bsd-uthread.c   [plain text]

/* BSD user-level threads support.

   Copyright 2005 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 2 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, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "gdbcore.h"
#include "gdbthread.h"
#include "inferior.h"
#include "objfiles.h"
#include "observer.h"
#include "regcache.h"
#include "solib.h"
#include "solist.h"
#include "symfile.h"
#include "target.h"

#include "gdb_assert.h"
#include "gdb_obstack.h"

#include "bsd-uthread.h"

/* HACK: Save the bsd_uthreads ops returned by bsd_uthread_target.  */
static struct target_ops *bsd_uthread_ops_hack;


/* Architecture-specific operations.  */

/* Per-architecture data key.  */
static struct gdbarch_data *bsd_uthread_data;

struct bsd_uthread_ops
{
  /* Supply registers for an inactive thread to a register cache.  */
  void (*supply_uthread)(struct regcache *, int, CORE_ADDR);

  /* Collect registers for an inactive thread from a register cache.  */
  void (*collect_uthread)(const struct regcache *, int, CORE_ADDR);
};

static void *
bsd_uthread_init (struct obstack *obstack)
{
  struct bsd_uthread_ops *ops;

  ops = OBSTACK_ZALLOC (obstack, struct bsd_uthread_ops);
  return ops;
}

/* Set the function that supplies registers from an inactive thread
   for architecture GDBARCH to SUPPLY_UTHREAD.  */

void
bsd_uthread_set_supply_uthread (struct gdbarch *gdbarch,
				void (*supply_uthread) (struct regcache *,
							int, CORE_ADDR))
{
  struct bsd_uthread_ops *ops = gdbarch_data (gdbarch, bsd_uthread_data);
  ops->supply_uthread = supply_uthread;
}

/* Set the function that collects registers for an inactive thread for
   architecture GDBARCH to SUPPLY_UTHREAD.  */

void
bsd_uthread_set_collect_uthread (struct gdbarch *gdbarch,
			 void (*collect_uthread) (const struct regcache *,
						  int, CORE_ADDR))
{
  struct bsd_uthread_ops *ops = gdbarch_data (gdbarch, bsd_uthread_data);
  ops->collect_uthread = collect_uthread;
}

/* Magic number to help recognize a valid thread structure.  */
#define BSD_UTHREAD_PTHREAD_MAGIC	0xd09ba115

/* Check whether the thread structure at ADDR is valid.  */

static void
bsd_uthread_check_magic (CORE_ADDR addr)
{
  ULONGEST magic = read_memory_unsigned_integer (addr, 4);

  if (magic != BSD_UTHREAD_PTHREAD_MAGIC)
    error (_("Bad magic"));
}

/* Thread states.  */
#define BSD_UTHREAD_PS_RUNNING	0
#define BSD_UTHREAD_PS_DEAD	18

/* Address of the pointer to the the thread structure for the running
   thread.  */
static CORE_ADDR bsd_uthread_thread_run_addr;

/* Address of the list of all threads.  */
static CORE_ADDR bsd_uthread_thread_list_addr;

/* Offsets of various "interesting" bits in the thread structure.  */
static int bsd_uthread_thread_state_offset = -1;
static int bsd_uthread_thread_next_offset = -1;
static int bsd_uthread_thread_ctx_offset;

/* Name of shared threads library.  */
static const char *bsd_uthread_solib_name;

/* Non-zero if the thread startum implemented by this module is active.  */
static int bsd_uthread_active;

static CORE_ADDR
bsd_uthread_lookup_address (const char *name, struct objfile *objfile)
{
  struct minimal_symbol *sym;

  sym = lookup_minimal_symbol (name, NULL, objfile);
  if (sym)
    return SYMBOL_VALUE_ADDRESS (sym);

  return 0;
}

static int
bsd_uthread_lookup_offset (const char *name, struct objfile *objfile)
{
  CORE_ADDR addr;

  addr = bsd_uthread_lookup_address (name, objfile);
  if (addr == 0)
    return 0;

  return read_memory_unsigned_integer (addr, 4);
}

/* If OBJFILE contains the symbols corresponding to one of the
   supported user-level threads libraries, activate the thread stratum
   implemented by this module.  */

static int
bsd_uthread_activate (struct objfile *objfile)
{
  struct gdbarch *gdbarch = current_gdbarch;
  struct bsd_uthread_ops *ops = gdbarch_data (gdbarch, bsd_uthread_data);

  /* Skip if the thread stratum has already been activated.  */
  if (bsd_uthread_active)
    return 0;

  /* There's no point in enabling this module if no
     architecture-specific operations are provided.  */
  if (!ops->supply_uthread)
    return 0;

  bsd_uthread_thread_run_addr =
    bsd_uthread_lookup_address ("_thread_run", objfile);
  if (bsd_uthread_thread_run_addr == 0)
    return 0;

  bsd_uthread_thread_list_addr =
    bsd_uthread_lookup_address ("_thread_list", objfile);
  if (bsd_uthread_thread_list_addr == 0)
    return 0;

  bsd_uthread_thread_state_offset =
    bsd_uthread_lookup_offset ("_thread_state_offset", objfile);
  if (bsd_uthread_thread_state_offset == 0)
    return 0;

  bsd_uthread_thread_next_offset =
    bsd_uthread_lookup_offset ("_thread_next_offset", objfile);
  if (bsd_uthread_thread_next_offset == 0)
    return 0;

  bsd_uthread_thread_ctx_offset =
    bsd_uthread_lookup_offset ("_thread_ctx_offset", objfile);

  push_target (bsd_uthread_ops_hack);
  bsd_uthread_active = 1;
  return 1;
}

/* Deactivate the thread stratum implemented by this module.  */

static void
bsd_uthread_deactivate (void)
{
  /* Skip if the thread stratum has already been deactivated.  */
  if (!bsd_uthread_active)
    return;

  bsd_uthread_active = 0;
  unpush_target (bsd_uthread_ops_hack);

  bsd_uthread_thread_run_addr = 0;
  bsd_uthread_thread_list_addr = 0;
  bsd_uthread_thread_state_offset = 0;
  bsd_uthread_thread_next_offset = 0;
  bsd_uthread_thread_ctx_offset = 0;
  bsd_uthread_solib_name = NULL;
}

void
bsd_uthread_inferior_created (struct target_ops *ops, int from_tty)
{
  bsd_uthread_activate (NULL);
}

/* Likely candidates for the threads library.  */
static const char *bsd_uthread_solib_names[] =
{
  "/usr/lib/libc_r.so",		/* FreeBSD */
  "/usr/lib/libpthread.so",	/* OpenBSD */
  NULL
};

void
bsd_uthread_solib_loaded (struct so_list *so)
{
  const char **names = bsd_uthread_solib_names;

  for (names = bsd_uthread_solib_names; *names; names++)
    {
      if (strncmp (so->so_original_name, *names, strlen (*names)) == 0)
	{
	  solib_read_symbols (so, so->from_tty);

	  if (bsd_uthread_activate (so->objfile))
	    {
	      bsd_uthread_solib_name == so->so_original_name;
	      return;
	    }
	}
    }
}

void
bsd_uthread_solib_unloaded (struct so_list *so)
{
  if (!bsd_uthread_solib_name)
    return;

  if (strcmp (so->so_original_name, bsd_uthread_solib_name) == 0)
    bsd_uthread_deactivate ();
}

static void
bsd_uthread_mourn_inferior (void)
{
  find_target_beneath (bsd_uthread_ops_hack)->to_mourn_inferior ();
  bsd_uthread_deactivate ();
}

static void
bsd_uthread_fetch_registers (int regnum)
{
  struct gdbarch *gdbarch = current_gdbarch;
  struct bsd_uthread_ops *ops = gdbarch_data (gdbarch, bsd_uthread_data);
  CORE_ADDR addr = ptid_get_tid (inferior_ptid);
  CORE_ADDR active_addr;

  /* Always fetch the appropriate registers from the layer beneath.  */
  find_target_beneath (bsd_uthread_ops_hack)->to_fetch_registers (regnum);

  /* FIXME: That might have gotten us more than we asked for.  Make
     sure we overwrite all relevant registers with values from the
     thread structure.  This can go once we fix the underlying target.  */
  regnum = -1;

  active_addr = read_memory_typed_address (bsd_uthread_thread_run_addr,
					   builtin_type_void_data_ptr);
  if (addr != 0 && addr != active_addr)
    {
      bsd_uthread_check_magic (addr);
      ops->supply_uthread (current_regcache, regnum,
			   addr + bsd_uthread_thread_ctx_offset);
    }
}

static void
bsd_uthread_store_registers (int regnum)
{
  struct gdbarch *gdbarch = current_gdbarch;
  struct bsd_uthread_ops *ops = gdbarch_data (gdbarch, bsd_uthread_data);
  CORE_ADDR addr = ptid_get_tid (inferior_ptid);
  CORE_ADDR active_addr;

  active_addr = read_memory_typed_address (bsd_uthread_thread_run_addr,
					   builtin_type_void_data_ptr);
  if (addr != 0 && addr != active_addr)
    {
      bsd_uthread_check_magic (addr);
      ops->collect_uthread (current_regcache, regnum,
			    addr + bsd_uthread_thread_ctx_offset);
    }
  else
    {
      /* Updating the thread that is currently running; pass the
         request to the layer beneath.  */
      find_target_beneath (bsd_uthread_ops_hack)->to_store_registers (regnum);
    }
}

/* FIXME: This function is only there because otherwise GDB tries to
   invoke deprecate_xfer_memory.  */

static LONGEST
bsd_uthread_xfer_partial (struct target_ops *ops, enum target_object object,
			  const char *annex, gdb_byte *readbuf,
			  const gdb_byte *writebuf,
			  ULONGEST offset, LONGEST len)
{
  gdb_assert (ops->beneath->to_xfer_partial);
  return ops->beneath->to_xfer_partial (ops->beneath, object, annex, readbuf,
					writebuf, offset, len);
}

static ptid_t
bsd_uthread_wait (ptid_t ptid, struct target_waitstatus *status)
{
  CORE_ADDR addr;

  /* Pass the request to the layer beneath.  */
  ptid = find_target_beneath (bsd_uthread_ops_hack)->to_wait (ptid, status);

  /* Fetch the corresponding thread ID, and augment the returned
     process ID with it.  */
  addr = read_memory_typed_address (bsd_uthread_thread_run_addr,
				    builtin_type_void_data_ptr);
  if (addr != 0)
    {
      gdb_byte buf[4];

      /* FIXME: For executables linked statically with the threads
         library, we end up here before the program has actually been
         executed.  In that case ADDR will be garbage since it has
         been read from the wrong virtual memory image.  */
      if (target_read_memory (addr, buf, 4) == 0)
	{
	  ULONGEST magic = extract_unsigned_integer (buf, 4);
	  if (magic == BSD_UTHREAD_PTHREAD_MAGIC)
	    ptid = ptid_build (ptid_get_pid (ptid), 0, addr);
	}
    }

  /* HACK: Twiddle INFERIOR_PTID such that the initial thread of a
     process isn't recognized as a new thread.  */
  if (ptid_get_tid (ptid) != 0 && !in_thread_list (ptid)
      && ptid_get_tid (inferior_ptid) == 0)
    {
      add_thread (ptid);
      inferior_ptid = ptid;
    }

  return ptid;
}

static void
bsd_uthread_resume (ptid_t ptid, int step, enum target_signal sig)
{
  /* Pass the request to the layer beneath.  */
  find_target_beneath (bsd_uthread_ops_hack)->to_resume (ptid, step, sig);
}

static int
bsd_uthread_thread_alive (ptid_t ptid)
{
  CORE_ADDR addr = ptid_get_tid (inferior_ptid);

  if (addr != 0)
    {
      int offset = bsd_uthread_thread_state_offset;
      ULONGEST state;

      bsd_uthread_check_magic (addr);

      state = read_memory_unsigned_integer (addr + offset, 4);
      if (state == BSD_UTHREAD_PS_DEAD)
	return 0;
    }

  return find_target_beneath (bsd_uthread_ops_hack)->to_thread_alive (ptid);
}

static void
bsd_uthread_find_new_threads (void)
{
  pid_t pid = ptid_get_pid (inferior_ptid);
  int offset = bsd_uthread_thread_next_offset;
  CORE_ADDR addr;

  addr = read_memory_typed_address (bsd_uthread_thread_list_addr,
				    builtin_type_void_data_ptr);
  while (addr != 0)
    {
      ptid_t ptid = ptid_build (pid, 0, addr);

      if (!in_thread_list (ptid))
	add_thread (ptid);

      addr = read_memory_typed_address (addr + offset,
					builtin_type_void_data_ptr);
    }
}

/* Possible states a thread can be in.  */
static char *bsd_uthread_state[] =
{
  "RUNNING",
  "SIGTHREAD",
  "MUTEX_WAIT",
  "COND_WAIT",
  "FDLR_WAIT",
  "FDLW_WAIT",
  "FDR_WAIT",
  "FDW_WAIT",
  "FILE_WAIT",
  "POLL_WAIT",
  "SELECT_WAIT",
  "SLEEP_WAIT",
  "WAIT_WAIT",
  "SIGSUSPEND",
  "SIGWAIT",
  "SPINBLOCK",
  "JOIN",
  "SUSPENDED",
  "DEAD",
  "DEADLOCK"
};

/* Return a string describing th state of the thread specified by
   INFO.  */

static char *
bsd_uthread_extra_thread_info (struct thread_info *info)
{
  CORE_ADDR addr = ptid_get_tid (info->ptid);

  if (addr != 0)
    {
      int offset = bsd_uthread_thread_state_offset;
      ULONGEST state;

      state = read_memory_unsigned_integer (addr + offset, 4);
      if (state < ARRAY_SIZE (bsd_uthread_state))
	return bsd_uthread_state[state];
    }

  return NULL;
}

static char *
bsd_uthread_pid_to_str (ptid_t ptid)
{
  if (ptid_get_tid (ptid) != 0)
    {
      static char buf[64];

      xsnprintf (buf, sizeof buf, "process %d, thread 0x%lx",
		 ptid_get_pid (ptid), ptid_get_tid (ptid));
      return buf;
    }

  return normal_pid_to_str (ptid);
}

struct target_ops *
bsd_uthread_target (void)
{
  struct target_ops *t = XZALLOC (struct target_ops);

  t->to_shortname = "bsd-uthreads";
  t->to_longname = "BSD user-level threads";
  t->to_doc = "BSD user-level threads";
  t->to_mourn_inferior = bsd_uthread_mourn_inferior;
  t->to_fetch_registers = bsd_uthread_fetch_registers;
  t->to_store_registers = bsd_uthread_store_registers;
  t->to_xfer_partial = bsd_uthread_xfer_partial;
  t->to_wait = bsd_uthread_wait;
  t->to_resume = bsd_uthread_resume;
  t->to_thread_alive = bsd_uthread_thread_alive;
  t->to_find_new_threads = bsd_uthread_find_new_threads;
  t->to_extra_thread_info = bsd_uthread_extra_thread_info;
  t->to_pid_to_str = bsd_uthread_pid_to_str;
  t->to_stratum = thread_stratum;
  t->to_magic = OPS_MAGIC;
  bsd_uthread_ops_hack = t;

  return t;
}

void
_initialize_bsd_uthread (void)
{
  add_target (bsd_uthread_target ());

  bsd_uthread_data = gdbarch_data_register_pre_init (bsd_uthread_init);

  observer_attach_inferior_created (bsd_uthread_inferior_created);
  observer_attach_solib_loaded (bsd_uthread_solib_loaded);
  observer_attach_solib_unloaded (bsd_uthread_solib_unloaded);
}