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/* AArch64 BTI functions.
Copyright (C) 2020-2024 Free Software Foundation, Inc.
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/>. */
#include <unistd.h>
#include <errno.h>
#include <libintl.h>
#include <ldsodefs.h>
#include <sys/mman.h>
/* See elf/dl-load.h. */
#ifndef MAP_COPY
# define MAP_COPY (MAP_PRIVATE | MAP_DENYWRITE)
#endif
/* Enable BTI protection for MAP. */
void
_dl_bti_protect (struct link_map *map, int fd)
{
const size_t pagesz = GLRO(dl_pagesize);
const ElfW(Phdr) *phdr;
for (phdr = map->l_phdr; phdr < &map->l_phdr[map->l_phnum]; ++phdr)
if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X))
{
size_t vstart = ALIGN_DOWN (phdr->p_vaddr, pagesz);
size_t vend = ALIGN_UP (phdr->p_vaddr + phdr->p_filesz, pagesz);
off_t off = ALIGN_DOWN (phdr->p_offset, pagesz);
void *start = (void *) (vstart + map->l_addr);
size_t len = vend - vstart;
unsigned prot = PROT_EXEC | PROT_BTI;
if (phdr->p_flags & PF_R)
prot |= PROT_READ;
if (phdr->p_flags & PF_W)
prot |= PROT_WRITE;
if (fd == -1)
/* Ignore failures for kernel mapped binaries. */
__mprotect (start, len, prot);
else
map->l_mach.bti_fail = __mmap (start, len, prot,
MAP_FIXED|MAP_COPY|MAP_FILE,
fd, off) == MAP_FAILED;
}
}
static void
bti_failed (struct link_map *l, const char *program)
{
if (program)
_dl_fatal_printf ("%s: %s: failed to turn on BTI protection\n",
program, l->l_name);
else
/* Note: the errno value is not available any more. */
_dl_signal_error (0, l->l_name, "dlopen",
N_("failed to turn on BTI protection"));
}
/* Enable BTI for L and its dependencies. */
void
_dl_bti_check (struct link_map *l, const char *program)
{
if (!GLRO(dl_aarch64_cpu_features).bti)
return;
if (l->l_mach.bti_fail)
bti_failed (l, program);
for (unsigned int i = 0; i < l->l_searchlist.r_nlist; i++)
{
struct link_map *dep = l->l_searchlist.r_list[i];
if (dep->l_mach.bti_fail)
bti_failed (dep, program);
}
}
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