elf/pldd-xx.c

   1 /* Copyright (C) 2011-2022 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #define E(name) E_(name, CLASS)
  19 #define E_(name, cl) E__(name, cl)
  20 #define E__(name, cl) name##cl
  21 #define EW(type) EW_(Elf, CLASS, type)
  22 #define EW_(e, w, t) EW__(e, w, _##t)
  23 #define EW__(e, w, t) e##w##t
  24
  25 struct E(link_map)
  26 {
  27   EW(Addr) l_addr;
  28   EW(Addr) l_name;
  29   EW(Addr) l_ld;
  30   EW(Addr) l_next;
  31   EW(Addr) l_prev;
  32   EW(Addr) l_real;
  33   Lmid_t l_ns;
  34   EW(Addr) l_libname;
  35 };
  36 #if CLASS == __ELF_NATIVE_CLASS
  37 _Static_assert (offsetof (struct link_map, l_addr)
  38                 == offsetof (struct E(link_map), l_addr), "l_addr");
  39 _Static_assert (offsetof (struct link_map, l_name)
  40                 == offsetof (struct E(link_map), l_name), "l_name");
  41 _Static_assert (offsetof (struct link_map, l_next)
  42                 == offsetof (struct E(link_map), l_next), "l_next");
  43 #endif
  44
  45
  46 struct E(libname_list)
  47 {
  48   EW(Addr) name;
  49   EW(Addr) next;
  50 };
  51 #if CLASS == __ELF_NATIVE_CLASS
  52 _Static_assert (offsetof (struct libname_list, name)
  53                 == offsetof (struct E(libname_list), name), "name");
  54 _Static_assert (offsetof (struct libname_list, next)
  55                 == offsetof (struct E(libname_list), next), "next");
  56 #endif
  57
  58 struct E(r_debug)
  59 {
  60   int r_version;
  61 #if CLASS == 64
  62   int pad;
  63 #endif
  64   EW(Addr) r_map;
  65 };
  66 #if CLASS == __ELF_NATIVE_CLASS
  67 _Static_assert (offsetof (struct r_debug, r_version)
  68                 == offsetof (struct E(r_debug), r_version), "r_version");
  69 _Static_assert (offsetof (struct r_debug, r_map)
  70                 == offsetof (struct E(r_debug), r_map), "r_map");
  71 #endif
  72
  73
  74 static int
  75
  76 E(find_maps) (const char *exe, int memfd, pid_t pid, void *auxv,
  77               size_t auxv_size)
  78 {
  79   EW(Addr) phdr = 0;
  80   unsigned int phnum = 0;
  81   unsigned int phent = 0;
  82
  83   EW(auxv_t) *auxvXX = (EW(auxv_t) *) auxv;
  84   for (int i = 0; i < auxv_size / sizeof (EW(auxv_t)); ++i)
  85     switch (auxvXX[i].a_type)
  86       {
  87       case AT_PHDR:
  88         phdr = auxvXX[i].a_un.a_val;
  89         break;
  90       case AT_PHNUM:
  91         phnum = auxvXX[i].a_un.a_val;
  92         break;
  93       case AT_PHENT:
  94         phent = auxvXX[i].a_un.a_val;
  95         break;
  96       default:
  97         break;
  98       }
  99
 100   if (phdr == 0 || phnum == 0 || phent == 0)
 101     error (EXIT_FAILURE, 0, gettext ("cannot find program header of process"));
 102
 103   EW(Phdr) *p = xmalloc (phnum * phent);
 104   if (pread (memfd, p, phnum * phent, phdr) != phnum * phent)
 105     error (EXIT_FAILURE, 0, gettext ("cannot read program header"));
 106
 107   /* Determine the load offset.  We need this for interpreting the
 108      other program header entries so we do this in a separate loop.
 109      Fortunately it is the first time unless someone does something
 110      stupid when linking the application.  */
 111   EW(Addr) offset = 0;
 112   for (unsigned int i = 0; i < phnum; ++i)
 113     if (p[i].p_type == PT_PHDR)
 114       {
 115         offset = phdr - p[i].p_vaddr;
 116         break;
 117       }
 118
 119   EW(Addr) list = 0;
 120   char *interp = NULL;
 121   for (unsigned int i = 0; i < phnum; ++i)
 122     if (p[i].p_type == PT_DYNAMIC)
 123       {
 124         EW(Dyn) *dyn = xmalloc (p[i].p_filesz);
 125         if (pread (memfd, dyn, p[i].p_filesz, offset + p[i].p_vaddr)
 126             != p[i].p_filesz)
 127           error (EXIT_FAILURE, 0, gettext ("cannot read dynamic section"));
 128
 129         /* Search for the DT_DEBUG entry.  */
 130         for (unsigned int j = 0; j < p[i].p_filesz / sizeof (EW(Dyn)); ++j)
 131           if (dyn[j].d_tag == DT_DEBUG && dyn[j].d_un.d_ptr != 0)
 132             {
 133               struct E(r_debug) r;
 134               if (pread (memfd, &r, sizeof (r), dyn[j].d_un.d_ptr)
 135                   != sizeof (r))
 136                 error (EXIT_FAILURE, 0, gettext ("cannot read r_debug"));
 137
 138               if (r.r_map != 0)
 139                 {
 140                   list = r.r_map;
 141                   break;
 142                 }
 143             }
 144
 145         free (dyn);
 146         break;
 147       }
 148     else if (p[i].p_type == PT_INTERP)
 149       {
 150         interp = xmalloc (p[i].p_filesz);
 151         if (pread (memfd, interp, p[i].p_filesz, offset + p[i].p_vaddr)
 152             != p[i].p_filesz)
 153           error (EXIT_FAILURE, 0, gettext ("cannot read program interpreter"));
 154       }
 155
 156   if (list == 0)
 157     {
 158       if (interp == NULL)
 159         {
 160           // XXX check whether the executable itself is the loader
 161           exit (EXIT_FAILURE);
 162         }
 163
 164       // XXX perhaps try finding ld.so and _r_debug in it
 165       exit (EXIT_FAILURE);
 166     }
 167
 168   free (p);
 169   free (interp);
 170
 171   /* Print the PID and program name first.  */
 172   printf ("%lu:\t%s\n", (unsigned long int) pid, exe);
 173
 174   /* Iterate over the list of objects and print the information.  */
 175   struct scratch_buffer tmpbuf;
 176   scratch_buffer_init (&tmpbuf);
 177   int status = 0;
 178   do
 179     {
 180       struct E(link_map) m;
 181       if (pread (memfd, &m, sizeof (m), list) != sizeof (m))
 182         error (EXIT_FAILURE, 0, gettext ("cannot read link map"));
 183
 184       EW(Addr) name_offset = m.l_name;
 185       while (1)
 186         {
 187           ssize_t n = pread (memfd, tmpbuf.data, tmpbuf.length, name_offset);
 188           if (n == -1)
 189             error (EXIT_FAILURE, 0, gettext ("cannot read object name"));
 190
 191           if (memchr (tmpbuf.data, '\0', n) != NULL)
 192             break;
 193
 194           if (!scratch_buffer_grow (&tmpbuf))
 195             error (EXIT_FAILURE, 0,
 196                    gettext ("cannot allocate buffer for object name"));
 197         }
 198
 199       /* The m.l_name and m.l_libname.name for loader linkmap points to same
 200          values (since BZ#387 fix).  Trying to use l_libname name as the
 201          shared object name might lead to an infinite loop (BZ#18035).  */
 202
 203       /* Skip over the executable.  */
 204       if (((char *)tmpbuf.data)[0] != '\0')
 205         printf ("%s\n", (char *)tmpbuf.data);
 206
 207       list = m.l_next;
 208     }
 209   while (list != 0);
 210
 211   scratch_buffer_free (&tmpbuf);
 212   return status;
 213 }
 214
 215
 216 #undef CLASS