[v4,07/10] mtrace: Wean away from malloc hooks

Split mtrace hooks into before and after and adapt to the new internal
debugging hooks infrastructure.  With this, the malloc hooks are
unused internally and can be removed from the main library.

This also eliminates the only use of memalign through a PLT in the
library, so checklocalplt data needs to be updated to reflect that.
---
 include/malloc.h                              |   1 +
 malloc/hooks.c                                |  40 ++-
 malloc/mtrace-hooks.c                         | 137 ++++++++++
 malloc/mtrace.c                               | 233 +-----------------
 sysdeps/generic/localplt.data                 |   1 -
 sysdeps/mach/hurd/i386/localplt.data          |   1 -
 sysdeps/unix/sysv/linux/aarch64/localplt.data |   1 -
 sysdeps/unix/sysv/linux/alpha/localplt.data   |   1 -
 sysdeps/unix/sysv/linux/arc/localplt.data     |   1 -
 sysdeps/unix/sysv/linux/arm/localplt.data     |   1 -
 sysdeps/unix/sysv/linux/csky/localplt.data    |   1 -
 sysdeps/unix/sysv/linux/hppa/localplt.data    |   1 -
 sysdeps/unix/sysv/linux/i386/localplt.data    |   1 -
 sysdeps/unix/sysv/linux/ia64/localplt.data    |   1 -
 .../sysv/linux/m68k/coldfire/localplt.data    |   1 -
 .../unix/sysv/linux/m68k/m680x0/localplt.data |   1 -
 .../unix/sysv/linux/microblaze/localplt.data  |   1 -
 sysdeps/unix/sysv/linux/nios2/localplt.data   |   1 -
 .../linux/powerpc/powerpc32/fpu/localplt.data |   1 -
 .../powerpc/powerpc32/nofpu/localplt.data     |   1 -
 .../linux/powerpc/powerpc64/localplt.data     |   1 -
 sysdeps/unix/sysv/linux/riscv/localplt.data   |   1 -
 sysdeps/unix/sysv/linux/s390/localplt.data    |   1 -
 sysdeps/unix/sysv/linux/sh/localplt.data      |   1 -
 .../sysv/linux/sparc/sparc32/localplt.data    |   1 -
 .../sysv/linux/sparc/sparc64/localplt.data    |   1 -
 sysdeps/x86_64/localplt.data                  |   1 -
 27 files changed, 182 insertions(+), 252 deletions(-)
 create mode 100644 malloc/mtrace-hooks.c

On 7/2/21 7:38 AM, Siddhesh Poyarekar wrote:
> Split mtrace hooks into before and after and adapt to the new internal
> debugging hooks infrastructure.  With this, the malloc hooks are
> unused internally and can be removed from the main library.

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
 
> This also eliminates the only use of memalign through a PLT in the
> library, so checklocalplt data needs to be updated to reflect that.
> ---
>  include/malloc.h                              |   1 +
>  malloc/hooks.c                                |  40 ++-
>  malloc/mtrace-hooks.c                         | 137 ++++++++++
>  malloc/mtrace.c                               | 233 +-----------------
>  sysdeps/generic/localplt.data                 |   1 -
>  sysdeps/mach/hurd/i386/localplt.data          |   1 -
>  sysdeps/unix/sysv/linux/aarch64/localplt.data |   1 -
>  sysdeps/unix/sysv/linux/alpha/localplt.data   |   1 -
>  sysdeps/unix/sysv/linux/arc/localplt.data     |   1 -
>  sysdeps/unix/sysv/linux/arm/localplt.data     |   1 -
>  sysdeps/unix/sysv/linux/csky/localplt.data    |   1 -
>  sysdeps/unix/sysv/linux/hppa/localplt.data    |   1 -
>  sysdeps/unix/sysv/linux/i386/localplt.data    |   1 -
>  sysdeps/unix/sysv/linux/ia64/localplt.data    |   1 -
>  .../sysv/linux/m68k/coldfire/localplt.data    |   1 -
>  .../unix/sysv/linux/m68k/m680x0/localplt.data |   1 -
>  .../unix/sysv/linux/microblaze/localplt.data  |   1 -
>  sysdeps/unix/sysv/linux/nios2/localplt.data   |   1 -
>  .../linux/powerpc/powerpc32/fpu/localplt.data |   1 -
>  .../powerpc/powerpc32/nofpu/localplt.data     |   1 -
>  .../linux/powerpc/powerpc64/localplt.data     |   1 -
>  sysdeps/unix/sysv/linux/riscv/localplt.data   |   1 -
>  sysdeps/unix/sysv/linux/s390/localplt.data    |   1 -
>  sysdeps/unix/sysv/linux/sh/localplt.data      |   1 -
>  .../sysv/linux/sparc/sparc32/localplt.data    |   1 -
>  .../sysv/linux/sparc/sparc64/localplt.data    |   1 -
>  sysdeps/x86_64/localplt.data                  |   1 -
>  27 files changed, 182 insertions(+), 252 deletions(-)
>  create mode 100644 malloc/mtrace-hooks.c
> 
> diff --git a/include/malloc.h b/include/malloc.h
> index bb1123d9d3..6169d486f5 100644
> --- a/include/malloc.h
> +++ b/include/malloc.h
> @@ -15,6 +15,7 @@ typedef struct malloc_state *mstate;
>  #define __malloc_initialized __libc_malloc_initialized
>  /* Nonzero if the malloc is already initialized.  */
>  extern int __malloc_initialized attribute_hidden;
> +extern FILE *__mtrace_mallstream attribute_hidden;
>  
>  enum mcheck_status __mcheck_checkptr (const void *) attribute_hidden;
>  extern int __mcheck_initialize (void (*) (enum mcheck_status), bool)
> diff --git a/malloc/hooks.c b/malloc/hooks.c
> index 7b500e5671..7f3b07ca44 100644
> --- a/malloc/hooks.c
> +++ b/malloc/hooks.c
> @@ -37,6 +37,7 @@ enum malloc_debug_hooks
>    MALLOC_NONE_HOOK = 0,
>    MALLOC_CHECK_HOOK = 1 << 0,	/* MALLOC_CHECK_ or glibc.malloc.check.  */
>    MALLOC_MCHECK_HOOK = 1 << 1,	/* mcheck()  */
> +  MALLOC_MTRACE_HOOK = 1 << 2,	/* mtrace()  */
>  };
>  static unsigned __malloc_debugging_hooks;
>  
> @@ -79,6 +80,7 @@ __malloc_debug_disable (enum malloc_debug_hooks flag)
>  
>  #include "malloc-check.c"
>  #include "mcheck-hooks.c"
> +#include "mtrace-hooks.c"
>  
>  static __always_inline bool
>  _malloc_debug_before (size_t *bytesp, void **victimp, const void *address)
> @@ -111,8 +113,13 @@ _malloc_debug_before (size_t *bytesp, void **victimp, const void *address)
>  static __always_inline void *
>  _malloc_debug_after (void *mem, size_t bytes, const void *address)
>  {
> -  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && mem != NULL)
> -    mem = malloc_mcheck_after (mem, bytes);
> +  if (__glibc_unlikely (__malloc_debugging_hooks))
> +    {
> +      if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && mem != NULL)
> +	mem = malloc_mcheck_after (mem, bytes);
> +      if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
> +	mem = malloc_mtrace_after (mem, bytes, address);
> +    }
>    return mem;
>  }
>  
> @@ -129,6 +136,8 @@ _free_debug_before (void **mem, const void *address)
>  
>    if (__glibc_unlikely (__malloc_debugging_hooks))
>      {
> +      if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
> +	free_mtrace (mem, address);
>        if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK))
>  	*mem = free_mcheck (*mem);
>        if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
> @@ -171,8 +180,13 @@ static __always_inline void *
>  _realloc_debug_after (void *mem, void *oldmem, size_t bytes, size_t oldsize,
>  		      const void *address)
>  {
> -  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && mem != NULL)
> -    mem = realloc_mcheck_after (mem, oldmem, bytes, oldsize);
> +  if (__glibc_unlikely (__malloc_debugging_hooks))
> +    {
> +      if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && mem != NULL)
> +	mem = realloc_mcheck_after (mem, oldmem, bytes, oldsize);
> +      if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
> +	mem = realloc_mtrace_after (mem, oldmem, bytes, address);
> +    }
>    return mem;
>  }
>  
> @@ -206,8 +220,13 @@ static __always_inline void *
>  _memalign_debug_after (void *mem, size_t alignment, size_t bytes,
>  		       const void *address)
>  {
> -  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && mem != NULL)
> -    mem = memalign_mcheck_after (mem, alignment, bytes);
> +  if (__glibc_unlikely (__malloc_debugging_hooks))
> +    {
> +      if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && mem != NULL)
> +	mem = memalign_mcheck_after (mem, alignment, bytes);
> +      if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
> +	mem = memalign_mtrace_after (mem, bytes, address);
> +    }
>    return mem;
>  }
>  
> @@ -244,11 +263,16 @@ _calloc_debug_before (size_t *bytesp, void **victimp, const void *address)
>  static __always_inline void *
>  _calloc_debug_after (void *mem, size_t bytes, const void *address)
>  {
> -  if (__glibc_unlikely (__malloc_debugging_hooks) && mem != NULL)
> +  if (__glibc_unlikely (__malloc_debugging_hooks))
>      {
>        if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK))
>  	mem = malloc_mcheck_after (mem, bytes);
> -      memset (mem, 0, bytes);
> +      if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
> +	mem = malloc_mtrace_after (mem, bytes, address);
> +      /* mtrace uses __libc_calloc to do the zeroing.  */
> +      if (mem != NULL && __is_malloc_debug_enabled (MALLOC_CHECK_HOOK
> +						    | MALLOC_MCHECK_HOOK))
> +	memset (mem, 0, bytes);
>      }
>    return mem;
>  }
> diff --git a/malloc/mtrace-hooks.c b/malloc/mtrace-hooks.c
> new file mode 100644
> index 0000000000..c1c6d6a6e9
> --- /dev/null
> +++ b/malloc/mtrace-hooks.c
> @@ -0,0 +1,137 @@
> +
> +# include <libc-lock.h>
> +
> +#include <kernel-features.h>
> +
> +FILE *__mtrace_mallstream;
> +
> +__libc_lock_define_initialized (static, lock);
> +
> +static void
> +tr_where (const void *caller, Dl_info *info)
> +{
> +  if (caller != NULL)
> +    {
> +      if (info != NULL)
> +        {
> +          char *buf = (char *) "";
> +          if (info->dli_sname != NULL)
> +            {
> +              size_t len = strlen (info->dli_sname);
> +              buf = alloca (len + 6 + 2 * sizeof (void *));
> +
> +              buf[0] = '(';
> +              __stpcpy (_fitoa (caller >= (const void *) info->dli_saddr
> +                                ? caller - (const void *) info->dli_saddr
> +                                : (const void *) info->dli_saddr - caller,
> +                                __stpcpy (__mempcpy (buf + 1, info->dli_sname,
> +                                                     len),
> +                                          caller >= (void *) info->dli_saddr
> +                                          ? "+0x" : "-0x"),
> +                                16, 0),
> +                        ")");
> +            }
> +
> +          fprintf (__mtrace_mallstream, "@ %s%s%s[%p] ",
> +                   info->dli_fname ? : "", info->dli_fname ? ":" : "",
> +                   buf, caller);
> +        }
> +      else
> +        fprintf (__mtrace_mallstream, "@ [%p] ", caller);
> +    }
> +}
> +
> +static Dl_info *
> +lock_and_info (const void *caller, Dl_info *mem)
> +{
> +  if (caller == NULL)
> +    return NULL;
> +
> +  Dl_info *res = _dl_addr (caller, mem, NULL, NULL) ? mem : NULL;
> +
> +  __libc_lock_lock (lock);
> +
> +  return res;
> +}
> +
> +static bool
> +free_mtrace (void *ptr, const void *caller)
> +{
> +  if (ptr == NULL)
> +    return true;
> +
> +  Dl_info mem;
> +  Dl_info *info = lock_and_info (caller, &mem);
> +  tr_where (caller, info);
> +  /* Be sure to print it first.  */
> +  fprintf (__mtrace_mallstream, "- %p\n", ptr);
> +  __libc_lock_unlock (lock);
> +
> +  /* Continue on to free.  */
> +  return false;
> +}
> +
> +static void *
> +malloc_mtrace_after (void *block, size_t size, const void *caller)
> +{
> +  Dl_info mem;
> +  Dl_info *info = lock_and_info (caller, &mem);
> +
> +  tr_where (caller, info);
> +  /* We could be printing a NULL here; that's OK.  */
> +  fprintf (__mtrace_mallstream, "+ %p %#lx\n", block,
> +	   (unsigned long int) size);
> +
> +  __libc_lock_unlock (lock);
> +
> +  return block;
> +}
> +
> +static void *
> +realloc_mtrace_after (void *block, const void *oldptr, size_t size,
> +		      const void *caller)
> +{
> +  Dl_info mem;
> +  Dl_info *info = lock_and_info (caller, &mem);
> +
> +  tr_where (caller, info);
> +  if (block == NULL)
> +    {
> +      if (size != 0)
> +        /* Failed realloc.  */
> +        fprintf (__mtrace_mallstream, "! %p %#lx\n", oldptr,
> +		 (unsigned long int) size);
> +      else
> +        fprintf (__mtrace_mallstream, "- %p\n", oldptr);
> +    }
> +  else if (oldptr == NULL)
> +    fprintf (__mtrace_mallstream, "+ %p %#lx\n", block,
> +	     (unsigned long int) size);
> +  else
> +    {
> +      fprintf (__mtrace_mallstream, "< %p\n", oldptr);
> +      tr_where (caller, info);
> +      fprintf (__mtrace_mallstream, "> %p %#lx\n", block,
> +	       (unsigned long int) size);
> +    }
> +
> +  __libc_lock_unlock (lock);
> +
> +  return block;
> +}
> +
> +static void *
> +memalign_mtrace_after (void *block, size_t size, const void *caller)
> +{
> +  Dl_info mem;
> +  Dl_info *info = lock_and_info (caller, &mem);
> +
> +  tr_where (caller, info);
> +  /* We could be printing a NULL here; that's OK.  */
> +  fprintf (__mtrace_mallstream, "+ %p %#lx\n", block,
> +	   (unsigned long int) size);
> +
> +  __libc_lock_unlock (lock);
> +
> +  return block;
> +}
> diff --git a/malloc/mtrace.c b/malloc/mtrace.c
> index 6c2c58b706..2cc4507e25 100644
> --- a/malloc/mtrace.c
> +++ b/malloc/mtrace.c
> @@ -22,7 +22,6 @@
>  # define _MALLOC_INTERNAL
>  # include <malloc.h>
>  # include <mcheck.h>
> -# include <libc-lock.h>
>  #endif
>  
>  #include <dlfcn.h>
> @@ -35,20 +34,14 @@
>  
>  #include <libc-internal.h>
>  #include <dso_handle.h>
> -
>  #include <libio/iolibio.h>
>  #define setvbuf(s, b, f, l) _IO_setvbuf (s, b, f, l)
>  #define fwrite(buf, size, count, fp) _IO_fwrite (buf, size, count, fp)
>  
> -#include <kernel-features.h>
> -
>  #define TRACE_BUFFER_SIZE 512
>  
> -static FILE *mallstream;
> -static const char mallenv[] = "MALLOC_TRACE";
>  static char *malloc_trace_buffer;
> -
> -__libc_lock_define_initialized (static, lock);
> +static const char mallenv[] = "MALLOC_TRACE";
>  
>  #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_34)
>  /* Compatibility symbols that were introduced to help break at allocation sites
> @@ -69,204 +62,6 @@ tr_break (void)
>  compat_symbol (libc, tr_break, tr_break, GLIBC_2_0);
>  #endif
>  
> -
> -/* Old hook values.  */
> -static void (*tr_old_free_hook) (void *ptr, const void *);
> -static void *(*tr_old_malloc_hook) (size_t size, const void *);
> -static void *(*tr_old_realloc_hook) (void *ptr, size_t size,
> -				     const void *);
> -static void *(*tr_old_memalign_hook) (size_t __alignment, size_t __size,
> -				      const void *);
> -
> -static void
> -tr_where (const void *caller, Dl_info *info)
> -{
> -  if (caller != NULL)
> -    {
> -      if (info != NULL)
> -        {
> -          char *buf = (char *) "";
> -          if (info->dli_sname != NULL)
> -            {
> -              size_t len = strlen (info->dli_sname);
> -              buf = alloca (len + 6 + 2 * sizeof (void *));
> -
> -              buf[0] = '(';
> -              __stpcpy (_fitoa (caller >= (const void *) info->dli_saddr
> -                                ? caller - (const void *) info->dli_saddr
> -                                : (const void *) info->dli_saddr - caller,
> -                                __stpcpy (__mempcpy (buf + 1, info->dli_sname,
> -                                                     len),
> -                                          caller >= (void *) info->dli_saddr
> -                                          ? "+0x" : "-0x"),
> -                                16, 0),
> -                        ")");
> -            }
> -
> -          fprintf (mallstream, "@ %s%s%s[%p] ",
> -                   info->dli_fname ? : "", info->dli_fname ? ":" : "",
> -                   buf, caller);
> -        }
> -      else
> -        fprintf (mallstream, "@ [%p] ", caller);
> -    }
> -}
> -
> -static Dl_info *
> -lock_and_info (const void *caller, Dl_info *mem)
> -{
> -  if (caller == NULL)
> -    return NULL;
> -
> -  Dl_info *res = _dl_addr (caller, mem, NULL, NULL) ? mem : NULL;
> -
> -  __libc_lock_lock (lock);
> -
> -  return res;
> -}
> -
> -static void tr_freehook (void *, const void *);
> -static void * tr_mallochook (size_t, const void *);
> -static void * tr_reallochook (void *, size_t, const void *);
> -static void * tr_memalignhook (size_t, size_t, const void *);
> -
> -/* Set all the default non-trace hooks.  */
> -static __always_inline void
> -set_default_hooks (void)
> -{
> -  __free_hook = tr_old_free_hook;
> -  __malloc_hook = tr_old_malloc_hook;
> -  __realloc_hook = tr_old_realloc_hook;
> -  __memalign_hook = tr_old_memalign_hook;
> -}
> -
> -/* Set all of the tracing hooks used for mtrace.  */
> -static __always_inline void
> -set_trace_hooks (void)
> -{
> -  __free_hook = tr_freehook;
> -  __malloc_hook = tr_mallochook;
> -  __realloc_hook = tr_reallochook;
> -  __memalign_hook = tr_memalignhook;
> -}
> -
> -/* Save the current set of hooks as the default hooks.  */
> -static __always_inline void
> -save_default_hooks (void)
> -{
> -  tr_old_free_hook = __free_hook;
> -  tr_old_malloc_hook = __malloc_hook;
> -  tr_old_realloc_hook = __realloc_hook;
> -  tr_old_memalign_hook = __memalign_hook;
> -}
> -
> -static void
> -tr_freehook (void *ptr, const void *caller)
> -{
> -  if (ptr == NULL)
> -    return;
> -
> -  Dl_info mem;
> -  Dl_info *info = lock_and_info (caller, &mem);
> -  tr_where (caller, info);
> -  /* Be sure to print it first.  */
> -  fprintf (mallstream, "- %p\n", ptr);
> -  set_default_hooks ();
> -  if (tr_old_free_hook != NULL)
> -    (*tr_old_free_hook)(ptr, caller);
> -  else
> -    free (ptr);
> -  set_trace_hooks ();
> -  __libc_lock_unlock (lock);
> -}
> -
> -static void *
> -tr_mallochook (size_t size, const void *caller)
> -{
> -  void *hdr;
> -
> -  Dl_info mem;
> -  Dl_info *info = lock_and_info (caller, &mem);
> -
> -  set_default_hooks ();
> -  if (tr_old_malloc_hook != NULL)
> -    hdr = (void *) (*tr_old_malloc_hook)(size, caller);
> -  else
> -    hdr = (void *) malloc (size);
> -  set_trace_hooks ();
> -
> -  tr_where (caller, info);
> -  /* We could be printing a NULL here; that's OK.  */
> -  fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size);
> -
> -  __libc_lock_unlock (lock);
> -
> -  return hdr;
> -}
> -
> -static void *
> -tr_reallochook (void *ptr, size_t size, const void *caller)
> -{
> -  void *hdr;
> -
> -  Dl_info mem;
> -  Dl_info *info = lock_and_info (caller, &mem);
> -
> -  set_default_hooks ();
> -  if (tr_old_realloc_hook != NULL)
> -    hdr = (void *) (*tr_old_realloc_hook)(ptr, size, caller);
> -  else
> -    hdr = (void *) realloc (ptr, size);
> -  set_trace_hooks ();
> -
> -  tr_where (caller, info);
> -  if (hdr == NULL)
> -    {
> -      if (size != 0)
> -        /* Failed realloc.  */
> -        fprintf (mallstream, "! %p %#lx\n", ptr, (unsigned long int) size);
> -      else
> -        fprintf (mallstream, "- %p\n", ptr);
> -    }
> -  else if (ptr == NULL)
> -    fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size);
> -  else
> -    {
> -      fprintf (mallstream, "< %p\n", ptr);
> -      tr_where (caller, info);
> -      fprintf (mallstream, "> %p %#lx\n", hdr, (unsigned long int) size);
> -    }
> -
> -  __libc_lock_unlock (lock);
> -
> -  return hdr;
> -}
> -
> -static void *
> -tr_memalignhook (size_t alignment, size_t size, const void *caller)
> -{
> -  void *hdr;
> -
> -  Dl_info mem;
> -  Dl_info *info = lock_and_info (caller, &mem);
> -
> -  set_default_hooks ();
> -  if (tr_old_memalign_hook != NULL)
> -    hdr = (void *) (*tr_old_memalign_hook)(alignment, size, caller);
> -  else
> -    hdr = (void *) memalign (alignment, size);
> -  set_trace_hooks ();
> -
> -  tr_where (caller, info);
> -  /* We could be printing a NULL here; that's OK.  */
> -  fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size);
> -
> -  __libc_lock_unlock (lock);
> -
> -  return hdr;
> -}
> -
> -
>  #ifdef _LIBC
>  
>  /* This function gets called to make sure all memory the library
> @@ -276,7 +71,7 @@ static void __libc_freeres_fn_section
>  release_libc_mem (void)
>  {
>    /* Only call the free function if we still are running in mtrace mode.  */
> -  if (mallstream != NULL)
> +  if (__mtrace_mallstream != NULL)
>      __libc_freeres ();
>  }
>  #endif
> @@ -293,7 +88,7 @@ mtrace (void)
>    char *mallfile;
>  
>    /* Don't panic if we're called more than once.  */
> -  if (mallstream != NULL)
> +  if (__mtrace_mallstream != NULL)
>      return;
>  
>  #ifdef _LIBC
> @@ -310,15 +105,15 @@ mtrace (void)
>        if (mtb == NULL)
>          return;
>  
> -      mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "wce");
> -      if (mallstream != NULL)
> +      __mtrace_mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null",
> +				   "wce");
> +      if (__mtrace_mallstream != NULL)
>          {
>            /* Be sure it doesn't malloc its buffer!  */
>            malloc_trace_buffer = mtb;
> -          setvbuf (mallstream, malloc_trace_buffer, _IOFBF, TRACE_BUFFER_SIZE);
> -          fprintf (mallstream, "= Start\n");
> -	  save_default_hooks ();
> -	  set_trace_hooks ();
> +          setvbuf (__mtrace_mallstream, malloc_trace_buffer, _IOFBF,
> +		   TRACE_BUFFER_SIZE);
> +          fprintf (__mtrace_mallstream, "= Start\n");
>  #ifdef _LIBC
>            if (!added_atexit_handler)
>              {
> @@ -336,15 +131,11 @@ mtrace (void)
>  void
>  muntrace (void)
>  {
> -  if (mallstream == NULL)
> +  if (__mtrace_mallstream == NULL)
>      return;
>  
> -  /* Do the reverse of what done in mtrace: first reset the hooks and
> -     MALLSTREAM, and only after that write the trailer and close the
> -     file.  */
> -  FILE *f = mallstream;
> -  mallstream = NULL;
> -  set_default_hooks ();
> +  FILE *f = __mtrace_mallstream;
> +  __mtrace_mallstream = NULL;
>  
>    fprintf (f, "= End\n");
>    fclose (f);
> diff --git a/sysdeps/generic/localplt.data b/sysdeps/generic/localplt.data
> index e2083c0ce6..9b4f35786a 100644
> --- a/sysdeps/generic/localplt.data
> +++ b/sysdeps/generic/localplt.data
> @@ -4,7 +4,6 @@
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/mach/hurd/i386/localplt.data b/sysdeps/mach/hurd/i386/localplt.data
> index 94064ecbc5..47fbe1e2a7 100644
> --- a/sysdeps/mach/hurd/i386/localplt.data
> +++ b/sysdeps/mach/hurd/i386/localplt.data
> @@ -6,7 +6,6 @@
>  libc.so: calloc + REL R_386_GLOB_DAT
>  libc.so: free + REL R_386_GLOB_DAT
>  libc.so: malloc + REL R_386_GLOB_DAT
> -libc.so: memalign + REL R_386_GLOB_DAT
>  libc.so: realloc + REL R_386_GLOB_DAT
>  libm.so: matherr + REL R_386_GLOB_DAT
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/unix/sysv/linux/aarch64/localplt.data b/sysdeps/unix/sysv/linux/aarch64/localplt.data
> index 2c14b652ef..348b3f3793 100644
> --- a/sysdeps/unix/sysv/linux/aarch64/localplt.data
> +++ b/sysdeps/unix/sysv/linux/aarch64/localplt.data
> @@ -4,7 +4,6 @@
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  # If outline atomics are used, libgcc (built outside of glibc) may
> diff --git a/sysdeps/unix/sysv/linux/alpha/localplt.data b/sysdeps/unix/sysv/linux/alpha/localplt.data
> index 43f6fdaea1..44bf36f4f1 100644
> --- a/sysdeps/unix/sysv/linux/alpha/localplt.data
> +++ b/sysdeps/unix/sysv/linux/alpha/localplt.data
> @@ -18,7 +18,6 @@ libc.so: _Unwind_Find_FDE
>  libc.so: calloc + RELA R_ALPHA_GLOB_DAT
>  libc.so: free + RELA R_ALPHA_GLOB_DAT
>  libc.so: malloc + RELA R_ALPHA_GLOB_DAT
> -libc.so: memalign + RELA R_ALPHA_GLOB_DAT
>  libc.so: realloc + RELA R_ALPHA_GLOB_DAT
>  libm.so: matherr + RELA R_ALPHA_GLOB_DAT
>  # We used to offer inline functions that used this, so it must be exported.
> diff --git a/sysdeps/unix/sysv/linux/arc/localplt.data b/sysdeps/unix/sysv/linux/arc/localplt.data
> index 4479e8ee8a..ac5332caf7 100644
> --- a/sysdeps/unix/sysv/linux/arc/localplt.data
> +++ b/sysdeps/unix/sysv/linux/arc/localplt.data
> @@ -1,6 +1,5 @@
>  libc.so: realloc
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: calloc
>  libc.so: free
>  # At -Os, a struct assignment in libgcc-static pulls this in
> diff --git a/sysdeps/unix/sysv/linux/arm/localplt.data b/sysdeps/unix/sysv/linux/arm/localplt.data
> index eb315da2f1..78896444c6 100644
> --- a/sysdeps/unix/sysv/linux/arm/localplt.data
> +++ b/sysdeps/unix/sysv/linux/arm/localplt.data
> @@ -1,7 +1,6 @@
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: raise
>  libc.so: realloc
>  libm.so: matherr
> diff --git a/sysdeps/unix/sysv/linux/csky/localplt.data b/sysdeps/unix/sysv/linux/csky/localplt.data
> index 0ed8650b65..817ab2659a 100644
> --- a/sysdeps/unix/sysv/linux/csky/localplt.data
> +++ b/sysdeps/unix/sysv/linux/csky/localplt.data
> @@ -4,7 +4,6 @@
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  # The TLS-enabled version of these functions is interposed from libc.so.
>  ld.so: _dl_signal_error
> diff --git a/sysdeps/unix/sysv/linux/hppa/localplt.data b/sysdeps/unix/sysv/linux/hppa/localplt.data
> index 09893d4dcf..baf857a750 100644
> --- a/sysdeps/unix/sysv/linux/hppa/localplt.data
> +++ b/sysdeps/unix/sysv/linux/hppa/localplt.data
> @@ -4,7 +4,6 @@
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libc.so: __sigsetjmp
>  libc.so: _IO_funlockfile
> diff --git a/sysdeps/unix/sysv/linux/i386/localplt.data b/sysdeps/unix/sysv/linux/i386/localplt.data
> index 5334875b4b..f9bf7fb410 100644
> --- a/sysdeps/unix/sysv/linux/i386/localplt.data
> +++ b/sysdeps/unix/sysv/linux/i386/localplt.data
> @@ -4,7 +4,6 @@ libc.so: _Unwind_Find_FDE + REL R_386_GLOB_DAT
>  libc.so: calloc + REL R_386_GLOB_DAT
>  libc.so: free + REL R_386_GLOB_DAT
>  libc.so: malloc + REL R_386_GLOB_DAT
> -libc.so: memalign + REL R_386_GLOB_DAT
>  libc.so: realloc + REL R_386_GLOB_DAT
>  libm.so: matherr + REL R_386_GLOB_DAT
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/unix/sysv/linux/ia64/localplt.data b/sysdeps/unix/sysv/linux/ia64/localplt.data
> index 1c566a503e..174fb88128 100644
> --- a/sysdeps/unix/sysv/linux/ia64/localplt.data
> +++ b/sysdeps/unix/sysv/linux/ia64/localplt.data
> @@ -1,7 +1,6 @@
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  libm.so: matherrf
> diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/localplt.data b/sysdeps/unix/sysv/linux/m68k/coldfire/localplt.data
> index 3c5efb7204..42fa90508c 100644
> --- a/sysdeps/unix/sysv/linux/m68k/coldfire/localplt.data
> +++ b/sysdeps/unix/sysv/linux/m68k/coldfire/localplt.data
> @@ -2,7 +2,6 @@ libc.so: __m68k_read_tp
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/localplt.data b/sysdeps/unix/sysv/linux/m68k/m680x0/localplt.data
> index 843f4e25f2..34bd4c1aca 100644
> --- a/sysdeps/unix/sysv/linux/m68k/m680x0/localplt.data
> +++ b/sysdeps/unix/sysv/linux/m68k/m680x0/localplt.data
> @@ -3,7 +3,6 @@ libc.so: __m68k_read_tp
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/unix/sysv/linux/microblaze/localplt.data b/sysdeps/unix/sysv/linux/microblaze/localplt.data
> index 0e98d5251e..c3801314c9 100644
> --- a/sysdeps/unix/sysv/linux/microblaze/localplt.data
> +++ b/sysdeps/unix/sysv/linux/microblaze/localplt.data
> @@ -2,7 +2,6 @@ libc.so: __errno_location
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  # The dynamic loader needs __tls_get_addr for TLS.
> diff --git a/sysdeps/unix/sysv/linux/nios2/localplt.data b/sysdeps/unix/sysv/linux/nios2/localplt.data
> index b37987c7c0..17fcfdd4db 100644
> --- a/sysdeps/unix/sysv/linux/nios2/localplt.data
> +++ b/sysdeps/unix/sysv/linux/nios2/localplt.data
> @@ -6,7 +6,6 @@ libc.so: __gedf2
>  libc.so: malloc
>  libc.so: __gtsf2 ?
>  libc.so: __nesf2
> -libc.so: memalign
>  libc.so: __mulsf3
>  libc.so: __floatunsisf
>  libc.so: __addsf3
> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/localplt.data b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/localplt.data
> index a02dd5cc24..c0af84eef7 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/localplt.data
> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/localplt.data
> @@ -2,7 +2,6 @@ libc.so: _Unwind_Find_FDE
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/localplt.data b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/localplt.data
> index d8072597b7..581e54b95c 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/localplt.data
> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/localplt.data
> @@ -30,7 +30,6 @@ libc.so: abort ?
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: memset ?
>  libc.so: realloc
>  libm.so: copysignl ?
> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/localplt.data b/sysdeps/unix/sysv/linux/powerpc/powerpc64/localplt.data
> index bb498fbe3a..d69b7ae646 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/localplt.data
> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/localplt.data
> @@ -1,7 +1,6 @@
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/unix/sysv/linux/riscv/localplt.data b/sysdeps/unix/sysv/linux/riscv/localplt.data
> index 0a235592c3..e6d5330d5b 100644
> --- a/sysdeps/unix/sysv/linux/riscv/localplt.data
> +++ b/sysdeps/unix/sysv/linux/riscv/localplt.data
> @@ -4,7 +4,6 @@
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: memset ?
>  libc.so: realloc
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/unix/sysv/linux/s390/localplt.data b/sysdeps/unix/sysv/linux/s390/localplt.data
> index a02dd5cc24..c0af84eef7 100644
> --- a/sysdeps/unix/sysv/linux/s390/localplt.data
> +++ b/sysdeps/unix/sysv/linux/s390/localplt.data
> @@ -2,7 +2,6 @@ libc.so: _Unwind_Find_FDE
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/unix/sysv/linux/sh/localplt.data b/sysdeps/unix/sysv/linux/sh/localplt.data
> index 3225177c50..6491b9e37b 100644
> --- a/sysdeps/unix/sysv/linux/sh/localplt.data
> +++ b/sysdeps/unix/sysv/linux/sh/localplt.data
> @@ -4,7 +4,6 @@
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libc.so: _Unwind_Find_FDE
>  libc.so: _exit
> diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/localplt.data b/sysdeps/unix/sysv/linux/sparc/sparc32/localplt.data
> index be51efd566..38309a1393 100644
> --- a/sysdeps/unix/sysv/linux/sparc/sparc32/localplt.data
> +++ b/sysdeps/unix/sysv/linux/sparc/sparc32/localplt.data
> @@ -16,7 +16,6 @@ libc.so: _Unwind_Find_FDE
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data b/sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data
> index 809062d46c..6a216f3a5a 100644
> --- a/sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data
> +++ b/sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data
> @@ -15,7 +15,6 @@ libc.so: _Unwind_Find_FDE
>  libc.so: calloc
>  libc.so: free
>  libc.so: malloc
> -libc.so: memalign
>  libc.so: realloc
>  libm.so: matherr
>  # The TLS-enabled version of these functions is interposed from libc.so.
> diff --git a/sysdeps/x86_64/localplt.data b/sysdeps/x86_64/localplt.data
> index 8f41e92870..d1f2e26612 100644
> --- a/sysdeps/x86_64/localplt.data
> +++ b/sysdeps/x86_64/localplt.data
> @@ -6,7 +6,6 @@
>  libc.so: calloc + RELA R_X86_64_GLOB_DAT
>  libc.so: free + RELA R_X86_64_GLOB_DAT
>  libc.so: malloc + RELA R_X86_64_GLOB_DAT
> -libc.so: memalign + RELA R_X86_64_GLOB_DAT
>  libc.so: realloc + RELA R_X86_64_GLOB_DAT
>  libm.so: matherr + RELA R_X86_64_GLOB_DAT
>  # The TLS-enabled version of these functions is interposed from libc.so.
>