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75 lines
2.5 KiB
C
75 lines
2.5 KiB
C
/* Erasure of sensitive data, generic implementation.
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Copyright (C) 2016-2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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/* An assembler implementation of explicit_bzero can be created as an
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assembler alias of an optimized bzero implementation.
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Architecture-specific implementations also need to define
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__explicit_bzero_chk. */
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#if !_LIBC
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# include <config.h>
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#endif
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/* memset_s need this define */
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#if HAVE_MEMSET_S
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# define __STDC_WANT_LIB_EXT1__ 1
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#endif
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#include <string.h>
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#if defined _WIN32 && !defined __CYGWIN__
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# define WIN32_LEAN_AND_MEAN
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# include <windows.h>
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#endif
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#if _LIBC
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/* glibc-internal users use __explicit_bzero_chk, and explicit_bzero
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redirects to that. */
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# undef explicit_bzero
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#endif
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/* Set LEN bytes of S to 0. The compiler will not delete a call to
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this function, even if S is dead after the call. */
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void
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explicit_bzero (void *s, size_t len)
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{
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#if defined _WIN32 && !defined __CYGWIN__
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(void) SecureZeroMemory (s, len);
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#elif HAVE_EXPLICIT_MEMSET
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explicit_memset (s, '\0', len);
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#elif HAVE_MEMSET_S
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(void) memset_s (s, len, '\0', len);
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#elif defined __GNUC__ && !defined __clang__
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memset (s, '\0', len);
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/* Compiler barrier. */
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asm volatile ("" ::: "memory");
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#elif defined __clang__
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memset (s, '\0', len);
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/* Compiler barrier. */
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/* With asm ("" ::: "memory") LLVM analyzes uses of 's' and finds that the
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whole thing is dead and eliminates it. Use 'g' to work around this
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problem. See <https://bugs.llvm.org/show_bug.cgi?id=15495#c11>. */
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__asm__ volatile ("" : : "g"(s) : "memory");
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#else
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/* Invoke memset through a volatile function pointer. This defeats compiler
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optimizations. */
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void * (* const volatile volatile_memset) (void *, int, size_t) = memset;
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(void) volatile_memset (s, '\0', len);
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#endif
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}
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