sysdeps/unix/sysv/linux/dl-sysdep.c

   1 /* Dynamic linker system dependencies for Linux.
   2    Copyright (C) 1995-2024 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 #include <_itoa.h>
  20 #include <assert.h>
  21 #include <dl-auxv.h>
  22 #include <dl-osinfo.h>
  23 #include <dl-parse_auxv.h>
  24 #include <dl-procinfo.h>
  25 #include <dl-tunables.h>
  26 #include <elf.h>
  27 #include <errno.h>
  28 #include <fcntl.h>
  29 #include <ldsodefs.h>
  30 #include <libc-internal.h>
  31 #include <libintl.h>
  32 #include <not-cancel.h>
  33 #include <stdlib.h>
  34 #include <string.h>
  35 #include <string.h>
  36 #include <sys/mman.h>
  37 #include <sys/param.h>
  38 #include <sys/stat.h>
  39 #include <sys/types.h>
  40 #include <sys/utsname.h>
  41 #include <tls.h>
  42 #include <unistd.h>
  43
  44 #include <dl-machine.h>
  45 #include <dl-hwcap-check.h>
  46
  47 #ifdef SHARED
  48 extern char **_environ attribute_hidden;
  49 extern char _end[] attribute_hidden;
  50
  51 /* Protect SUID program against misuse of file descriptors.  */
  52 extern void __libc_check_standard_fds (void);
  53
  54 int __libc_enable_secure attribute_relro = 0;
  55 rtld_hidden_data_def (__libc_enable_secure)
  56 /* This variable contains the lowest stack address ever used.  */
  57 void *__libc_stack_end attribute_relro = NULL;
  58 rtld_hidden_data_def(__libc_stack_end)
  59 void *_dl_random attribute_relro = NULL;
  60
  61 #ifndef DL_STACK_END
  62 # define DL_STACK_END(cookie) ((void *) (cookie))
  63 #endif
  64
  65 /* Arguments passed to dl_main.  */
  66 struct dl_main_arguments
  67 {
  68   const ElfW(Phdr) *phdr;
  69   ElfW(Word) phnum;
  70   ElfW(Addr) user_entry;
  71 };
  72
  73 /* Separate function, so that dl_main can be called without the large
  74    array on the stack.  */
  75 static void
  76 _dl_sysdep_parse_arguments (void **start_argptr,
  77                             struct dl_main_arguments *args)
  78 {
  79   _dl_argc = (intptr_t) *start_argptr;
  80   _dl_argv = (char **) (start_argptr + 1); /* Necessary aliasing violation.  */
  81   _environ = _dl_argv + _dl_argc + 1;
  82   for (char **tmp = _environ; ; ++tmp)
  83     if (*tmp == NULL)
  84       {
  85         /* Another necessary aliasing violation.  */
  86         GLRO(dl_auxv) = (ElfW(auxv_t) *) (tmp + 1);
  87         break;
  88       }
  89
  90   dl_parse_auxv_t auxv_values = { 0, };
  91   _dl_parse_auxv (GLRO(dl_auxv), auxv_values);
  92
  93   args->phdr = (const ElfW(Phdr) *) auxv_values[AT_PHDR];
  94   args->phnum = auxv_values[AT_PHNUM];
  95   args->user_entry = auxv_values[AT_ENTRY];
  96 }
  97
  98 ElfW(Addr)
  99 _dl_sysdep_start (void **start_argptr,
 100                   void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
 101                                    ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv))
 102 {
 103   __libc_stack_end = DL_STACK_END (start_argptr);
 104
 105   struct dl_main_arguments dl_main_args;
 106   _dl_sysdep_parse_arguments (start_argptr, &dl_main_args);
 107
 108   dl_hwcap_check ();
 109
 110   __tunables_init (_environ);
 111
 112   /* Initialize DSO sorting algorithm after tunables.  */
 113   _dl_sort_maps_init ();
 114
 115   __brk (0);                    /* Initialize the break.  */
 116
 117 #ifdef DL_PLATFORM_INIT
 118   DL_PLATFORM_INIT;
 119 #endif
 120
 121   /* Determine the length of the platform name.  */
 122   if (GLRO(dl_platform) != NULL)
 123     GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
 124
 125   if (__sbrk (0) == _end)
 126     /* The dynamic linker was run as a program, and so the initial break
 127        starts just after our bss, at &_end.  The malloc in dl-minimal.c
 128        will consume the rest of this page, so tell the kernel to move the
 129        break up that far.  When the user program examines its break, it
 130        will see this new value and not clobber our data.  */
 131     __sbrk (GLRO(dl_pagesize)
 132             - (((uintptr_t) _end) & (GLRO(dl_pagesize) - 1)));
 133
 134   /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
 135      allocated.  If necessary we are doing it ourself.  If it is not
 136      possible we stop the program.  */
 137   if (__builtin_expect (__libc_enable_secure, 0))
 138     __libc_check_standard_fds ();
 139
 140   (*dl_main) (dl_main_args.phdr, dl_main_args.phnum,
 141               &dl_main_args.user_entry, GLRO(dl_auxv));
 142   return dl_main_args.user_entry;
 143 }
 144
 145 void
 146 _dl_sysdep_start_cleanup (void)
 147 {
 148 }
 149
 150 void
 151 _dl_show_auxv (void)
 152 {
 153   char buf[64];
 154   ElfW(auxv_t) *av;
 155
 156   /* Terminate string.  */
 157   buf[63] = '\0';
 158
 159   /* The following code assumes that the AT_* values are encoded
 160      starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
 161      close by (otherwise the array will be too large).  In case we have
 162      to support a platform where these requirements are not fulfilled
 163      some alternative implementation has to be used.  */
 164   for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
 165     {
 166       static const struct
 167       {
 168         const char label[22];
 169         enum { unknown = 0, dec, hex, str, ignore } form : 8;
 170       } auxvars[] =
 171         {
 172           [AT_EXECFD - 2] =             { "EXECFD:            ", dec },
 173           [AT_EXECFN - 2] =             { "EXECFN:            ", str },
 174           [AT_PHDR - 2] =               { "PHDR:              0x", hex },
 175           [AT_PHENT - 2] =              { "PHENT:             ", dec },
 176           [AT_PHNUM - 2] =              { "PHNUM:             ", dec },
 177           [AT_PAGESZ - 2] =             { "PAGESZ:            ", dec },
 178           [AT_BASE - 2] =               { "BASE:              0x", hex },
 179           [AT_FLAGS - 2] =              { "FLAGS:             0x", hex },
 180           [AT_ENTRY - 2] =              { "ENTRY:             0x", hex },
 181           [AT_NOTELF - 2] =             { "NOTELF:            ", hex },
 182           [AT_UID - 2] =                { "UID:               ", dec },
 183           [AT_EUID - 2] =               { "EUID:              ", dec },
 184           [AT_GID - 2] =                { "GID:               ", dec },
 185           [AT_EGID - 2] =               { "EGID:              ", dec },
 186           [AT_PLATFORM - 2] =           { "PLATFORM:          ", str },
 187           [AT_HWCAP - 2] =              { "HWCAP:             ", hex },
 188           [AT_CLKTCK - 2] =             { "CLKTCK:            ", dec },
 189           [AT_FPUCW - 2] =              { "FPUCW:             ", hex },
 190           [AT_DCACHEBSIZE - 2] =        { "DCACHEBSIZE:       0x", hex },
 191           [AT_ICACHEBSIZE - 2] =        { "ICACHEBSIZE:       0x", hex },
 192           [AT_UCACHEBSIZE - 2] =        { "UCACHEBSIZE:       0x", hex },
 193           [AT_IGNOREPPC - 2] =          { "IGNOREPPC", ignore },
 194           [AT_SECURE - 2] =             { "SECURE:            ", dec },
 195           [AT_BASE_PLATFORM - 2] =      { "BASE_PLATFORM:     ", str },
 196           [AT_SYSINFO - 2] =            { "SYSINFO:           0x", hex },
 197           [AT_SYSINFO_EHDR - 2] =       { "SYSINFO_EHDR:      0x", hex },
 198           [AT_RANDOM - 2] =             { "RANDOM:            0x", hex },
 199           [AT_HWCAP2 - 2] =             { "HWCAP2:            0x", hex },
 200           [AT_HWCAP3 - 2] =             { "HWCAP3:            0x", hex },
 201           [AT_HWCAP4 - 2] =             { "HWCAP4:            0x", hex },
 202           [AT_MINSIGSTKSZ - 2] =        { "MINSIGSTKSZ:       ", dec },
 203           [AT_L1I_CACHESIZE - 2] =      { "L1I_CACHESIZE:     ", dec },
 204           [AT_L1I_CACHEGEOMETRY - 2] =  { "L1I_CACHEGEOMETRY: 0x", hex },
 205           [AT_L1D_CACHESIZE - 2] =      { "L1D_CACHESIZE:     ", dec },
 206           [AT_L1D_CACHEGEOMETRY - 2] =  { "L1D_CACHEGEOMETRY: 0x", hex },
 207           [AT_L2_CACHESIZE - 2] =       { "L2_CACHESIZE:      ", dec },
 208           [AT_L2_CACHEGEOMETRY - 2] =   { "L2_CACHEGEOMETRY:  0x", hex },
 209           [AT_L3_CACHESIZE - 2] =       { "L3_CACHESIZE:      ", dec },
 210           [AT_L3_CACHEGEOMETRY - 2] =   { "L3_CACHEGEOMETRY:  0x", hex },
 211         };
 212       unsigned int idx = (unsigned int) (av->a_type - 2);
 213
 214       if ((unsigned int) av->a_type < 2u
 215           || (idx < sizeof (auxvars) / sizeof (auxvars[0])
 216               && auxvars[idx].form == ignore))
 217         continue;
 218
 219       assert (AT_NULL == 0);
 220       assert (AT_IGNORE == 1);
 221
 222       /* Some entries are handled in a special way per platform.  */
 223       if (_dl_procinfo (av->a_type, av->a_un.a_val) == 0)
 224         continue;
 225
 226       if (idx < sizeof (auxvars) / sizeof (auxvars[0])
 227           && auxvars[idx].form != unknown)
 228         {
 229           const char *val = (char *) av->a_un.a_val;
 230
 231           if (__builtin_expect (auxvars[idx].form, dec) == dec)
 232             val = _itoa ((unsigned long int) av->a_un.a_val,
 233                          buf + sizeof buf - 1, 10, 0);
 234           else if (__builtin_expect (auxvars[idx].form, hex) == hex)
 235             val = _itoa ((unsigned long int) av->a_un.a_val,
 236                          buf + sizeof buf - 1, 16, 0);
 237
 238           _dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
 239
 240           continue;
 241         }
 242
 243       /* Unknown value: print a generic line.  */
 244       char buf2[17];
 245       buf2[sizeof (buf2) - 1] = '\0';
 246       const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
 247                                 buf2 + sizeof buf2 - 1, 16, 0);
 248       const char *val =  _itoa ((unsigned long int) av->a_type,
 249                                 buf + sizeof buf - 1, 16, 0);
 250       _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
 251     }
 252 }
 253
 254 #endif /* SHARED */