Move malloc hooks into a compat DSO

Remove all malloc hook uses from core malloc functions and move it
into a new library libc_malloc_debug.so.  With this, the hooks now no
longer have any effect on the core library.

libc_malloc_debug.so is a malloc interposer that needs to be preloaded
to get hooks functionality back so that the debugging features that
depend on the hooks, i.e. malloc-check, mcheck and mtrace work again.
Without the preloaded DSO these debugging features will be nops.
These features will be ported away from hooks in subsequent patches.

Similarly, legacy applications that need hooks functionality need to
preload libc_malloc_debug.so.

The symbols exported by libc_malloc_debug.so are maintained at exactly
the same version as libc.so.

Finally, static binaries will no longer be able to use malloc
debugging features since they cannot preload the debugging DSO.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

13 files changed, 453 insertions, 111 deletions

diff --git a/malloc/Makefile b/malloc/Makefile
index bbb70f6f87..cafe427097 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -46,12 +46,11 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
 
 tests-static := \
 	 tst-interpose-static-nothread \
-	 tst-interpose-static-thread \
-	 tst-malloc-usable-static \
+	 tst-interpose-static-thread
 
 # Test for the malloc_set_state symbol removed in glibc 2.25.
-ifeq ($(have-GLIBC_2.24)$(build-shared),yesyes)
-tests += tst-mallocstate
+ifeq ($(have-GLIBC_2.23)$(build-shared),yesyes)
+tests += tst-mallocstate tst-compathooks-off tst-compathooks-on
 endif
 
 tests-internal := tst-scratch_buffer
@@ -64,7 +63,6 @@ tests-internal += \
 
 ifneq (no,$(have-tunables))
 tests += tst-malloc-usable-tunables tst-mxfast
-tests-static += tst-malloc-usable-static-tunables
 endif
 
 tests += $(tests-static)
@@ -73,7 +71,8 @@ test-srcs = tst-mtrace
 # These tests either are run with MALLOC_CHECK_=3 by default or do not work
 # with MALLOC_CHECK_=3 because they expect a specific failure.
 tests-exclude-malloc-check = tst-malloc-check tst-malloc-usable \
-	tst-mxfast tst-safe-linking
+	tst-mxfast tst-safe-linking \
+	tst-compathooks-off tst-compathooks-on
 
 # Run all tests with MALLOC_CHECK_=3
 tests-malloc-check = $(filter-out $(tests-exclude-malloc-check),$(tests))
@@ -91,15 +90,14 @@ tests-exclude-mcheck = tst-mallocstate \
 	tst-malloc-tcache-leak \
 	tst-malloc-thread-exit \
 	tst-malloc-thread-fail \
-	tst-malloc-usable-static \
-	tst-malloc-usable-static-tunables \
 	tst-malloc-usable-tunables \
 	tst-malloc_info \
 	tst-memalign \
 	tst-posix_memalign \
 	tst-realloc \
 	tst-pvalloc-fortify \
-	tst-reallocarray
+	tst-reallocarray \
+	tst-compathooks-off tst-compathooks-on
 
 tests-mcheck = $(filter-out $(tests-exclude-mcheck), $(tests))
 endif
@@ -122,8 +120,8 @@ routines = malloc mcheck mtrace obstack reallocarray \
 install-lib := libmcheck.a
 non-lib.a := libmcheck.a
 
-# Additional library.
-extra-libs = libmemusage
+# Additional libraries.
+extra-libs = libmemusage libc_malloc_debug
 extra-libs-others = $(extra-libs)
 
 # Helper objects for some tests.
@@ -138,6 +136,9 @@ test-extras = \
 libmemusage-routines = memusage
 libmemusage-inhibit-o = $(filter-out .os,$(object-suffixes))
 
+libc_malloc_debug-routines = malloc-debug
+libc_malloc_debug-inhibit-o = $(filter-out .os,$(object-suffixes))
+
 $(objpfx)tst-malloc-backtrace: $(shared-thread-library)
 $(objpfx)tst-malloc-thread-exit: $(shared-thread-library)
 $(objpfx)tst-malloc-thread-fail: $(shared-thread-library)
@@ -244,11 +245,12 @@ endif
 endif
 endif
 
-tst-malloc-check-ENV = MALLOC_CHECK_=3
-tst-malloc-usable-ENV = MALLOC_CHECK_=3
-tst-malloc-usable-static-ENV = $(tst-malloc-usable-ENV)
-tst-malloc-usable-tunables-ENV = GLIBC_TUNABLES=glibc.malloc.check=3
-tst-malloc-usable-static-tunables-ENV = $(tst-malloc-usable-tunables-ENV)
+tst-malloc-check-ENV = MALLOC_CHECK_=3 \
+		       LD_PRELOAD=$(objpfx)/libc_malloc_debug.so
+tst-malloc-usable-ENV = MALLOC_CHECK_=3 \
+		       LD_PRELOAD=$(objpfx)/libc_malloc_debug.so
+tst-malloc-usable-tunables-ENV = GLIBC_TUNABLES=glibc.malloc.check=3 \
+				 LD_PRELOAD=$(objpfx)/libc_malloc_debug.so
 
 tst-mxfast-ENV = GLIBC_TUNABLES=glibc.malloc.tcache_count=0:glibc.malloc.mxfast=0
 
@@ -303,12 +305,14 @@ $(objpfx)tst-interpose-static-thread-mcheck: \
 $(objpfx)tst-interpose-static-thread-malloc-check: \
   $(objpfx)tst-interpose-aux-thread.o $(static-thread-library)
 
-tst-dynarray-ENV = MALLOC_TRACE=$(objpfx)tst-dynarray.mtrace
+tst-dynarray-ENV = MALLOC_TRACE=$(objpfx)tst-dynarray.mtrace \
+		   LD_PRELOAD=$(objpfx)libc_malloc_debug.so
 $(objpfx)tst-dynarray-mem.out: $(objpfx)tst-dynarray.out
 	$(common-objpfx)malloc/mtrace $(objpfx)tst-dynarray.mtrace > $@; \
 	$(evaluate-test)
 
-tst-dynarray-fail-ENV = MALLOC_TRACE=$(objpfx)tst-dynarray-fail.mtrace
+tst-dynarray-fail-ENV = MALLOC_TRACE=$(objpfx)tst-dynarray-fail.mtrace \
+			LD_PRELOAD=$(objpfx)libc_malloc_debug.so
 $(objpfx)tst-dynarray-fail-mem.out: $(objpfx)tst-dynarray-fail.out
 	$(common-objpfx)malloc/mtrace $(objpfx)tst-dynarray-fail.mtrace > $@; \
 	$(evaluate-test)
@@ -322,3 +326,10 @@ $(objpfx)tst-mallocfork2-mcheck: $(shared-thread-library)
 $(objpfx)tst-malloc-tcache-leak-malloc-check: $(shared-thread-library)
 $(objpfx)tst-malloc_info-malloc-check: $(shared-thread-library)
 $(objpfx)tst-mallocfork2-malloc-check: $(shared-thread-library)
+
+tst-compathooks-on-ENV = LD_PRELOAD=$(objpfx)libc_malloc_debug.so
+tst-compathooks-on-mcheck-ENV = LD_PRELOAD=$(objpfx)libc_malloc_debug.so
+tst-compathooks-on-malloc-check-ENV = \
+	LD_PRELOAD=$(objpfx)libc_malloc_debug.so
+tst-mallocstate-ENV = LD_PRELOAD=$(objpfx)libc_malloc_debug.so
+tst-mallocstate-malloc-check-ENV = LD_PRELOAD=$(objpfx)libc_malloc_debug.so
diff --git a/malloc/Versions b/malloc/Versions
index 470a940666..c87f6df8ca 100644
--- a/malloc/Versions
+++ b/malloc/Versions
@@ -98,3 +98,23 @@ libc {
     __libc_alloc_buffer_create_failure;
   }
 }
+
+# Keep in sync with symbols in libc.
+libc_malloc_debug {
+  GLIBC_2.0 {
+    calloc;
+    free;
+    malloc;
+    memalign;
+    pvalloc;
+    realloc;
+    valloc;
+
+  }
+  GLIBC_2.2 {
+    posix_memalign;
+  }
+  GLIBC_2.16 {
+    aligned_alloc;
+  }
+}
diff --git a/malloc/arena.c b/malloc/arena.c
index f1693ed48f..9111b49589 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -404,13 +404,6 @@ ptmalloc_init (void)
   if (s && s[0] != '\0' && s[0] != '0')
     __malloc_check_init ();
 #endif
-
-#if HAVE_MALLOC_INIT_HOOK
-  void (*hook) (void) = atomic_forced_read (__malloc_initialize_hook);
-  if (hook != NULL)
-    (*hook)();
-#endif
-  __malloc_initialized = 1;
 }
 
 /* Managing heaps and arenas (for concurrent threads) */
diff --git a/malloc/hooks.c b/malloc/hooks.c
index 4aa6dadcff..3cd44eeb84 100644
--- a/malloc/hooks.c
+++ b/malloc/hooks.c
@@ -1,4 +1,4 @@
-/* Malloc implementation for multiple threads without lock contention.
+/* Compatibility code for malloc debugging and state management.
    Copyright (C) 2001-2021 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Wolfram Gloger <wg@malloc.de>, 2001.
@@ -17,6 +17,16 @@
    License along with the GNU C Library; see the file COPYING.LIB.  If
    not, see <https://www.gnu.org/licenses/>.  */
 
+#ifndef weak_variable
+# define weak_variable weak_function
+#endif
+
+#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_24)
+void (*__malloc_initialize_hook) (void);
+compat_symbol (libc, __malloc_initialize_hook,
+	       __malloc_initialize_hook, GLIBC_2_0);
+#endif
+
 #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_34)
 void weak_variable (*__after_morecore_hook) (void) = NULL;
 compat_symbol (libc, __after_morecore_hook, __after_morecore_hook, GLIBC_2_0);
@@ -24,32 +34,64 @@ void *(*__morecore)(ptrdiff_t);
 compat_symbol (libc, __morecore, __morecore, GLIBC_2_0);
 #endif
 
+static void *malloc_hook_ini (size_t, const void *) __THROW;
+static void *realloc_hook_ini (void *, size_t, const void *) __THROW;
+static void *memalign_hook_ini (size_t, size_t, const void *) __THROW;
+
+void weak_variable (*__free_hook) (void *, const void *) = NULL;
+void *weak_variable (*__malloc_hook)
+  (size_t, const void *) = malloc_hook_ini;
+void *weak_variable (*__realloc_hook)
+  (void *, size_t, const void *) = realloc_hook_ini;
+void *weak_variable (*__memalign_hook)
+  (size_t, size_t, const void *) = memalign_hook_ini;
+
 /* Hooks for debugging versions.  The initial hooks just call the
    initialization routine, then do the normal work. */
 
-static void *
-malloc_hook_ini (size_t sz, const void *caller)
+/* These hooks will get executed only through the interposed allocator
+   functions in libc_malloc_debug.so.  This means that the calls to malloc,
+   realloc, etc. will lead back into the interposed functions, which is what we
+   want.
+
+   These initial hooks are assumed to be called in a single-threaded context,
+   so it is safe to reset all hooks at once upon initialization.  */
+
+static void
+generic_hook_ini (void)
 {
   __malloc_hook = NULL;
+  __realloc_hook = NULL;
+  __memalign_hook = NULL;
   ptmalloc_init ();
-  return __libc_malloc (sz);
+
+#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_24)
+  void (*hook) (void) = atomic_forced_read (__malloc_initialize_hook);
+  if (hook != NULL)
+    (*hook)();
+#endif
+  __malloc_initialized = 1;
+}
+
+static void *
+malloc_hook_ini (size_t sz, const void *caller)
+{
+  generic_hook_ini ();
+  return malloc (sz);
 }
 
 static void *
 realloc_hook_ini (void *ptr, size_t sz, const void *caller)
 {
-  __malloc_hook = NULL;
-  __realloc_hook = NULL;
-  ptmalloc_init ();
-  return __libc_realloc (ptr, sz);
+  generic_hook_ini ();
+  return realloc (ptr, sz);
 }
 
 static void *
 memalign_hook_ini (size_t alignment, size_t sz, const void *caller)
 {
-  __memalign_hook = NULL;
-  ptmalloc_init ();
-  return __libc_memalign (alignment, sz);
+  generic_hook_ini ();
+  return memalign (alignment, sz);
 }
 
 #include "malloc-check.c"
diff --git a/malloc/malloc-debug.c b/malloc/malloc-debug.c
new file mode 100644
index 0000000000..41dfcd3369
--- /dev/null
+++ b/malloc/malloc-debug.c
@@ -0,0 +1,189 @@
+/* Malloc debug DSO.
+   Copyright (C) 2021 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 <https://www.gnu.org/licenses/>.  */
+
+#include <atomic.h>
+#include <libc-symbols.h>
+#include <shlib-compat.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/param.h>
+
+/* Support only the glibc allocators.  */
+extern void *__libc_malloc (size_t);
+extern void __libc_free (void *);
+extern void *__libc_realloc (void *, size_t);
+extern void *__libc_memalign (size_t, size_t);
+extern void *__libc_valloc (size_t);
+extern void *__libc_pvalloc (size_t);
+extern void *__libc_calloc (size_t, size_t);
+
+#define DEBUG_FN(fn) \
+  static __typeof (__libc_ ## fn) __debug_ ## fn
+
+DEBUG_FN(malloc);
+DEBUG_FN(free);
+DEBUG_FN(realloc);
+DEBUG_FN(memalign);
+DEBUG_FN(valloc);
+DEBUG_FN(pvalloc);
+DEBUG_FN(calloc);
+
+extern void (*__free_hook) (void *, const void *);
+compat_symbol_reference (libc, __free_hook, __free_hook, GLIBC_2_0);
+extern void * (*__malloc_hook) (size_t, const void *);
+compat_symbol_reference (libc, __malloc_hook, __malloc_hook, GLIBC_2_0);
+extern void * (*__realloc_hook) (void *, size_t, const void *);
+compat_symbol_reference (libc, __realloc_hook, __realloc_hook, GLIBC_2_0);
+extern void * (*__memalign_hook) (size_t, size_t, const void *);
+compat_symbol_reference (libc, __memalign_hook, __memalign_hook, GLIBC_2_0);
+
+static size_t pagesize;
+
+/* The allocator functions.  */
+
+static void *
+__debug_malloc (size_t bytes)
+{
+  void *(*hook) (size_t, const void *) = atomic_forced_read (__malloc_hook);
+  if (__builtin_expect (hook != NULL, 0))
+    return (*hook)(bytes, RETURN_ADDRESS (0));
+
+  return __libc_malloc (bytes);
+}
+strong_alias (__debug_malloc, malloc)
+
+static void
+__debug_free (void *mem)
+{
+  void (*hook) (void *, const void *) = atomic_forced_read (__free_hook);
+  if (__builtin_expect (hook != NULL, 0))
+    {
+      (*hook)(mem, RETURN_ADDRESS (0));
+      return;
+    }
+  __libc_free (mem);
+}
+strong_alias (__debug_free, free)
+
+static void *
+__debug_realloc (void *oldmem, size_t bytes)
+{
+  void *(*hook) (void *, size_t, const void *) =
+    atomic_forced_read (__realloc_hook);
+  if (__builtin_expect (hook != NULL, 0))
+    return (*hook)(oldmem, bytes, RETURN_ADDRESS (0));
+
+  return __libc_realloc (oldmem, bytes);
+}
+strong_alias (__debug_realloc, realloc)
+
+static void *
+_debug_mid_memalign (size_t alignment, size_t bytes, const void *address)
+{
+  void *(*hook) (size_t, size_t, const void *) =
+    atomic_forced_read (__memalign_hook);
+  if (__builtin_expect (hook != NULL, 0))
+    return (*hook)(alignment, bytes, address);
+
+  return __libc_memalign (alignment, bytes);
+}
+
+static void *
+__debug_memalign (size_t alignment, size_t bytes)
+{
+  return _debug_mid_memalign (alignment, bytes, RETURN_ADDRESS (0));
+}
+strong_alias (__debug_memalign, memalign)
+strong_alias (__debug_memalign, aligned_alloc)
+
+static void *
+__debug_pvalloc (size_t bytes)
+{
+  size_t rounded_bytes;
+
+  if (!pagesize)
+    pagesize = sysconf (_SC_PAGESIZE);
+
+  /* ALIGN_UP with overflow check.  */
+  if (__glibc_unlikely (__builtin_add_overflow (bytes,
+						pagesize - 1,
+						&rounded_bytes)))
+    {
+      errno = ENOMEM;
+      return NULL;
+    }
+  rounded_bytes = rounded_bytes & -(pagesize - 1);
+
+  return _debug_mid_memalign (pagesize, rounded_bytes, RETURN_ADDRESS (0));
+}
+strong_alias (__debug_pvalloc, pvalloc)
+
+static void *
+__debug_valloc (size_t bytes)
+{
+  if (!pagesize)
+    pagesize = sysconf (_SC_PAGESIZE);
+
+  return _debug_mid_memalign (pagesize, bytes, RETURN_ADDRESS (0));
+}
+strong_alias (__debug_valloc, valloc)
+
+static int
+__debug_posix_memalign (void **memptr, size_t alignment, size_t bytes)
+{
+  /* Test whether the SIZE argument is valid.  It must be a power of
+     two multiple of sizeof (void *).  */
+  if (alignment % sizeof (void *) != 0
+      || !powerof2 (alignment / sizeof (void *))
+      || alignment == 0)
+    return EINVAL;
+
+  *memptr = _debug_mid_memalign (alignment, bytes, RETURN_ADDRESS (0));
+
+  if (*memptr == NULL)
+    return ENOMEM;
+
+  return 0;
+}
+strong_alias (__debug_posix_memalign, posix_memalign)
+
+static void *
+__debug_calloc (size_t nmemb, size_t size)
+{
+  void *(*hook) (size_t, const void *) = atomic_forced_read (__malloc_hook);
+  if (__builtin_expect (hook != NULL, 0))
+    {
+      size_t bytes;
+
+      if (__glibc_unlikely (__builtin_mul_overflow (nmemb, size, &bytes)))
+	{
+	  errno = ENOMEM;
+	  return NULL;
+	}
+
+      void *mem = (*hook)(bytes, RETURN_ADDRESS (0));
+
+      if (mem != NULL)
+	memset (mem, 0, bytes);
+
+      return mem;
+    }
+
+  return __libc_calloc (nmemb, size);
+}
+strong_alias (__debug_calloc, calloc)
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 6e8fa9e424..cf71314b2b 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -573,16 +573,6 @@ tag_at (void *ptr)
 #define HAVE_MREMAP 0
 #endif
 
-/* We may need to support __malloc_initialize_hook for backwards
-   compatibility.  */
-
-#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_24)
-# define HAVE_MALLOC_INIT_HOOK 1
-#else
-# define HAVE_MALLOC_INIT_HOOK 0
-#endif
-
-
 /*
   This version of malloc supports the standard SVID/XPG mallinfo
   routine that returns a struct containing usage properties and
@@ -2008,38 +1998,6 @@ static void     malloc_consolidate (mstate);
 
 /* -------------- Early definitions for debugging hooks ---------------- */
 
-/* Define and initialize the hook variables.  These weak definitions must
-   appear before any use of the variables in a function (arena.c uses one).  */
-#ifndef weak_variable
-/* In GNU libc we want the hook variables to be weak definitions to
-   avoid a problem with Emacs.  */
-# define weak_variable weak_function
-#endif
-
-/* Forward declarations.  */
-static void *malloc_hook_ini (size_t sz,
-                              const void *caller) __THROW;
-static void *realloc_hook_ini (void *ptr, size_t sz,
-                               const void *caller) __THROW;
-static void *memalign_hook_ini (size_t alignment, size_t sz,
-                                const void *caller) __THROW;
-
-#if HAVE_MALLOC_INIT_HOOK
-void (*__malloc_initialize_hook) (void);
-compat_symbol (libc, __malloc_initialize_hook,
-	       __malloc_initialize_hook, GLIBC_2_0);
-#endif
-
-void weak_variable (*__free_hook) (void *__ptr,
-                                   const void *) = NULL;
-void *weak_variable (*__malloc_hook)
-  (size_t __size, const void *) = malloc_hook_ini;
-void *weak_variable (*__realloc_hook)
-  (void *__ptr, size_t __size, const void *)
-  = realloc_hook_ini;
-void *weak_variable (*__memalign_hook)
-  (size_t __alignment, size_t __size, const void *)
-  = memalign_hook_ini;
 /* This function is called from the arena shutdown hook, to free the
    thread cache (if it exists).  */
 static void tcache_thread_shutdown (void);
@@ -3237,10 +3195,8 @@ __libc_malloc (size_t bytes)
   _Static_assert (PTRDIFF_MAX <= SIZE_MAX / 2,
                   "PTRDIFF_MAX is not more than half of SIZE_MAX");
 
-  void *(*hook) (size_t, const void *)
-    = atomic_forced_read (__malloc_hook);
-  if (__builtin_expect (hook != NULL, 0))
-    return (*hook)(bytes, RETURN_ADDRESS (0));
+  if (__malloc_initialized < 0)
+    ptmalloc_init ();
 #if USE_TCACHE
   /* int_free also calls request2size, be careful to not pad twice.  */
   size_t tbytes;
@@ -3301,14 +3257,6 @@ __libc_free (void *mem)
   mstate ar_ptr;
   mchunkptr p;                          /* chunk corresponding to mem */
 
-  void (*hook) (void *, const void *)
-    = atomic_forced_read (__free_hook);
-  if (__builtin_expect (hook != NULL, 0))
-    {
-      (*hook)(mem, RETURN_ADDRESS (0));
-      return;
-    }
-
   if (mem == 0)                              /* free(0) has no effect */
     return;
 
@@ -3360,10 +3308,8 @@ __libc_realloc (void *oldmem, size_t bytes)
 
   void *newp;             /* chunk to return */
 
-  void *(*hook) (void *, size_t, const void *) =
-    atomic_forced_read (__realloc_hook);
-  if (__builtin_expect (hook != NULL, 0))
-    return (*hook)(oldmem, bytes, RETURN_ADDRESS (0));
+  if (__malloc_initialized < 0)
+    ptmalloc_init ();
 
 #if REALLOC_ZERO_BYTES_FREES
   if (bytes == 0 && oldmem != NULL)
@@ -3498,6 +3444,9 @@ libc_hidden_def (__libc_realloc)
 void *
 __libc_memalign (size_t alignment, size_t bytes)
 {
+  if (__malloc_initialized < 0)
+    ptmalloc_init ();
+
   void *address = RETURN_ADDRESS (0);
   return _mid_memalign (alignment, bytes, address);
 }
@@ -3508,11 +3457,6 @@ _mid_memalign (size_t alignment, size_t bytes, void *address)
   mstate ar_ptr;
   void *p;
 
-  void *(*hook) (size_t, size_t, const void *) =
-    atomic_forced_read (__memalign_hook);
-  if (__builtin_expect (hook != NULL, 0))
-    return (*hook)(alignment, bytes, address);
-
   /* If we need less alignment than we give anyway, just relay to malloc.  */
   if (alignment <= MALLOC_ALIGNMENT)
     return __libc_malloc (bytes);
@@ -3621,16 +3565,8 @@ __libc_calloc (size_t n, size_t elem_size)
 
   sz = bytes;
 
-  void *(*hook) (size_t, const void *) =
-    atomic_forced_read (__malloc_hook);
-  if (__builtin_expect (hook != NULL, 0))
-    {
-      mem = (*hook)(sz, RETURN_ADDRESS (0));
-      if (mem == 0)
-        return 0;
-
-      return memset (mem, 0, sz);
-    }
+  if (__malloc_initialized < 0)
+    ptmalloc_init ();
 
   MAYBE_INIT_TCACHE ();
 
@@ -5659,6 +5595,9 @@ __posix_memalign (void **memptr, size_t alignment, size_t size)
 {
   void *mem;
 
+  if (__malloc_initialized < 0)
+    ptmalloc_init ();
+
   /* Test whether the SIZE argument is valid.  It must be a power of
      two multiple of sizeof (void *).  */
   if (alignment % sizeof (void *) != 0
diff --git a/malloc/mcheck.c b/malloc/mcheck.c
index d2efcfb742..1e68cedbf5 100644
--- a/malloc/mcheck.c
+++ b/malloc/mcheck.c
@@ -26,6 +26,7 @@
 # include <stdio.h>
 # include <libintl.h>
 # include <errno.h>
+# include <malloc-internal.h>
 #endif
 
 /* Old hook values.  */
diff --git a/malloc/mtrace.c b/malloc/mtrace.c
index 6c2c58b706..fb58413d39 100644
--- a/malloc/mtrace.c
+++ b/malloc/mtrace.c
@@ -22,6 +22,7 @@
 # define _MALLOC_INTERNAL
 # include <malloc.h>
 # include <mcheck.h>
+# include <malloc-internal.h>
 # include <libc-lock.h>
 #endif
 
diff --git a/malloc/tst-compathooks-off.c b/malloc/tst-compathooks-off.c
new file mode 100644
index 0000000000..7b3722d8b3
--- /dev/null
+++ b/malloc/tst-compathooks-off.c
@@ -0,0 +1,145 @@
+/* Minimal tests to verify libc_malloc_debug.so functionality.
+   Copyright (C) 2021 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <malloc.h>
+#include <shlib-compat.h>
+#include <libc-diag.h>
+
+#include <support/check.h>
+#include <support/support.h>
+
+extern void (*volatile __free_hook) (void *, const void *);
+extern void *(*volatile __malloc_hook)(size_t, const void *);
+extern void *(*volatile __realloc_hook)(void *, size_t, const void *);
+extern void *(*volatile __memalign_hook)(size_t, size_t, const void *);
+
+int hook_count, call_count;
+
+DIAG_PUSH_NEEDS_COMMENT;
+DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wdeprecated-declarations");
+
+void
+free_called (void *mem, const void *address)
+{
+  hook_count++;
+  __free_hook = NULL;
+  free (mem);
+  __free_hook = free_called;
+}
+
+void *
+malloc_called (size_t bytes, const void *address)
+{
+  hook_count++;
+  __malloc_hook = NULL;
+  void *mem = malloc (bytes);
+  __malloc_hook = malloc_called;
+  return mem;
+}
+
+void *
+realloc_called (void *oldptr, size_t bytes, const void *address)
+{
+  hook_count++;
+  __realloc_hook = NULL;
+  void *mem = realloc (oldptr, bytes);
+  __realloc_hook = realloc_called;
+  return mem;
+}
+
+void *
+calloc_called (size_t n, size_t size, const void *address)
+{
+  hook_count++;
+  __malloc_hook = NULL;
+  void *mem = calloc (n, size);
+  __malloc_hook = malloc_called;
+  return mem;
+}
+
+void *
+memalign_called (size_t align, size_t size, const void *address)
+{
+  hook_count++;
+  __memalign_hook = NULL;
+  void *mem = memalign (align, size);
+  __memalign_hook = memalign_called;
+  return mem;
+}
+
+static void initialize_hooks (void)
+{
+  __free_hook = free_called;
+  __malloc_hook = malloc_called;
+  __realloc_hook = realloc_called;
+  __memalign_hook = memalign_called;
+}
+void (*__malloc_initialize_hook) (void) = initialize_hooks;
+compat_symbol_reference (libc, __malloc_initialize_hook,
+			 __malloc_initialize_hook, GLIBC_2_0);
+compat_symbol_reference (libc, __free_hook,
+			 __free_hook, GLIBC_2_0);
+compat_symbol_reference (libc, __malloc_hook,
+			 __malloc_hook, GLIBC_2_0);
+compat_symbol_reference (libc, __realloc_hook,
+			 __realloc_hook, GLIBC_2_0);
+compat_symbol_reference (libc, __memalign_hook,
+			 __memalign_hook, GLIBC_2_0);
+
+DIAG_POP_NEEDS_COMMENT;
+
+static int
+do_test (void)
+{
+  void *p;
+  p = malloc (0);
+  TEST_VERIFY_EXIT (p != NULL);
+  call_count++;
+
+  p = realloc (p, 0);
+  TEST_VERIFY_EXIT (p == NULL);
+  call_count++;
+
+  p = calloc (512, 1);
+  TEST_VERIFY_EXIT (p != NULL);
+  call_count++;
+
+  free (p);
+  call_count++;
+
+  p = memalign (0x100, 0x100);
+  TEST_VERIFY_EXIT (p != NULL);
+  call_count++;
+
+  free (p);
+  call_count++;
+
+  printf ("call_count: %d, hook_count: %d\n", call_count, hook_count);
+
+#ifdef HOOKS_ENABLED
+  TEST_VERIFY_EXIT (call_count == hook_count);
+#else
+  TEST_VERIFY_EXIT (hook_count == 0);
+#endif
+
+  exit (0);
+}
+
+#include <support/test-driver.c>
diff --git a/malloc/tst-compathooks-on.c b/malloc/tst-compathooks-on.c
new file mode 100644
index 0000000000..4da183687a
--- /dev/null
+++ b/malloc/tst-compathooks-on.c
@@ -0,0 +1,2 @@
+#define HOOKS_ENABLED 1
+#include "tst-compathooks-off.c"
diff --git a/malloc/tst-malloc-usable-static-tunables.c b/malloc/tst-malloc-usable-static-tunables.c
deleted file mode 100644
index 8907db01a5..0000000000
--- a/malloc/tst-malloc-usable-static-tunables.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <malloc/tst-malloc-usable.c>
diff --git a/malloc/tst-malloc-usable-static.c b/malloc/tst-malloc-usable-static.c
deleted file mode 100644
index 8907db01a5..0000000000
--- a/malloc/tst-malloc-usable-static.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <malloc/tst-malloc-usable.c>
diff --git a/malloc/tst-mtrace.sh b/malloc/tst-mtrace.sh
index 9295683aff..a830204d5e 100755
--- a/malloc/tst-mtrace.sh
+++ b/malloc/tst-mtrace.sh
@@ -30,6 +30,7 @@ trap "rm -f ${common_objpfx}malloc/tst-mtrace.leak; exit 1" 1 2 15
 ${test_program_prefix_before_env} \
 ${run_program_env} \
 MALLOC_TRACE=${common_objpfx}malloc/tst-mtrace.leak \
+LD_PRELOAD=${common_objpfx}malloc/libc_malloc_debug.so \
 ${test_program_prefix_after_env} \
   ${common_objpfx}malloc/tst-mtrace || status=1