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.

(cherry picked from commit ef4f97648dc95849e417dd3e6328165de4c22185)

Conflicts:
	nptl/tst-tls3-malloc.c

9 files changed, 390 insertions, 6 deletions

diff --git a/ChangeLog b/ChangeLog
index 32faf08e7d..8dbaef6547 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,22 @@
+2016-08-26  Florian Weimer  <fweimer@redhat.com>
+
+	[BZ #20432]
+	Avoid strong references to malloc-internal symbols when linking
+	statically, to support statically interposed mallocs.
+	* include/libc-symbols.h (call_function_static_weak): New macro.
+	* malloc/Makefile (extra-tests-objs): Add tst-interpose-aux-nothread.o,
+	tst-interpose-aux-thread.o.
+	(test-extras): Add tst-interpose-aux-nothread,
+	tst-interpose-aux-thread.
+	* malloc/tst-interpose-aux-nothread.c: New file.
+	* malloc/tst-interpose-aux-thread.c: Likewise.
+	* malloc/tst-interpose-aux.c: Likewise.
+	* malloc/tst-interpose-aux.h: Likewise.
+	* sysdeps/mach/hurd/fork.c (__fork): Only call
+	__malloc_fork_lock_parent, __malloc_fork_unlock_parent,
+	__malloc_fork_unlock_child if defined.
+	* sysdeps/nptl/fork.c (__libc_fork): Likewise.
+
 2016-08-02  Florian Weimer  <fweimer@redhat.com>
 
 	[BZ #19469]
diff --git a/include/libc-symbols.h b/include/libc-symbols.h
index 4548e097dc..8245885c9f 100644
--- a/include/libc-symbols.h
+++ b/include/libc-symbols.h
@@ -121,6 +121,21 @@
 # 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__ */
 
diff --git a/malloc/Makefile b/malloc/Makefile
index 4d5c81dce6..e683daab35 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -31,6 +31,7 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
 	 tst-malloc-backtrace tst-malloc-thread-exit \
 	 tst-malloc-thread-fail tst-malloc-fork-deadlock \
 	 tst-mallocfork2
+
 test-srcs = tst-mtrace
 
 routines = malloc morecore mcheck mtrace obstack \
@@ -44,6 +45,15 @@ 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))
 
diff --git a/malloc/tst-interpose-aux-nothread.c b/malloc/tst-interpose-aux-nothread.c
new file mode 100644
index 0000000000..0eae66fa6c
--- /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"
diff --git a/malloc/tst-interpose-aux-thread.c b/malloc/tst-interpose-aux-thread.c
new file mode 100644
index 0000000000..354e4d8ed1
--- /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"
diff --git a/malloc/tst-interpose-aux.c b/malloc/tst-interpose-aux.c
new file mode 100644
index 0000000000..77866b2e5d
--- /dev/null
+++ b/malloc/tst-interpose-aux.c
@@ -0,0 +1,270 @@
+/* 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;
+    }
+}
diff --git a/malloc/tst-interpose-aux.h b/malloc/tst-interpose-aux.h
new file mode 100644
index 0000000000..2fb22d312a
--- /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 */
diff --git a/sysdeps/mach/hurd/fork.c b/sysdeps/mach/hurd/fork.c
index 2e8b59e7c0..9973b1bb9e 100644
--- a/sysdeps/mach/hurd/fork.c
+++ b/sysdeps/mach/hurd/fork.c
@@ -112,7 +112,7 @@ __fork (void)
 	 handlers may use malloc, and the libio list lock has an
 	 indirect malloc dependency as well (via the getdelim
 	 function).  */
-      __malloc_fork_lock_parent ();
+      call_function_static_weak (__malloc_fork_lock_parent);
 
       /* Lock things that want to be locked before we fork.  */
       {
@@ -612,7 +612,7 @@ __fork (void)
 	}
 
       /* Release malloc locks.  */
-      __malloc_fork_unlock_parent ();
+      call_function_static_weak (__malloc_fork_unlock_parent);
 
       /* Run things that want to run in the parent to restore it to
 	 normality.  Usually prepare hooks and parent hooks are
@@ -666,7 +666,7 @@ __fork (void)
       __sigemptyset (&_hurdsig_traced);
 
       /* Release malloc locks.  */
-      __malloc_fork_unlock_child ();
+      call_function_static_weak (__malloc_fork_unlock_child);
 
       /* Run things that want to run in the child task to set up.  */
       RUN_HOOK (_hurd_fork_child_hook, ());
diff --git a/sysdeps/nptl/fork.c b/sysdeps/nptl/fork.c
index 616d897a36..ea135f8e18 100644
--- a/sysdeps/nptl/fork.c
+++ b/sysdeps/nptl/fork.c
@@ -128,7 +128,7 @@ __libc_fork (void)
 	 handlers may use malloc, and the libio list lock has an
 	 indirect malloc dependency as well (via the getdelim
 	 function).  */
-      __malloc_fork_lock_parent ();
+      call_function_static_weak (__malloc_fork_lock_parent);
     }
 
 #ifndef NDEBUG
@@ -192,7 +192,7 @@ __libc_fork (void)
       if (multiple_threads)
 	{
 	  /* Release malloc locks.  */
-	  __malloc_fork_unlock_child ();
+	  call_function_static_weak (__malloc_fork_unlock_child);
 
 	  /* Reset the file list.  These are recursive mutexes.  */
 	  fresetlockfiles ();
@@ -240,7 +240,7 @@ __libc_fork (void)
       if (multiple_threads)
 	{
 	  /* Release malloc locks, parent process variant.  */
-	  __malloc_fork_unlock_parent ();
+	  call_function_static_weak (__malloc_fork_unlock_parent);
 
 	  /* We execute this even if the 'fork' call failed.  */
 	  _IO_list_unlock ();