Based on the following upstream commit:

commit ef4f97648dc95849e417dd3e6328165de4c22185

Author: Florian Weimer <fweimer@redhat.com>

Date:   Fri Aug 26 22:40:27 2016 +0200

    malloc: Simplify static malloc interposition [BZ #20432]

    Existing interposed mallocs do not define the glibc-internal

    fork callbacks (and they should not), so statically interposed

    mallocs lead to link failures because the strong reference from

    fork pulls in glibc's malloc, resulting in multiple definitions

    of malloc-related symbols.

Adjustments: __libc_memalign is defined.  <support/xthread.h> is

included because libsupport provides definitions of xthread_*

functions, but not our version of the test skeleton.

Index: b/include/libc-symbols.h

===================================================================

--- a/include/libc-symbols.h

+++ b/include/libc-symbols.h

@@ -119,6 +119,21 @@

 # define weak_extern(symbol) _weak_extern (weak symbol)

 # define _weak_extern(expr) _Pragma (#expr)

+/* In shared builds, the expression call_function_static_weak

+   (FUNCTION-SYMBOL, ARGUMENTS) invokes FUNCTION-SYMBOL (an

+   identifier) unconditionally, with the (potentially empty) argument

+   list ARGUMENTS.  In static builds, if FUNCTION-SYMBOL has a

+   definition, the function is invoked as before; if FUNCTION-SYMBOL

+   is NULL, no call is performed.  */

+# ifdef SHARED

+#  define call_function_static_weak(func, ...) func (__VA_ARGS__)

+# else	/* !SHARED */

+#  define call_function_static_weak(func, ...)		\

+  ({							\

+    extern __typeof__ (func) func weak_function;	\

+    (func != NULL ? func (__VA_ARGS__) : (void)0);	\

+  })

+# endif

 #else /* __ASSEMBLER__ */

Index: b/malloc/Makefile

===================================================================

--- a/malloc/Makefile

+++ b/malloc/Makefile

@@ -28,7 +28,16 @@ tests := mallocbug tst-malloc tst-valloc

 	 tst-mallocstate tst-mcheck tst-mallocfork tst-trim1 \

 	 tst-malloc-usable \

 	 tst-malloc-backtrace tst-malloc-thread-exit \

-	 tst-malloc-thread-fail tst-malloc-fork-deadlock

+	 tst-malloc-thread-fail tst-malloc-fork-deadlock \

+	 tst-interpose-nothread \

+	 tst-interpose-thread \

+	 tst-interpose-static-nothread \

+	 tst-interpose-static-thread \

+

+tests-static := \

+	 tst-interpose-static-nothread \

+	 tst-interpose-static-thread \

+

 test-srcs = tst-mtrace

 routines = malloc morecore mcheck mtrace obstack

@@ -40,6 +49,15 @@ non-lib.a := libmcheck.a

 extra-libs = libmemusage

 extra-libs-others = $(extra-libs)

+# Helper objects for some tests.

+extra-tests-objs += \

+  tst-interpose-aux-nothread.o \

+  tst-interpose-aux-thread.o \

+

+test-extras = \

+  tst-interpose-aux-nothread \

+  tst-interpose-aux-thread \

+

 libmemusage-routines = memusage

 libmemusage-inhibit-o = $(filter-out .os,$(object-suffixes))

@@ -157,6 +175,17 @@ $(objpfx)libmemusage.so: $(common-objpfx

 # Extra dependencies

 $(foreach o,$(all-object-suffixes),$(objpfx)malloc$(o)): arena.c hooks.c

+# max_align_t requires C11.

+CFLAGS-tst-interpose-aux-nothread.c = -std=gnu11

+CFLAGS-tst-interpose-aux-thread.c = -std=gnu11

+

+$(objpfx)tst-interpose-nothread: $(objpfx)tst-interpose-aux-nothread.o

+$(objpfx)tst-interpose-thread: \

+  $(objpfx)tst-interpose-aux-thread.o $(shared-thread-library)

+$(objpfx)tst-interpose-static-nothread: $(objpfx)tst-interpose-aux-nothread.o

+$(objpfx)tst-interpose-static-thread: \

+  $(objpfx)tst-interpose-aux-thread.o $(static-thread-library)

+

 # Compile the tests with a flag which suppresses the mallopt call in

 # the test skeleton.

 $(tests:%=$(objpfx)%.o): CPPFLAGS += -DTEST_NO_MALLOPT

Index: b/malloc/tst-interpose-aux-nothread.c

===================================================================

--- /dev/null

+++ b/malloc/tst-interpose-aux-nothread.c

@@ -0,0 +1,20 @@

+/* Interposed malloc, version without threading support.

+   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; see the file COPYING.LIB.  If

+   not, see <http://www.gnu.org/licenses/>.  */

+

+#define INTERPOSE_THREADS 0

+#include "tst-interpose-aux.c"

Index: b/malloc/tst-interpose-aux-thread.c

===================================================================

--- /dev/null

+++ b/malloc/tst-interpose-aux-thread.c

@@ -0,0 +1,20 @@

+/* Interposed malloc, version with threading support.

+   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; see the file COPYING.LIB.  If

+   not, see <http://www.gnu.org/licenses/>.  */

+

+#define INTERPOSE_THREADS 1

+#include "tst-interpose-aux.c"

Index: b/malloc/tst-interpose-aux.c

===================================================================

--- /dev/null

+++ b/malloc/tst-interpose-aux.c

@@ -0,0 +1,283 @@

+/* Minimal malloc implementation for interposition tests.

+   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; see the file COPYING.LIB.  If

+   not, see <http://www.gnu.org/licenses/>.  */

+

+#include "tst-interpose-aux.h"

+

+#include <errno.h>

+#include <stdarg.h>

+#include <stddef.h>

+#include <stdio.h>

+#include <stdlib.h>

+#include <string.h>

+#include <sys/mman.h>

+#include <sys/uio.h>

+#include <unistd.h>

+

+#if INTERPOSE_THREADS

+#include <pthread.h>

+#endif

+

+/* Print the error message and terminate the process with status 1.  */

+__attribute__ ((noreturn))

+__attribute__ ((format (printf, 1, 2)))

+static void *

+fail (const char *format, ...)

+{

+  /* This assumes that vsnprintf will not call malloc.  It does not do

+     so for the format strings we use.  */

+  char message[4096];

+  va_list ap;

+  va_start (ap, format);

+  vsnprintf (message, sizeof (message), format, ap);

+  va_end (ap);

+

+  enum { count = 3 };

+  struct iovec iov[count];

+

+  iov[0].iov_base = (char *) "error: ";

+  iov[1].iov_base = (char *) message;

+  iov[2].iov_base = (char *) "\n";

+

+  for (int i = 0; i < count; ++i)

+    iov[i].iov_len = strlen (iov[i].iov_base);

+

+  int unused __attribute__ ((unused));

+  unused = writev (STDOUT_FILENO, iov, count);

+  _exit (1);

+}

+

+#if INTERPOSE_THREADS

+static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

+#endif

+

+static void

+lock (void)

+{

+#if INTERPOSE_THREADS

+  int ret = pthread_mutex_lock (&mutex);

+  if (ret != 0)

+    {

+      errno = ret;

+      fail ("pthread_mutex_lock: %m");

+    }

+#endif

+}

+

+static void

+unlock (void)

+{

+#if INTERPOSE_THREADS

+  int ret = pthread_mutex_unlock (&mutex);

+  if (ret != 0)

+    {

+      errno = ret;

+      fail ("pthread_mutex_unlock: %m");

+    }

+#endif

+}

+

+struct __attribute__ ((aligned (__alignof__ (max_align_t)))) allocation_header

+{

+  size_t allocation_index;

+  size_t allocation_size;

+};

+

+/* Array of known allocations, to track invalid frees.  */

+enum { max_allocations = 65536 };

+static struct allocation_header *allocations[max_allocations];

+static size_t allocation_index;

+static size_t deallocation_count;

+

+/* Sanity check for successful malloc interposition.  */

+__attribute__ ((destructor))

+static void

+check_for_allocations (void)

+{

+  if (allocation_index == 0)

+    {

+      /* Make sure that malloc is called at least once from libc.  */

+      void *volatile ptr = strdup ("ptr");

+      free (ptr);

+      /* Compiler barrier.  The strdup function calls malloc, which

+         updates allocation_index, but strdup is marked __THROW, so

+         the compiler could optimize away the reload.  */

+      __asm__ volatile ("" ::: "memory");

+      /* If the allocation count is still zero, it means we did not

+         interpose malloc successfully.  */

+      if (allocation_index == 0)

+        fail ("malloc does not seem to have been interposed");

+    }

+}

+

+static struct allocation_header *get_header (const char *op, void *ptr)

+{

+  struct allocation_header *header = ((struct allocation_header *) ptr) - 1;

+  if (header->allocation_index >= allocation_index)

+    fail ("%s: %p: invalid allocation index: %zu (not less than %zu)",

+          op, ptr, header->allocation_index, allocation_index);

+  if (allocations[header->allocation_index] != header)

+    fail ("%s: %p: allocation pointer does not point to header, but %p",

+          op, ptr, allocations[header->allocation_index]);

+  return header;

+}

+

+/* Internal helper functions.  Those must be called while the lock is

+   acquired.  */

+

+static void *

+malloc_internal (size_t size)

+{

+  if (allocation_index == max_allocations)

+    {

+      errno = ENOMEM;

+      return NULL;

+    }

+  size_t allocation_size = size + sizeof (struct allocation_header);

+  if (allocation_size < size)

+    {

+      errno = ENOMEM;

+      return NULL;

+    }

+

+  size_t index = allocation_index++;

+  void *result = mmap (NULL, allocation_size, PROT_READ | PROT_WRITE,

+                       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

+  if (result == MAP_FAILED)

+    return NULL;

+  allocations[index] = result;

+  *allocations[index] = (struct allocation_header)

+    {

+      .allocation_index = index,

+      .allocation_size = allocation_size

+    };

+  return allocations[index] + 1;

+}

+

+static void

+free_internal (const char *op, struct allocation_header *header)

+{

+  size_t index = header->allocation_index;

+  int result = mprotect (header, header->allocation_size, PROT_NONE);

+  if (result != 0)

+    fail ("%s: mprotect (%p, %zu): %m", op, header, header->allocation_size);

+  /* Catch double-free issues.  */

+  allocations[index] = NULL;

+  ++deallocation_count;

+}

+

+static void *

+realloc_internal (void *ptr, size_t new_size)

+{

+  struct allocation_header *header = get_header ("realloc", ptr);

+  size_t old_size = header->allocation_size - sizeof (struct allocation_header);

+  if (old_size >= new_size)

+    return ptr;

+

+  void *newptr = malloc_internal (new_size);

+  if (newptr == NULL)

+    return NULL;

+  memcpy (newptr, ptr, old_size);

+  free_internal ("realloc", header);

+  return newptr;

+}

+

+/* Public interfaces.  These functions must perform locking.  */

+

+size_t

+malloc_allocation_count (void)

+{

+  lock ();

+  size_t count = allocation_index;

+  unlock ();

+  return count;

+}

+

+size_t

+malloc_deallocation_count (void)

+{

+  lock ();

+  size_t count = deallocation_count;

+  unlock ();

+  return count;

+}

+

+void *

+malloc (size_t size)

+{

+  lock ();

+  void *result = malloc_internal (size);

+  unlock ();

+  return result;

+}

+

+void

+free (void *ptr)

+{

+  if (ptr == NULL)

+    return;

+  lock ();

+  struct allocation_header *header = get_header ("free", ptr);

+  free_internal ("free", header);

+  unlock ();

+}

+

+void *

+calloc (size_t a, size_t b)

+{

+  if (b > 0 && a > SIZE_MAX / b)

+    {

+      errno = ENOMEM;

+      return NULL;

+    }

+  lock ();

+  /* malloc_internal uses mmap, so the memory is zeroed.  */

+  void *result = malloc_internal (a * b);

+  unlock ();

+  return result;

+}

+

+void *

+realloc (void *ptr, size_t n)

+{

+  if (n ==0)

+    {

+      free (ptr);

+      return NULL;

+    }

+  else if (ptr == NULL)

+    return malloc (n);

+  else

+    {

+      lock ();

+      void *result = realloc_internal (ptr, n);

+      unlock ();

+      return result;

+    }

+}

+

+/* The dyanmic linker still uses __libc_memalign because we have not

+   backported the fix for swbz#17730.  It does not normally request

+   large alignments, so we can call malloc directly.  */

+void *

+__libc_memalign (size_t alignment, size_t size)

+{

+  void *result = malloc (size);

+  if (((uintptr_t) result % alignment) != 0)

+    fail ("could not fulfill requested alignment %zu", alignment);

+  return result;

+}

Index: b/malloc/tst-interpose-aux.h

===================================================================

--- /dev/null

+++ b/malloc/tst-interpose-aux.h

@@ -0,0 +1,30 @@

+/* Statistics interface for the minimal malloc implementation.

+   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; see the file COPYING.LIB.  If

+   not, see <http://www.gnu.org/licenses/>.  */

+

+#ifndef TST_INTERPOSE_AUX_H

+#define TST_INTERPOSE_AUX_H

+

+#include <stddef.h>

+

+/* Return the number of allocations performed.  */

+size_t malloc_allocation_count (void);

+

+/* Return the number of deallocations performed.  */

+size_t malloc_deallocation_count (void);

+

+#endif /* TST_INTERPOSE_AUX_H */

Index: b/malloc/tst-interpose-nothread.c

===================================================================

--- /dev/null

+++ b/malloc/tst-interpose-nothread.c

@@ -0,0 +1,20 @@

+/* Malloc interposition test, dynamically-linked version without threads.

+   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; see the file COPYING.LIB.  If

+   not, see <http://www.gnu.org/licenses/>.  */

+

+#define INTERPOSE_THREADS 0

+#include "tst-interpose-skeleton.c"

Index: b/malloc/tst-interpose-skeleton.c

===================================================================

--- /dev/null

+++ b/malloc/tst-interpose-skeleton.c

@@ -0,0 +1,204 @@

+/* Test driver for malloc interposition tests.

+   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; see the file COPYING.LIB.  If

+   not, see <http://www.gnu.org/licenses/>.  */

+

+#include <stdio.h>

+#include <stdlib.h>

+#include <string.h>

+#include <unistd.h>

+

+#if INTERPOSE_THREADS

+#include <support/xthread.h>

+#endif

+

+static int do_test (void);

+#define TEST_FUNCTION do_test ()

+#include "../test-skeleton.c"

+

+/* Fills BUFFER with a test string.  */

+static void

+line_string (int number, char *buffer, size_t length)

+{

+  for (size_t i = 0; i < length - 2; ++i)

+    buffer[i] = 'A' + ((number + i) % 26);

+  buffer[length - 2] = '\n';

+  buffer[length - 1] = '\0';

+}

+

+/* Perform the tests.  */

+static void *

+run_tests (void *closure)

+{

+  char *temp_file_path;

+  int fd = create_temp_file ("tst-malloc-interpose", &temp_file_path);

+  if (fd < 0)

+    _exit (1);

+

+  /* Line lengths excluding the line terminator.  */

+  static const int line_lengths[] = { 0, 45, 80, 2, 8201, 0, 17, -1 };

+

+  /* Fill the test file with data.  */

+  {

+    FILE *fp = fdopen (fd, "w");

+    for (int lineno = 0; line_lengths[lineno] >= 0; ++lineno)

+      {

+        char buffer[line_lengths[lineno] + 2];

+        line_string (lineno, buffer, sizeof (buffer));

+        fprintf (fp, "%s", buffer);

+      }

+

+    if (ferror (fp))

+      {

+        printf ("error: fprintf: %m\n");

+        _exit (1);

+      }

+    if (fclose (fp) != 0)

+      {

+        printf ("error: fclose: %m\n");

+        _exit (1);

+      }

+  }

+

+  /* Read the test file.  This tests libc-internal allocation with

+     realloc.  */

+  {

+    FILE *fp = fopen (temp_file_path, "r");

+

+    char *actual = NULL;

+    size_t actual_size = 0;

+    for (int lineno = 0; ; ++lineno)

+      {

+        errno = 0;

+        ssize_t result = getline (&actual, &actual_size, fp);

+        if (result == 0)

+          {

+            printf ("error: invalid return value 0 from getline\n");

+            _exit (1);

+          }

+        if (result < 0 && errno != 0)

+          {

+            printf ("error: getline: %m\n");

+            _exit (1);

+          }

+        if (result < 0 && line_lengths[lineno] >= 0)

+          {

+            printf ("error: unexpected end of file after line %d\n", lineno);

+            _exit (1);

+          }

+        if (result > 0 && line_lengths[lineno] < 0)

+          {

+            printf ("error: no end of file after line %d\n", lineno);

+            _exit (1);

+          }

+        if (result == -1 && line_lengths[lineno] == -1)

+          /* End of file reached as expected.  */

+          break;

+

+        if (result != line_lengths[lineno] + 1)

+          {

+            printf ("error: line length mismatch: expected %d, got %zd\n",

+                    line_lengths[lineno], result);

+            _exit (1);

+          }

+

+        char expected[line_lengths[lineno] + 2];

+        line_string (lineno, expected, sizeof (expected));

+        if (strcmp (actual, expected) != 0)

+          {

+            printf ("error: line mismatch\n");

+            printf ("error:   expected: [[%s]]\n", expected);

+            printf ("error:   actual:   [[%s]]\n", actual);

+            _exit (1);

+          }

+      }

+

+    if (fclose (fp) != 0)

+      {

+        printf ("error: fclose (after reading): %m\n");

+        _exit (1);

+      }

+  }

+

+  free (temp_file_path);

+

+  /* Make sure that fork is working.  */

+  pid_t pid = fork ();

+  if (pid == -1)

+    {

+      printf ("error: fork: %m\n");

+      _exit (1);

+    }

+  enum { exit_code = 55 };

+  if (pid == 0)

+    _exit (exit_code);

+  int status;

+  int ret = waitpid (pid, &status, 0);

+  if (ret < 0)

+    {

+      printf ("error: waitpid: %m\n");

+      _exit (1);

+    }

+  if (!WIFEXITED (status) || WEXITSTATUS (status) != exit_code)

+    {

+      printf ("error: unexpected exit status from child process: %d\n",

+              status);

+      _exit (1);

+    }

+

+  return NULL;

+}

+

+/* This is used to detect if malloc has not been successfully

+   interposed.  The interposed malloc does not use brk/sbrk.  */

+static void *initial_brk;

+__attribute__ ((constructor))

+static void

+set_initial_brk (void)

+{

+  initial_brk = sbrk (0);

+}

+

+/* Terminate the process if the break value has been changed.  */

+__attribute__ ((destructor))

+static void

+check_brk (void)

+{

+  void *current = sbrk (0);

+  if (current != initial_brk)

+    {

+      printf ("error: brk changed from %p to %p; no interposition?\n",

+              initial_brk, current);

+      _exit (1);

+    }

+}

+

+static int

+do_test (void)

+{

+  check_brk ();

+

+#if INTERPOSE_THREADS

+  pthread_t thr = xpthread_create (NULL, run_tests, NULL);

+  xpthread_join (thr);

+#else

+  run_tests (NULL);

+#endif

+

+  check_brk ();

+

+  return 0;

+}

Index: b/malloc/tst-interpose-static-nothread.c

===================================================================

--- /dev/null

+++ b/malloc/tst-interpose-static-nothread.c

@@ -0,0 +1,19 @@

+/* Malloc interposition test, static version without threads.

+   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