	if (kvm_read (core_kd, (unsigned long) paddr, &pcb, sizeof pcb) == -1)
	error (("%s"), kvm_geterr (core_kd));

	gdb_assert (bsd_kvm_supply_pcb);
	return bsd_kvm_supply_pcb (regcache, &pcb);
	}

	static void
	bsd_kvm_fetch_registers (struct target_ops *ops,
	struct regcache *regcache, int regnum)
	{
	struct nlist nl[2];

	if (bsd_kvm_paddr)
	{
	bsd_kvm_fetch_pcb (regcache, bsd_kvm_paddr);
	return;
	}

	/* On dumping core, BSD kernels store the faulting context (PCB)
	in the variable "dumppcb". */
	memset (nl, 0, sizeof nl);
	nl[0].n_name = "_dumppcb";

	if (kvm_nlist (core_kd, nl) == -1)
	error (("%s"), kvm_geterr (core_kd));

	if (nl[0].n_value != 0)
	{
	/* Found dumppcb. If it contains a valid context, return
	immediately. */
	if (bsd_kvm_fetch_pcb (regcache, (struct pcb *) nl[0].n_value))
	return;
	}

	/* Traditional BSD kernels have a process proc0 that should always
	be present. The address of proc0's PCB is stored in the variable
	"proc0paddr". */

	memset (nl, 0, sizeof nl);
	nl[0].n_name = "_proc0paddr";

	if (kvm_nlist (core_kd, nl) == -1)
	error (("%s"), kvm_geterr (core_kd));

	if (nl[0].n_value != 0)
	{
	struct pcb *paddr;

	/* Found proc0paddr. */
	if (kvm_read (core_kd, nl[0].n_value, &paddr, sizeof paddr) == -1)
	error (("%s"), kvm_geterr (core_kd));

	bsd_kvm_fetch_pcb (regcache, paddr);
	return;
	}

	#ifdef HAVE_STRUCT_THREAD_TD_PCB
	/* In FreeBSD kernels for 5.0-RELEASE and later, the PCB no longer
	lives in `struct proc' but in `struct thread'. The `struct
	thread' for the initial thread for proc0 can be found in the
	variable "thread0". */

	memset (nl, 0, sizeof nl);
	nl[0].n_name = "_thread0";

	if (kvm_nlist (core_kd, nl) == -1)
	error (("%s"), kvm_geterr (core_kd));

	if (nl[0].n_value != 0)
	{
	struct pcb *paddr;

	/* Found thread0. */
	nl[0].n_value += offsetof (struct thread, td_pcb);
	if (kvm_read (core_kd, nl[0].n_value, &paddr, sizeof paddr) == -1)
	error (("%s"), kvm_geterr (core_kd));

	bsd_kvm_fetch_pcb (regcache, paddr);
	return;
	}
	#endif

	/* i18n: PCB == "Process Control Block". */
	error (_("Cannot find a valid PCB"));
	}


	/* Kernel memory interface commands. */
	struct cmd_list_element *bsd_kvm_cmdlist;

	static void
	bsd_kvm_cmd (char *arg, int fromtty)
	{
	/* ??? Should this become an alias for "target kvm"? */
	}

	#ifndef HAVE_STRUCT_THREAD_TD_PCB

	static void
	bsd_kvm_proc_cmd (char *arg, int fromtty)
	{
	CORE_ADDR addr;

	if (arg == NULL)
	error_no_arg (_("proc address"));

	if (core_kd == NULL)
	error (_("No kernel memory image."));

	addr = parse_and_eval_address (arg);
	#ifdef HAVE_STRUCT_LWP
	addr += offsetof (struct lwp, l_addr);
	#else
	addr += offsetof (struct proc, p_addr);
	#endif

	if (kvm_read (core_kd, addr, &bsd_kvm_paddr, sizeof bsd_kvm_paddr) == -1)
	error (("%s"), kvm_geterr (core_kd));

	target_fetch_registers (get_current_regcache (), -1);

	reinit_frame_cache ();
	print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
	}

	#endif

	static void
	bsd_kvm_pcb_cmd (char *arg, int fromtty)
	{
	if (arg == NULL)
	/* i18n: PCB == "Process Control Block". */
	error_no_arg (_("pcb address"));

	if (core_kd == NULL)
	error (_("No kernel memory image."));

	bsd_kvm_paddr = (struct pcb *)(u_long) parse_and_eval_address (arg);

	target_fetch_registers (get_current_regcache (), -1);

	reinit_frame_cache ();
	print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
	}

	static int
	bsd_kvm_thread_alive (struct target_ops *ops,
	ptid_t ptid)
	{
	return 1;
	}

	static char *
	bsd_kvm_pid_to_str (struct target_ops *ops, ptid_t ptid)
	{
	static char buf[64];
	xsnprintf (buf, sizeof buf, "<kvm>");
	return buf;
	}

	static int
	bsd_kvm_return_one (struct target_ops *ops)
	{
	return 1;
	}

	/* Add the libkvm interface to the list of all possible targets and
	register CUPPLY_PCB as the architecture-specific process control
	block interpreter. */

	void
	bsd_kvm_add_target (int (supply_pcb)(struct regcache , struct pcb *))
	{
	gdb_assert (bsd_kvm_supply_pcb == NULL);
	bsd_kvm_supply_pcb = supply_pcb;

	bsd_kvm_ops.to_shortname = "kvm";
	bsd_kvm_ops.to_longname = _("Kernel memory interface");
	bsd_kvm_ops.to_doc = _("Use a kernel virtual memory image as a target.\n\
	Optionally specify the filename of a core dump.");
	bsd_kvm_ops.to_open = bsd_kvm_open;
	bsd_kvm_ops.to_close = bsd_kvm_close;
	bsd_kvm_ops.to_fetch_registers = bsd_kvm_fetch_registers;
	bsd_kvm_ops.to_xfer_partial = bsd_kvm_xfer_partial;
	bsd_kvm_ops.to_files_info = bsd_kvm_files_info;
	bsd_kvm_ops.to_thread_alive = bsd_kvm_thread_alive;
	bsd_kvm_ops.to_pid_to_str = bsd_kvm_pid_to_str;
	bsd_kvm_ops.to_stratum = process_stratum;
	bsd_kvm_ops.to_has_memory = bsd_kvm_return_one;
	bsd_kvm_ops.to_has_stack = bsd_kvm_return_one;
	bsd_kvm_ops.to_has_registers = bsd_kvm_return_one;
	bsd_kvm_ops.to_magic = OPS_MAGIC;

	add_target (&bsd_kvm_ops);

	add_prefix_cmd ("kvm", class_obscure, bsd_kvm_cmd, _("\
	Generic command for manipulating the kernel memory interface."),
	&bsd_kvm_cmdlist, "kvm ", 0, &cmdlist);

	#ifndef HAVE_STRUCT_THREAD_TD_PCB
	add_cmd ("proc", class_obscure, bsd_kvm_proc_cmd,
	_("Set current context from proc address"), &bsd_kvm_cmdlist);
	#endif
	add_cmd ("pcb", class_obscure, bsd_kvm_pcb_cmd,
	/* i18n: PCB == "Process Control Block". */
	_("Set current context from pcb address"), &bsd_kvm_cmdlist);

	/* Some notes on the ptid usage on this target.

	The pid field represents the kvm inferior instance. Currently,
	we don't support multiple kvm inferiors, but we start at 1
	anyway. The lwp field is set to != 0, in case the core wants to
	refer to the whole kvm inferior with ptid(1,0,0).

	If kvm is made to export running processes as gdb threads,
	the following form can be used:
	ptid (1, 1, 0) -> kvm inferior 1, in kernel
	ptid (1, 1, 1) -> kvm inferior 1, process 1
	ptid (1, 1, 2) -> kvm inferior 1, process 2
	ptid (1, 1, n) -> kvm inferior 1, process n */

	bsd_kvm_ptid = ptid_build (1, 1, 0);
	}