lib/explicit_bzero.c

   1 /* Erasure of sensitive data, generic implementation.
   2    Copyright (C) 2016-2019 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 /* An assembler implementation of explicit_bzero can be created as an
  20    assembler alias of an optimized bzero implementation.
  21    Architecture-specific implementations also need to define
  22    __explicit_bzero_chk.  */
  23
  24 #if !_LIBC
  25 # include <config.h>
  26 #endif
  27
  28 #include <string.h>
  29
  30 #if _LIBC
  31 /* glibc-internal users use __explicit_bzero_chk, and explicit_bzero
  32    redirects to that.  */
  33 # undef explicit_bzero
  34 #endif
  35
  36 /* Set LEN bytes of S to 0.  The compiler will not delete a call to
  37    this function, even if S is dead after the call.  */
  38 void
  39 explicit_bzero (void *s, size_t len)
  40 {
  41 #ifdef HAVE_EXPLICIT_MEMSET
  42   explicit_memset (s, 0, len);
  43 #else
  44   memset (s, '\0', len);
  45 # if defined __GNUC__ && !defined __clang__
  46   /* Compiler barrier.  */
  47   asm volatile ("" ::: "memory");
  48 # endif
  49 #endif
  50 }