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-rw-r--r--lib/explicit_bzero.c69
1 files changed, 11 insertions, 58 deletions
diff --git a/lib/explicit_bzero.c b/lib/explicit_bzero.c
index ad0bfd170ca..fc309f81d61 100644
--- a/lib/explicit_bzero.c
+++ b/lib/explicit_bzero.c
@@ -1,74 +1,27 @@
1/* Erasure of sensitive data, generic implementation. 1/* Erasure of sensitive data, generic implementation.
2 Copyright (C) 2016-2022 Free Software Foundation, Inc. 2 Copyright (C) 2016-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 3
5 The GNU C Library is free software; you can redistribute it and/or 4 This file is free software: you can redistribute it and/or modify
6 modify it under the terms of the GNU Lesser General Public 5 it under the terms of the GNU Lesser General Public License as
7 License as published by the Free Software Foundation; either 6 published by the Free Software Foundation; either version 2.1 of the
8 version 2.1 of the License, or (at your option) any later version. 7 License, or (at your option) any later version.
9 8
10 The GNU C Library is distributed in the hope that it will be useful, 9 This file is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of 10 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 Lesser General Public License for more details. 12 GNU Lesser General Public License for more details.
14 13
15 You should have received a copy of the GNU Lesser General Public 14 You should have received a copy of the GNU Lesser General Public License
16 License along with the GNU C Library; if not, see 15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
17 <https://www.gnu.org/licenses/>. */
18 16
19/* An assembler implementation of explicit_bzero can be created as an 17#include <config.h>
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/* memset_s need this define */
29#if HAVE_MEMSET_S
30# define __STDC_WANT_LIB_EXT1__ 1
31#endif
32 18
33#include <string.h> 19#include <string.h>
34 20
35#if defined _WIN32 && !defined __CYGWIN__
36# define WIN32_LEAN_AND_MEAN
37# include <windows.h>
38#endif
39
40#if _LIBC
41/* glibc-internal users use __explicit_bzero_chk, and explicit_bzero
42 redirects to that. */
43# undef explicit_bzero
44#endif
45
46/* Set LEN bytes of S to 0. The compiler will not delete a call to 21/* Set LEN bytes of S to 0. The compiler will not delete a call to
47 this function, even if S is dead after the call. */ 22 this function, even if S is dead after the call. */
48void 23void
49explicit_bzero (void *s, size_t len) 24explicit_bzero (void *s, size_t len)
50{ 25{
51#if defined _WIN32 && !defined __CYGWIN__ 26 memset_explicit (s, 0, len);
52 (void) SecureZeroMemory (s, len);
53#elif HAVE_EXPLICIT_MEMSET
54 explicit_memset (s, '\0', len);
55#elif HAVE_MEMSET_S
56 (void) memset_s (s, len, '\0', len);
57#elif defined __GNUC__ && !defined __clang__
58 memset (s, '\0', len);
59 /* Compiler barrier. */
60 asm volatile ("" ::: "memory");
61#elif defined __clang__
62 memset (s, '\0', len);
63 /* Compiler barrier. */
64 /* With asm ("" ::: "memory") LLVM analyzes uses of 's' and finds that the
65 whole thing is dead and eliminates it. Use 'g' to work around this
66 problem. See <https://bugs.llvm.org/show_bug.cgi?id=15495#c11>. */
67 __asm__ volatile ("" : : "g"(s) : "memory");
68#else
69 /* Invoke memset through a volatile function pointer. This defeats compiler
70 optimizations. */
71 void * (* const volatile volatile_memset) (void *, int, size_t) = memset;
72 (void) volatile_memset (s, '\0', len);
73#endif
74} 27}