sysdeps/x86/dl-prop.h

   1 /* Support for GNU properties.  x86 version.
   2    Copyright (C) 2018-2021 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 #ifndef _DL_PROP_H
  20 #define _DL_PROP_H
  21
  22 extern void _dl_cet_check (struct link_map *, const char *)
  23     attribute_hidden;
  24 extern void _dl_cet_open_check (struct link_map *)
  25     attribute_hidden;
  26
  27 static inline void __attribute__ ((always_inline))
  28 _rtld_main_check (struct link_map *m, const char *program)
  29 {
  30 #if CET_ENABLED
  31   _dl_cet_check (m, program);
  32 #endif
  33 }
  34
  35 static inline void __attribute__ ((always_inline))
  36 _dl_open_check (struct link_map *m)
  37 {
  38 #if CET_ENABLED
  39   _dl_cet_open_check (m);
  40 #endif
  41 }
  42
  43 static inline void __attribute__ ((unused))
  44 _dl_process_cet_property_note (struct link_map *l,
  45                               const ElfW(Nhdr) *note,
  46                               const ElfW(Addr) size,
  47                               const ElfW(Addr) align)
  48 {
  49 #if CET_ENABLED
  50   /* Skip if we have seen a NT_GNU_PROPERTY_TYPE_0 note before.  */
  51   if (l->l_cet != lc_unknown)
  52     return;
  53
  54   /* The NT_GNU_PROPERTY_TYPE_0 note must be aliged to 4 bytes in
  55      32-bit objects and to 8 bytes in 64-bit objects.  Skip notes
  56      with incorrect alignment.  */
  57   if (align != (__ELF_NATIVE_CLASS / 8))
  58     return;
  59
  60   const ElfW(Addr) start = (ElfW(Addr)) note;
  61
  62   unsigned int feature_1 = 0;
  63   unsigned int last_type = 0;
  64
  65   while ((ElfW(Addr)) (note + 1) - start < size)
  66     {
  67       /* Find the NT_GNU_PROPERTY_TYPE_0 note.  */
  68       if (note->n_namesz == 4
  69           && note->n_type == NT_GNU_PROPERTY_TYPE_0
  70           && memcmp (note + 1, "GNU", 4) == 0)
  71         {
  72           /* Stop if we see more than one GNU property note which may
  73              be generated by the older linker.  */
  74           if (l->l_cet != lc_unknown)
  75             return;
  76
  77           /* Check CET status now.  */
  78           l->l_cet = lc_none;
  79
  80           /* Check for invalid property.  */
  81           if (note->n_descsz < 8
  82               || (note->n_descsz % sizeof (ElfW(Addr))) != 0)
  83             return;
  84
  85           /* Start and end of property array.  */
  86           unsigned char *ptr = (unsigned char *) (note + 1) + 4;
  87           unsigned char *ptr_end = ptr + note->n_descsz;
  88
  89           do
  90             {
  91               unsigned int type = *(unsigned int *) ptr;
  92               unsigned int datasz = *(unsigned int *) (ptr + 4);
  93
  94               /* Property type must be in ascending order.  */
  95               if (type < last_type)
  96                 return;
  97
  98               ptr += 8;
  99               if ((ptr + datasz) > ptr_end)
 100                 return;
 101
 102               last_type = type;
 103
 104               if (type == GNU_PROPERTY_X86_FEATURE_1_AND)
 105                 {
 106                   /* The size of GNU_PROPERTY_X86_FEATURE_1_AND is 4
 107                      bytes.  When seeing GNU_PROPERTY_X86_FEATURE_1_AND,
 108                      we stop the search regardless if its size is correct
 109                      or not.  There is no point to continue if this note
 110                      is ill-formed.  */
 111                   if (datasz != 4)
 112                     return;
 113
 114                   feature_1 = *(unsigned int *) ptr;
 115
 116                   /* Keep searching for the next GNU property note
 117                      generated by the older linker.  */
 118                   break;
 119                 }
 120               else if (type > GNU_PROPERTY_X86_FEATURE_1_AND)
 121                 {
 122                   /* Stop since property type is in ascending order.  */
 123                   return;
 124                 }
 125
 126               /* Check the next property item.  */
 127               ptr += ALIGN_UP (datasz, sizeof (ElfW(Addr)));
 128             }
 129           while ((ptr_end - ptr) >= 8);
 130         }
 131
 132       /* NB: Note sections like .note.ABI-tag and .note.gnu.build-id are
 133          aligned to 4 bytes in 64-bit ELF objects.  */
 134       note = ((const void *) note
 135               + ELF_NOTE_NEXT_OFFSET (note->n_namesz, note->n_descsz,
 136                                       align));
 137     }
 138
 139   /* We get here only if there is one or no GNU property note.  */
 140   if ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT))
 141     l->l_cet |= lc_ibt;
 142   if ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_SHSTK))
 143     l->l_cet |= lc_shstk;
 144 #endif
 145 }
 146
 147 static inline void __attribute__ ((unused))
 148 _dl_process_pt_note (struct link_map *l, int fd, const ElfW(Phdr) *ph)
 149 {
 150   const ElfW(Nhdr) *note = (const void *) (ph->p_vaddr + l->l_addr);
 151   _dl_process_cet_property_note (l, note, ph->p_memsz, ph->p_align);
 152 }
 153
 154 static inline int __attribute__ ((always_inline))
 155 _dl_process_gnu_property (struct link_map *l, int fd, uint32_t type,
 156                           uint32_t datasz, void *data)
 157 {
 158   return 0;
 159 }
 160
 161 #endif /* _DL_PROP_H */