gdb/jit.c

/* Handle JIT code generation in the inferior for GDB, the GNU Debugger.

   Copyright (C) 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 "jit.h"
#include "breakpoint.h"
#include "command.h"
#include "gdbcmd.h"
#include "gdbcore.h"
#include "inferior.h"
#include "observer.h"
#include "objfiles.h"
#include "symfile.h"
#include "symtab.h"
#include "target.h"
#include "gdb_stat.h"

static const struct objfile_data *jit_objfile_data;

static const char *const jit_break_name = "__jit_debug_register_code";

static const char *const jit_descriptor_name = "__jit_debug_descriptor";

static const struct inferior_data *jit_inferior_data = NULL;

/* Non-zero if we want to see trace of jit level stuff.  */

static int jit_debug = 0;

static void
show_jit_debug (struct ui_file *file, int from_tty,
		struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("JIT debugging is %s.\n"), value);
}

struct target_buffer
{
  CORE_ADDR base;
  ULONGEST size;
};

/* Openning the file is a no-op.  */

static void *
mem_bfd_iovec_open (struct bfd *abfd, void *open_closure)
{
  return open_closure;
}

/* Closing the file is just freeing the base/size pair on our side.  */

static int
mem_bfd_iovec_close (struct bfd *abfd, void *stream)
{
  xfree (stream);
  return 1;
}

/* For reading the file, we just need to pass through to target_read_memory and
   fix up the arguments and return values.  */

static file_ptr
mem_bfd_iovec_pread (struct bfd *abfd, void *stream, void *buf,
                     file_ptr nbytes, file_ptr offset)
{
  int err;
  struct target_buffer *buffer = (struct target_buffer *) stream;

  /* If this read will read all of the file, limit it to just the rest.  */
  if (offset + nbytes > buffer->size)
    nbytes = buffer->size - offset;

  /* If there are no more bytes left, we've reached EOF.  */
  if (nbytes == 0)
    return 0;

  err = target_read_memory (buffer->base + offset, (gdb_byte *) buf, nbytes);
  if (err)
    return -1;

  return nbytes;
}

/* For statting the file, we only support the st_size attribute.  */

static int
mem_bfd_iovec_stat (struct bfd *abfd, void *stream, struct stat *sb)
{
  struct target_buffer *buffer = (struct target_buffer*) stream;

  sb->st_size = buffer->size;
  return 0;
}

/* Open a BFD from the target's memory.  */

static struct bfd *
bfd_open_from_target_memory (CORE_ADDR addr, ULONGEST size, char *target)
{
  const char *filename = xstrdup ("<in-memory>");
  struct target_buffer *buffer = xmalloc (sizeof (struct target_buffer));

  buffer->base = addr;
  buffer->size = size;
  return bfd_openr_iovec (filename, target,
                          mem_bfd_iovec_open,
                          buffer,
                          mem_bfd_iovec_pread,
                          mem_bfd_iovec_close,
                          mem_bfd_iovec_stat);
}

/* Per-inferior structure recording the addresses in the inferior.  */

struct jit_inferior_data
{
  CORE_ADDR breakpoint_addr;  /* &__jit_debug_register_code()  */
  CORE_ADDR descriptor_addr;  /* &__jit_debug_descriptor  */
};

/* Return jit_inferior_data for current inferior.  Allocate if not already
   present.  */

static struct jit_inferior_data *
get_jit_inferior_data (void)
{
  struct inferior *inf;
  struct jit_inferior_data *inf_data;

  inf = current_inferior ();
  inf_data = inferior_data (inf, jit_inferior_data);
  if (inf_data == NULL)
    {
      inf_data = XZALLOC (struct jit_inferior_data);
      set_inferior_data (inf, jit_inferior_data, inf_data);
    }

  return inf_data;
}

static void
jit_inferior_data_cleanup (struct inferior *inf, void *arg)
{
  xfree (arg);
}

/* Helper function for reading the global JIT descriptor from remote
   memory.  */

static void
jit_read_descriptor (struct gdbarch *gdbarch,
		     struct jit_descriptor *descriptor,
		     CORE_ADDR descriptor_addr)
{
  int err;
  struct type *ptr_type;
  int ptr_size;
  int desc_size;
  gdb_byte *desc_buf;
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  /* Figure out how big the descriptor is on the remote and how to read it.  */
  ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
  ptr_size = TYPE_LENGTH (ptr_type);
  desc_size = 8 + 2 * ptr_size;  /* Two 32-bit ints and two pointers.  */
  desc_buf = alloca (desc_size);

  /* Read the descriptor.  */
  err = target_read_memory (descriptor_addr, desc_buf, desc_size);
  if (err)
    error (_("Unable to read JIT descriptor from remote memory!"));

  /* Fix the endianness to match the host.  */
  descriptor->version = extract_unsigned_integer (&desc_buf[0], 4, byte_order);
  descriptor->action_flag =
      extract_unsigned_integer (&desc_buf[4], 4, byte_order);
  descriptor->relevant_entry = extract_typed_address (&desc_buf[8], ptr_type);
  descriptor->first_entry =
      extract_typed_address (&desc_buf[8 + ptr_size], ptr_type);
}

/* Helper function for reading a JITed code entry from remote memory.  */

static void
jit_read_code_entry (struct gdbarch *gdbarch,
		     CORE_ADDR code_addr, struct jit_code_entry *code_entry)
{
  int err;
  struct type *ptr_type;
  int ptr_size;
  int entry_size;
  gdb_byte *entry_buf;
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  /* Figure out how big the entry is on the remote and how to read it.  */
  ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
  ptr_size = TYPE_LENGTH (ptr_type);
  entry_size = 3 * ptr_size + 8;  /* Three pointers and one 64-bit int.  */
  entry_buf = alloca (entry_size);

  /* Read the entry.  */
  err = target_read_memory (code_addr, entry_buf, entry_size);
  if (err)
    error (_("Unable to read JIT code entry from remote memory!"));

  /* Fix the endianness to match the host.  */
  ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
  code_entry->next_entry = extract_typed_address (&entry_buf[0], ptr_type);
  code_entry->prev_entry =
      extract_typed_address (&entry_buf[ptr_size], ptr_type);
  code_entry->symfile_addr =
      extract_typed_address (&entry_buf[2 * ptr_size], ptr_type);
  code_entry->symfile_size =
      extract_unsigned_integer (&entry_buf[3 * ptr_size], 8, byte_order);
}

/* This function registers code associated with a JIT code entry.  It uses the
   pointer and size pair in the entry to read the symbol file from the remote
   and then calls symbol_file_add_from_local_memory to add it as though it were
   a symbol file added by the user.  */

static void
jit_register_code (struct gdbarch *gdbarch,
		   CORE_ADDR entry_addr, struct jit_code_entry *code_entry)
{
  bfd *nbfd;
  struct section_addr_info *sai;
  struct bfd_section *sec;
  struct objfile *objfile;
  struct cleanup *old_cleanups, *my_cleanups;
  int i;
  const struct bfd_arch_info *b;
  CORE_ADDR *entry_addr_ptr;

  if (jit_debug)
    fprintf_unfiltered (gdb_stdlog,
			"jit_register_code, symfile_addr = %s, "
			"symfile_size = %s\n",
			paddress (gdbarch, code_entry->symfile_addr),
			pulongest (code_entry->symfile_size));

  nbfd = bfd_open_from_target_memory (code_entry->symfile_addr,
                                      code_entry->symfile_size, gnutarget);
  old_cleanups = make_cleanup_bfd_close (nbfd);

  /* Check the format.  NOTE: This initializes important data that GDB uses!
     We would segfault later without this line.  */
  if (!bfd_check_format (nbfd, bfd_object))
    {
      printf_unfiltered (_("\
JITed symbol file is not an object file, ignoring it.\n"));
      do_cleanups (old_cleanups);
      return;
    }

  /* Check bfd arch.  */
  b = gdbarch_bfd_arch_info (gdbarch);
  if (b->compatible (b, bfd_get_arch_info (nbfd)) != b)
    warning (_("JITed object file architecture %s is not compatible "
               "with target architecture %s."), bfd_get_arch_info
             (nbfd)->printable_name, b->printable_name);

  /* Read the section address information out of the symbol file.  Since the
     file is generated by the JIT at runtime, it should all of the absolute
     addresses that we care about.  */
  sai = alloc_section_addr_info (bfd_count_sections (nbfd));
  make_cleanup_free_section_addr_info (sai);
  i = 0;
  for (sec = nbfd->sections; sec != NULL; sec = sec->next)
    if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
      {
        /* We assume that these virtual addresses are absolute, and do not
           treat them as offsets.  */
        sai->other[i].addr = bfd_get_section_vma (nbfd, sec);
        sai->other[i].name = xstrdup (bfd_get_section_name (nbfd, sec));
        sai->other[i].sectindex = sec->index;
        ++i;
      }

  /* This call takes ownership of sai.  */
  objfile = symbol_file_add_from_bfd (nbfd, 0, sai, OBJF_SHARED, NULL);

  /* Remember a mapping from entry_addr to objfile.  */
  entry_addr_ptr = xmalloc (sizeof (CORE_ADDR));
  *entry_addr_ptr = entry_addr;
  set_objfile_data (objfile, jit_objfile_data, entry_addr_ptr);

  discard_cleanups (old_cleanups);
}

/* This function unregisters JITed code and frees the corresponding
   objfile.  */

static void
jit_unregister_code (struct objfile *objfile)
{
  free_objfile (objfile);
}

/* Look up the objfile with this code entry address.  */

static struct objfile *
jit_find_objf_with_entry_addr (CORE_ADDR entry_addr)
{
  struct objfile *objf;
  CORE_ADDR *objf_entry_addr;

  ALL_OBJFILES (objf)
    {
      objf_entry_addr = (CORE_ADDR *) objfile_data (objf, jit_objfile_data);
      if (objf_entry_addr != NULL && *objf_entry_addr == entry_addr)
        return objf;
    }
  return NULL;
}

/* (Re-)Initialize the jit breakpoint if necessary.
   Return 0 on success.  */

static int
jit_breakpoint_re_set_internal (struct gdbarch *gdbarch,
				struct jit_inferior_data *inf_data)
{
  if (inf_data->breakpoint_addr == 0)
    {
      struct minimal_symbol *reg_symbol;

      /* Lookup the registration symbol.  If it is missing, then we assume
	 we are not attached to a JIT.  */
      reg_symbol = lookup_minimal_symbol (jit_break_name, NULL, NULL);
      if (reg_symbol == NULL)
	return 1;
      inf_data->breakpoint_addr = SYMBOL_VALUE_ADDRESS (reg_symbol);
      if (inf_data->breakpoint_addr == 0)
	return 2;
    }
  else
    return 0;

  if (jit_debug)
    fprintf_unfiltered (gdb_stdlog,
			"jit_breakpoint_re_set_internal, "
			"breakpoint_addr = %s\n",
			paddress (gdbarch, inf_data->breakpoint_addr));

  /* Put a breakpoint in the registration symbol.  */
  create_jit_event_breakpoint (gdbarch, inf_data->breakpoint_addr);

  return 0;
}

/* Register any already created translations.  */

static void
jit_inferior_init (struct gdbarch *gdbarch)
{
  struct jit_descriptor descriptor;
  struct jit_code_entry cur_entry;
  struct jit_inferior_data *inf_data;
  CORE_ADDR cur_entry_addr;

  if (jit_debug)
    fprintf_unfiltered (gdb_stdlog, "jit_inferior_init\n");

  inf_data = get_jit_inferior_data ();
  if (jit_breakpoint_re_set_internal (gdbarch, inf_data) != 0)
    return;

  if (inf_data->descriptor_addr == 0)
    {
      struct minimal_symbol *desc_symbol;

      /* Lookup the descriptor symbol and cache the addr.  If it is
	 missing, we assume we are not attached to a JIT and return early.  */
      desc_symbol = lookup_minimal_symbol (jit_descriptor_name, NULL, NULL);
      if (desc_symbol == NULL)
	return;

      inf_data->descriptor_addr = SYMBOL_VALUE_ADDRESS (desc_symbol);
      if (inf_data->descriptor_addr == 0)
	return;
    }

  if (jit_debug)
    fprintf_unfiltered (gdb_stdlog,
			"jit_inferior_init, descriptor_addr = %s\n",
			paddress (gdbarch, inf_data->descriptor_addr));

  /* Read the descriptor so we can check the version number and load
     any already JITed functions.  */
  jit_read_descriptor (gdbarch, &descriptor, inf_data->descriptor_addr);

  /* Check that the version number agrees with that we support.  */
  if (descriptor.version != 1)
    error (_("Unsupported JIT protocol version in descriptor!"));

  /* If we've attached to a running program, we need to check the descriptor
     to register any functions that were already generated.  */
  for (cur_entry_addr = descriptor.first_entry;
       cur_entry_addr != 0;
       cur_entry_addr = cur_entry.next_entry)
    {
      jit_read_code_entry (gdbarch, cur_entry_addr, &cur_entry);

      /* This hook may be called many times during setup, so make sure we don't
         add the same symbol file twice.  */
      if (jit_find_objf_with_entry_addr (cur_entry_addr) != NULL)
        continue;

      jit_register_code (gdbarch, cur_entry_addr, &cur_entry);
    }
}

/* Exported routine to call when an inferior has been created.  */

void
jit_inferior_created_hook (void)
{
  jit_inferior_init (target_gdbarch);
}

/* Exported routine to call to re-set the jit breakpoints,
   e.g. when a program is rerun.  */

void
jit_breakpoint_re_set (void)
{
  jit_breakpoint_re_set_internal (target_gdbarch,
				  get_jit_inferior_data ());
}

/* Reset inferior_data, so sybols will be looked up again, and jit_breakpoint
   will be reset.  */

static void
jit_reset_inferior_data_and_breakpoints (void)
{
  struct jit_inferior_data *inf_data;

  /* Force jit_inferior_init to re-lookup of jit symbol addresses.  */
  inf_data = get_jit_inferior_data ();
  inf_data->breakpoint_addr = 0;
  inf_data->descriptor_addr = 0;

  /* Remove any existing JIT breakpoint(s).  */
  remove_jit_event_breakpoints ();

  jit_inferior_init (target_gdbarch);
}

/* Wrapper to match the observer function pointer prototype.  */

static void
jit_inferior_created_observer (struct target_ops *objfile, int from_tty)
{
  jit_reset_inferior_data_and_breakpoints ();
}

/* This function cleans up any code entries left over when the
   inferior exits.  We get left over code when the inferior exits
   without unregistering its code, for example when it crashes.  */

static void
jit_inferior_exit_hook (struct inferior *inf)
{
  struct objfile *objf;
  struct objfile *temp;

  ALL_OBJFILES_SAFE (objf, temp)
    if (objfile_data (objf, jit_objfile_data) != NULL)
      jit_unregister_code (objf);
}

static void
jit_executable_changed_observer (void)
{
  jit_reset_inferior_data_and_breakpoints ();
}

void
jit_event_handler (struct gdbarch *gdbarch)
{
  struct jit_descriptor descriptor;
  struct jit_code_entry code_entry;
  CORE_ADDR entry_addr;
  struct objfile *objf;

  /* Read the descriptor from remote memory.  */
  jit_read_descriptor (gdbarch, &descriptor,
		       get_jit_inferior_data ()->descriptor_addr);
  entry_addr = descriptor.relevant_entry;

  /* Do the corresponding action.  */
  switch (descriptor.action_flag)
    {
    case JIT_NOACTION:
      break;
    case JIT_REGISTER:
      jit_read_code_entry (gdbarch, entry_addr, &code_entry);
      jit_register_code (gdbarch, entry_addr, &code_entry);
      break;
    case JIT_UNREGISTER:
      objf = jit_find_objf_with_entry_addr (entry_addr);
      if (objf == NULL)
	printf_unfiltered (_("Unable to find JITed code "
			     "entry at address: %s\n"),
			   paddress (gdbarch, entry_addr));
      else
        jit_unregister_code (objf);

      break;
    default:
      error (_("Unknown action_flag value in JIT descriptor!"));
      break;
    }
}

/* Provide a prototype to silence -Wmissing-prototypes.  */

extern void _initialize_jit (void);

void
_initialize_jit (void)
{
  add_setshow_zinteger_cmd ("jit", class_maintenance, &jit_debug,
			    _("Set JIT debugging."),
			    _("Show JIT debugging."),
			    _("When non-zero, JIT debugging is enabled."),
			    NULL,
			    show_jit_debug,
			    &setdebuglist, &showdebuglist);

  observer_attach_inferior_created (jit_inferior_created_observer);
  observer_attach_inferior_exit (jit_inferior_exit_hook);
  observer_attach_executable_changed (jit_executable_changed_observer);
  jit_objfile_data = register_objfile_data ();
  jit_inferior_data =
    register_inferior_data_with_cleanup (jit_inferior_data_cleanup);
}