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7ebd114211
Use PROT_READ and PROT_WRITE according to the load segment p_flags when adding PROT_BTI. This is before processing relocations which may drop PROT_BTI in case of textrels. Executable stacks are not protected via PROT_BTI either. PROT_BTI is hardening in case memory corruption happened, it's value is reduced if there is writable and executable memory available so missing it on such memory is fine, but we should respect the p_flags and should not drop PROT_WRITE.
62 lines
1.7 KiB
C
62 lines
1.7 KiB
C
/* AArch64 BTI functions.
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Copyright (C) 2020 Free Software Foundation, Inc.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <unistd.h>
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#include <errno.h>
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#include <libintl.h>
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#include <ldsodefs.h>
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static int
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enable_bti (struct link_map *map, const char *program)
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{
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const ElfW(Phdr) *phdr;
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unsigned prot;
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for (phdr = map->l_phdr; phdr < &map->l_phdr[map->l_phnum]; ++phdr)
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if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X))
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{
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void *start = (void *) (phdr->p_vaddr + map->l_addr);
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size_t len = phdr->p_memsz;
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prot = PROT_EXEC | PROT_BTI;
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if (phdr->p_flags & PF_R)
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prot |= PROT_READ;
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if (phdr->p_flags & PF_W)
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prot |= PROT_WRITE;
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if (__mprotect (start, len, prot) < 0)
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{
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if (program)
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_dl_fatal_printf ("%s: mprotect failed to turn on BTI\n",
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map->l_name);
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else
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_dl_signal_error (errno, map->l_name, "dlopen",
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N_("mprotect failed to turn on BTI"));
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}
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}
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return 0;
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}
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/* Enable BTI for L if required. */
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void
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_dl_bti_check (struct link_map *l, const char *program)
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{
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if (GLRO(dl_aarch64_cpu_features).bti && l->l_mach.bti)
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enable_bti (l, program);
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}
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