debug/explicit_bzero_chk.c

   1 /* Generic implementation of __explicit_bzero_chk.
   2    Copyright (C) 1991-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Torbjorn Granlund (tege@sics.se).
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 /* This is the generic definition of __explicit_bzero_chk.  The
  21    __explicit_bzero_chk symbol is used as the implementation of
  22    explicit_bzero throughout glibc.  If this file is overriden by an
  23    architecture, both __explicit_bzero_chk and
  24    __explicit_bzero_chk_internal have to be defined (the latter not as
  25    an IFUNC).  */
  26
  27 #include <string.h>
  28
  29 void
  30 __explicit_bzero_chk (void *dst, size_t len, size_t dstlen)
  31 {
  32   /* Inline __memset_chk to avoid a PLT reference to __memset_chk.  */
  33   if (__glibc_unlikely (dstlen < len))
  34     __chk_fail ();
  35   memset (dst, '\0', len);
  36   /* Compiler barrier.  */
  37   asm volatile ("" ::: "memory");
  38 }
  39
  40 /* libc-internal references use the hidden
  41    __explicit_bzero_chk_internal symbol.  This is necessary if
  42    __explicit_bzero_chk is implemented as an IFUNC because some
  43    targets do not support hidden references to IFUNC symbols.  */
  44 strong_alias (__explicit_bzero_chk, __explicit_bzero_chk_internal)