* dwarf2read.c (follow_die_ref): Add comment.

[deliverable/binutils-gdb.git] / gdb / corelow.c

/* Core dump and executable file functions below target vector, for GDB.

   Copyright (C) 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997,
   1998, 1999, 2000, 2001, 2003, 2004, 2005, 2006, 2007, 2008, 2009
   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 "arch-utils.h"
#include "gdb_string.h"
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
#ifdef HAVE_SYS_FILE_H
#include <sys/file.h>           /* needed for F_OK and friends */
#endif
#include "frame.h"              /* required by inferior.h */
#include "inferior.h"
#include "symtab.h"
#include "command.h"
#include "bfd.h"
#include "target.h"
#include "gdbcore.h"
#include "gdbthread.h"
#include "regcache.h"
#include "regset.h"
#include "symfile.h"
#include "exec.h"
#include "readline/readline.h"
#include "gdb_assert.h"
#include "exceptions.h"
#include "solib.h"
#include "filenames.h"


#ifndef O_LARGEFILE
#define O_LARGEFILE 0
#endif

/* List of all available core_fns.  On gdb startup, each core file
   register reader calls deprecated_add_core_fns() to register
   information on each core format it is prepared to read.  */

static struct core_fns *core_file_fns = NULL;

/* The core_fns for a core file handler that is prepared to read the core
   file currently open on core_bfd. */

static struct core_fns *core_vec = NULL;

/* FIXME: kettenis/20031023: Eventually this variable should
   disappear.  */

struct gdbarch *core_gdbarch = NULL;

static void core_files_info (struct target_ops *);

static struct core_fns *sniff_core_bfd (bfd *);

static int gdb_check_format (bfd *);

static void core_open (char *, int);

static void core_detach (struct target_ops *ops, char *, int);

static void core_close (int);

static void core_close_cleanup (void *ignore);

static void add_to_thread_list (bfd *, asection *, void *);

static void init_core_ops (void);

void _initialize_corelow (void);

struct target_ops core_ops;

/* An arbitrary identifier for the core inferior.  */
#define CORELOW_PID 1

/* Link a new core_fns into the global core_file_fns list.  Called on gdb
   startup by the _initialize routine in each core file register reader, to
   register information about each format the the reader is prepared to
   handle. */

void
deprecated_add_core_fns (struct core_fns *cf)
{
  cf->next = core_file_fns;
  core_file_fns = cf;
}

/* The default function that core file handlers can use to examine a
   core file BFD and decide whether or not to accept the job of
   reading the core file. */

int
default_core_sniffer (struct core_fns *our_fns, bfd *abfd)
{
  int result;

  result = (bfd_get_flavour (abfd) == our_fns -> core_flavour);
  return (result);
}

/* Walk through the list of core functions to find a set that can
   handle the core file open on ABFD.  Default to the first one in the
   list if nothing matches.  Returns pointer to set that is
   selected. */

static struct core_fns *
sniff_core_bfd (bfd *abfd)
{
  struct core_fns *cf;
  struct core_fns *yummy = NULL;
  int matches = 0;;

  /* Don't sniff if we have support for register sets in CORE_GDBARCH.  */
  if (core_gdbarch && gdbarch_regset_from_core_section_p (core_gdbarch))
    return NULL;

  for (cf = core_file_fns; cf != NULL; cf = cf->next)
    {
      if (cf->core_sniffer (cf, abfd))
        {
          yummy = cf;
          matches++;
        }
    }
  if (matches > 1)
    {
      warning (_("\"%s\": ambiguous core format, %d handlers match"),
               bfd_get_filename (abfd), matches);
    }
  else if (matches == 0)
    {
      warning (_("\"%s\": no core file handler recognizes format, using default"),
               bfd_get_filename (abfd));
    }
  if (yummy == NULL)
    {
      yummy = core_file_fns;
    }
  return (yummy);
}

/* The default is to reject every core file format we see.  Either
   BFD has to recognize it, or we have to provide a function in the
   core file handler that recognizes it. */

int
default_check_format (bfd *abfd)
{
  return (0);
}

/* Attempt to recognize core file formats that BFD rejects. */

static int
gdb_check_format (bfd *abfd)
{
  struct core_fns *cf;

  for (cf = core_file_fns; cf != NULL; cf = cf->next)
    {
      if (cf->check_format (abfd))
        {
          return (1);
        }
    }
  return (0);
}

/* Discard all vestiges of any previous core file and mark data and stack
   spaces as empty.  */

static void
core_close (int quitting)
{
  char *name;

  if (core_bfd)
    {
      int pid = ptid_get_pid (inferior_ptid);
      inferior_ptid = null_ptid;        /* Avoid confusion from thread stuff */
      delete_inferior_silent (pid);

      /* Clear out solib state while the bfd is still open. See
         comments in clear_solib in solib.c. */
      clear_solib ();

      name = bfd_get_filename (core_bfd);
      if (!bfd_close (core_bfd))
        warning (_("cannot close \"%s\": %s"),
                 name, bfd_errmsg (bfd_get_error ()));
      xfree (name);
      core_bfd = NULL;
      if (core_ops.to_sections)
        {
          xfree (core_ops.to_sections);
          core_ops.to_sections = NULL;
          core_ops.to_sections_end = NULL;
        }
    }
  core_vec = NULL;
  core_gdbarch = NULL;
}

static void
core_close_cleanup (void *ignore)
{
  core_close (0/*ignored*/);
}

/* Look for sections whose names start with `.reg/' so that we can extract the
   list of threads in a core file.  */

static void
add_to_thread_list (bfd *abfd, asection *asect, void *reg_sect_arg)
{
  ptid_t ptid;
  int thread_id;
  asection *reg_sect = (asection *) reg_sect_arg;

  if (strncmp (bfd_section_name (abfd, asect), ".reg/", 5) != 0)
    return;

  thread_id = atoi (bfd_section_name (abfd, asect) + 5);

  if (core_gdbarch
      && gdbarch_core_reg_section_encodes_pid (core_gdbarch))
    {
      uint32_t merged_pid = thread_id;
      ptid = ptid_build (merged_pid & 0xffff,
                         merged_pid >> 16, 0);
    }
  else
    ptid = ptid_build (ptid_get_pid (inferior_ptid), thread_id, 0);

  if (ptid_get_lwp (inferior_ptid) == 0)
    /* The main thread has already been added before getting here, and
       this is the first time we hear about a thread id.  Assume this
       is the main thread.  */
    thread_change_ptid (inferior_ptid, ptid);
  else
    /* Nope, really a new thread.  */
    add_thread (ptid);

/* Warning, Will Robinson, looking at BFD private data! */

  if (reg_sect != NULL
      && asect->filepos == reg_sect->filepos)   /* Did we find .reg? */
    inferior_ptid = ptid;                        /* Yes, make it current */
}

/* This routine opens and sets up the core file bfd.  */

static void
core_open (char *filename, int from_tty)
{
  const char *p;
  int siggy;
  struct cleanup *old_chain;
  char *temp;
  bfd *temp_bfd;
  int scratch_chan;
  int flags;
  int corelow_pid = CORELOW_PID;

  target_preopen (from_tty);
  if (!filename)
    {
      if (core_bfd)
        error (_("No core file specified.  (Use `detach' to stop debugging a core file.)"));
      else
        error (_("No core file specified."));
    }

  filename = tilde_expand (filename);
  if (!IS_ABSOLUTE_PATH(filename))
    {
      temp = concat (current_directory, "/", filename, (char *)NULL);
      xfree (filename);
      filename = temp;
    }

  old_chain = make_cleanup (xfree, filename);

  flags = O_BINARY | O_LARGEFILE;
  if (write_files)
    flags |= O_RDWR;
  else
    flags |= O_RDONLY;
  scratch_chan = open (filename, flags, 0);
  if (scratch_chan < 0)
    perror_with_name (filename);

  temp_bfd = bfd_fopen (filename, gnutarget, 
                        write_files ? FOPEN_RUB : FOPEN_RB,
                        scratch_chan);
  if (temp_bfd == NULL)
    perror_with_name (filename);

  if (!bfd_check_format (temp_bfd, bfd_core) &&
      !gdb_check_format (temp_bfd))
    {
      /* Do it after the err msg */
      /* FIXME: should be checking for errors from bfd_close (for one thing,
         on error it does not free all the storage associated with the
         bfd).  */
      make_cleanup_bfd_close (temp_bfd);
      error (_("\"%s\" is not a core dump: %s"),
             filename, bfd_errmsg (bfd_get_error ()));
    }

  /* Looks semi-reasonable.  Toss the old core file and work on the new.  */

  discard_cleanups (old_chain); /* Don't free filename any more */
  unpush_target (&core_ops);
  core_bfd = temp_bfd;
  old_chain = make_cleanup (core_close_cleanup, 0 /*ignore*/);

  /* FIXME: kettenis/20031023: This is very dangerous.  The
     CORE_GDBARCH that results from this call may very well be
     different from CURRENT_GDBARCH.  However, its methods may only
     work if it is selected as the current architecture, because they
     rely on swapped data (see gdbarch.c).  We should get rid of that
     swapped data.  */
  core_gdbarch = gdbarch_from_bfd (core_bfd);

  /* Find a suitable core file handler to munch on core_bfd */
  core_vec = sniff_core_bfd (core_bfd);

  validate_files ();

  /* Find the data section */
  if (build_section_table (core_bfd, &core_ops.to_sections,
                           &core_ops.to_sections_end))
    error (_("\"%s\": Can't find sections: %s"),
           bfd_get_filename (core_bfd), bfd_errmsg (bfd_get_error ()));

  /* If we have no exec file, try to set the architecture from the
     core file.  We don't do this unconditionally since an exec file
     typically contains more information that helps us determine the
     architecture than a core file.  */
  if (!exec_bfd)
    set_gdbarch_from_file (core_bfd);

  push_target (&core_ops);
  discard_cleanups (old_chain);

  add_inferior_silent (corelow_pid);

  /* Do this before acknowledging the inferior, so if
     post_create_inferior throws (can happen easilly if you're loading
     a core file with the wrong exec), we aren't left with threads
     from the previous inferior.  */
  init_thread_list ();

  /* Set INFERIOR_PTID early, so an upper layer can rely on it being
     set while in the target_find_new_threads call below.  */
  inferior_ptid = pid_to_ptid (corelow_pid);

  /* Assume ST --- Add a main task.  We'll later detect when we go
     from ST to MT.  */
  add_thread_silent (inferior_ptid);

  /* Need to flush the register cache (and the frame cache) from a
     previous debug session.  If inferior_ptid ends up the same as the
     last debug session --- e.g., b foo; run; gcore core1; step; gcore
     core2; core core1; core core2 --- then there's potential for
     get_current_regcache to return the cached regcache of the
     previous session, and the frame cache being stale.  */
  registers_changed ();

  /* Build up thread list from BFD sections, and possibly set the
     current thread to the .reg/NN section matching the .reg
     section. */
  bfd_map_over_sections (core_bfd, add_to_thread_list,
                         bfd_get_section_by_name (core_bfd, ".reg"));

  post_create_inferior (&core_ops, from_tty);

  /* Now go through the target stack looking for threads since there
     may be a thread_stratum target loaded on top of target core by
     now.  The layer above should claim threads found in the BFD
     sections.  */
  target_find_new_threads ();

  p = bfd_core_file_failing_command (core_bfd);
  if (p)
    printf_filtered (_("Core was generated by `%s'.\n"), p);

  siggy = bfd_core_file_failing_signal (core_bfd);
  if (siggy > 0)
    /* NOTE: target_signal_from_host() converts a target signal value
       into gdb's internal signal value.  Unfortunately gdb's internal
       value is called ``target_signal'' and this function got the
       name ..._from_host(). */
    printf_filtered (_("Program terminated with signal %d, %s.\n"), siggy,
                     target_signal_to_string (
                       gdbarch_target_signal_from_host (core_gdbarch, siggy)));

  /* Fetch all registers from core file.  */
  target_fetch_registers (get_current_regcache (), -1);

  /* Now, set up the frame cache, and print the top of stack.  */
  reinit_frame_cache ();
  print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC);
}

static void
core_detach (struct target_ops *ops, char *args, int from_tty)
{
  if (args)
    error (_("Too many arguments"));
  unpush_target (ops);
  reinit_frame_cache ();
  if (from_tty)
    printf_filtered (_("No core file now.\n"));
}


/* Try to retrieve registers from a section in core_bfd, and supply
   them to core_vec->core_read_registers, as the register set numbered
   WHICH.

   If inferior_ptid's lwp member is zero, do the single-threaded
   thing: look for a section named NAME.  If inferior_ptid's lwp
   member is non-zero, do the multi-threaded thing: look for a section
   named "NAME/LWP", where LWP is the shortest ASCII decimal
   representation of inferior_ptid's lwp member.

   HUMAN_NAME is a human-readable name for the kind of registers the
   NAME section contains, for use in error messages.

   If REQUIRED is non-zero, print an error if the core file doesn't
   have a section by the appropriate name.  Otherwise, just do nothing.  */

static void
get_core_register_section (struct regcache *regcache,
                           char *name,
                           int which,
                           char *human_name,
                           int required)
{
  static char *section_name = NULL;
  struct bfd_section *section;
  bfd_size_type size;
  char *contents;

  xfree (section_name);

  if (core_gdbarch
      && gdbarch_core_reg_section_encodes_pid (core_gdbarch))
    {
      uint32_t merged_pid;

      merged_pid = ptid_get_lwp (inferior_ptid);
      merged_pid = merged_pid << 16 | ptid_get_pid (inferior_ptid);

      section_name = xstrprintf ("%s/%s", name, plongest (merged_pid));
    }
  else if (ptid_get_lwp (inferior_ptid))
    section_name = xstrprintf ("%s/%ld", name, ptid_get_lwp (inferior_ptid));
  else
    section_name = xstrdup (name);

  section = bfd_get_section_by_name (core_bfd, section_name);
  if (! section)
    {
      if (required)
        warning (_("Couldn't find %s registers in core file."), human_name);
      return;
    }

  size = bfd_section_size (core_bfd, section);
  contents = alloca (size);
  if (! bfd_get_section_contents (core_bfd, section, contents,
                                  (file_ptr) 0, size))
    {
      warning (_("Couldn't read %s registers from `%s' section in core file."),
               human_name, name);
      return;
    }

  if (core_gdbarch && gdbarch_regset_from_core_section_p (core_gdbarch))
    {
      const struct regset *regset;

      regset = gdbarch_regset_from_core_section (core_gdbarch, name, size);
      if (regset == NULL)
        {
          if (required)
            warning (_("Couldn't recognize %s registers in core file."),
                     human_name);
          return;
        }

      regset->supply_regset (regset, regcache, -1, contents, size);
      return;
    }

  gdb_assert (core_vec);
  core_vec->core_read_registers (regcache, contents, size, which,
                                 ((CORE_ADDR)
                                  bfd_section_vma (core_bfd, section)));
}


/* Get the registers out of a core file.  This is the machine-
   independent part.  Fetch_core_registers is the machine-dependent
   part, typically implemented in the xm-file for each architecture.  */

/* We just get all the registers, so we don't use regno.  */

static void
get_core_registers (struct target_ops *ops,
                    struct regcache *regcache, int regno)
{
  int i;

  if (!(core_gdbarch && gdbarch_regset_from_core_section_p (core_gdbarch))
      && (core_vec == NULL || core_vec->core_read_registers == NULL))
    {
      fprintf_filtered (gdb_stderr,
                     "Can't fetch registers from this type of core file\n");
      return;
    }

  get_core_register_section (regcache,
                             ".reg", 0, "general-purpose", 1);
  get_core_register_section (regcache,
                             ".reg2", 2, "floating-point", 0);
  get_core_register_section (regcache,
                             ".reg-xfp", 3, "extended floating-point", 0);
  get_core_register_section (regcache,
                             ".reg-ppc-vmx", 3, "ppc Altivec", 0);
  get_core_register_section (regcache,
                             ".reg-ppc-vsx", 4, "POWER7 VSX", 0);

  /* Supply dummy value for all registers not found in the core.  */
  for (i = 0; i < gdbarch_num_regs (get_regcache_arch (regcache)); i++)
    if (!regcache_valid_p (regcache, i))
      regcache_raw_supply (regcache, i, NULL);
}

static void
core_files_info (struct target_ops *t)
{
  print_section_info (t, core_bfd);
}
\f
static LONGEST
core_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:
      if (readbuf)
        return (*ops->deprecated_xfer_memory) (offset, readbuf,
                                               len, 0/*read*/, NULL, ops);
      if (writebuf)
        return (*ops->deprecated_xfer_memory) (offset, (gdb_byte *) writebuf,
                                               len, 1/*write*/, NULL, ops);
      return -1;

    case TARGET_OBJECT_AUXV:
      if (readbuf)
        {
          /* When the aux vector is stored in core file, BFD
             represents this with a fake section called ".auxv".  */

          struct bfd_section *section;
          bfd_size_type size;
          char *contents;

          section = bfd_get_section_by_name (core_bfd, ".auxv");
          if (section == NULL)
            return -1;

          size = bfd_section_size (core_bfd, section);
          if (offset >= size)
            return 0;
          size -= offset;
          if (size > len)
            size = len;
          if (size > 0
              && !bfd_get_section_contents (core_bfd, section, readbuf,
                                            (file_ptr) offset, size))
            {
              warning (_("Couldn't read NT_AUXV note in core file."));
              return -1;
            }

          return size;
        }
      return -1;

    case TARGET_OBJECT_WCOOKIE:
      if (readbuf)
        {
          /* When the StackGhost cookie is stored in core file, BFD
             represents this with a fake section called ".wcookie".  */

          struct bfd_section *section;
          bfd_size_type size;
          char *contents;

          section = bfd_get_section_by_name (core_bfd, ".wcookie");
          if (section == NULL)
            return -1;

          size = bfd_section_size (core_bfd, section);
          if (offset >= size)
            return 0;
          size -= offset;
          if (size > len)
            size = len;
          if (size > 0
              && !bfd_get_section_contents (core_bfd, section, readbuf,
                                            (file_ptr) offset, size))
            {
              warning (_("Couldn't read StackGhost cookie in core file."));
              return -1;
            }

          return size;
        }
      return -1;

    case TARGET_OBJECT_LIBRARIES:
      if (core_gdbarch
          && gdbarch_core_xfer_shared_libraries_p (core_gdbarch))
        {
          if (writebuf)
            return -1;
          return
            gdbarch_core_xfer_shared_libraries (core_gdbarch,
                                                readbuf, offset, len);
        }
      /* FALL THROUGH */

    default:
      if (ops->beneath != NULL)
        return ops->beneath->to_xfer_partial (ops->beneath, object, annex,
                                              readbuf, writebuf, offset, len);
      return -1;
    }
}

\f
/* If mourn is being called in all the right places, this could be say
   `gdb internal error' (since generic_mourn calls breakpoint_init_inferior).  */

static int
ignore (struct bp_target_info *bp_tgt)
{
  return 0;
}


/* Okay, let's be honest: threads gleaned from a core file aren't
   exactly lively, are they?  On the other hand, if we don't claim
   that each & every one is alive, then we don't get any of them
   to appear in an "info thread" command, which is quite a useful
   behaviour.
 */
static int
core_thread_alive (struct target_ops *ops, ptid_t ptid)
{
  return 1;
}

/* Ask the current architecture what it knows about this core file.
   That will be used, in turn, to pick a better architecture.  This
   wrapper could be avoided if targets got a chance to specialize
   core_ops.  */

static const struct target_desc *
core_read_description (struct target_ops *target)
{
  if (gdbarch_core_read_description_p (current_gdbarch))
    return gdbarch_core_read_description (current_gdbarch, target, core_bfd);

  return NULL;
}

static char *
core_pid_to_str (struct target_ops *ops, ptid_t ptid)
{
  static char buf[64];

  if (core_gdbarch
      && gdbarch_core_pid_to_str_p (core_gdbarch))
    {
      char *ret = gdbarch_core_pid_to_str (core_gdbarch, ptid);
      if (ret != NULL)
        return ret;
    }

  if (ptid_get_lwp (ptid) == 0)
    xsnprintf (buf, sizeof buf, "<main task>");
  else
    xsnprintf (buf, sizeof buf, "Thread %ld", ptid_get_lwp (ptid));

  return buf;
}

/* Fill in core_ops with its defined operations and properties.  */

static void
init_core_ops (void)
{
  core_ops.to_shortname = "core";
  core_ops.to_longname = "Local core dump file";
  core_ops.to_doc =
    "Use a core file as a target.  Specify the filename of the core file.";
  core_ops.to_open = core_open;
  core_ops.to_close = core_close;
  core_ops.to_attach = find_default_attach;
  core_ops.to_detach = core_detach;
  core_ops.to_fetch_registers = get_core_registers;
  core_ops.to_xfer_partial = core_xfer_partial;
  core_ops.deprecated_xfer_memory = xfer_memory;
  core_ops.to_files_info = core_files_info;
  core_ops.to_insert_breakpoint = ignore;
  core_ops.to_remove_breakpoint = ignore;
  core_ops.to_create_inferior = find_default_create_inferior;
  core_ops.to_thread_alive = core_thread_alive;
  core_ops.to_read_description = core_read_description;
  core_ops.to_pid_to_str = core_pid_to_str;
  core_ops.to_stratum = core_stratum;
  core_ops.to_has_memory = 1;
  core_ops.to_has_stack = 1;
  core_ops.to_has_registers = 1;
  core_ops.to_magic = OPS_MAGIC;
}

void
_initialize_corelow (void)
{
  init_core_ops ();

  add_target (&core_ops);
}