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