aarch64: enable BTI at runtime

[thirdparty/glibc.git] / sysdeps / aarch64 / dl-bti.c

/* AArch64 BTI functions.
   Copyright (C) 2020 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>

static int
enable_bti (struct link_map *map, const char *program)
{
  const ElfW(Phdr) *phdr;
  unsigned prot = PROT_READ | PROT_EXEC | PROT_BTI;

  for (phdr = map->l_phdr; phdr < &map->l_phdr[map->l_phnum]; ++phdr)
    if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X))
      {
	void *start = (void *) (phdr->p_vaddr + map->l_addr);
	size_t len = phdr->p_memsz;
	if (__mprotect (start, len, prot) < 0)
	  {
	    if (program)
	      _dl_fatal_printf ("%s: mprotect failed to turn on BTI\n",
				map->l_name);
	    else
	      _dl_signal_error (errno, map->l_name, "dlopen",
				N_("mprotect failed to turn on BTI"));
	  }
      }
  return 0;
}

/* Enable BTI for L if required.  */

void
_dl_bti_check (struct link_map *l, const char *program)
{
  if (GLRO(dl_aarch64_cpu_features).bti && l->l_mach.bti)
    enable_bti (l, program);
}