malloc: Set and reset all hooks for tracing (Bug 16573)

Message ID 4830451c-2bd1-e019-51f3-ee3e6b806529@redhat.com
State Superseded
Headers show
Series
  • malloc: Set and reset all hooks for tracing (Bug 16573)
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Commit Message

Carlos O'Donell April 8, 2019, 10:06 p.m.
Kwok,

This is a rebase and refactor of an old patch of yours. I'm cleaning up
the malloc patch queue, and this is still applicable because we haven't
yet removed the old tracer for the new tracer.

The exact failure you saw can't happen again today because we don't
do backtraces on malloc corruption, we would have just aborted the
process without a hang. However, I think the patch is still valid
because _dl_addr() could do any number of operations calling back into
one of the other trace handlers and hang.

Does this look OK to you for master?

8< --- 8< --- 8<
If an error occurs during the tracing operation, particularly during a
call to lock_and_info() which calls _dl_addr, we may end up calling back
into the malloc-subsystem and relock the loader lock and deadlock. For
all intents and purposes the call to _dl_addr can call any of the malloc
family API functions and so we should disable all tracing before calling
such loader functions.  This is similar to the strategy that the new
malloc tracer takes when calling the real malloc, namely that all
tracing ceases at the boundary to the real function and any faults at
that point are the purvue of the library (though the new tracer does
this on a per-thread basis in an MT-safe fashion). Since the new tracer
and the hook deprecation are not yet complete we must fix these issues
where we can.

Tested on x86_64 with no regressions.

Co-authored-by: Kwok Cheung Yeung <kcy@codesourcery.com>
---
  ChangeLog       | 15 +++++++++++
  malloc/mtrace.c | 72 +++++++++++++++++++++++++++++++------------------
  2 files changed, 61 insertions(+), 26 deletions(-)

-- 
2.21.0

Patch

diff --git a/ChangeLog b/ChangeLog
index 6b7f19a1f3..786bb52400 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@ 
+2019-04-08  Carlos O'Donell  <carlos@redhat.com>
+	    Kwok Cheung Yeung  <kcy@codesourcery.com>
+
+	[BZ #16573]
+	* malloc/mtrace.c: Define prototypes for all hooks.
+	(set_default_hooks): New function.
+	(set_trace_hooks): Likewise.
+	(save_default_hooks): Likewise.
+	(tr_freehook): Use new s*_hooks functions.
+	(tr_mallochook): Likewise.
+	(tr_reallochook): Likewise.
+	(tr_memalignhook): Likewise.
+	(mtrace): Likewise.
+	(muntrace): Likewise.
+
  2019-04-08  Florian Weimer  <fweimer@redhat.com>
  
  	* resolv/resolv.h (RES_INSECURE1, RES_INSECURE2): Remove
diff --git a/malloc/mtrace.c b/malloc/mtrace.c
index a2facf65ea..7c6af9e693 100644
--- a/malloc/mtrace.c
+++ b/malloc/mtrace.c
@@ -121,6 +121,41 @@  lock_and_info (const void *caller, Dl_info *mem)
    return res;
  }
  
+static void tr_freehook (__ptr_t, const __ptr_t);
+static __ptr_t tr_mallochook (size_t, const __ptr_t);
+static __ptr_t tr_reallochook (__ptr_t, size_t, const __ptr_t);
+static __ptr_t tr_memalignhook (size_t, size_t, const __ptr_t);
+
+/* 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)
  {
@@ -138,12 +173,12 @@  tr_freehook (void *ptr, const void *caller)
        tr_break ();
        __libc_lock_lock (lock);
      }
-  __free_hook = tr_old_free_hook;
+  set_default_hooks ();
    if (tr_old_free_hook != NULL)
      (*tr_old_free_hook)(ptr, caller);
    else
      free (ptr);
-  __free_hook = tr_freehook;
+  set_trace_hooks ();
    __libc_lock_unlock (lock);
  }
  
@@ -155,12 +190,12 @@  tr_mallochook (size_t size, const void *caller)
    Dl_info mem;
    Dl_info *info = lock_and_info (caller, &mem);
  
-  __malloc_hook = tr_old_malloc_hook;
+  set_default_hooks ();
    if (tr_old_malloc_hook != NULL)
      hdr = (void *) (*tr_old_malloc_hook)(size, caller);
    else
      hdr = (void *) malloc (size);
-  __malloc_hook = tr_mallochook;
+  set_trace_hooks ();
  
    tr_where (caller, info);
    /* We could be printing a NULL here; that's OK.  */
@@ -185,16 +220,12 @@  tr_reallochook (void *ptr, size_t size, const void *caller)
    Dl_info mem;
    Dl_info *info = lock_and_info (caller, &mem);
  
-  __free_hook = tr_old_free_hook;
-  __malloc_hook = tr_old_malloc_hook;
-  __realloc_hook = tr_old_realloc_hook;
+  set_default_hooks ();
    if (tr_old_realloc_hook != NULL)
      hdr = (void *) (*tr_old_realloc_hook)(ptr, size, caller);
    else
      hdr = (void *) realloc (ptr, size);
-  __free_hook = tr_freehook;
-  __malloc_hook = tr_mallochook;
-  __realloc_hook = tr_reallochook;
+  set_trace_hooks ();
  
    tr_where (caller, info);
    if (hdr == NULL)
@@ -230,14 +261,12 @@  tr_memalignhook (size_t alignment, size_t size, const void *caller)
    Dl_info mem;
    Dl_info *info = lock_and_info (caller, &mem);
  
-  __memalign_hook = tr_old_memalign_hook;
-  __malloc_hook = tr_old_malloc_hook;
+  set_default_hooks ();
    if (tr_old_memalign_hook != NULL)
      hdr = (void *) (*tr_old_memalign_hook)(alignment, size, caller);
    else
      hdr = (void *) memalign (alignment, size);
-  __memalign_hook = tr_memalignhook;
-  __malloc_hook = tr_mallochook;
+  set_trace_hooks ();
  
    tr_where (caller, info);
    /* We could be printing a NULL here; that's OK.  */
@@ -305,14 +334,8 @@  mtrace (void)
            malloc_trace_buffer = mtb;
            setvbuf (mallstream, malloc_trace_buffer, _IOFBF, TRACE_BUFFER_SIZE);
            fprintf (mallstream, "= Start\n");
-          tr_old_free_hook = __free_hook;
-          __free_hook = tr_freehook;
-          tr_old_malloc_hook = __malloc_hook;
-          __malloc_hook = tr_mallochook;
-          tr_old_realloc_hook = __realloc_hook;
-          __realloc_hook = tr_reallochook;
-          tr_old_memalign_hook = __memalign_hook;
-          __memalign_hook = tr_memalignhook;
+	  save_default_hooks ();
+	  set_trace_hooks ();
  #ifdef _LIBC
            if (!added_atexit_handler)
              {
@@ -338,10 +361,7 @@  muntrace (void)
       file.  */
    FILE *f = mallstream;
    mallstream = NULL;
-  __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_default_hooks ();
  
    fprintf (f, "= End\n");
    fclose (f);