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[PATCH 1/3] New string function explicit_bzero (from OpenBSD).


explicit_bzero(s, n) is the same as memset(s, 0, n), except that the
compiler is not allowed to delete a call to explicit_bzero even if the
memory pointed to by 's' is dead after the call.  We achieve this effect
by defining it to call memset() and then a second function,

    extern void __glibc_read_memory (const void *, size_t)
       __attribute_noinline__;

which does nothing -- but the compiler is prevented from knowing that
it does nothing, and so the pointer "escapes" and the memory is not
treated as dead.  (Concretely, __glibc_read_memory is forced
out-of-line, defined in a file containing nothing else, and comments
in both string/read_memory.c and string/Makefile document that it must
not be subject to link-time optimization.)

There are two new tests: test-explicit_bzero.c verifies the
visible semantics in the same way as the existing test-bzero.c,
and tst-xbzero-opt.c verifies the not-being-optimized-out property.
The latter is conceptually based on a test written by Matthew Dempsky
for the OpenBSD regression suite.

	* string/explicit_bzero.c, string/read_memory.c: New routines.
	* string/test-explicit_bzero.c, string/tst-xbzero-opt.c: New tests.
	* string/Makefile (routines, strop-tests, tests): Add them.
	* string/test-memset.c: Add ifdeffage for testing explicit_bzero.

	* string/string.h [__USE_MISC]: Declare explicit_bzero and
        __glibc_read_memory.
        * include/string.h: Declare __internal_glibc_read_memory,
        __explicit_bzero, and __internal_explicit_bzero.

	* manual/string.texi: Document explicit_bzero.

	* string/Versions [GLIBC_2.25]: Add explicit_bzero,
        __explicit_bzero, and __glibc_read_memory.
	* sysdeps/arm/nacl/libc.abilist
	* sysdeps/unix/sysv/linux/aarch64/libc.abilist
	* sysdeps/unix/sysv/linux/alpha/libc.abilist
	* sysdeps/unix/sysv/linux/arm/libc.abilist
	* sysdeps/unix/sysv/linux/hppa/libc.abilist
	* sysdeps/unix/sysv/linux/i386/libc.abilist
	* sysdeps/unix/sysv/linux/ia64/libc.abilist
	* sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
	* sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
	* sysdeps/unix/sysv/linux/microblaze/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
	* sysdeps/unix/sysv/linux/nios2/libc.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
	* sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
	* sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
	* sysdeps/unix/sysv/linux/sh/libc.abilist
	* sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
	* sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
	* sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist
	* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
	* sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist:
	Add entries for explicit_bzero, __explicit_bzero,
        and __glibc_read_memory.
---
 include/string.h                                   |  12 +
 manual/string.texi                                 | 124 ++++++++
 string/Makefile                                    |  12 +-
 string/Versions                                    |  10 +
 string/explicit_bzero.c                            |  33 ++
 string/read_memory.c                               |  41 +++
 string/string.h                                    |   9 +
 string/test-explicit_bzero.c                       |  20 ++
 string/test-memset.c                               |  10 +-
 string/tst-xbzero-opt.c                            | 348 +++++++++++++++++++++
 sysdeps/arm/nacl/libc.abilist                      |   3 +
 sysdeps/unix/sysv/linux/aarch64/libc.abilist       |   3 +
 sysdeps/unix/sysv/linux/alpha/libc.abilist         |   3 +
 sysdeps/unix/sysv/linux/arm/libc.abilist           |   3 +
 sysdeps/unix/sysv/linux/hppa/libc.abilist          |   3 +
 sysdeps/unix/sysv/linux/i386/libc.abilist          |   3 +
 sysdeps/unix/sysv/linux/ia64/libc.abilist          |   3 +
 sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist |   3 +
 sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist   |   3 +
 sysdeps/unix/sysv/linux/microblaze/libc.abilist    |   3 +
 .../unix/sysv/linux/mips/mips32/fpu/libc.abilist   |   3 +
 .../unix/sysv/linux/mips/mips32/nofpu/libc.abilist |   3 +
 .../unix/sysv/linux/mips/mips64/n32/libc.abilist   |   3 +
 .../unix/sysv/linux/mips/mips64/n64/libc.abilist   |   3 +
 sysdeps/unix/sysv/linux/nios2/libc.abilist         |   3 +
 .../sysv/linux/powerpc/powerpc32/fpu/libc.abilist  |   3 +
 .../linux/powerpc/powerpc32/nofpu/libc.abilist     |   3 +
 .../sysv/linux/powerpc/powerpc64/libc-le.abilist   |   3 +
 .../unix/sysv/linux/powerpc/powerpc64/libc.abilist |   3 +
 sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist  |   3 +
 sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist  |   3 +
 sysdeps/unix/sysv/linux/sh/libc.abilist            |   3 +
 sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist |   3 +
 sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist |   3 +
 .../sysv/linux/tile/tilegx/tilegx32/libc.abilist   |   3 +
 .../sysv/linux/tile/tilegx/tilegx64/libc.abilist   |   3 +
 sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist  |   3 +
 sysdeps/unix/sysv/linux/x86_64/64/libc.abilist     |   3 +
 sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist    |   3 +
 39 files changed, 702 insertions(+), 4 deletions(-)
 create mode 100644 string/explicit_bzero.c
 create mode 100644 string/read_memory.c
 create mode 100644 string/test-explicit_bzero.c
 create mode 100644 string/tst-xbzero-opt.c

diff --git a/include/string.h b/include/string.h
index e145bfd..4185521 100644
--- a/include/string.h
+++ b/include/string.h
@@ -100,6 +100,18 @@ extern __typeof (memmem) __memmem;
 libc_hidden_proto (__memmem)
 libc_hidden_proto (__ffs)
 
+/* explicit_bzero is used in libcrypt.  */
+extern __typeof (explicit_bzero) __explicit_bzero;
+extern __typeof (explicit_bzero) __internal_explicit_bzero;
+libc_hidden_proto (__internal_explicit_bzero)
+extern __typeof (__glibc_read_memory) __internal_glibc_read_memory;
+libc_hidden_proto (__internal_glibc_read_memory)
+/* Honor string[23].h overrides when present.  */
+#ifdef explicit_bzero
+# define __explicit_bzero(s,n) explicit_bzero (s,n)
+# define __internal_explicit_bzero(s,n) explicit_bzero (s,n)
+#endif
+
 libc_hidden_builtin_proto (memchr)
 libc_hidden_builtin_proto (memcpy)
 libc_hidden_builtin_proto (mempcpy)
diff --git a/manual/string.texi b/manual/string.texi
index 1986357..3e1bf8d 100644
--- a/manual/string.texi
+++ b/manual/string.texi
@@ -34,6 +34,8 @@ too.
 * Search Functions::            Searching for a specific element or substring.
 * Finding Tokens in a String::  Splitting a string into tokens by looking
 				 for delimiters.
+* Erasing Sensitive Data::      Clearing memory which contains sensitive
+                                 data, after it's no longer needed.
 * strfry::                      Function for flash-cooking a string.
 * Trivial Encryption::          Obscuring data.
 * Encode Binary Data::          Encoding and Decoding of Binary Data.
@@ -2404,6 +2406,128 @@ contains no '/' bytes, then "." is returned.  The prototype for this
 function can be found in @file{libgen.h}.
 @end deftypefun
 
+@node Erasing Sensitive Data
+@section Erasing Sensitive Data
+
+It is sometimes necessary to make sure that data in memory is erased
+after use, even if no correct C program could access it again.  For
+instance, a cryptographic key should not be left in memory after the
+program is finished using it, because there might be a bug that causes
+junk data, including the key, to be revealed to the outside world.
+
+However, the C compiler knows that no correct program can access data
+after it's deallocated, so it may delete ``unnecessary'' stores that
+erase data just before deallocating it.  @code{memset}, @code{bzero},
+and a manually-written loop are all equally unreliable, and
+@code{volatile} will not help.
+
+For this situation, @theglibc{} provides @code{explicit_bzero}.  It is
+functionally identical to @code{bzero}, but the C compiler will not
+treat any use of it as unnecessary.
+
+@comment string.h
+@comment BSD
+@deftypefun void explicit_bzero (void *@var{block}, size_t @var{len})
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+
+@code{explicit_bzero} writes zero into each of the first @var{len}
+bytes of the object beginning at @var{block}, just as @code{bzero}
+would.  The zeroes are always written, even if the object is about to
+be deallocated.  (Variables on the stack are deallocated when they go
+out of scope; heap blocks created by @code{malloc} are deallocated
+when passed to @code{free}.)
+
+@smallexample
+@group
+#include <string.h>
+
+extern void encrypt (const char *key, const char *in,
+                     char *out, size_t n);
+extern void genkey (const char *phrase, char *key);
+
+void encrypt_with_phrase (const char *phrase, const char *in,
+                          char *out, size_t n)
+@{
+  char key[16];
+  genkey (phrase, key);
+  encrypt (key, in, out, n);
+  explicit_bzero (key, 16);
+@}
+@end group
+@end smallexample
+
+@noindent
+If @code{bzero} or @code{memset} had been used in this function, the C
+compiler might remove it as unnecessary, but it will not do this with
+@code{explicit_bzero}.
+
+@strong{Warning:} The @emph{only} optimization disabled by
+@code{explicit_bzero} is removal of ``unnecessary'' writes to memory.
+In all other respects, the compiler is allowed to optimize as it would
+for @code{memset}.  For instance, it may replace the function call
+with inline memory writes, and it may deduce that @var{block} cannot
+be a null pointer.
+
+@strong{Warning:} The compiler may make copies of any object, or parts
+of it, in temporary storage areas, such as registers and ``scratch''
+stack space.  @code{explicit_bzero} does not erase copies of sensitive
+data.  At present, there is no way to prevent temporary copies from
+being made, nor to arrange for them to be erased.  Declaring sensitive
+variables as @code{volatile} will make the problem @emph{worse}; the
+compiler needs to make @emph{more} copies of @code{volatile} data in
+order to operate on it correctly.
+
+@strong{Warning:} In some situations, using @code{explicit_bzero} will
+@emph{cause} creation of an additional copy of sensitive data, and
+only that copy will be cleared:
+
+@smallexample
+@group
+#include <string.h>
+
+struct key
+@{
+  unsigned long long low;
+  unsigned long long high;
+@};
+
+struct key get_key (void);
+void use_key (struct key);
+
+void
+with_clear (void)
+@{
+  struct key k;
+  k = get_key ();
+  use_key (k);
+  explicit_bzero (&k, sizeof (k));
+@}
+@end group
+@end smallexample
+
+@noindent
+Without the call to @code{explicit_bzero}, @var{k} might not need to
+be stored in memory: perhaps its value could be returned from
+@code{get_key} and passed to @code{use_key} using only CPU registers.
+@code{explicit_bzero} operates on memory, so the compiler has to make
+a copy of @var{k} in memory for it, and the original in the CPU
+registers remains intact.  This can occur for any variable whose
+address is only taken in a call to @code{explicit_bzero}, even if it
+might seem ``too large'' to be stored in registers.
+
+There is currently no way to avoid this problem.  @Theglibc{}'s
+implementation of @code{explicit_bzero} contains a hack that can
+sometimes prevent the sensitive data from being copied into memory,
+but it is not guaranteed to work, and the original in the CPU
+registers is unaffected.  Again, declaring sensitive variables as
+@code{volatile} will make the problem worse.
+
+@strong{Portability Note:} This function first appeared in OpenBSD 5.5
+and has not been standardized.  @Theglibc{} declares this function in
+@file{string.h}, but on other systems it may be in @file{strings.h}
+instead.
+@end deftypefun
+
 @node strfry
 @section strfry
 
diff --git a/string/Makefile b/string/Makefile
index 69d3f80..0b6486e 100644
--- a/string/Makefile
+++ b/string/Makefile
@@ -41,20 +41,26 @@ routines	:= strcat strchr strcmp strcoll strcpy strcspn		\
 				     addsep replace)			\
 		   envz basename					\
 		   strcoll_l strxfrm_l string-inlines memrchr		\
-		   xpg-strerror strerror_l
+		   xpg-strerror strerror_l explicit_bzero
+
+# Attention future hackers trying to enable link-time optimization for
+# glibc: this file *must not* be subject to LTO.  It is added separately
+# to 'routines' to document this.  See comments in this file for details.
+routines	+= read_memory
 
 strop-tests	:= memchr memcmp memcpy memmove mempcpy memset memccpy	\
 		   stpcpy stpncpy strcat strchr strcmp strcpy strcspn	\
 		   strlen strncmp strncpy strpbrk strrchr strspn memmem	\
 		   strstr strcasestr strnlen strcasecmp strncasecmp	\
-		   strncat rawmemchr strchrnul bcopy bzero memrchr
+		   strncat rawmemchr strchrnul bcopy bzero memrchr	\
+		   explicit_bzero
 tests		:= tester inl-tester noinl-tester testcopy test-ffs	\
 		   tst-strlen stratcliff tst-svc tst-inlcall		\
 		   bug-strncat1 bug-strspn1 bug-strpbrk1 tst-bswap	\
 		   tst-strtok tst-strxfrm bug-strcoll1 tst-strfry	\
 		   bug-strtok1 $(addprefix test-,$(strop-tests))	\
 		   bug-envz1 tst-strxfrm2 tst-endian tst-svc2		\
-		   tst-strtok_r bug-strcoll2 tst-cmp
+		   tst-strtok_r bug-strcoll2 tst-cmp tst-xbzero-opt
 
 xtests = tst-strcoll-overflow
 
diff --git a/string/Versions b/string/Versions
index 475c1fd..4f434f3 100644
--- a/string/Versions
+++ b/string/Versions
@@ -82,4 +82,14 @@ libc {
   }
   GLIBC_2.24 {
   }
+  GLIBC_2.25 {
+    # used by inlines in bits/string2.h and bits/string3.h
+    __glibc_read_memory;
+
+    # used by libcrypt
+    __explicit_bzero;
+
+    # e*
+    explicit_bzero;
+  }
 }
diff --git a/string/explicit_bzero.c b/string/explicit_bzero.c
new file mode 100644
index 0000000..6c3dc9a
--- /dev/null
+++ b/string/explicit_bzero.c
@@ -0,0 +1,33 @@
+/* Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library 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.
+
+   The GNU C Library 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 the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <features.h>
+#undef __USE_STRING_INLINES
+#define __NO_STRING_INLINES
+#include <string.h>
+
+/* Set LEN bytes of S to 0.  The compiler will not delete a call to
+   this function, even if S is dead after the call.  */
+void
+__internal_explicit_bzero (void *s, size_t len)
+{
+  memset (s, '\0', len);
+  __internal_glibc_read_memory (s, len);
+}
+libc_hidden_def (__internal_explicit_bzero)
+strong_alias (__internal_explicit_bzero, __explicit_bzero)
+weak_alias (__internal_explicit_bzero, explicit_bzero)
diff --git a/string/read_memory.c b/string/read_memory.c
new file mode 100644
index 0000000..c4a5990
--- /dev/null
+++ b/string/read_memory.c
@@ -0,0 +1,41 @@
+/* Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library 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.
+
+   The GNU C Library 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 the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+
+/* This function is an optimization fence.  It doesn't do anything
+   itself, but calls to it prevent calls to explicit_bzero from being
+   optimized away.  In order to achieve this effect, this function
+   must never, under any circumstances, be inlined or subjected to
+   inter-procedural optimization.  string.h declares this function
+   with attributes that, in conjunction with the no-op asm insert, are
+   sufficient to prevent problems in the current (2016) generation of
+   compilers, but *only if* this file is *not* compiled with -flto.
+   At present, this is not an issue since glibc is never compiled with
+   -flto, but should that ever change, this file must be excepted.
+
+   The 'volatile' below is technically not necessary but is included
+   for explicitness.  */
+
+void
+internal_function
+__internal_glibc_read_memory(const void *s, size_t len)
+{
+  asm volatile ("");
+}
+libc_hidden_def (__internal_glibc_read_memory)
+strong_alias (__internal_glibc_read_memory, __glibc_read_memory)
diff --git a/string/string.h b/string/string.h
index 57deaa4..682661a 100644
--- a/string/string.h
+++ b/string/string.h
@@ -455,6 +455,15 @@ extern void bcopy (const void *__src, void *__dest, size_t __n)
 /* Set N bytes of S to 0.  */
 extern void bzero (void *__s, size_t __n) __THROW __nonnull ((1));
 
+/* As bzero, but the compiler will not delete a call to this
+   function, even if S is dead after the call.  */
+extern void explicit_bzero (void *__s, size_t __n) __THROW __nonnull ((1));
+
+/* Optimization fence, used by bits/string2.h and bits/string3.h
+   inline versions of explicit_bzero.  */
+extern void __glibc_read_memory (const void *__s, size_t __n)
+     __THROW __nonnull ((1)) __attribute_noinline__;
+
 /* Compare N bytes of S1 and S2 (same as memcmp).  */
 extern int bcmp (const void *__s1, const void *__s2, size_t __n)
      __THROW __attribute_pure__ __nonnull ((1, 2));
diff --git a/string/test-explicit_bzero.c b/string/test-explicit_bzero.c
new file mode 100644
index 0000000..5a4543b
--- /dev/null
+++ b/string/test-explicit_bzero.c
@@ -0,0 +1,20 @@
+/* Test and measure explicit_bzero.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library 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.
+
+   The GNU C Library 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 the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+#define TEST_EXPLICIT_BZERO
+#define TEST_BZERO
+#include "test-memset.c"
diff --git a/string/test-memset.c b/string/test-memset.c
index fee3bdf..7ca4f20 100644
--- a/string/test-memset.c
+++ b/string/test-memset.c
@@ -19,7 +19,11 @@
 
 #define TEST_MAIN
 #ifdef TEST_BZERO
-# define TEST_NAME "bzero"
+# ifdef TEST_EXPLICIT_BZERO
+#  define TEST_NAME "explicit_bzero"
+# else
+#  define TEST_NAME "bzero"
+# endif
 #else
 # ifndef WIDE
 #  define TEST_NAME "memset"
@@ -56,7 +60,11 @@ void builtin_bzero (char *, size_t);
 
 IMPL (simple_bzero, 0)
 IMPL (builtin_bzero, 0)
+#ifdef TEST_EXPLICIT_BZERO
+IMPL (explicit_bzero, 1)
+#else
 IMPL (bzero, 1)
+#endif
 
 void
 simple_bzero (char *s, size_t n)
diff --git a/string/tst-xbzero-opt.c b/string/tst-xbzero-opt.c
new file mode 100644
index 0000000..da35669
--- /dev/null
+++ b/string/tst-xbzero-opt.c
@@ -0,0 +1,348 @@
+/* Test that explicit_bzero block clears are not optimized out.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library 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.
+
+   The GNU C Library 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 the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This test is conceptually based on a test designed by Matthew
+   Dempsky for the OpenBSD regression suite:
+   <openbsd>/src/regress/lib/libc/explicit_bzero/explicit_bzero.c.
+   The basic idea is, we have a function that contains a
+   block-clearing operation (not necessarily explicit_bzero), after
+   which the block is dead, in the compiler-jargon sense.  Execute
+   that function from a signal handler running on an alternative
+   signal stack.  Then we have another pointer to the memory region
+   affected by the block clear -- namely, the sigaltstack buffer --
+   and can find out whether it actually happened.
+
+   The OpenBSD test cautions that some operating systems (e.g. Solaris
+   and OSX) wipe the signal stack upon returning to the normal stack,
+   so the test has to happen while still executing on the signal
+   stack.  This, of course, means that the buffer might be clobbered
+   by normal stack operations after the function with the block clear
+   returns (it has to return, so that the block is truly dead).  The
+   most straightforward way to deal with this is to have a large block
+   containing several copies of a byte pattern that is unlikely to
+   occur by chance, and check whether _any_ of them survives.  */
+
+#define _GNU_SOURCE 1
+
+#include <errno.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* test-skeleton.c unconditionally sets stdout to be unbuffered.
+   vfprintf allocates a great deal of memory on the stack if called
+   with an unbuffered FILE*, overflowing the alt-stack.  do_test
+   therefore resets stdout to fully buffered, and we use this wrapper
+   exclusively for output.  */
+static void
+xprintf (const char *msg, ...)
+{
+  va_list ap;
+  va_start (ap, msg);
+  vfprintf (stdout, msg, ap);
+  va_end (ap);
+  fflush (stdout);
+}
+#define printf dont_use_printf_in_this_file
+
+/* The "byte pattern that is unlikely to occur by chance": the first
+   16 prime numbers (OEIS A000040).  */
+static const unsigned char test_pattern[16] =
+{
+  2, 3, 5, 7,  11, 13, 17, 19,  23, 29, 31, 37,  41, 43, 47, 53
+};
+
+#define PATTERN_SIZE (sizeof test_pattern)
+#define PATTERN_REPS 32
+#define TEST_BUFFER_SIZE (PATTERN_SIZE * PATTERN_REPS)
+
+static void
+fill_with_test_pattern (unsigned char *buf)
+{
+  for (unsigned int i = 0; i < PATTERN_REPS; i++)
+    memcpy (buf + i*PATTERN_SIZE, test_pattern, PATTERN_SIZE);
+}
+
+static unsigned int
+count_test_patterns (unsigned char *buf, size_t bufsiz)
+{
+  unsigned char *first = memmem (buf, bufsiz, test_pattern, PATTERN_SIZE);
+  if (!first)
+    return 0;
+  unsigned int cnt = 0;
+  for (unsigned int i = 0; i < PATTERN_REPS; i++)
+    {
+      unsigned char *p = first + i*PATTERN_SIZE;
+      if (p + PATTERN_SIZE - buf > bufsiz)
+        break;
+      if (memcmp (p, test_pattern, PATTERN_SIZE) == 0)
+        cnt++;
+    }
+  return cnt;
+}
+
+/* Global test state.  */
+static int failed_subtests;
+static bool this_subtest_failed;
+
+/* The signal stack is allocated with memalign.  */
+static unsigned char *signal_stack_buffer;
+#define SIGNAL_STACK_SIZE (SIGSTKSZ + TEST_BUFFER_SIZE)
+
+enum test_expectation { EXPECT_NONE, EXPECT_SOME, EXPECT_ALL };
+
+static void
+check_test_buffer (enum test_expectation expected,
+                   const char *label, const char *stage)
+{
+  unsigned int cnt = count_test_patterns (signal_stack_buffer,
+                                          SIGNAL_STACK_SIZE);
+  switch (expected)
+    {
+    case EXPECT_NONE:
+      if (cnt == 0)
+        xprintf ("PASS: %s/%s: expected 0 got %d\n", label, stage, cnt);
+      else
+        {
+          xprintf ("FAIL: %s/%s: expected 0 got %d\n", label, stage, cnt);
+          this_subtest_failed = true;
+          failed_subtests++;
+        }
+      break;
+
+    case EXPECT_SOME:
+      if (cnt > 0)
+        xprintf ("PASS: %s/%s: expected some got %d\n", label, stage, cnt);
+      else
+        {
+          xprintf ("FAIL: %s/%s: expected some got 0\n", label, stage);
+          this_subtest_failed = true;
+          failed_subtests++;
+        }
+      break;
+
+     case EXPECT_ALL:
+      if (cnt == PATTERN_REPS)
+        xprintf ("PASS: %s/%s: expected %d got %d\n", label, stage,
+                 PATTERN_REPS, cnt);
+      else
+        {
+          xprintf ("FAIL: %s/%s: expected %d got %d\n", label, stage,
+                   PATTERN_REPS, cnt);
+          this_subtest_failed = true;
+          failed_subtests++;
+        }
+      break;
+
+    default:
+      xprintf ("ERROR: %s/%s: invalid value for 'expected' = %d\n",
+               label, stage, (int)expected);
+      this_subtest_failed = true;
+      failed_subtests++;
+    }
+}
+
+/* Always check the test buffer immediately after filling it; this
+   makes externally visible side effects depend on the buffer existing
+   and having been filled in.  */
+static void
+prepare_test_buffer (unsigned char *buf, const char *label)
+{
+  fill_with_test_pattern (buf);
+  check_test_buffer (EXPECT_ALL, label, "prepare");
+
+  unsigned char *loc = memmem (signal_stack_buffer, SIGNAL_STACK_SIZE,
+                               test_pattern, PATTERN_SIZE);
+  if (loc == buf)
+      xprintf ("PASS: %s/prepare: expected buffer location %p got %p\n",
+               label, buf, loc);
+  else
+    {
+      xprintf ("FAIL: %s/prepare: expected buffer location %p got %p\n",
+               label, buf, loc);
+      this_subtest_failed = true;
+      failed_subtests++;
+    }
+}
+
+/* There are three subtests, two of which are sanity checks.
+
+   In the "no_clear" case, we don't do anything to the test buffer
+   between preparing it and letting it go out of scope, and we expect
+   to find it.  This confirms that the test buffer does get filled in
+   and we can find it from the stack buffer.  In the "ordinary_clear"
+   case, we clear it using memset, and we expect to find it.  This
+   confirms that the compiler can optimize out block clears in this
+   context; if it can't, the real test might be succeeding for the
+   wrong reason.  Finally, the "explicit_clear" case uses
+   explicit_bzero and expects _not_ to find the test buffer, which is
+   the real test.  */
+
+static void
+setup_no_clear (void)
+{
+  unsigned char buf[TEST_BUFFER_SIZE];
+  prepare_test_buffer (buf, "no clear");
+}
+
+static void
+setup_ordinary_clear (void)
+{
+  unsigned char buf[TEST_BUFFER_SIZE];
+  prepare_test_buffer (buf, "ordinary clear");
+  if (this_subtest_failed)
+    return;
+  memset (buf, 0, TEST_BUFFER_SIZE);
+}
+
+static void
+setup_explicit_clear (void)
+{
+  unsigned char buf[TEST_BUFFER_SIZE];
+  prepare_test_buffer (buf, "explicit clear");
+  if (this_subtest_failed)
+    return;
+  explicit_bzero (buf, TEST_BUFFER_SIZE);
+}
+
+struct subtest
+{
+  void (*setup_subtest) (void);
+  const char *label;
+  enum test_expectation expected;
+};
+
+static const struct subtest subtests[] =
+{
+  { setup_no_clear,       "no clear",       EXPECT_SOME },
+  { setup_ordinary_clear, "ordinary clear", EXPECT_SOME },
+  { setup_explicit_clear, "explicit clear", EXPECT_NONE },
+  { 0,                    0,                -1          }
+};
+static const struct subtest *this_subtest;
+
+/* This function is called as a signal handler.  The signal is
+   triggered by a call to sigsuspend, therefore it is safe to do
+   non-async-signal-safe things within this function.  */
+static void
+do_subtest (int signo __attribute__ ((unused)))
+{
+  this_subtest->setup_subtest ();
+  if (!this_subtest_failed)
+    check_test_buffer (this_subtest->expected, this_subtest->label, "test");
+}
+
+static int
+do_test (void)
+{
+  /* test-skeleton.c unconditionally sets stdout to be unbuffered.
+     vfprintf allocates a great deal of memory on the stack if called
+     with an unbuffered FILE*, overflowing the alt-stack.  Reset stdout
+     to fully buffered to prevent this.  */
+  if (setvbuf (stdout, 0, _IOFBF, 0))
+    {
+      xprintf ("ERROR: restoring stdout buffering: %s\n", strerror (errno));
+      return 2;
+    }
+
+  size_t page_alignment = sysconf (_SC_PAGESIZE);
+  if (page_alignment < sizeof (void *))
+    page_alignment = sizeof (void *);
+
+  void *p;
+  int err = posix_memalign (&p, page_alignment, SIGNAL_STACK_SIZE);
+  if (err || !p)
+    {
+      xprintf ("ERROR: allocating alt stack: %s\n", strerror (err));
+      return 2;
+    }
+  signal_stack_buffer = p;
+
+  /* This program will malfunction if it receives SIGUSR1 signals at any
+     time other than when it's just sent one to itself.  Therefore, keep
+     it blocked most of the time.  */
+  sigset_t normal_mask;
+  sigset_t sigsusp_mask;
+  sigemptyset (&normal_mask);
+  sigaddset (&normal_mask, SIGUSR1);
+  if (sigprocmask (SIG_BLOCK, &normal_mask, &sigsusp_mask))
+    {
+      xprintf ("ERROR: block(SIGUSR1): %s\n", strerror (errno));
+      return 2;
+    }
+  /* But ensure that SIGUSR1 is _not_ blocked during calls to
+     sigsuspend, even if the invoking process blocked it.  */
+  sigdelset (&sigsusp_mask, SIGUSR1);
+
+  stack_t ss;
+  ss.ss_sp    = signal_stack_buffer;
+  ss.ss_flags = 0;
+  ss.ss_size  = SIGNAL_STACK_SIZE;
+  if (sigaltstack (&ss, 0))
+    {
+      xprintf ("ERROR: sigaltstack: %s\n", strerror (errno));
+      return 2;
+    }
+
+  struct sigaction sa;
+  sa.sa_mask = normal_mask;
+  sa.sa_handler = do_subtest;
+  sa.sa_flags = SA_RESTART | SA_ONSTACK;
+  if (sigaction (SIGUSR1, &sa, 0))
+    {
+      xprintf ("ERROR: sigaction(SIGUSR1): %s\n", strerror (errno));
+      return 2;
+    }
+
+  /* We use kill instead of raise, because raise may internally modify
+     the signal mask.  */
+  pid_t self = getpid ();
+
+  this_subtest = subtests;
+  while (this_subtest->label)
+    {
+      this_subtest_failed = false;
+
+      /* Completely clear the signal stack between tests, so that junk
+         from previous tests cannot interfere with the current one.  */
+      memset (signal_stack_buffer, 0, SIGNAL_STACK_SIZE);
+
+      /* Raise SIGUSR1, then call sigsuspend with a mask that unblocks
+         SIGUSR1.  This will trigger do_subtest to run _once_ on the
+         alternative stack, at the point of the sigsuspend.  */
+      if (kill (self, SIGUSR1))
+        {
+          xprintf ("ERROR: raise(SIGUSR1): %s\n", strerror (errno));
+          return 2;
+        }
+      /* The return value of sigsuspend is not meaningful.  */
+      sigsuspend (&sigsusp_mask);
+
+      this_subtest++;
+    }
+
+  return failed_subtests ? 1 : 0;
+}
+
+#undef printf
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/sysdeps/arm/nacl/libc.abilist b/sysdeps/arm/nacl/libc.abilist
index 807e43d..b074374 100644
--- a/sysdeps/arm/nacl/libc.abilist
+++ b/sysdeps/arm/nacl/libc.abilist
@@ -1843,6 +1843,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 gnu_dev_major F
 GLIBC_2.25 gnu_dev_makedev F
 GLIBC_2.25 gnu_dev_minor F
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
index 77accdf..e265325 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@@ -2090,6 +2090,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
index 659b7fc..393dd4c 100644
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@@ -2001,6 +2001,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/arm/libc.abilist b/sysdeps/unix/sysv/linux/arm/libc.abilist
index 8bc979a..b92eccb 100644
--- a/sysdeps/unix/sysv/linux/arm/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/libc.abilist
@@ -91,6 +91,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
index 299b705..3b1661d 100644
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@@ -1855,6 +1855,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index f00345f..452e013 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -2013,6 +2013,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/ia64/libc.abilist b/sysdeps/unix/sysv/linux/ia64/libc.abilist
index e5fcf88..0196234 100644
--- a/sysdeps/unix/sysv/linux/ia64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/ia64/libc.abilist
@@ -1877,6 +1877,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
index 8f382f6..d6e0e16 100644
--- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
@@ -92,6 +92,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
index 320b7fe..c3a5f24 100644
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@@ -1969,6 +1969,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/microblaze/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/libc.abilist
index 21b1426..fa72a0d 100644
--- a/sysdeps/unix/sysv/linux/microblaze/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/libc.abilist
@@ -2090,6 +2090,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
index 5c4b596..03d3c0c 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@@ -1944,6 +1944,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
index 001fa6c..a1c9cd2 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
@@ -1942,6 +1942,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
index 2d87001..a8671ba 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@@ -1940,6 +1940,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
index aa1ee66..e71283f 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@@ -1935,6 +1935,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/nios2/libc.abilist b/sysdeps/unix/sysv/linux/nios2/libc.abilist
index 2471d68..f92545c 100644
--- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
+++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
@@ -2131,6 +2131,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
index 4b0cde8..d8427ca 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@@ -1973,6 +1973,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
index 0557c16..fa26199 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
@@ -1978,6 +1978,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist
index 821384e..73488a4 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist
@@ -2178,6 +2178,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
index c40a3f1..ac9cc69 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
@@ -92,6 +92,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
index 5b39a60..933a00a 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@@ -1973,6 +1973,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
index a9db32f..eb74169 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@@ -1874,6 +1874,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/sh/libc.abilist b/sysdeps/unix/sysv/linux/sh/libc.abilist
index 294af0a..37aded2 100644
--- a/sysdeps/unix/sysv/linux/sh/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/libc.abilist
@@ -1859,6 +1859,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
index 32747bd..5b7c54e 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@@ -1965,6 +1965,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
index b0ac4d4..4854351 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@@ -1903,6 +1903,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist b/sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
index 4d92d81..18f61ba 100644
--- a/sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
@@ -2097,6 +2097,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist b/sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
index a68aef7..53a0db1 100644
--- a/sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
@@ -2097,6 +2097,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist b/sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist
index 4d92d81..18f61ba 100644
--- a/sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist
+++ b/sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist
@@ -2097,6 +2097,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index b8623fc..d4add67 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -1854,6 +1854,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index a61d874..18717fa 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2097,6 +2097,9 @@ GLIBC_2.23 fts64_set F
 GLIBC_2.24 GLIBC_2.24 A
 GLIBC_2.24 quick_exit F
 GLIBC_2.25 GLIBC_2.25 A
+GLIBC_2.25 __explicit_bzero F
+GLIBC_2.25 __glibc_read_memory F
+GLIBC_2.25 explicit_bzero F
 GLIBC_2.25 strfromd F
 GLIBC_2.25 strfromf F
 GLIBC_2.25 strfroml F
-- 
2.10.2


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