gdb/auxv.c

   1 /* Auxiliary vector support for GDB, the GNU debugger.
   2
   3    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include "defs.h"
  22 #include "target.h"
  23 #include "gdbtypes.h"
  24 #include "command.h"
  25 #include "inferior.h"
  26 #include "valprint.h"
  27 #include "gdb_assert.h"
  28 #include "gdbcore.h"
  29
  30 #include "auxv.h"
  31 #include "elf/common.h"
  32
  33 #include <unistd.h>
  34 #include <fcntl.h>
  35
  36
  37 /* This function handles access via /proc/PID/auxv, which is a common method
  38    for native targets.  */
  39
  40 static LONGEST
  41 procfs_xfer_auxv (gdb_byte *readbuf,
  42                   const gdb_byte *writebuf,
  43                   ULONGEST offset,
  44                   LONGEST len)
  45 {
  46   char *pathname;
  47   int fd;
  48   LONGEST n;
  49
  50   pathname = xstrprintf ("/proc/%d/auxv", PIDGET (inferior_ptid));
  51   fd = open (pathname, writebuf != NULL ? O_WRONLY : O_RDONLY);
  52   xfree (pathname);
  53   if (fd < 0)
  54     return -1;
  55
  56   if (offset != (ULONGEST) 0
  57       && lseek (fd, (off_t) offset, SEEK_SET) != (off_t) offset)
  58     n = -1;
  59   else if (readbuf != NULL)
  60     n = read (fd, readbuf, len);
  61   else
  62     n = write (fd, writebuf, len);
  63
  64   (void) close (fd);
  65
  66   return n;
  67 }
  68
  69 /* This function handles access via ld.so's symbol `_dl_auxv'.  */
  70
  71 static LONGEST
  72 ld_so_xfer_auxv (gdb_byte *readbuf,
  73                  const gdb_byte *writebuf,
  74                  ULONGEST offset,
  75                  LONGEST len)
  76 {
  77   struct minimal_symbol *msym;
  78   CORE_ADDR data_address, pointer_address;
  79   struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
  80   size_t ptr_size = TYPE_LENGTH (ptr_type);
  81   size_t auxv_pair_size = 2 * ptr_size;
  82   gdb_byte *ptr_buf = alloca (ptr_size);
  83   LONGEST retval;
  84   size_t block;
  85
  86   msym = lookup_minimal_symbol ("_dl_auxv", NULL, NULL);
  87   if (msym == NULL)
  88     return -1;
  89
  90   if (MSYMBOL_SIZE (msym) != ptr_size)
  91     return -1;
  92
  93   /* POINTER_ADDRESS is a location where the `_dl_auxv' variable resides.
  94      DATA_ADDRESS is the inferior value present in `_dl_auxv', therefore the
  95      real inferior AUXV address.  */
  96
  97   pointer_address = SYMBOL_VALUE_ADDRESS (msym);
  98
  99   data_address = read_memory_typed_address (pointer_address, ptr_type);
 100
 101   /* Possibly still not initialized such as during an inferior startup.  */
 102   if (data_address == 0)
 103     return -1;
 104
 105   data_address += offset;
 106
 107   if (writebuf != NULL)
 108     {
 109       if (target_write_memory (data_address, writebuf, len) == 0)
 110         return len;
 111       else
 112         return -1;
 113     }
 114
 115   /* Stop if trying to read past the existing AUXV block.  The final AT_NULL
 116      was already returned before.  */
 117
 118   if (offset >= auxv_pair_size)
 119     {
 120       if (target_read_memory (data_address - auxv_pair_size, ptr_buf,
 121                               ptr_size) != 0)
 122         return -1;
 123
 124       if (extract_typed_address (ptr_buf, ptr_type) == AT_NULL)
 125         return 0;
 126     }
 127
 128   retval = 0;
 129   block = 0x400;
 130   gdb_assert (block % auxv_pair_size == 0);
 131
 132   while (len > 0)
 133     {
 134       if (block > len)
 135         block = len;
 136
 137       /* Reading sizes smaller than AUXV_PAIR_SIZE is not supported.  Tails
 138          unaligned to AUXV_PAIR_SIZE will not be read during a call (they
 139          should be completed during next read with new/extended buffer).  */
 140
 141       block &= -auxv_pair_size;
 142       if (block == 0)
 143         return retval;
 144
 145       if (target_read_memory (data_address, readbuf, block) != 0)
 146         {
 147           if (block <= auxv_pair_size)
 148             return retval;
 149
 150           block = auxv_pair_size;
 151           continue;
 152         }
 153
 154       data_address += block;
 155       len -= block;
 156
 157       /* Check terminal AT_NULL.  This function is being called indefinitely
 158          being extended its READBUF until it returns EOF (0).  */
 159
 160       while (block >= auxv_pair_size)
 161         {
 162           retval += auxv_pair_size;
 163
 164           if (extract_typed_address (readbuf, ptr_type) == AT_NULL)
 165             return retval;
 166
 167           readbuf += auxv_pair_size;
 168           block -= auxv_pair_size;
 169         }
 170     }
 171
 172   return retval;
 173 }
 174
 175 /* This function is called like a to_xfer_partial hook, but must be
 176    called with TARGET_OBJECT_AUXV.  It handles access to AUXV.  */
 177
 178 LONGEST
 179 memory_xfer_auxv (struct target_ops *ops,
 180                   enum target_object object,
 181                   const char *annex,
 182                   gdb_byte *readbuf,
 183                   const gdb_byte *writebuf,
 184                   ULONGEST offset,
 185                   LONGEST len)
 186 {
 187   gdb_assert (object == TARGET_OBJECT_AUXV);
 188   gdb_assert (readbuf || writebuf);
 189
 190    /* ld_so_xfer_auxv is the only function safe for virtual executables being
 191       executed by valgrind's memcheck.  As using ld_so_xfer_auxv is problematic
 192       during inferior startup GDB does call it only for attached processes.  */
 193
 194   if (current_inferior ()->attach_flag != 0)
 195     {
 196       LONGEST retval;
 197
 198       retval = ld_so_xfer_auxv (readbuf, writebuf, offset, len);
 199       if (retval != -1)
 200         return retval;
 201     }
 202
 203   return procfs_xfer_auxv (readbuf, writebuf, offset, len);
 204 }
 205
 206 /* Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
 207    Return 0 if *READPTR is already at the end of the buffer.
 208    Return -1 if there is insufficient buffer for a whole entry.
 209    Return 1 if an entry was read into *TYPEP and *VALP.  */
 210 static int
 211 default_auxv_parse (struct target_ops *ops, gdb_byte **readptr,
 212                    gdb_byte *endptr, CORE_ADDR *typep, CORE_ADDR *valp)
 213 {
 214   const int sizeof_auxv_field = gdbarch_ptr_bit (target_gdbarch)
 215                                 / TARGET_CHAR_BIT;
 216   const enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
 217   gdb_byte *ptr = *readptr;
 218
 219   if (endptr == ptr)
 220     return 0;
 221
 222   if (endptr - ptr < sizeof_auxv_field * 2)
 223     return -1;
 224
 225   *typep = extract_unsigned_integer (ptr, sizeof_auxv_field, byte_order);
 226   ptr += sizeof_auxv_field;
 227   *valp = extract_unsigned_integer (ptr, sizeof_auxv_field, byte_order);
 228   ptr += sizeof_auxv_field;
 229
 230   *readptr = ptr;
 231   return 1;
 232 }
 233
 234 /* Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
 235    Return 0 if *READPTR is already at the end of the buffer.
 236    Return -1 if there is insufficient buffer for a whole entry.
 237    Return 1 if an entry was read into *TYPEP and *VALP.  */
 238 int
 239 target_auxv_parse (struct target_ops *ops, gdb_byte **readptr,
 240                   gdb_byte *endptr, CORE_ADDR *typep, CORE_ADDR *valp)
 241 {
 242   struct target_ops *t;
 243   for (t = ops; t != NULL; t = t->beneath)
 244     if (t->to_auxv_parse != NULL)
 245       return t->to_auxv_parse (t, readptr, endptr, typep, valp);
 246
 247   return default_auxv_parse (ops, readptr, endptr, typep, valp);
 248 }
 249
 250 /* Extract the auxiliary vector entry with a_type matching MATCH.
 251    Return zero if no such entry was found, or -1 if there was
 252    an error getting the information.  On success, return 1 after
 253    storing the entry's value field in *VALP.  */
 254 int
 255 target_auxv_search (struct target_ops *ops, CORE_ADDR match, CORE_ADDR *valp)
 256 {
 257   CORE_ADDR type, val;
 258   gdb_byte *data;
 259   LONGEST n = target_read_alloc (ops, TARGET_OBJECT_AUXV, NULL, &data);
 260   gdb_byte *ptr = data;
 261   int ents = 0;
 262
 263   if (n <= 0)
 264     return n;
 265
 266   while (1)
 267     switch (target_auxv_parse (ops, &ptr, data + n, &type, &val))
 268       {
 269       case 1:                   /* Here's an entry, check it.  */
 270         if (type == match)
 271           {
 272             xfree (data);
 273             *valp = val;
 274             return 1;
 275           }
 276         break;
 277       case 0:                   /* End of the vector.  */
 278         xfree (data);
 279         return 0;
 280       default:                  /* Bogosity.  */
 281         xfree (data);
 282         return -1;
 283       }
 284
 285   /*NOTREACHED*/
 286 }
 287
 288
 289 /* Print the contents of the target's AUXV on the specified file. */
 290 int
 291 fprint_target_auxv (struct ui_file *file, struct target_ops *ops)
 292 {
 293   CORE_ADDR type, val;
 294   gdb_byte *data;
 295   LONGEST len = target_read_alloc (ops, TARGET_OBJECT_AUXV, NULL,
 296                                    &data);
 297   gdb_byte *ptr = data;
 298   int ents = 0;
 299
 300   if (len <= 0)
 301     return len;
 302
 303   while (target_auxv_parse (ops, &ptr, data + len, &type, &val) > 0)
 304     {
 305       const char *name = "???";
 306       const char *description = "";
 307       enum { dec, hex, str } flavor = hex;
 308
 309       switch (type)
 310         {
 311 #define TAG(tag, text, kind) \
 312         case tag: name = #tag; description = text; flavor = kind; break
 313           TAG (AT_NULL, _("End of vector"), hex);
 314           TAG (AT_IGNORE, _("Entry should be ignored"), hex);
 315           TAG (AT_EXECFD, _("File descriptor of program"), dec);
 316           TAG (AT_PHDR, _("Program headers for program"), hex);
 317           TAG (AT_PHENT, _("Size of program header entry"), dec);
 318           TAG (AT_PHNUM, _("Number of program headers"), dec);
 319           TAG (AT_PAGESZ, _("System page size"), dec);
 320           TAG (AT_BASE, _("Base address of interpreter"), hex);
 321           TAG (AT_FLAGS, _("Flags"), hex);
 322           TAG (AT_ENTRY, _("Entry point of program"), hex);
 323           TAG (AT_NOTELF, _("Program is not ELF"), dec);
 324           TAG (AT_UID, _("Real user ID"), dec);
 325           TAG (AT_EUID, _("Effective user ID"), dec);
 326           TAG (AT_GID, _("Real group ID"), dec);
 327           TAG (AT_EGID, _("Effective group ID"), dec);
 328           TAG (AT_CLKTCK, _("Frequency of times()"), dec);
 329           TAG (AT_PLATFORM, _("String identifying platform"), str);
 330           TAG (AT_HWCAP, _("Machine-dependent CPU capability hints"), hex);
 331           TAG (AT_FPUCW, _("Used FPU control word"), dec);
 332           TAG (AT_DCACHEBSIZE, _("Data cache block size"), dec);
 333           TAG (AT_ICACHEBSIZE, _("Instruction cache block size"), dec);
 334           TAG (AT_UCACHEBSIZE, _("Unified cache block size"), dec);
 335           TAG (AT_IGNOREPPC, _("Entry should be ignored"), dec);
 336           TAG (AT_BASE_PLATFORM, _("String identifying base platform"), str);
 337           TAG (AT_RANDOM, _("Address of 16 random bytes"), hex);
 338           TAG (AT_EXECFN, _("File name of executable"), str);
 339           TAG (AT_SECURE, _("Boolean, was exec setuid-like?"), dec);
 340           TAG (AT_SYSINFO, _("Special system info/entry points"), hex);
 341           TAG (AT_SYSINFO_EHDR, _("System-supplied DSO's ELF header"), hex);
 342           TAG (AT_SUN_UID, _("Effective user ID"), dec);
 343           TAG (AT_SUN_RUID, _("Real user ID"), dec);
 344           TAG (AT_SUN_GID, _("Effective group ID"), dec);
 345           TAG (AT_SUN_RGID, _("Real group ID"), dec);
 346           TAG (AT_SUN_LDELF, _("Dynamic linker's ELF header"), hex);
 347           TAG (AT_SUN_LDSHDR, _("Dynamic linker's section headers"), hex);
 348           TAG (AT_SUN_LDNAME, _("String giving name of dynamic linker"), str);
 349           TAG (AT_SUN_LPAGESZ, _("Large pagesize"), dec);
 350           TAG (AT_SUN_PLATFORM, _("Platform name string"), str);
 351           TAG (AT_SUN_HWCAP, _("Machine-dependent CPU capability hints"), hex);
 352           TAG (AT_SUN_IFLUSH, _("Should flush icache?"), dec);
 353           TAG (AT_SUN_CPU, _("CPU name string"), str);
 354           TAG (AT_SUN_EMUL_ENTRY, _("COFF entry point address"), hex);
 355           TAG (AT_SUN_EMUL_EXECFD, _("COFF executable file descriptor"), dec);
 356           TAG (AT_SUN_EXECNAME,
 357                _("Canonicalized file name given to execve"), str);
 358           TAG (AT_SUN_MMU, _("String for name of MMU module"), str);
 359           TAG (AT_SUN_LDDATA, _("Dynamic linker's data segment address"), hex);
 360           TAG (AT_SUN_AUXFLAGS,
 361                _("AF_SUN_ flags passed from the kernel"), hex);
 362         }
 363
 364       fprintf_filtered (file, "%-4s %-20s %-30s ",
 365                         plongest (type), name, description);
 366       switch (flavor)
 367         {
 368         case dec:
 369           fprintf_filtered (file, "%s\n", plongest (val));
 370           break;
 371         case hex:
 372           fprintf_filtered (file, "%s\n", paddress (target_gdbarch, val));
 373           break;
 374         case str:
 375           {
 376             struct value_print_options opts;
 377             get_user_print_options (&opts);
 378             if (opts.addressprint)
 379               fprintf_filtered (file, "%s", paddress (target_gdbarch, val));
 380             val_print_string (builtin_type (target_gdbarch)->builtin_char,
 381                               val, -1, file, &opts);
 382             fprintf_filtered (file, "\n");
 383           }
 384           break;
 385         }
 386       ++ents;
 387       if (type == AT_NULL)
 388         break;
 389     }
 390
 391   xfree (data);
 392
 393   return ents;
 394 }
 395
 396 static void
 397 info_auxv_command (char *cmd, int from_tty)
 398 {
 399   if (! target_has_stack)
 400     error (_("The program has no auxiliary information now."));
 401   else
 402     {
 403       int ents = fprint_target_auxv (gdb_stdout, &current_target);
 404       if (ents < 0)
 405         error (_("No auxiliary vector found, or failed reading it."));
 406       else if (ents == 0)
 407         error (_("Auxiliary vector is empty."));
 408     }
 409 }
 410
 411
 412 extern initialize_file_ftype _initialize_auxv; /* -Wmissing-prototypes; */
 413
 414 void
 415 _initialize_auxv (void)
 416 {
 417   add_info ("auxv", info_auxv_command,
 418             _("Display the inferior's auxiliary vector.\n\
 419 This is information provided by the operating system at program startup."));
 420 }