52 lines
1.8 KiB
C
52 lines
1.8 KiB
C
/* Erase sensitive data from memory.
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Copyright 2022-2024 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file 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
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#include <config.h>
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/* Specification. */
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#include <string.h>
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/* Set S's bytes to C, where S has LEN bytes. The compiler will not
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optimize effects away, even if S is dead after the call. */
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void *
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memset_explicit (void *s, int c, size_t len)
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{
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#if HAVE_EXPLICIT_MEMSET
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return explicit_memset (s, c, len);
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#elif HAVE_MEMSET_S
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(void) memset_s (s, len, c, len);
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return s;
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#elif defined __GNUC__ && !defined __clang__
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memset (s, c, len);
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/* Compiler barrier. */
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__asm__ volatile ("" ::: "memory");
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return s;
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#elif defined __clang__
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memset (s, c, 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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return s;
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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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return volatile_memset (s, c, len);
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#endif
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}
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