1 files changed, 55 insertions, 0 deletions
diff --git a/lib/memset_explicit.c b/lib/memset_explicit.c
new file mode 100644
index 00000000000..6d21a5e8797
--- /dev/null
+++ b/lib/memset_explicit.c
@@ -0,0 +1,55 @@
+/* Erase sensitive data from memory.
+   Copyright 2022-2023 Free Software Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   This file is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* memset_s need this define */
+#if HAVE_MEMSET_S
+# define __STDC_WANT_LIB_EXT1__ 1
+#endif
+
+#include <string.h>
+
+/* Set S's bytes to C, where S has LEN bytes.  The compiler will not
+   optimize effects away, even if S is dead after the call.  */
+void *
+memset_explicit (void *s, int c, size_t len)
+{
+#if HAVE_EXPLICIT_MEMSET
+  return explicit_memset (s, c, len);
+#elif HAVE_MEMSET_S
+  (void) memset_s (s, len, c, len);
+  return s;
+#elif defined __GNUC__ && !defined __clang__
+  memset (s, c, len);
+  /* Compiler barrier.  */
+  __asm__ volatile ("" ::: "memory");
+  return s;
+#elif defined __clang__
+  memset (s, c, len);
+  /* Compiler barrier.  */
+  /* With asm ("" ::: "memory") LLVM analyzes uses of 's' and finds that the
+     whole thing is dead and eliminates it.  Use 'g' to work around this
+     problem.  See <https://bugs.llvm.org/show_bug.cgi?id=15495#c11>.  */
+  __asm__ volatile ("" : : "g"(s) : "memory");
+  return s;
+#else
+  /* Invoke memset through a volatile function pointer.  This defeats compiler
+     optimizations.  */
+  void * (* const volatile volatile_memset) (void *, int, size_t) = memset;
+  return volatile_memset (s, c, len);
+#endif
+}