about summary refs log tree commit diff
path: root/sysdeps/x86/dl-prop.h
blob: 516f88ea80c0a7eb9c78510b00642ee84c46d95d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
/* Support for GNU properties.  x86 version.
   Copyright (C) 2018-2020 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#ifndef _DL_PROP_H
#define _DL_PROP_H

#include <not-cancel.h>

extern void _dl_cet_check (struct link_map *, const char *)
    attribute_hidden;
extern void _dl_cet_open_check (struct link_map *)
    attribute_hidden;

static inline void __attribute__ ((always_inline))
_rtld_main_check (struct link_map *m, const char *program)
{
#if CET_ENABLED
  _dl_cet_check (m, program);
#endif
}

static inline void __attribute__ ((always_inline))
_dl_open_check (struct link_map *m)
{
#if CET_ENABLED
  _dl_cet_open_check (m);
#endif
}

static inline void __attribute__ ((unused))
_dl_process_cet_property_note (struct link_map *l,
			      const ElfW(Nhdr) *note,
			      const ElfW(Addr) size,
			      const ElfW(Addr) align)
{
#if CET_ENABLED
  /* Skip if we have seen a NT_GNU_PROPERTY_TYPE_0 note before.  */
  if (l->l_cet != lc_unknown)
    return;

  /* The NT_GNU_PROPERTY_TYPE_0 note must be aliged to 4 bytes in
     32-bit objects and to 8 bytes in 64-bit objects.  Skip notes
     with incorrect alignment.  */
  if (align != (__ELF_NATIVE_CLASS / 8))
    return;

  const ElfW(Addr) start = (ElfW(Addr)) note;

  unsigned int feature_1 = 0;
  unsigned int last_type = 0;

  while ((ElfW(Addr)) (note + 1) - start < size)
    {
      /* Find the NT_GNU_PROPERTY_TYPE_0 note.  */
      if (note->n_namesz == 4
	  && note->n_type == NT_GNU_PROPERTY_TYPE_0
	  && memcmp (note + 1, "GNU", 4) == 0)
	{
	  /* Stop if we see more than one GNU property note which may
	     be generated by the older linker.  */
	  if (l->l_cet != lc_unknown)
	    return;

	  /* Check CET status now.  */
	  l->l_cet = lc_none;

	  /* Check for invalid property.  */
	  if (note->n_descsz < 8
	      || (note->n_descsz % sizeof (ElfW(Addr))) != 0)
	    return;

	  /* Start and end of property array.  */
	  unsigned char *ptr = (unsigned char *) (note + 1) + 4;
	  unsigned char *ptr_end = ptr + note->n_descsz;

	  do
	    {
	      unsigned int type = *(unsigned int *) ptr;
	      unsigned int datasz = *(unsigned int *) (ptr + 4);

	      /* Property type must be in ascending order.  */
	      if (type < last_type)
		return;

	      ptr += 8;
	      if ((ptr + datasz) > ptr_end)
		return;

	      last_type = type;

	      if (type == GNU_PROPERTY_X86_FEATURE_1_AND)
		{
		  /* The size of GNU_PROPERTY_X86_FEATURE_1_AND is 4
		     bytes.  When seeing GNU_PROPERTY_X86_FEATURE_1_AND,
		     we stop the search regardless if its size is correct
		     or not.  There is no point to continue if this note
		     is ill-formed.  */
		  if (datasz != 4)
		    return;

		  feature_1 = *(unsigned int *) ptr;

		  /* Keep searching for the next GNU property note
		     generated by the older linker.  */
		  break;
		}
	      else if (type > GNU_PROPERTY_X86_FEATURE_1_AND)
		{
		  /* Stop since property type is in ascending order.  */
		  return;
		}

	      /* Check the next property item.  */
	      ptr += ALIGN_UP (datasz, sizeof (ElfW(Addr)));
	    }
	  while ((ptr_end - ptr) >= 8);
	}

      /* NB: Note sections like .note.ABI-tag and .note.gnu.build-id are
	 aligned to 4 bytes in 64-bit ELF objects.  */
      note = ((const void *) note
	      + ELF_NOTE_NEXT_OFFSET (note->n_namesz, note->n_descsz,
				      align));
    }

  /* We get here only if there is one or no GNU property note.  */
  if ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT))
    l->l_cet |= lc_ibt;
  if ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_SHSTK))
    l->l_cet |= lc_shstk;
#endif
}

#ifdef FILEBUF_SIZE
static inline int __attribute__ ((unused))
_dl_process_pt_note (struct link_map *l, const ElfW(Phdr) *ph,
		     int fd, struct filebuf *fbp)
{
# if CET_ENABLED
  const ElfW(Nhdr) *note;
  ElfW(Nhdr) *note_malloced = NULL;
  ElfW(Addr) size = ph->p_filesz;

  if (ph->p_offset + size <= (size_t) fbp->len)
    note = (const void *) (fbp->buf + ph->p_offset);
  else
    {
      if (size < __MAX_ALLOCA_CUTOFF)
	note = alloca (size);
      else
	{
	  note_malloced = malloc (size);
	  note = note_malloced;
	}
      if (__pread64_nocancel (fd, (void *) note, size, ph->p_offset) != size)
	{
	  if (note_malloced)
	    free (note_malloced);
	  return -1;
	}
    }

  _dl_process_cet_property_note (l, note, size, ph->p_align);
  if (note_malloced)
    free (note_malloced);
# endif
  return 0;
}
#endif

static inline int __attribute__ ((unused))
_rtld_process_pt_note (struct link_map *l, const ElfW(Phdr) *ph)
{
  const ElfW(Nhdr) *note = (const void *) (ph->p_vaddr + l->l_addr);
  _dl_process_cet_property_note (l, note, ph->p_memsz, ph->p_align);
  return 0;
}

#endif /* _DL_PROP_H */