gdb/bsd-kvm.c

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

   Copyright (C) 2004, 2005, 2007, 2008, 2009, 2010, 2011
   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 "gdb_assert.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 (char *filename, int from_tty)
{
  char errbuf[_POSIX2_LINE_MAX];
  char *execfile = NULL;
  kvm_t *temp_kd;

  target_preopen (from_tty);

  if (filename)
    {
      char *temp;

      filename = tilde_expand (filename);
      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), -1, 1);
}

static void
bsd_kvm_close (int quitting)
{
  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 LONGEST
bsd_kvm_xfer_partial (struct target_ops *ops, enum target_object object,
		      const char *annex, gdb_byte *readbuf,
		      const gdb_byte *writebuf,
		      ULONGEST offset, LONGEST len)
{
  switch (object)
    {
    case TARGET_OBJECT_MEMORY:
      return bsd_kvm_xfer_memory (offset, len, readbuf, writebuf);

    default:
      return -1;
    }
}

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), -1, 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), -1, 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);
}