elf/pldd.c

   1 /* List dynamic shared objects linked into given process.
   2    Copyright (C) 2011-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #define _FILE_OFFSET_BITS 64
  20
  21 #include <argp.h>
  22 #include <dirent.h>
  23 #include <error.h>
  24 #include <fcntl.h>
  25 #include <libintl.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <unistd.h>
  29 #include <sys/ptrace.h>
  30 #include <sys/wait.h>
  31 #include <scratch_buffer.h>
  32
  33 #include <ldsodefs.h>
  34 #include <version.h>
  35
  36 /* Global variables.  */
  37 extern char *program_invocation_short_name;
  38 #define PACKAGE _libc_intl_domainname
  39
  40 /* External functions.  */
  41 #include <programs/xmalloc.h>
  42
  43 /* Name and version of program.  */
  44 static void print_version (FILE *stream, struct argp_state *state);
  45 void (*argp_program_version_hook) (FILE *, struct argp_state *) = print_version;
  46
  47 /* Function to print some extra text in the help message.  */
  48 static char *more_help (int key, const char *text, void *input);
  49
  50 /* Definitions of arguments for argp functions.  */
  51 static const struct argp_option options[] =
  52 {
  53   { NULL, 0, NULL, 0, NULL }
  54 };
  55
  56 /* Short description of program.  */
  57 static const char doc[] = N_("\
  58 List dynamic shared objects loaded into process.");
  59
  60 /* Strings for arguments in help texts.  */
  61 static const char args_doc[] = N_("PID");
  62
  63 /* Prototype for option handler.  */
  64 static error_t parse_opt (int key, char *arg, struct argp_state *state);
  65
  66 /* Data structure to communicate with argp functions.  */
  67 static struct argp argp =
  68 {
  69   options, parse_opt, args_doc, doc, NULL, more_help, NULL
  70 };
  71
  72
  73 /* Local functions.  */
  74 static int get_process_info (const char *exe, int dfd, long int pid);
  75 static void wait_for_ptrace_stop (long int pid);
  76
  77
  78 int
  79 main (int argc, char *argv[])
  80 {
  81   /* Parse and process arguments.  */
  82   int remaining;
  83   argp_parse (&argp, argc, argv, 0, &remaining, NULL);
  84
  85   if (remaining != argc - 1)
  86     {
  87       fprintf (stderr,
  88                gettext ("Exactly one parameter with process ID required.\n"));
  89       argp_help (&argp, stderr, ARGP_HELP_SEE, program_invocation_short_name);
  90       return 1;
  91     }
  92
  93   _Static_assert (sizeof (pid_t) == sizeof (int)
  94                   || sizeof (pid_t) == sizeof (long int),
  95                   "sizeof (pid_t) != sizeof (int) or sizeof (long int)");
  96
  97   char *endp;
  98   errno = 0;
  99   long int pid = strtol (argv[remaining], &endp, 10);
 100   if (pid < 0 || (pid == ULONG_MAX && errno == ERANGE) || *endp != '\0'
 101       || (sizeof (pid_t) < sizeof (pid) && pid > INT_MAX))
 102     error (EXIT_FAILURE, 0, gettext ("invalid process ID '%s'"),
 103            argv[remaining]);
 104
 105   /* Determine the program name.  */
 106   char buf[7 + 3 * sizeof (pid)];
 107   snprintf (buf, sizeof (buf), "/proc/%lu", pid);
 108   int dfd = open (buf, O_RDONLY | O_DIRECTORY);
 109   if (dfd == -1)
 110     error (EXIT_FAILURE, errno, gettext ("cannot open %s"), buf);
 111
 112   /* Name of the executable  */
 113   struct scratch_buffer exe;
 114   scratch_buffer_init (&exe);
 115   ssize_t nexe;
 116   while ((nexe = readlinkat (dfd, "exe",
 117                              exe.data, exe.length)) == exe.length)
 118     {
 119       if (!scratch_buffer_grow (&exe))
 120         {
 121           nexe = -1;
 122           break;
 123         }
 124     }
 125   if (nexe == -1)
 126     /* Default stack allocation is at least 1024.  */
 127     snprintf (exe.data, exe.length, "<program name undetermined>");
 128   else
 129     ((char*)exe.data)[nexe] = '\0';
 130
 131   /* Stop all threads since otherwise the list of loaded modules might
 132      change while we are reading it.  */
 133   struct thread_list
 134   {
 135     pid_t tid;
 136     struct thread_list *next;
 137   } *thread_list = NULL;
 138
 139   int taskfd = openat (dfd, "task", O_RDONLY | O_DIRECTORY | O_CLOEXEC);
 140   if (taskfd == 1)
 141     error (EXIT_FAILURE, errno, gettext ("cannot open %s/task"), buf);
 142   DIR *dir = fdopendir (taskfd);
 143   if (dir == NULL)
 144     error (EXIT_FAILURE, errno, gettext ("cannot prepare reading %s/task"),
 145            buf);
 146
 147   struct dirent *d;
 148   while ((d = readdir (dir)) != NULL)
 149     {
 150       if (! isdigit (d->d_name[0]))
 151         continue;
 152
 153       errno = 0;
 154       long int tid = strtol (d->d_name, &endp, 10);
 155       if (tid < 0 || (tid == ULONG_MAX && errno == ERANGE) || *endp != '\0'
 156           || (sizeof (pid_t) < sizeof (pid) && tid > INT_MAX))
 157         error (EXIT_FAILURE, 0, gettext ("invalid thread ID '%s'"),
 158                d->d_name);
 159
 160       if (ptrace (PTRACE_ATTACH, tid, NULL, NULL) != 0)
 161         {
 162           /* There might be a race between reading the directory and
 163              threads terminating.  Ignore errors attaching to unknown
 164              threads unless this is the main thread.  */
 165           if (errno == ESRCH && tid != pid)
 166             continue;
 167
 168           error (EXIT_FAILURE, errno, gettext ("cannot attach to process %lu"),
 169                  tid);
 170         }
 171
 172       wait_for_ptrace_stop (tid);
 173
 174       struct thread_list *newp = xmalloc (sizeof (*newp));
 175       newp->tid = tid;
 176       newp->next = thread_list;
 177       thread_list = newp;
 178     }
 179
 180   closedir (dir);
 181
 182   if (thread_list == NULL)
 183     error (EXIT_FAILURE, 0, gettext ("no valid %s/task entries"), buf);
 184
 185   int status = get_process_info (exe.data, dfd, pid);
 186
 187   do
 188     {
 189       ptrace (PTRACE_DETACH, thread_list->tid, NULL, NULL);
 190       struct thread_list *prev = thread_list;
 191       thread_list = thread_list->next;
 192       free (prev);
 193     }
 194   while (thread_list != NULL);
 195
 196   close (dfd);
 197   scratch_buffer_free (&exe);
 198
 199   return status;
 200 }
 201
 202
 203 /* Wait for PID to enter ptrace-stop state after being attached.  */
 204 static void
 205 wait_for_ptrace_stop (long int pid)
 206 {
 207   int status;
 208
 209   /* While waiting for SIGSTOP being delivered to the tracee we have to
 210      reinject any other pending signal.  Ignore all other errors.  */
 211   while (waitpid (pid, &status, __WALL) == pid && WIFSTOPPED (status))
 212     {
 213       /* The STOP signal should not be delivered to the tracee.  */
 214       if (WSTOPSIG (status) == SIGSTOP)
 215         return;
 216       if (ptrace (PTRACE_CONT, pid, NULL,
 217                   (void *) (uintptr_t) WSTOPSIG (status)))
 218         /* The only possible error is that the process died.  */
 219         return;
 220     }
 221 }
 222
 223
 224 /* Handle program arguments.  */
 225 static error_t
 226 parse_opt (int key, char *arg, struct argp_state *state)
 227 {
 228   switch (key)
 229     {
 230     default:
 231       return ARGP_ERR_UNKNOWN;
 232     }
 233   return 0;
 234 }
 235
 236
 237 /* Print bug-reporting information in the help message.  */
 238 static char *
 239 more_help (int key, const char *text, void *input)
 240 {
 241   char *tp = NULL;
 242   switch (key)
 243     {
 244     case ARGP_KEY_HELP_EXTRA:
 245       /* We print some extra information.  */
 246       if (asprintf (&tp, gettext ("\
 247 For bug reporting instructions, please see:\n\
 248 %s.\n"), REPORT_BUGS_TO) < 0)
 249         return NULL;
 250       return tp;
 251     default:
 252       break;
 253     }
 254   return (char *) text;
 255 }
 256
 257 /* Print the version information.  */
 258 static void
 259 print_version (FILE *stream, struct argp_state *state)
 260 {
 261   fprintf (stream, "pldd %s%s\n", PKGVERSION, VERSION);
 262   fprintf (stream, gettext ("\
 263 Copyright (C) %s Free Software Foundation, Inc.\n\
 264 This is free software; see the source for copying conditions.  There is NO\n\
 265 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\
 266 "), "2022");
 267   fprintf (stream, gettext ("Written by %s.\n"), "Ulrich Drepper");
 268 }
 269
 270
 271 #define CLASS 32
 272 #include "pldd-xx.c"
 273 #define CLASS 64
 274 #include "pldd-xx.c"
 275
 276
 277 static int
 278 get_process_info (const char *exe, int dfd, long int pid)
 279 {
 280   /* File descriptor of /proc/<pid>/mem file.  */
 281   int memfd = openat (dfd, "mem", O_RDONLY);
 282   if (memfd == -1)
 283     goto no_info;
 284
 285   int fd = openat (dfd, "exe", O_RDONLY);
 286   if (fd == -1)
 287     {
 288     no_info:
 289       error (0, errno, gettext ("cannot get information about process %lu"),
 290              pid);
 291       return EXIT_FAILURE;
 292     }
 293
 294   char e_ident[EI_NIDENT];
 295   if (read (fd, e_ident, EI_NIDENT) != EI_NIDENT)
 296     goto no_info;
 297
 298   close (fd);
 299
 300   if (memcmp (e_ident, ELFMAG, SELFMAG) != 0)
 301     {
 302       error (0, 0, gettext ("process %lu is no ELF program"), pid);
 303       return EXIT_FAILURE;
 304     }
 305
 306   fd = openat (dfd, "auxv", O_RDONLY);
 307   if (fd == -1)
 308     goto no_info;
 309
 310   size_t auxv_size = 0;
 311   void *auxv = NULL;
 312   while (1)
 313     {
 314       auxv_size += 512;
 315       auxv = xrealloc (auxv, auxv_size);
 316
 317       ssize_t n = pread (fd, auxv, auxv_size, 0);
 318       if (n < 0)
 319         goto no_info;
 320       if (n < auxv_size)
 321         {
 322           auxv_size = n;
 323           break;
 324         }
 325     }
 326
 327   close (fd);
 328
 329   int retval;
 330   if (e_ident[EI_CLASS] == ELFCLASS32)
 331     retval = find_maps32 (exe, memfd, pid, auxv, auxv_size);
 332   else
 333     retval = find_maps64 (exe, memfd, pid, auxv, auxv_size);
 334
 335   free (auxv);
 336   close (memfd);
 337
 338   return retval;
 339 }