1 /* AArch64 BTI functions.
2 Copyright (C) 2020-2021 Free Software Foundation, Inc.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18 #include <unistd.h>
19 #include <errno.h>
20 #include <libintl.h>
21 #include <ldsodefs.h>
22 #include <sys/mman.h>
23
24 /* See elf/dl-load.h. */
25 #ifndef MAP_COPY
26 # define MAP_COPY (MAP_PRIVATE | MAP_DENYWRITE)
27 #endif
28
29 /* Enable BTI protection for MAP. */
30
31 void
_dl_bti_protect(struct link_map * map,int fd)32 _dl_bti_protect (struct link_map *map, int fd)
33 {
34 const size_t pagesz = GLRO(dl_pagesize);
35 const ElfW(Phdr) *phdr;
36
37 for (phdr = map->l_phdr; phdr < &map->l_phdr[map->l_phnum]; ++phdr)
38 if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X))
39 {
40 size_t vstart = ALIGN_DOWN (phdr->p_vaddr, pagesz);
41 size_t vend = ALIGN_UP (phdr->p_vaddr + phdr->p_filesz, pagesz);
42 off_t off = ALIGN_DOWN (phdr->p_offset, pagesz);
43 void *start = (void *) (vstart + map->l_addr);
44 size_t len = vend - vstart;
45
46 unsigned prot = PROT_EXEC | PROT_BTI;
47 if (phdr->p_flags & PF_R)
48 prot |= PROT_READ;
49 if (phdr->p_flags & PF_W)
50 prot |= PROT_WRITE;
51
52 if (fd == -1)
53 /* Ignore failures for kernel mapped binaries. */
54 __mprotect (start, len, prot);
55 else
56 map->l_mach.bti_fail = __mmap (start, len, prot,
57 MAP_FIXED|MAP_COPY|MAP_FILE,
58 fd, off) == MAP_FAILED;
59 }
60 }
61
62
63 static void
bti_failed(struct link_map * l,const char * program)64 bti_failed (struct link_map *l, const char *program)
65 {
66 if (program)
67 _dl_fatal_printf ("%s: %s: failed to turn on BTI protection\n",
68 program, l->l_name);
69 else
70 /* Note: the errno value is not available any more. */
71 _dl_signal_error (0, l->l_name, "dlopen",
72 N_("failed to turn on BTI protection"));
73 }
74
75
76 /* Enable BTI for L and its dependencies. */
77
78 void
_dl_bti_check(struct link_map * l,const char * program)79 _dl_bti_check (struct link_map *l, const char *program)
80 {
81 if (!GLRO(dl_aarch64_cpu_features).bti)
82 return;
83
84 if (l->l_mach.bti_fail)
85 bti_failed (l, program);
86
87 unsigned int i = l->l_searchlist.r_nlist;
88 while (i-- > 0)
89 {
90 struct link_map *dep = l->l_initfini[i];
91 if (dep->l_mach.bti_fail)
92 bti_failed (dep, program);
93 }
94 }
95