1/* Support for GNU properties. x86 version.
2 Copyright (C) 2018-2024 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#ifndef _DL_PROP_H
20#define _DL_PROP_H
21
22#include <libintl.h>
23
24extern void _dl_cet_check (struct link_map *, const char *)
25 attribute_hidden;
26extern void _dl_cet_open_check (struct link_map *)
27 attribute_hidden;
28
29static void
30dl_isa_level_check (struct link_map *m, const char *program)
31{
32 const struct cpu_features *cpu_features = __get_cpu_features ();
33 unsigned int i;
34 struct link_map *l;
35
36 i = m->l_searchlist.r_nlist;
37 while (i-- > 0)
38 {
39 /* Check each shared object to see if ISA level is compatible. */
40 l = m->l_initfini[i];
41
42 /* Skip ISA level check if functions have been executed. */
43 if (l->l_init_called)
44 continue;
45
46#ifdef SHARED
47 /* Skip ISA level check for ld.so since ld.so won't run if its ISA
48 level is higher than CPU. */
49 if (l == &GL(dl_rtld_map) || l->l_real == &GL(dl_rtld_map))
50 continue;
51#endif
52
53 if ((l->l_x86_isa_1_needed & cpu_features->isa_1)
54 != l->l_x86_isa_1_needed)
55 {
56 if (program)
57 _dl_fatal_printf (fmt: "%s: CPU ISA level is lower than required\n",
58 *l->l_name != '\0' ? l->l_name : program);
59 else
60 _dl_signal_error (errcode: 0, object: l->l_name, occasion: "dlopen",
61 N_("CPU ISA level is lower than required"));
62 }
63 }
64}
65
66static inline void __attribute__ ((always_inline))
67_rtld_main_check (struct link_map *m, const char *program)
68{
69 dl_isa_level_check (m, program);
70#if CET_ENABLED
71 _dl_cet_check (m, program);
72#endif
73}
74
75static inline void __attribute__ ((always_inline))
76_dl_open_check (struct link_map *m)
77{
78 dl_isa_level_check (m, NULL);
79#if CET_ENABLED
80 _dl_cet_open_check (m);
81#endif
82}
83
84/* Check the GNU property and return its value. It returns:
85 -1: Skip this note.
86 0: Stop checking.
87 1: Continue to check.
88 */
89static inline int
90_dl_check_gnu_property (unsigned int type, unsigned int datasz,
91 void *ptr, unsigned int *feature_1_and,
92 unsigned int *needed_1,
93 unsigned int *isa_1_needed)
94{
95 if (type == GNU_PROPERTY_X86_FEATURE_1_AND
96 || type == GNU_PROPERTY_X86_ISA_1_NEEDED
97 || type == GNU_PROPERTY_1_NEEDED)
98 {
99 /* The sizes of types which we are searching for are
100 4 bytes. There is no point to continue if this
101 note is ill-formed. */
102 if (datasz != 4)
103 return -1;
104
105 /* NB: Stop the scan only after seeing all types which
106 we are searching for. */
107 _Static_assert (((GNU_PROPERTY_X86_ISA_1_NEEDED
108 > GNU_PROPERTY_X86_FEATURE_1_AND)
109 && (GNU_PROPERTY_X86_FEATURE_1_AND
110 > GNU_PROPERTY_1_NEEDED)),
111 "GNU_PROPERTY_X86_ISA_1_NEEDED > "
112 "GNU_PROPERTY_X86_FEATURE_1_AND && "
113 "GNU_PROPERTY_X86_FEATURE_1_AND > "
114 "GNU_PROPERTY_1_NEEDED");
115 if (type == GNU_PROPERTY_X86_FEATURE_1_AND)
116 *feature_1_and = *(unsigned int *) ptr;
117 else if (type == GNU_PROPERTY_1_NEEDED)
118 *needed_1 = *(unsigned int *) ptr;
119 else
120 {
121 *isa_1_needed = *(unsigned int *) ptr;
122
123 /* Keep searching for the next GNU property note
124 generated by the older linker. */
125 return 0;
126 }
127 }
128 else if (type > GNU_PROPERTY_X86_ISA_1_NEEDED)
129 {
130 /* Stop the scan since property type is in ascending
131 order. */
132 return 0;
133 }
134
135 return 1;
136}
137
138static inline void __attribute__ ((unused))
139_dl_process_property_note (struct link_map *l, const ElfW(Nhdr) *note,
140 const ElfW(Addr) size, const ElfW(Addr) align)
141{
142 /* Skip if we have seen a NT_GNU_PROPERTY_TYPE_0 note before. */
143 if (l->l_property != lc_property_unknown)
144 return;
145
146 /* The NT_GNU_PROPERTY_TYPE_0 note must be aligned to 4 bytes in
147 32-bit objects and to 8 bytes in 64-bit objects. Skip notes
148 with incorrect alignment. */
149 if (align != (__ELF_NATIVE_CLASS / 8))
150 return;
151
152 const ElfW(Addr) start = (ElfW(Addr)) note;
153
154 unsigned int needed_1 = 0;
155 unsigned int feature_1_and = 0;
156 unsigned int isa_1_needed = 0;
157 unsigned int last_type = 0;
158
159 while ((ElfW(Addr)) (note + 1) - start < size)
160 {
161 /* Find the NT_GNU_PROPERTY_TYPE_0 note. */
162 if (note->n_namesz == 4
163 && note->n_type == NT_GNU_PROPERTY_TYPE_0
164 && memcmp (note + 1, "GNU", 4) == 0)
165 {
166 /* Stop if we see more than one GNU property note which may
167 be generated by the older linker. */
168 if (l->l_property != lc_property_unknown)
169 return;
170
171 /* Check CET status and ISA levels now. */
172 l->l_property = lc_property_none;
173
174 /* Check for invalid property. */
175 if (note->n_descsz < 8
176 || (note->n_descsz % sizeof (ElfW(Addr))) != 0)
177 return;
178
179 /* Start and end of property array. */
180 unsigned char *ptr = (unsigned char *) (note + 1) + 4;
181 unsigned char *ptr_end = ptr + note->n_descsz;
182
183 do
184 {
185 unsigned int type = *(unsigned int *) ptr;
186 unsigned int datasz = *(unsigned int *) (ptr + 4);
187
188 /* Property type must be in ascending order. */
189 if (type < last_type)
190 return;
191
192 ptr += 8;
193 if ((ptr + datasz) > ptr_end)
194 return;
195
196 last_type = type;
197
198 int result = _dl_check_gnu_property (type, datasz, ptr,
199 feature_1_and: &feature_1_and,
200 needed_1: &needed_1,
201 isa_1_needed: &isa_1_needed);
202 if (result == -1)
203 return; /* Skip this note. */
204 else if (result == 0)
205 break; /* Stop checking. */
206
207 /* Check the next property item. */
208 ptr += ALIGN_UP (datasz, sizeof (ElfW(Addr)));
209 }
210 while ((ptr_end - ptr) >= 8);
211 }
212
213 /* NB: Note sections like .note.ABI-tag and .note.gnu.build-id are
214 aligned to 4 bytes in 64-bit ELF objects. */
215 note = ((const void *) note
216 + ELF_NOTE_NEXT_OFFSET (note->n_namesz, note->n_descsz,
217 align));
218 }
219
220 /* We get here only if there is one or no GNU property note. */
221 if (needed_1 != 0 || isa_1_needed != 0 || feature_1_and != 0)
222 {
223 l->l_property = lc_property_valid;
224 l->l_1_needed = needed_1;
225 l->l_x86_isa_1_needed = isa_1_needed;
226 l->l_x86_feature_1_and = feature_1_and;
227 }
228 else
229 l->l_property = lc_property_none;
230}
231
232static inline void __attribute__ ((unused))
233_dl_process_pt_note (struct link_map *l, int fd, const ElfW(Phdr) *ph)
234{
235 const ElfW(Nhdr) *note = (const void *) (ph->p_vaddr + l->l_addr);
236 _dl_process_property_note (l, note, size: ph->p_memsz, align: ph->p_align);
237}
238
239static inline int __attribute__ ((always_inline))
240_dl_process_gnu_property (struct link_map *l, int fd, uint32_t type,
241 uint32_t datasz, void *data)
242{
243 /* This is called on each GNU property. */
244 unsigned int needed_1 = 0;
245 unsigned int feature_1_and = 0;
246 unsigned int isa_1_needed = 0;
247 int result = _dl_check_gnu_property (type, datasz, ptr: data,
248 feature_1_and: &feature_1_and, needed_1: &needed_1,
249 isa_1_needed: &isa_1_needed);
250 if (needed_1 != 0)
251 l->l_1_needed = needed_1;
252 if (isa_1_needed != 0)
253 l->l_x86_isa_1_needed = isa_1_needed;
254 if (feature_1_and != 0)
255 l->l_x86_feature_1_and = feature_1_and;
256 if ((needed_1 | isa_1_needed | feature_1_and) != 0)
257 l->l_property = lc_property_valid;
258 else if (l->l_property == lc_property_unknown)
259 l->l_property = lc_property_none;
260 return result <= 0 ? 0 : result;
261}
262
263#endif /* _DL_PROP_H */
264

source code of glibc/sysdeps/x86/dl-prop.h