elf/pldd-xx.c

   1 /* Copyright (C) 2011-2024 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 #include <dl-r_debug.h>
  26
  27 struct E(link_map)
  28 {
  29   EW(Addr) l_addr;
  30   EW(Addr) l_name;
  31   EW(Addr) l_ld;
  32   EW(Addr) l_next;
  33   EW(Addr) l_prev;
  34   EW(Addr) l_real;
  35   Lmid_t l_ns;
  36   EW(Addr) l_libname;
  37 };
  38 #if CLASS == __ELF_NATIVE_CLASS
  39 _Static_assert (offsetof (struct link_map, l_addr)
  40                 == offsetof (struct E(link_map), l_addr), "l_addr");
  41 _Static_assert (offsetof (struct link_map, l_name)
  42                 == offsetof (struct E(link_map), l_name), "l_name");
  43 _Static_assert (offsetof (struct link_map, l_next)
  44                 == offsetof (struct E(link_map), l_next), "l_next");
  45 #endif
  46
  47
  48 struct E(libname_list)
  49 {
  50   EW(Addr) name;
  51   EW(Addr) next;
  52 };
  53 #if CLASS == __ELF_NATIVE_CLASS
  54 _Static_assert (offsetof (struct libname_list, name)
  55                 == offsetof (struct E(libname_list), name), "name");
  56 _Static_assert (offsetof (struct libname_list, next)
  57                 == offsetof (struct E(libname_list), next), "next");
  58 #endif
  59
  60 struct E(r_debug)
  61 {
  62   int r_version;
  63 #if CLASS == 64
  64   int pad;
  65 #endif
  66   EW(Addr) r_map;
  67 };
  68 #if CLASS == __ELF_NATIVE_CLASS
  69 _Static_assert (offsetof (struct r_debug, r_version)
  70                 == offsetof (struct E(r_debug), r_version), "r_version");
  71 _Static_assert (offsetof (struct r_debug, r_map)
  72                 == offsetof (struct E(r_debug), r_map), "r_map");
  73 #endif
  74
  75
  76 static int
  77
  78 E(find_maps) (const char *exe, int memfd, pid_t pid, void *auxv,
  79               size_t auxv_size)
  80 {
  81   EW(Addr) phdr = 0;
  82   unsigned int phnum = 0;
  83   unsigned int phent = 0;
  84
  85   EW(auxv_t) *auxvXX = (EW(auxv_t) *) auxv;
  86   for (int i = 0; i < auxv_size / sizeof (EW(auxv_t)); ++i)
  87     switch (auxvXX[i].a_type)
  88       {
  89       case AT_PHDR:
  90         phdr = auxvXX[i].a_un.a_val;
  91         break;
  92       case AT_PHNUM:
  93         phnum = auxvXX[i].a_un.a_val;
  94         break;
  95       case AT_PHENT:
  96         phent = auxvXX[i].a_un.a_val;
  97         break;
  98       default:
  99         break;
 100       }
 101
 102   if (phdr == 0 || phnum == 0 || phent == 0)
 103     error (EXIT_FAILURE, 0, gettext ("cannot find program header of process"));
 104
 105   EW(Phdr) *p = xmalloc (phnum * phent);
 106   if (pread (memfd, p, phnum * phent, phdr) != phnum * phent)
 107     error (EXIT_FAILURE, 0, gettext ("cannot read program header"));
 108
 109   /* Determine the load offset.  We need this for interpreting the
 110      other program header entries so we do this in a separate loop.
 111      Fortunately it is the first time unless someone does something
 112      stupid when linking the application.  */
 113   EW(Addr) offset = 0;
 114   for (unsigned int i = 0; i < phnum; ++i)
 115     if (p[i].p_type == PT_PHDR)
 116       {
 117         offset = phdr - p[i].p_vaddr;
 118         break;
 119       }
 120
 121   EW(Addr) list = 0;
 122   char *interp = NULL;
 123   for (unsigned int i = 0; i < phnum; ++i)
 124     if (p[i].p_type == PT_DYNAMIC)
 125       {
 126         EW(Dyn) *dyn = xmalloc (p[i].p_filesz);
 127         if (pread (memfd, dyn, p[i].p_filesz, offset + p[i].p_vaddr)
 128             != p[i].p_filesz)
 129           error (EXIT_FAILURE, 0, gettext ("cannot read dynamic section"));
 130
 131         /* Search for the struct r_debug.  */
 132         for (unsigned int j = 0; j < p[i].p_filesz / sizeof (EW(Dyn)); ++j)
 133           {
 134             EW(Addr) off = offset + p[i].p_vaddr + sizeof (EW(Dyn)) * j;
 135             off = E(r_debug_offset) (&dyn[j], memfd, off);
 136             if (off != 0)
 137               {
 138                 struct E(r_debug) r;
 139                 if (pread (memfd, &r, sizeof (r), off)
 140                     != sizeof (r))
 141                   error (EXIT_FAILURE, 0, gettext ("cannot read r_debug"));
 142
 143                 if (r.r_map != 0)
 144                   {
 145                     list = r.r_map;
 146                     break;
 147                   }
 148               }
 149           }
 150
 151         free (dyn);
 152         break;
 153       }
 154     else if (p[i].p_type == PT_INTERP)
 155       {
 156         interp = xmalloc (p[i].p_filesz);
 157         if (pread (memfd, interp, p[i].p_filesz, offset + p[i].p_vaddr)
 158             != p[i].p_filesz)
 159           error (EXIT_FAILURE, 0, gettext ("cannot read program interpreter"));
 160       }
 161
 162   if (list == 0)
 163     {
 164       if (interp == NULL)
 165         {
 166           // XXX check whether the executable itself is the loader
 167           exit (EXIT_FAILURE);
 168         }
 169
 170       // XXX perhaps try finding ld.so and _r_debug in it
 171       exit (EXIT_FAILURE);
 172     }
 173
 174   free (p);
 175   free (interp);
 176
 177   /* Print the PID and program name first.  */
 178   printf ("%lu:\t%s\n", (unsigned long int) pid, exe);
 179
 180   /* Iterate over the list of objects and print the information.  */
 181   struct scratch_buffer tmpbuf;
 182   scratch_buffer_init (&tmpbuf);
 183   int status = 0;
 184   do
 185     {
 186       struct E(link_map) m;
 187       if (pread (memfd, &m, sizeof (m), list) != sizeof (m))
 188         error (EXIT_FAILURE, 0, gettext ("cannot read link map"));
 189
 190       EW(Addr) name_offset = m.l_name;
 191       while (1)
 192         {
 193           ssize_t n = pread (memfd, tmpbuf.data, tmpbuf.length, name_offset);
 194           if (n == -1)
 195             error (EXIT_FAILURE, 0, gettext ("cannot read object name"));
 196
 197           if (memchr (tmpbuf.data, '\0', n) != NULL)
 198             break;
 199
 200           if (!scratch_buffer_grow (&tmpbuf))
 201             error (EXIT_FAILURE, 0,
 202                    gettext ("cannot allocate buffer for object name"));
 203         }
 204
 205       /* The m.l_name and m.l_libname.name for loader linkmap points to same
 206          values (since BZ#387 fix).  Trying to use l_libname name as the
 207          shared object name might lead to an infinite loop (BZ#18035).  */
 208
 209       /* Skip over the executable.  */
 210       if (((char *)tmpbuf.data)[0] != '\0')
 211         printf ("%s\n", (char *)tmpbuf.data);
 212
 213       list = m.l_next;
 214     }
 215   while (list != 0);
 216
 217   scratch_buffer_free (&tmpbuf);
 218   return status;
 219 }
 220
 221
 222 #undef CLASS