gdb/jit.c

   1 /* Handle JIT code generation in the inferior for GDB, the GNU Debugger.
   2
   3    Copyright (C) 2009, 2010, 2011 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21
  22 #include "jit.h"
  23 #include "breakpoint.h"
  24 #include "command.h"
  25 #include "gdbcmd.h"
  26 #include "gdbcore.h"
  27 #include "inferior.h"
  28 #include "observer.h"
  29 #include "objfiles.h"
  30 #include "symfile.h"
  31 #include "symtab.h"
  32 #include "target.h"
  33 #include "gdb_stat.h"
  34
  35 static const struct objfile_data *jit_objfile_data;
  36
  37 static const char *const jit_break_name = "__jit_debug_register_code";
  38
  39 static const char *const jit_descriptor_name = "__jit_debug_descriptor";
  40
  41 static const struct inferior_data *jit_inferior_data = NULL;
  42
  43 static void
  44 jit_inferior_init (struct gdbarch *gdbarch);
  45
  46 /* Non-zero if we want to see trace of jit level stuff.  */
  47
  48 static int jit_debug = 0;
  49
  50 static void
  51 show_jit_debug (struct ui_file *file, int from_tty,
  52                 struct cmd_list_element *c, const char *value)
  53 {
  54   fprintf_filtered (file, _("JIT debugging is %s.\n"), value);
  55 }
  56
  57 struct target_buffer
  58 {
  59   CORE_ADDR base;
  60   ULONGEST size;
  61 };
  62
  63 /* Openning the file is a no-op.  */
  64
  65 static void *
  66 mem_bfd_iovec_open (struct bfd *abfd, void *open_closure)
  67 {
  68   return open_closure;
  69 }
  70
  71 /* Closing the file is just freeing the base/size pair on our side.  */
  72
  73 static int
  74 mem_bfd_iovec_close (struct bfd *abfd, void *stream)
  75 {
  76   xfree (stream);
  77   return 1;
  78 }
  79
  80 /* For reading the file, we just need to pass through to target_read_memory and
  81    fix up the arguments and return values.  */
  82
  83 static file_ptr
  84 mem_bfd_iovec_pread (struct bfd *abfd, void *stream, void *buf,
  85                      file_ptr nbytes, file_ptr offset)
  86 {
  87   int err;
  88   struct target_buffer *buffer = (struct target_buffer *) stream;
  89
  90   /* If this read will read all of the file, limit it to just the rest.  */
  91   if (offset + nbytes > buffer->size)
  92     nbytes = buffer->size - offset;
  93
  94   /* If there are no more bytes left, we've reached EOF.  */
  95   if (nbytes == 0)
  96     return 0;
  97
  98   err = target_read_memory (buffer->base + offset, (gdb_byte *) buf, nbytes);
  99   if (err)
 100     return -1;
 101
 102   return nbytes;
 103 }
 104
 105 /* For statting the file, we only support the st_size attribute.  */
 106
 107 static int
 108 mem_bfd_iovec_stat (struct bfd *abfd, void *stream, struct stat *sb)
 109 {
 110   struct target_buffer *buffer = (struct target_buffer*) stream;
 111
 112   sb->st_size = buffer->size;
 113   return 0;
 114 }
 115
 116 /* Open a BFD from the target's memory.  */
 117
 118 static struct bfd *
 119 bfd_open_from_target_memory (CORE_ADDR addr, ULONGEST size, char *target)
 120 {
 121   const char *filename = xstrdup ("<in-memory>");
 122   struct target_buffer *buffer = xmalloc (sizeof (struct target_buffer));
 123
 124   buffer->base = addr;
 125   buffer->size = size;
 126   return bfd_openr_iovec (filename, target,
 127                           mem_bfd_iovec_open,
 128                           buffer,
 129                           mem_bfd_iovec_pread,
 130                           mem_bfd_iovec_close,
 131                           mem_bfd_iovec_stat);
 132 }
 133
 134 /* Per-inferior structure recording the addresses in the inferior.  */
 135
 136 struct jit_inferior_data
 137 {
 138   CORE_ADDR breakpoint_addr;  /* &__jit_debug_register_code()  */
 139   CORE_ADDR descriptor_addr;  /* &__jit_debug_descriptor  */
 140 };
 141
 142 /* Return jit_inferior_data for current inferior.  Allocate if not already
 143    present.  */
 144
 145 static struct jit_inferior_data *
 146 get_jit_inferior_data (void)
 147 {
 148   struct inferior *inf;
 149   struct jit_inferior_data *inf_data;
 150
 151   inf = current_inferior ();
 152   inf_data = inferior_data (inf, jit_inferior_data);
 153   if (inf_data == NULL)
 154     {
 155       inf_data = XZALLOC (struct jit_inferior_data);
 156       set_inferior_data (inf, jit_inferior_data, inf_data);
 157     }
 158
 159   return inf_data;
 160 }
 161
 162 static void
 163 jit_inferior_data_cleanup (struct inferior *inf, void *arg)
 164 {
 165   xfree (arg);
 166 }
 167
 168 /* Helper function for reading the global JIT descriptor from remote
 169    memory.  */
 170
 171 static void
 172 jit_read_descriptor (struct gdbarch *gdbarch,
 173                      struct jit_descriptor *descriptor,
 174                      CORE_ADDR descriptor_addr)
 175 {
 176   int err;
 177   struct type *ptr_type;
 178   int ptr_size;
 179   int desc_size;
 180   gdb_byte *desc_buf;
 181   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 182
 183   /* Figure out how big the descriptor is on the remote and how to read it.  */
 184   ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
 185   ptr_size = TYPE_LENGTH (ptr_type);
 186   desc_size = 8 + 2 * ptr_size;  /* Two 32-bit ints and two pointers.  */
 187   desc_buf = alloca (desc_size);
 188
 189   /* Read the descriptor.  */
 190   err = target_read_memory (descriptor_addr, desc_buf, desc_size);
 191   if (err)
 192     error (_("Unable to read JIT descriptor from remote memory!"));
 193
 194   /* Fix the endianness to match the host.  */
 195   descriptor->version = extract_unsigned_integer (&desc_buf[0], 4, byte_order);
 196   descriptor->action_flag =
 197       extract_unsigned_integer (&desc_buf[4], 4, byte_order);
 198   descriptor->relevant_entry = extract_typed_address (&desc_buf[8], ptr_type);
 199   descriptor->first_entry =
 200       extract_typed_address (&desc_buf[8 + ptr_size], ptr_type);
 201 }
 202
 203 /* Helper function for reading a JITed code entry from remote memory.  */
 204
 205 static void
 206 jit_read_code_entry (struct gdbarch *gdbarch,
 207                      CORE_ADDR code_addr, struct jit_code_entry *code_entry)
 208 {
 209   int err;
 210   struct type *ptr_type;
 211   int ptr_size;
 212   int entry_size;
 213   gdb_byte *entry_buf;
 214   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 215
 216   /* Figure out how big the entry is on the remote and how to read it.  */
 217   ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
 218   ptr_size = TYPE_LENGTH (ptr_type);
 219   entry_size = 3 * ptr_size + 8;  /* Three pointers and one 64-bit int.  */
 220   entry_buf = alloca (entry_size);
 221
 222   /* Read the entry.  */
 223   err = target_read_memory (code_addr, entry_buf, entry_size);
 224   if (err)
 225     error (_("Unable to read JIT code entry from remote memory!"));
 226
 227   /* Fix the endianness to match the host.  */
 228   ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
 229   code_entry->next_entry = extract_typed_address (&entry_buf[0], ptr_type);
 230   code_entry->prev_entry =
 231       extract_typed_address (&entry_buf[ptr_size], ptr_type);
 232   code_entry->symfile_addr =
 233       extract_typed_address (&entry_buf[2 * ptr_size], ptr_type);
 234   code_entry->symfile_size =
 235       extract_unsigned_integer (&entry_buf[3 * ptr_size], 8, byte_order);
 236 }
 237
 238 /* This function registers code associated with a JIT code entry.  It uses the
 239    pointer and size pair in the entry to read the symbol file from the remote
 240    and then calls symbol_file_add_from_local_memory to add it as though it were
 241    a symbol file added by the user.  */
 242
 243 static void
 244 jit_register_code (struct gdbarch *gdbarch,
 245                    CORE_ADDR entry_addr, struct jit_code_entry *code_entry)
 246 {
 247   bfd *nbfd;
 248   struct section_addr_info *sai;
 249   struct bfd_section *sec;
 250   struct objfile *objfile;
 251   struct cleanup *old_cleanups, *my_cleanups;
 252   int i;
 253   const struct bfd_arch_info *b;
 254   CORE_ADDR *entry_addr_ptr;
 255
 256   if (jit_debug)
 257     fprintf_unfiltered (gdb_stdlog,
 258                         "jit_register_code, symfile_addr = %s, "
 259                         "symfile_size = %s\n",
 260                         paddress (gdbarch, code_entry->symfile_addr),
 261                         pulongest (code_entry->symfile_size));
 262
 263   nbfd = bfd_open_from_target_memory (code_entry->symfile_addr,
 264                                       code_entry->symfile_size, gnutarget);
 265   old_cleanups = make_cleanup_bfd_close (nbfd);
 266
 267   /* Check the format.  NOTE: This initializes important data that GDB uses!
 268      We would segfault later without this line.  */
 269   if (!bfd_check_format (nbfd, bfd_object))
 270     {
 271       printf_unfiltered (_("\
 272 JITed symbol file is not an object file, ignoring it.\n"));
 273       do_cleanups (old_cleanups);
 274       return;
 275     }
 276
 277   /* Check bfd arch.  */
 278   b = gdbarch_bfd_arch_info (gdbarch);
 279   if (b->compatible (b, bfd_get_arch_info (nbfd)) != b)
 280     warning (_("JITed object file architecture %s is not compatible "
 281                "with target architecture %s."), bfd_get_arch_info
 282              (nbfd)->printable_name, b->printable_name);
 283
 284   /* Read the section address information out of the symbol file.  Since the
 285      file is generated by the JIT at runtime, it should all of the absolute
 286      addresses that we care about.  */
 287   sai = alloc_section_addr_info (bfd_count_sections (nbfd));
 288   make_cleanup_free_section_addr_info (sai);
 289   i = 0;
 290   for (sec = nbfd->sections; sec != NULL; sec = sec->next)
 291     if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
 292       {
 293         /* We assume that these virtual addresses are absolute, and do not
 294            treat them as offsets.  */
 295         sai->other[i].addr = bfd_get_section_vma (nbfd, sec);
 296         sai->other[i].name = xstrdup (bfd_get_section_name (nbfd, sec));
 297         sai->other[i].sectindex = sec->index;
 298         ++i;
 299       }
 300
 301   /* This call takes ownership of sai.  */
 302   objfile = symbol_file_add_from_bfd (nbfd, 0, sai, OBJF_SHARED, NULL);
 303
 304   /* Remember a mapping from entry_addr to objfile.  */
 305   entry_addr_ptr = xmalloc (sizeof (CORE_ADDR));
 306   *entry_addr_ptr = entry_addr;
 307   set_objfile_data (objfile, jit_objfile_data, entry_addr_ptr);
 308
 309   discard_cleanups (old_cleanups);
 310 }
 311
 312 /* This function unregisters JITed code and frees the corresponding
 313    objfile.  */
 314
 315 static void
 316 jit_unregister_code (struct objfile *objfile)
 317 {
 318   free_objfile (objfile);
 319 }
 320
 321 /* Look up the objfile with this code entry address.  */
 322
 323 static struct objfile *
 324 jit_find_objf_with_entry_addr (CORE_ADDR entry_addr)
 325 {
 326   struct objfile *objf;
 327   CORE_ADDR *objf_entry_addr;
 328
 329   ALL_OBJFILES (objf)
 330     {
 331       objf_entry_addr = (CORE_ADDR *) objfile_data (objf, jit_objfile_data);
 332       if (objf_entry_addr != NULL && *objf_entry_addr == entry_addr)
 333         return objf;
 334     }
 335   return NULL;
 336 }
 337
 338 /* (Re-)Initialize the jit breakpoint if necessary.
 339    Return 0 on success.  */
 340
 341 static int
 342 jit_breakpoint_re_set_internal (struct gdbarch *gdbarch,
 343                                 struct jit_inferior_data *inf_data)
 344 {
 345   if (inf_data->breakpoint_addr == 0)
 346     {
 347       struct minimal_symbol *reg_symbol;
 348
 349       /* Lookup the registration symbol.  If it is missing, then we assume
 350          we are not attached to a JIT.  */
 351       reg_symbol = lookup_minimal_symbol (jit_break_name, NULL, NULL);
 352       if (reg_symbol == NULL)
 353         return 1;
 354       inf_data->breakpoint_addr = SYMBOL_VALUE_ADDRESS (reg_symbol);
 355       if (inf_data->breakpoint_addr == 0)
 356         return 2;
 357
 358       /* If we have not read the jit descriptor yet (e.g. because the JITer
 359          itself is in a shared library which just got loaded), do so now.  */
 360       if (inf_data->descriptor_addr == 0)
 361         jit_inferior_init (gdbarch);
 362     }
 363   else
 364     return 0;
 365
 366   if (jit_debug)
 367     fprintf_unfiltered (gdb_stdlog,
 368                         "jit_breakpoint_re_set_internal, "
 369                         "breakpoint_addr = %s\n",
 370                         paddress (gdbarch, inf_data->breakpoint_addr));
 371
 372   /* Put a breakpoint in the registration symbol.  */
 373   create_jit_event_breakpoint (gdbarch, inf_data->breakpoint_addr);
 374
 375   return 0;
 376 }
 377
 378 /* Register any already created translations.  */
 379
 380 static void
 381 jit_inferior_init (struct gdbarch *gdbarch)
 382 {
 383   struct jit_descriptor descriptor;
 384   struct jit_code_entry cur_entry;
 385   struct jit_inferior_data *inf_data;
 386   CORE_ADDR cur_entry_addr;
 387
 388   if (jit_debug)
 389     fprintf_unfiltered (gdb_stdlog, "jit_inferior_init\n");
 390
 391   inf_data = get_jit_inferior_data ();
 392   if (jit_breakpoint_re_set_internal (gdbarch, inf_data) != 0)
 393     return;
 394
 395   if (inf_data->descriptor_addr == 0)
 396     {
 397       struct minimal_symbol *desc_symbol;
 398
 399       /* Lookup the descriptor symbol and cache the addr.  If it is
 400          missing, we assume we are not attached to a JIT and return early.  */
 401       desc_symbol = lookup_minimal_symbol (jit_descriptor_name, NULL, NULL);
 402       if (desc_symbol == NULL)
 403         return;
 404
 405       inf_data->descriptor_addr = SYMBOL_VALUE_ADDRESS (desc_symbol);
 406       if (inf_data->descriptor_addr == 0)
 407         return;
 408     }
 409
 410   if (jit_debug)
 411     fprintf_unfiltered (gdb_stdlog,
 412                         "jit_inferior_init, descriptor_addr = %s\n",
 413                         paddress (gdbarch, inf_data->descriptor_addr));
 414
 415   /* Read the descriptor so we can check the version number and load
 416      any already JITed functions.  */
 417   jit_read_descriptor (gdbarch, &descriptor, inf_data->descriptor_addr);
 418
 419   /* Check that the version number agrees with that we support.  */
 420   if (descriptor.version != 1)
 421     error (_("Unsupported JIT protocol version in descriptor!"));
 422
 423   /* If we've attached to a running program, we need to check the descriptor
 424      to register any functions that were already generated.  */
 425   for (cur_entry_addr = descriptor.first_entry;
 426        cur_entry_addr != 0;
 427        cur_entry_addr = cur_entry.next_entry)
 428     {
 429       jit_read_code_entry (gdbarch, cur_entry_addr, &cur_entry);
 430
 431       /* This hook may be called many times during setup, so make sure we don't
 432          add the same symbol file twice.  */
 433       if (jit_find_objf_with_entry_addr (cur_entry_addr) != NULL)
 434         continue;
 435
 436       jit_register_code (gdbarch, cur_entry_addr, &cur_entry);
 437     }
 438 }
 439
 440 /* Exported routine to call when an inferior has been created.  */
 441
 442 void
 443 jit_inferior_created_hook (void)
 444 {
 445   jit_inferior_init (target_gdbarch);
 446 }
 447
 448 /* Exported routine to call to re-set the jit breakpoints,
 449    e.g. when a program is rerun.  */
 450
 451 void
 452 jit_breakpoint_re_set (void)
 453 {
 454   jit_breakpoint_re_set_internal (target_gdbarch,
 455                                   get_jit_inferior_data ());
 456 }
 457
 458 /* Reset inferior_data, so sybols will be looked up again, and jit_breakpoint
 459    will be reset.  */
 460
 461 static void
 462 jit_reset_inferior_data_and_breakpoints (void)
 463 {
 464   struct jit_inferior_data *inf_data;
 465
 466   /* Force jit_inferior_init to re-lookup of jit symbol addresses.  */
 467   inf_data = get_jit_inferior_data ();
 468   inf_data->breakpoint_addr = 0;
 469   inf_data->descriptor_addr = 0;
 470
 471   /* Remove any existing JIT breakpoint(s).  */
 472   remove_jit_event_breakpoints ();
 473
 474   jit_inferior_init (target_gdbarch);
 475 }
 476
 477 /* Wrapper to match the observer function pointer prototype.  */
 478
 479 static void
 480 jit_inferior_created_observer (struct target_ops *objfile, int from_tty)
 481 {
 482   jit_reset_inferior_data_and_breakpoints ();
 483 }
 484
 485 /* This function cleans up any code entries left over when the
 486    inferior exits.  We get left over code when the inferior exits
 487    without unregistering its code, for example when it crashes.  */
 488
 489 static void
 490 jit_inferior_exit_hook (struct inferior *inf)
 491 {
 492   struct objfile *objf;
 493   struct objfile *temp;
 494
 495   ALL_OBJFILES_SAFE (objf, temp)
 496     if (objfile_data (objf, jit_objfile_data) != NULL)
 497       jit_unregister_code (objf);
 498 }
 499
 500 static void
 501 jit_executable_changed_observer (void)
 502 {
 503   jit_reset_inferior_data_and_breakpoints ();
 504 }
 505
 506 void
 507 jit_event_handler (struct gdbarch *gdbarch)
 508 {
 509   struct jit_descriptor descriptor;
 510   struct jit_code_entry code_entry;
 511   CORE_ADDR entry_addr;
 512   struct objfile *objf;
 513
 514   /* Read the descriptor from remote memory.  */
 515   jit_read_descriptor (gdbarch, &descriptor,
 516                        get_jit_inferior_data ()->descriptor_addr);
 517   entry_addr = descriptor.relevant_entry;
 518
 519   /* Do the corresponding action.  */
 520   switch (descriptor.action_flag)
 521     {
 522     case JIT_NOACTION:
 523       break;
 524     case JIT_REGISTER:
 525       jit_read_code_entry (gdbarch, entry_addr, &code_entry);
 526       jit_register_code (gdbarch, entry_addr, &code_entry);
 527       break;
 528     case JIT_UNREGISTER:
 529       objf = jit_find_objf_with_entry_addr (entry_addr);
 530       if (objf == NULL)
 531         printf_unfiltered (_("Unable to find JITed code "
 532                              "entry at address: %s\n"),
 533                            paddress (gdbarch, entry_addr));
 534       else
 535         jit_unregister_code (objf);
 536
 537       break;
 538     default:
 539       error (_("Unknown action_flag value in JIT descriptor!"));
 540       break;
 541     }
 542 }
 543
 544 /* Provide a prototype to silence -Wmissing-prototypes.  */
 545
 546 extern void _initialize_jit (void);
 547
 548 void
 549 _initialize_jit (void)
 550 {
 551   add_setshow_zinteger_cmd ("jit", class_maintenance, &jit_debug,
 552                             _("Set JIT debugging."),
 553                             _("Show JIT debugging."),
 554                             _("When non-zero, JIT debugging is enabled."),
 555                             NULL,
 556                             show_jit_debug,
 557                             &setdebuglist, &showdebuglist);
 558
 559   observer_attach_inferior_created (jit_inferior_created_observer);
 560   observer_attach_inferior_exit (jit_inferior_exit_hook);
 561   observer_attach_executable_changed (jit_executable_changed_observer);
 562   jit_objfile_data = register_objfile_data ();
 563   jit_inferior_data =
 564     register_inferior_data_with_cleanup (jit_inferior_data_cleanup);
 565 }