gdb/fbsd-nat.c

   1 /* Native-dependent code for FreeBSD.
   2
   3    Copyright (C) 2002-2015 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 #include "gdbcore.h"
  22 #include "inferior.h"
  23 #include "regcache.h"
  24 #include "regset.h"
  25 #include "gdbthread.h"
  26 #include "gdb_wait.h"
  27 #include <sys/types.h>
  28 #include <sys/procfs.h>
  29 #include <sys/ptrace.h>
  30 #include <sys/sysctl.h>
  31 #ifdef HAVE_KINFO_GETVMMAP
  32 #include <sys/user.h>
  33 #include <libutil.h>
  34 #endif
  35
  36 #include "elf-bfd.h"
  37 #include "fbsd-nat.h"
  38
  39 /* Return the name of a file that can be opened to get the symbols for
  40    the child process identified by PID.  */
  41
  42 static char *
  43 fbsd_pid_to_exec_file (struct target_ops *self, int pid)
  44 {
  45   ssize_t len = PATH_MAX;
  46   static char buf[PATH_MAX];
  47   char name[PATH_MAX];
  48
  49 #ifdef KERN_PROC_PATHNAME
  50   int mib[4];
  51
  52   mib[0] = CTL_KERN;
  53   mib[1] = KERN_PROC;
  54   mib[2] = KERN_PROC_PATHNAME;
  55   mib[3] = pid;
  56   if (sysctl (mib, 4, buf, &len, NULL, 0) == 0)
  57     return buf;
  58 #endif
  59
  60   xsnprintf (name, PATH_MAX, "/proc/%d/exe", pid);
  61   len = readlink (name, buf, PATH_MAX - 1);
  62   if (len != -1)
  63     {
  64       buf[len] = '\0';
  65       return buf;
  66     }
  67
  68   return NULL;
  69 }
  70
  71 #ifdef HAVE_KINFO_GETVMMAP
  72 /* Iterate over all the memory regions in the current inferior,
  73    calling FUNC for each memory region.  OBFD is passed as the last
  74    argument to FUNC.  */
  75
  76 static int
  77 fbsd_find_memory_regions (struct target_ops *self,
  78                           find_memory_region_ftype func, void *obfd)
  79 {
  80   pid_t pid = ptid_get_pid (inferior_ptid);
  81   struct kinfo_vmentry *vmentl, *kve;
  82   uint64_t size;
  83   struct cleanup *cleanup;
  84   int i, nitems;
  85
  86   vmentl = kinfo_getvmmap (pid, &nitems);
  87   if (vmentl == NULL)
  88     perror_with_name (_("Couldn't fetch VM map entries."));
  89   cleanup = make_cleanup (free, vmentl);
  90
  91   for (i = 0; i < nitems; i++)
  92     {
  93       kve = &vmentl[i];
  94
  95       /* Skip unreadable segments and those where MAP_NOCORE has been set.  */
  96       if (!(kve->kve_protection & KVME_PROT_READ)
  97           || kve->kve_flags & KVME_FLAG_NOCOREDUMP)
  98         continue;
  99
 100       /* Skip segments with an invalid type.  */
 101       if (kve->kve_type != KVME_TYPE_DEFAULT
 102           && kve->kve_type != KVME_TYPE_VNODE
 103           && kve->kve_type != KVME_TYPE_SWAP
 104           && kve->kve_type != KVME_TYPE_PHYS)
 105         continue;
 106
 107       size = kve->kve_end - kve->kve_start;
 108       if (info_verbose)
 109         {
 110           fprintf_filtered (gdb_stdout,
 111                             "Save segment, %ld bytes at %s (%c%c%c)\n",
 112                             (long) size,
 113                             paddress (target_gdbarch (), kve->kve_start),
 114                             kve->kve_protection & KVME_PROT_READ ? 'r' : '-',
 115                             kve->kve_protection & KVME_PROT_WRITE ? 'w' : '-',
 116                             kve->kve_protection & KVME_PROT_EXEC ? 'x' : '-');
 117         }
 118
 119       /* Invoke the callback function to create the corefile segment.
 120          Pass MODIFIED as true, we do not know the real modification state.  */
 121       func (kve->kve_start, size, kve->kve_protection & KVME_PROT_READ,
 122             kve->kve_protection & KVME_PROT_WRITE,
 123             kve->kve_protection & KVME_PROT_EXEC, 1, obfd);
 124     }
 125   do_cleanups (cleanup);
 126   return 0;
 127 }
 128 #else
 129 static int
 130 fbsd_read_mapping (FILE *mapfile, unsigned long *start, unsigned long *end,
 131                    char *protection)
 132 {
 133   /* FreeBSD 5.1-RELEASE uses a 256-byte buffer.  */
 134   char buf[256];
 135   int resident, privateresident;
 136   unsigned long obj;
 137   int ret = EOF;
 138
 139   /* As of FreeBSD 5.0-RELEASE, the layout is described in
 140      /usr/src/sys/fs/procfs/procfs_map.c.  Somewhere in 5.1-CURRENT a
 141      new column was added to the procfs map.  Therefore we can't use
 142      fscanf since we need to support older releases too.  */
 143   if (fgets (buf, sizeof buf, mapfile) != NULL)
 144     ret = sscanf (buf, "%lx %lx %d %d %lx %s", start, end,
 145                   &resident, &privateresident, &obj, protection);
 146
 147   return (ret != 0 && ret != EOF);
 148 }
 149
 150 /* Iterate over all the memory regions in the current inferior,
 151    calling FUNC for each memory region.  OBFD is passed as the last
 152    argument to FUNC.  */
 153
 154 static int
 155 fbsd_find_memory_regions (struct target_ops *self,
 156                           find_memory_region_ftype func, void *obfd)
 157 {
 158   pid_t pid = ptid_get_pid (inferior_ptid);
 159   char *mapfilename;
 160   FILE *mapfile;
 161   unsigned long start, end, size;
 162   char protection[4];
 163   int read, write, exec;
 164   struct cleanup *cleanup;
 165
 166   mapfilename = xstrprintf ("/proc/%ld/map", (long) pid);
 167   cleanup = make_cleanup (xfree, mapfilename);
 168   mapfile = fopen (mapfilename, "r");
 169   if (mapfile == NULL)
 170     error (_("Couldn't open %s."), mapfilename);
 171   make_cleanup_fclose (mapfile);
 172
 173   if (info_verbose)
 174     fprintf_filtered (gdb_stdout,
 175                       "Reading memory regions from %s\n", mapfilename);
 176
 177   /* Now iterate until end-of-file.  */
 178   while (fbsd_read_mapping (mapfile, &start, &end, &protection[0]))
 179     {
 180       size = end - start;
 181
 182       read = (strchr (protection, 'r') != 0);
 183       write = (strchr (protection, 'w') != 0);
 184       exec = (strchr (protection, 'x') != 0);
 185
 186       if (info_verbose)
 187         {
 188           fprintf_filtered (gdb_stdout,
 189                             "Save segment, %ld bytes at %s (%c%c%c)\n",
 190                             size, paddress (target_gdbarch (), start),
 191                             read ? 'r' : '-',
 192                             write ? 'w' : '-',
 193                             exec ? 'x' : '-');
 194         }
 195
 196       /* Invoke the callback function to create the corefile segment.
 197          Pass MODIFIED as true, we do not know the real modification state.  */
 198       func (start, size, read, write, exec, 1, obfd);
 199     }
 200
 201   do_cleanups (cleanup);
 202   return 0;
 203 }
 204 #endif
 205
 206 #ifdef PT_LWPINFO
 207 static ptid_t (*super_wait) (struct target_ops *,
 208                              ptid_t,
 209                              struct target_waitstatus *,
 210                              int);
 211
 212 #ifdef TDP_RFPPWAIT
 213 /*
 214   To catch fork events, PT_FOLLOW_FORK is set on every traced process
 215   to enable stops on returns from fork or vfork.  Note that both the
 216   parent and child will always stop, even if system call stops are not
 217   enabled.
 218
 219   After a fork, both the child and parent process will stop and report
 220   an event.  However, there is no guarantee of order.  If the parent
 221   reports its stop first, then fbsd_wait explicitly waits for the new
 222   child before returning.  If the child reports its stop first, then
 223   the event is saved on a list and ignored until the parent's stop is
 224   reported.  fbsd_wait could have been changed to fetch the parent PID
 225   of the new child and used that to wait for the parent explicitly.
 226   However, if two threads in the parent fork at the same time, then
 227   the wait on the parent might return the "wrong" fork event.
 228
 229   The initial version of PT_FOLLOW_FORK did not set PL_FLAG_CHILD for
 230   the new child process.  This flag could be inferred by treating any
 231   events for an unknown pid as a new child.
 232
 233   In addition, the initial version of PT_FOLLOW_FORK did not report a
 234   stop event for the parent process of a vfork until after the child
 235   process executed a new program or exited.  The kernel was changed to
 236   defer the wait for exit or exec of the child until after posting the
 237   stop event shortly after the change to introduce PL_FLAG_CHILD.
 238   This could be worked around by reporting a vfork event when the
 239   child event posted and ignoring the subsequent event from the
 240   parent.
 241
 242   This implementation requires both of these fixes for simplicity's
 243   sake.  FreeBSD versions newer than 9.1 contain both fixes.
 244 */
 245
 246 struct fbsd_fork_child_info
 247 {
 248   struct fbsd_fork_child_info *next;
 249   pid_t child;                  /* Pid of new child.  */
 250 };
 251
 252 static struct fbsd_fork_child_info *fbsd_pending_children;
 253
 254 /* Record a new child process event that is reported before the
 255    corresponding fork event in the parent.  */
 256
 257 static void
 258 fbsd_remember_child (pid_t pid)
 259 {
 260   struct fbsd_fork_child_info *info;
 261
 262   info = xcalloc (1, sizeof *info);
 263
 264   info->child = pid;
 265   info->next = fbsd_pending_children;
 266   fbsd_pending_children = info;
 267 }
 268
 269 /* Check for a previously-recorded new child process event for PID.
 270    If one is found, remove it from the list.  */
 271
 272 static int
 273 fbsd_is_child_pending (pid_t pid)
 274 {
 275   struct fbsd_fork_child_info *info, *prev;
 276
 277   prev = NULL;
 278   for (info = fbsd_pending_children; info; prev = info, info = info->next)
 279     {
 280       if (info->child == pid)
 281         {
 282           if (prev == NULL)
 283             fbsd_pending_children = info->next;
 284           else
 285             prev->next = info->next;
 286           xfree (info);
 287           return 1;
 288         }
 289     }
 290   return 0;
 291 }
 292
 293 /* Fetch the external variant of the kernel's internal process
 294    structure for the process PID into KP.  */
 295
 296 static void
 297 fbsd_fetch_kinfo_proc (pid_t pid, struct kinfo_proc *kp)
 298 {
 299   size_t len;
 300   int mib[4];
 301
 302   len = sizeof *kp;
 303   mib[0] = CTL_KERN;
 304   mib[1] = KERN_PROC;
 305   mib[2] = KERN_PROC_PID;
 306   mib[3] = pid;
 307   if (sysctl (mib, 4, kp, &len, NULL, 0) == -1)
 308     perror_with_name (("sysctl"));
 309 }
 310 #endif
 311
 312 /* Wait for the child specified by PTID to do something.  Return the
 313    process ID of the child, or MINUS_ONE_PTID in case of error; store
 314    the status in *OURSTATUS.  */
 315
 316 static ptid_t
 317 fbsd_wait (struct target_ops *ops,
 318            ptid_t ptid, struct target_waitstatus *ourstatus,
 319            int target_options)
 320 {
 321   ptid_t wptid;
 322
 323   while (1)
 324     {
 325       wptid = super_wait (ops, ptid, ourstatus, target_options);
 326       if (ourstatus->kind == TARGET_WAITKIND_STOPPED)
 327         {
 328           struct ptrace_lwpinfo pl;
 329           pid_t pid;
 330           int status;
 331
 332           pid = ptid_get_pid (wptid);
 333           if (ptrace (PT_LWPINFO, pid, (caddr_t)&pl, sizeof pl) == -1)
 334             perror_with_name (("ptrace"));
 335
 336 #ifdef TDP_RFPPWAIT
 337           if (pl.pl_flags & PL_FLAG_FORKED)
 338             {
 339               struct kinfo_proc kp;
 340               pid_t child;
 341
 342               child = pl.pl_child_pid;
 343               ourstatus->kind = TARGET_WAITKIND_FORKED;
 344               ourstatus->value.related_pid = pid_to_ptid (child);
 345
 346               /* Make sure the other end of the fork is stopped too.  */
 347               if (!fbsd_is_child_pending (child))
 348                 {
 349                   pid = waitpid (child, &status, 0);
 350                   if (pid == -1)
 351                     perror_with_name (("waitpid"));
 352
 353                   gdb_assert (pid == child);
 354
 355                   if (ptrace (PT_LWPINFO, child, (caddr_t)&pl, sizeof pl) == -1)
 356                     perror_with_name (("ptrace"));
 357
 358                   gdb_assert (pl.pl_flags & PL_FLAG_CHILD);
 359                 }
 360
 361               /* For vfork, the child process will have the P_PPWAIT
 362                  flag set.  */
 363               fbsd_fetch_kinfo_proc (child, &kp);
 364               if (kp.ki_flag & P_PPWAIT)
 365                 ourstatus->kind = TARGET_WAITKIND_VFORKED;
 366
 367               return wptid;
 368             }
 369
 370           if (pl.pl_flags & PL_FLAG_CHILD)
 371             {
 372               /* Remember that this child forked, but do not report it
 373                  until the parent reports its corresponding fork
 374                  event.  */
 375               fbsd_remember_child (ptid_get_pid (wptid));
 376               continue;
 377             }
 378 #endif
 379
 380 #ifdef PL_FLAG_EXEC
 381           if (pl.pl_flags & PL_FLAG_EXEC)
 382             {
 383               ourstatus->kind = TARGET_WAITKIND_EXECD;
 384               ourstatus->value.execd_pathname
 385                 = xstrdup (fbsd_pid_to_exec_file (NULL, pid));
 386               return wptid;
 387             }
 388 #endif
 389         }
 390       return wptid;
 391     }
 392 }
 393
 394 #ifdef TDP_RFPPWAIT
 395 /* Target hook for follow_fork.  On entry and at return inferior_ptid is
 396    the ptid of the followed inferior.  */
 397
 398 static int
 399 fbsd_follow_fork (struct target_ops *ops, int follow_child,
 400                         int detach_fork)
 401 {
 402   if (!follow_child)
 403     {
 404       struct thread_info *tp = inferior_thread ();
 405       pid_t child_pid = ptid_get_pid (tp->pending_follow.value.related_pid);
 406
 407       /* Breakpoints have already been detached from the child by
 408          infrun.c.  */
 409
 410       if (ptrace (PT_DETACH, child_pid, (PTRACE_TYPE_ARG3)1, 0) == -1)
 411         perror_with_name (("ptrace"));
 412     }
 413
 414   return 0;
 415 }
 416
 417 static int
 418 fbsd_insert_fork_catchpoint (struct target_ops *self, int pid)
 419 {
 420   return 0;
 421 }
 422
 423 static int
 424 fbsd_remove_fork_catchpoint (struct target_ops *self, int pid)
 425 {
 426   return 0;
 427 }
 428
 429 static int
 430 fbsd_insert_vfork_catchpoint (struct target_ops *self, int pid)
 431 {
 432   return 0;
 433 }
 434
 435 static int
 436 fbsd_remove_vfork_catchpoint (struct target_ops *self, int pid)
 437 {
 438   return 0;
 439 }
 440
 441 /* Enable fork tracing for a specific process.
 442
 443    To catch fork events, PT_FOLLOW_FORK is set on every traced process
 444    to enable stops on returns from fork or vfork.  Note that both the
 445    parent and child will always stop, even if system call stops are
 446    not enabled.  */
 447
 448 static void
 449 fbsd_enable_follow_fork (pid_t pid)
 450 {
 451   if (ptrace (PT_FOLLOW_FORK, pid, (PTRACE_TYPE_ARG3)0, 1) == -1)
 452     perror_with_name (("ptrace"));
 453 }
 454
 455 /* Implement the "to_post_startup_inferior" target_ops method.  */
 456
 457 static void
 458 fbsd_post_startup_inferior (struct target_ops *self, ptid_t pid)
 459 {
 460   fbsd_enable_follow_fork (ptid_get_pid (pid));
 461 }
 462
 463 /* Implement the "to_post_attach" target_ops method.  */
 464
 465 static void
 466 fbsd_post_attach (struct target_ops *self, int pid)
 467 {
 468   fbsd_enable_follow_fork (pid);
 469 }
 470 #endif
 471
 472 #ifdef PL_FLAG_EXEC
 473 /* If the FreeBSD kernel supports PL_FLAG_EXEC, then traced processes
 474    will always stop after exec.  */
 475
 476 static int
 477 fbsd_insert_exec_catchpoint (struct target_ops *self, int pid)
 478 {
 479   return 0;
 480 }
 481
 482 static int
 483 fbsd_remove_exec_catchpoint (struct target_ops *self, int pid)
 484 {
 485   return 0;
 486 }
 487 #endif
 488 #endif
 489
 490 void
 491 fbsd_nat_add_target (struct target_ops *t)
 492 {
 493   t->to_pid_to_exec_file = fbsd_pid_to_exec_file;
 494   t->to_find_memory_regions = fbsd_find_memory_regions;
 495 #ifdef PT_LWPINFO
 496   super_wait = t->to_wait;
 497   t->to_wait = fbsd_wait;
 498 #ifdef TDP_RFPPWAIT
 499   t->to_follow_fork = fbsd_follow_fork;
 500   t->to_insert_fork_catchpoint = fbsd_insert_fork_catchpoint;
 501   t->to_remove_fork_catchpoint = fbsd_remove_fork_catchpoint;
 502   t->to_insert_vfork_catchpoint = fbsd_insert_vfork_catchpoint;
 503   t->to_remove_vfork_catchpoint = fbsd_remove_vfork_catchpoint;
 504   t->to_post_startup_inferior = fbsd_post_startup_inferior;
 505   t->to_post_attach = fbsd_post_attach;
 506 #endif
 507 #ifdef PL_FLAG_EXEC
 508   t->to_insert_exec_catchpoint = fbsd_insert_exec_catchpoint;
 509   t->to_remove_exec_catchpoint = fbsd_remove_exec_catchpoint;
 510 #endif
 511 #endif
 512   add_target (t);
 513 }