gdb/auxv.c - gdb

Global variables defined

Data types defined

Functions defined

Macros defined

Source code

  1. /* Auxiliary vector support for GDB, the GNU debugger.

  3.    Copyright (C) 2004-2015 Free Software Foundation, Inc.

  5.    This file is part of GDB.

  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.

  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.

  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/>.  */

  20. #include "defs.h"
  21. #include "target.h"
  22. #include "gdbtypes.h"
  23. #include "command.h"
  24. #include "inferior.h"
  25. #include "valprint.h"
  26. #include "gdbcore.h"
  27. #include "observer.h"
  28. #include "filestuff.h"
  29. #include "objfiles.h"

  31. #include "auxv.h"
  32. #include "elf/common.h"

  34. #include <unistd.h>
  35. #include <fcntl.h>


  38. /* Implement the to_xfer_partial target_ops method.  This function
  39.    handles access via /proc/PID/auxv, which is a common method for
  40.    native targets.  */

  42. static enum target_xfer_status
  43. ‌procfs_xfer_auxv (gdb_byte *readbuf,
  44.                   const gdb_byte *writebuf,
  45.                   ULONGEST offset,
  46.                   ULONGEST len,
  47.                   ULONGEST *xfered_len)
  48. {
  49.   char *pathname;
  50.   int fd;
  51.   ssize_t l;

  53.   pathname = xstrprintf ("/proc/%d/auxv", ptid_get_pid (inferior_ptid));
  54.   fd = gdb_open_cloexec (pathname, writebuf != NULL ? O_WRONLY : O_RDONLY, 0);
  55.   xfree (pathname);
  56.   if (fd < 0)
  57.     return TARGET_XFER_E_IO;

  59.   if (offset != (ULONGEST) 0
  60.       && lseek (fd, (off_t) offset, SEEK_SET) != (off_t) offset)
  61.     l = -1;
  62.   else if (readbuf != NULL)
  63.     l = read (fd, readbuf, (size_t) len);
  64.   else
  65.     l = write (fd, writebuf, (size_t) len);

  67.   (void) close (fd);

  69.   if (l < 0)
  70.     return TARGET_XFER_E_IO;
  71.   else if (l == 0)
  72.     return TARGET_XFER_EOF;
  73.   else
  74.     {
  75.       *xfered_len = (ULONGEST) l;
  76.       return TARGET_XFER_OK;
  77.     }
  78. }

  80. /* This function handles access via ld.so's symbol `_dl_auxv'.  */

  82. static enum target_xfer_status
  83. ‌ld_so_xfer_auxv (gdb_byte *readbuf,
  84.                  const gdb_byte *writebuf,
  85.                  ULONGEST offset,
  86.                  ULONGEST len, ULONGEST *xfered_len)
  87. {
  88.   struct bound_minimal_symbol msym;
  89.   CORE_ADDR data_address, pointer_address;
  90.   struct type *ptr_type = builtin_type (target_gdbarch ())->builtin_data_ptr;
  91.   size_t ptr_size = TYPE_LENGTH (ptr_type);
  92.   size_t auxv_pair_size = 2 * ptr_size;
  93.   gdb_byte *ptr_buf = alloca (ptr_size);
  94.   LONGEST retval;
  95.   size_t block;

  97.   msym = lookup_minimal_symbol ("_dl_auxv", NULL, NULL);
  98.   if (msym.minsym == NULL)
  99.     return TARGET_XFER_E_IO;

  101.   if (MSYMBOL_SIZE (msym.minsym) != ptr_size)
  102.     return TARGET_XFER_E_IO;

  104.   /* POINTER_ADDRESS is a location where the `_dl_auxv' variable
  105.      resides.  DATA_ADDRESS is the inferior value present in
  106.      `_dl_auxv', therefore the real inferior AUXV address.  */

  108.   pointer_address = BMSYMBOL_VALUE_ADDRESS (msym);

  110.   /* The location of the _dl_auxv symbol may no longer be correct if
  111.      ld.so runs at a different address than the one present in the
  112.      file.  This is very common case - for unprelinked ld.so or with a
  113.      PIE executable.  PIE executable forces random address even for
  114.      libraries already being prelinked to some address.  PIE
  115.      executables themselves are never prelinked even on prelinked
  116.      systems.  Prelinking of a PIE executable would block their
  117.      purpose of randomizing load of everything including the
  118.      executable.

  120.      If the memory read fails, return -1 to fallback on another
  121.      mechanism for retrieving the AUXV.

  123.      In most cases of a PIE running under valgrind there is no way to
  124.      find out the base addresses of any of ld.so, executable or AUXV
  125.      as everything is randomized and /proc information is not relevant
  126.      for the virtual executable running under valgrind.  We think that
  127.      we might need a valgrind extension to make it work.  This is PR
  128.      11440.  */

  130.   if (target_read_memory (pointer_address, ptr_buf, ptr_size) != 0)
  131.     return TARGET_XFER_E_IO;

  133.   data_address = extract_typed_address (ptr_buf, ptr_type);

  135.   /* Possibly still not initialized such as during an inferior
  136.      startup.  */
  137.   if (data_address == 0)
  138.     return TARGET_XFER_E_IO;

  140.   data_address += offset;

  142.   if (writebuf != NULL)
  143.     {
  144.       if (target_write_memory (data_address, writebuf, len) == 0)
  145.         {
  146.           *xfered_len = (ULONGEST) len;
  147.           return TARGET_XFER_OK;
  148.         }
  149.       else
  150.         return TARGET_XFER_E_IO;
  151.     }

  153.   /* Stop if trying to read past the existing AUXV block.  The final
  154.      AT_NULL was already returned before.  */

  156.   if (offset >= auxv_pair_size)
  157.     {
  158.       if (target_read_memory (data_address - auxv_pair_size, ptr_buf,
  159.                               ptr_size) != 0)
  160.         return TARGET_XFER_E_IO;

  162.       if (extract_typed_address (ptr_buf, ptr_type) == AT_NULL)
  163.         return TARGET_XFER_EOF;
  164.     }

  166.   retval = 0;
  167.   block = 0x400;
  168.   gdb_assert (block % auxv_pair_size == 0);

  170.   while (len > 0)
  171.     {
  172.       if (block > len)
  173.         block = len;

  175.       /* Reading sizes smaller than AUXV_PAIR_SIZE is not supported.
  176.          Tails unaligned to AUXV_PAIR_SIZE will not be read during a
  177.          call (they should be completed during next read with
  178.          new/extended buffer).  */

  180.       block &= -auxv_pair_size;
  181.       if (block == 0)
  182.         break;

  184.       if (target_read_memory (data_address, readbuf, block) != 0)
  185.         {
  186.           if (block <= auxv_pair_size)
  187.             break;

  189.           block = auxv_pair_size;
  190.           continue;
  191.         }

  193.       data_address += block;
  194.       len -= block;

  196.       /* Check terminal AT_NULL.  This function is being called
  197.          indefinitely being extended its READBUF until it returns EOF
  198.          (0).  */

  200.       while (block >= auxv_pair_size)
  201.         {
  202.           retval += auxv_pair_size;

  204.           if (extract_typed_address (readbuf, ptr_type) == AT_NULL)
  205.             {
  206.               *xfered_len = (ULONGEST) retval;
  207.               return TARGET_XFER_OK;
  208.             }

  210.           readbuf += auxv_pair_size;
  211.           block -= auxv_pair_size;
  212.         }
  213.     }

  215.   *xfered_len = (ULONGEST) retval;
  216.   return TARGET_XFER_OK;
  217. }

  219. /* Implement the to_xfer_partial target_ops method for
  220.    TARGET_OBJECT_AUXV.  It handles access to AUXV.  */

  222. enum target_xfer_status
  223. ‌memory_xfer_auxv (struct target_ops *ops,
  224.                   enum target_object object,
  225.                   const char *annex,
  226.                   gdb_byte *readbuf,
  227.                   const gdb_byte *writebuf,
  228.                   ULONGEST offset,
  229.                   ULONGEST len, ULONGEST *xfered_len)
  230. {
  231.   gdb_assert (object == TARGET_OBJECT_AUXV);
  232.   gdb_assert (readbuf || writebuf);

  234.    /* ld_so_xfer_auxv is the only function safe for virtual
  235.       executables being executed by valgrind's memcheck.  Using
  236.       ld_so_xfer_auxv during inferior startup is problematic, because
  237.       ld.so symbol tables have not yet been relocated.  So GDB uses
  238.       this function only when attaching to a process.
  239.       */

  241.   if (current_inferior ()->attach_flag != 0)
  242.     {
  243.       enum target_xfer_status ret;

  245.       ret = ld_so_xfer_auxv (readbuf, writebuf, offset, len, xfered_len);
  246.       if (ret != TARGET_XFER_E_IO)
  247.         return ret;
  248.     }

  250.   return procfs_xfer_auxv (readbuf, writebuf, offset, len, xfered_len);
  251. }

  253. /* Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
  254.    Return 0 if *READPTR is already at the end of the buffer.
  255.    Return -1 if there is insufficient buffer for a whole entry.
  256.    Return 1 if an entry was read into *TYPEP and *VALP.  */
  257. int
  258. ‌default_auxv_parse (struct target_ops *ops, gdb_byte **readptr,
  259.                    gdb_byte *endptr, CORE_ADDR *typep, CORE_ADDR *valp)
  260. {
  261.   const int sizeof_auxv_field = gdbarch_ptr_bit (target_gdbarch ())
  262.                                 / TARGET_CHAR_BIT;
  263.   const enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
  264.   gdb_byte *ptr = *readptr;

  266.   if (endptr == ptr)
  267.     return 0;

  269.   if (endptr - ptr < sizeof_auxv_field * 2)
  270.     return -1;

  272.   *typep = extract_unsigned_integer (ptr, sizeof_auxv_field, byte_order);
  273.   ptr += sizeof_auxv_field;
  274.   *valp = extract_unsigned_integer (ptr, sizeof_auxv_field, byte_order);
  275.   ptr += sizeof_auxv_field;

  277.   *readptr = ptr;
  278.   return 1;
  279. }

  281. /* Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
  282.    Return 0 if *READPTR is already at the end of the buffer.
  283.    Return -1 if there is insufficient buffer for a whole entry.
  284.    Return 1 if an entry was read into *TYPEP and *VALP.  */
  285. int
  286. ‌target_auxv_parse (struct target_ops *ops, gdb_byte **readptr,
  287.                   gdb_byte *endptr, CORE_ADDR *typep, CORE_ADDR *valp)
  288. {
  289.   struct gdbarch *gdbarch = target_gdbarch();

  291.   if (gdbarch_auxv_parse_p (gdbarch))
  292.     return gdbarch_auxv_parse (gdbarch, readptr, endptr, typep, valp);

  294.   return current_target.to_auxv_parse (&current_target, readptr, endptr,
  295.                                        typep, valp);
  296. }


  299. /* Per-inferior data key for auxv.  */
  300. ‌static const struct inferior_data *auxv_inferior_data;

  302. /*  Auxiliary Vector information structure.  This is used by GDB
  303.     for caching purposes for each inferior.  This helps reduce the
  304.     overhead of transfering data from a remote target to the local host.  */
  305. ‌struct auxv_info
  306. {
  307.   LONGEST length;
  308.   gdb_byte *data;
  309. };

  311. /* Handles the cleanup of the auxv cache for inferior INF.  ARG is ignored.
  312.    Frees whatever allocated space there is to be freed and sets INF's auxv cache
  313.    data pointer to NULL.

  315.    This function is called when the following events occur: inferior_appeared,
  316.    inferior_exit and executable_changed.  */

  318. static void
  319. ‌auxv_inferior_data_cleanup (struct inferior *inf, void *arg)
  320. {
  321.   struct auxv_info *info;

  323.   info = inferior_data (inf, auxv_inferior_data);
  324.   if (info != NULL)
  325.     {
  326.       xfree (info->data);
  327.       xfree (info);
  328.       set_inferior_data (inf, auxv_inferior_data, NULL);
  329.     }
  330. }

  332. /* Invalidate INF's auxv cache.  */

  334. static void
  335. ‌invalidate_auxv_cache_inf (struct inferior *inf)
  336. {
  337.   auxv_inferior_data_cleanup (inf, NULL);
  338. }

  340. /* Invalidate current inferior's auxv cache.  */

  342. static void
  343. ‌invalidate_auxv_cache (void)
  344. {
  345.   invalidate_auxv_cache_inf (current_inferior ());
  346. }

  348. /* Fetch the auxv object from inferior INF.  If auxv is cached already,
  349.    return a pointer to the cache.  If not, fetch the auxv object from the
  350.    target and cache it.  This function always returns a valid INFO pointer.  */

  352. static struct auxv_info *
  353. ‌get_auxv_inferior_data (struct target_ops *ops)
  354. {
  355.   struct auxv_info *info;
  356.   struct inferior *inf = current_inferior ();

  358.   info = inferior_data (inf, auxv_inferior_data);
  359.   if (info == NULL)
  360.     {
  361.       info = XCNEW (struct auxv_info);
  362.       info->length = target_read_alloc (ops, TARGET_OBJECT_AUXV,
  363.                                         NULL, &info->data);
  364.       set_inferior_data (inf, auxv_inferior_data, info);
  365.     }

  367.   return info;
  368. }

  370. /* Extract the auxiliary vector entry with a_type matching MATCH.
  371.    Return zero if no such entry was found, or -1 if there was
  372.    an error getting the information.  On success, return 1 after
  373.    storing the entry's value field in *VALP.  */
  374. int
  375. ‌target_auxv_search (struct target_ops *ops, CORE_ADDR match, CORE_ADDR *valp)
  376. {
  377.   CORE_ADDR type, val;
  378.   gdb_byte *data;
  379.   gdb_byte *ptr;
  380.   struct auxv_info *info;

  382.   info = get_auxv_inferior_data (ops);

  384.   data = info->data;
  385.   ptr = data;

  387.   if (info->length <= 0)
  388.     return info->length;

  390.   while (1)
  391.     switch (target_auxv_parse (ops, &ptr, data + info->length, &type, &val))
  392.       {
  393.       case 1:                        /* Here's an entry, check it.  */
  394.         if (type == match)
  395.           {
  396.             *valp = val;
  397.             return 1;
  398.           }
  399.         break;
  400.       case 0:                        /* End of the vector.  */
  401.         return 0;
  402.       default:                        /* Bogosity.  */
  403.         return -1;
  404.       }

  406.   /*NOTREACHED*/
  407. }


  410. /* Print the contents of the target's AUXV on the specified file.  */
  411. int
  412. ‌fprint_target_auxv (struct ui_file *file, struct target_ops *ops)
  413. {
  414.   CORE_ADDR type, val;
  415.   gdb_byte *data;
  416.   gdb_byte *ptr;
  417.   struct auxv_info *info;
  418.   int ents = 0;

  420.   info = get_auxv_inferior_data (ops);

  422.   data = info->data;
  423.   ptr = data;
  424.   if (info->length <= 0)
  425.     return info->length;

  427.   while (target_auxv_parse (ops, &ptr, data + info->length, &type, &val) > 0)
  428.     {
  429.       const char *name = "???";
  430.       const char *description = "";
  431.       enum { dec, hex, str } flavor = hex;

  433.       switch (type)
  434.         {
  435. ‌#define TAG(tag, text, kind) \
  436.         case tag: name = #tag; description = text; flavor = kind; break
  437.           TAG (AT_NULL, _("End of vector"), hex);
  438.           TAG (AT_IGNORE, _("Entry should be ignored"), hex);
  439.           TAG (AT_EXECFD, _("File descriptor of program"), dec);
  440.           TAG (AT_PHDR, _("Program headers for program"), hex);
  441.           TAG (AT_PHENT, _("Size of program header entry"), dec);
  442.           TAG (AT_PHNUM, _("Number of program headers"), dec);
  443.           TAG (AT_PAGESZ, _("System page size"), dec);
  444.           TAG (AT_BASE, _("Base address of interpreter"), hex);
  445.           TAG (AT_FLAGS, _("Flags"), hex);
  446.           TAG (AT_ENTRY, _("Entry point of program"), hex);
  447.           TAG (AT_NOTELF, _("Program is not ELF"), dec);
  448.           TAG (AT_UID, _("Real user ID"), dec);
  449.           TAG (AT_EUID, _("Effective user ID"), dec);
  450.           TAG (AT_GID, _("Real group ID"), dec);
  451.           TAG (AT_EGID, _("Effective group ID"), dec);
  452.           TAG (AT_CLKTCK, _("Frequency of times()"), dec);
  453.           TAG (AT_PLATFORM, _("String identifying platform"), str);
  454.           TAG (AT_HWCAP, _("Machine-dependent CPU capability hints"), hex);
  455.           TAG (AT_FPUCW, _("Used FPU control word"), dec);
  456.           TAG (AT_DCACHEBSIZE, _("Data cache block size"), dec);
  457.           TAG (AT_ICACHEBSIZE, _("Instruction cache block size"), dec);
  458.           TAG (AT_UCACHEBSIZE, _("Unified cache block size"), dec);
  459.           TAG (AT_IGNOREPPC, _("Entry should be ignored"), dec);
  460.           TAG (AT_BASE_PLATFORM, _("String identifying base platform"), str);
  461.           TAG (AT_RANDOM, _("Address of 16 random bytes"), hex);
  462.           TAG (AT_HWCAP2, _("Extension of AT_HWCAP"), hex);
  463.           TAG (AT_EXECFN, _("File name of executable"), str);
  464.           TAG (AT_SECURE, _("Boolean, was exec setuid-like?"), dec);
  465.           TAG (AT_SYSINFO, _("Special system info/entry points"), hex);
  466.           TAG (AT_SYSINFO_EHDR, _("System-supplied DSO's ELF header"), hex);
  467.           TAG (AT_L1I_CACHESHAPE, _("L1 Instruction cache information"), hex);
  468.           TAG (AT_L1D_CACHESHAPE, _("L1 Data cache information"), hex);
  469.           TAG (AT_L2_CACHESHAPE, _("L2 cache information"), hex);
  470.           TAG (AT_L3_CACHESHAPE, _("L3 cache information"), hex);
  471.           TAG (AT_SUN_UID, _("Effective user ID"), dec);
  472.           TAG (AT_SUN_RUID, _("Real user ID"), dec);
  473.           TAG (AT_SUN_GID, _("Effective group ID"), dec);
  474.           TAG (AT_SUN_RGID, _("Real group ID"), dec);
  475.           TAG (AT_SUN_LDELF, _("Dynamic linker's ELF header"), hex);
  476.           TAG (AT_SUN_LDSHDR, _("Dynamic linker's section headers"), hex);
  477.           TAG (AT_SUN_LDNAME, _("String giving name of dynamic linker"), str);
  478.           TAG (AT_SUN_LPAGESZ, _("Large pagesize"), dec);
  479.           TAG (AT_SUN_PLATFORM, _("Platform name string"), str);
  480.           TAG (AT_SUN_HWCAP, _("Machine-dependent CPU capability hints"), hex);
  481.           TAG (AT_SUN_IFLUSH, _("Should flush icache?"), dec);
  482.           TAG (AT_SUN_CPU, _("CPU name string"), str);
  483.           TAG (AT_SUN_EMUL_ENTRY, _("COFF entry point address"), hex);
  484.           TAG (AT_SUN_EMUL_EXECFD, _("COFF executable file descriptor"), dec);
  485.           TAG (AT_SUN_EXECNAME,
  486.                _("Canonicalized file name given to execve"), str);
  487.           TAG (AT_SUN_MMU, _("String for name of MMU module"), str);
  488.           TAG (AT_SUN_LDDATA, _("Dynamic linker's data segment address"), hex);
  489.           TAG (AT_SUN_AUXFLAGS,
  490.                _("AF_SUN_ flags passed from the kernel"), hex);
  491.         }

  493.       fprintf_filtered (file, "%-4s %-20s %-30s ",
  494.                         plongest (type), name, description);
  495.       switch (flavor)
  496.         {
  497.         case dec:
  498.           fprintf_filtered (file, "%s\n", plongest (val));
  499.           break;
  500.         case hex:
  501.           fprintf_filtered (file, "%s\n", paddress (target_gdbarch (), val));
  502.           break;
  503.         case str:
  504.           {
  505.             struct value_print_options opts;

  507.             get_user_print_options (&opts);
  508.             if (opts.addressprint)
  509.               fprintf_filtered (file, "%s ", paddress (target_gdbarch (), val));
  510.             val_print_string (builtin_type (target_gdbarch ())->builtin_char,
  511.                               NULL, val, -1, file, &opts);
  512.             fprintf_filtered (file, "\n");
  513.           }
  514.           break;
  515.         }
  516.       ++ents;
  517.       if (type == AT_NULL)
  518.         break;
  519.     }

  521.   return ents;
  522. }

  524. static void
  525. ‌info_auxv_command (char *cmd, int from_tty)
  526. {
  527.   if (! target_has_stack)
  528.     error (_("The program has no auxiliary information now."));
  529.   else
  530.     {
  531.       int ents = fprint_target_auxv (gdb_stdout, &current_target);

  533.       if (ents < 0)
  534.         error (_("No auxiliary vector found, or failed reading it."));
  535.       else if (ents == 0)
  536.         error (_("Auxiliary vector is empty."));
  537.     }
  538. }


  541. extern initialize_file_ftype _initialize_auxv; /* -Wmissing-prototypes; */

  543. void
  544. ‌_initialize_auxv (void)
  545. {
  546.   add_info ("auxv", info_auxv_command,
  547.             _("Display the inferior's auxiliary vector.\n\
  548. This is information provided by the operating system at program startup."));

  550.   /* Set an auxv cache per-inferior.  */
  551.   auxv_inferior_data
  552.     = register_inferior_data_with_cleanup (NULL, auxv_inferior_data_cleanup);

  554.   /* Observers used to invalidate the auxv cache when needed.  */
  555.   observer_attach_inferior_exit (invalidate_auxv_cache_inf);
  556.   observer_attach_inferior_appeared (invalidate_auxv_cache_inf);
  557.   observer_attach_executable_changed (invalidate_auxv_cache);
  558. }