diff mbox series

[v5,4/8] mtrace: Wean away from malloc hooks

Message ID 20210705170814.4132997-5-siddhesh@sourceware.org
State Superseded
Headers show
Series malloc hooks removal | expand

Checks

Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent

Commit Message

Siddhesh Poyarekar July 5, 2021, 5:08 p.m. UTC
Wean mtrace away from the malloc hooks and move them into the debug
DSO.  Split the API away from the implementation so that we can add
the API to libc.so as well as libc_malloc_debug.so, with the libc
implementations being empty.
---
 malloc/malloc-debug.c |  13 ++
 malloc/mtrace-impl.c  | 224 ++++++++++++++++++++++++++++++
 malloc/mtrace.c       | 314 ++----------------------------------------
 3 files changed, 249 insertions(+), 302 deletions(-)
 create mode 100644 malloc/mtrace-impl.c
diff mbox series

Patch

diff --git a/malloc/malloc-debug.c b/malloc/malloc-debug.c
index daf48e0633..e810d47107 100644
--- a/malloc/malloc-debug.c
+++ b/malloc/malloc-debug.c
@@ -49,6 +49,7 @@  enum malloc_debug_hooks
 {
   MALLOC_NONE_HOOK = 0,
   MALLOC_MCHECK_HOOK = 1 << 0, /* mcheck()  */
+  MALLOC_MTRACE_HOOK = 1 << 1, /* mtrace()  */
 };
 static unsigned __malloc_debugging_hooks;
 
@@ -71,6 +72,7 @@  __malloc_debug_disable (enum malloc_debug_hooks flag)
 }
 
 #include "mcheck.c"
+#include "mtrace.c"
 
 extern void (*__free_hook) (void *, const void *);
 compat_symbol_reference (libc, __free_hook, __free_hook, GLIBC_2_0);
@@ -103,6 +105,8 @@  __debug_malloc (size_t bytes)
     }
   if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && victim != NULL)
     victim = malloc_mcheck_after (victim, orig_bytes);
+  if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
+    malloc_mtrace_after (victim, orig_bytes, RETURN_ADDRESS (0));
 
   return victim;
 }
@@ -120,6 +124,8 @@  __debug_free (void *mem)
 
   if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK))
     mem = free_mcheck (mem);
+  if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
+    free_mtrace (mem, RETURN_ADDRESS (0));
 
   __libc_free (mem);
 }
@@ -146,6 +152,8 @@  __debug_realloc (void *oldmem, size_t bytes)
   if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && victim != NULL)
     victim = realloc_mcheck_after (victim, oldmem, orig_bytes,
 				   oldsize);
+  if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
+    realloc_mtrace_after (victim, oldmem, orig_bytes, RETURN_ADDRESS (0));
 
   return victim;
 }
@@ -171,6 +179,8 @@  _mid_memalign (size_t alignment, size_t bytes, const void *address)
     }
   if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && victim != NULL)
     victim = memalign_mcheck_after (victim, alignment, orig_bytes);
+  if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
+    memalign_mtrace_after (victim, orig_bytes, address);
 
   return victim;
 }
@@ -272,6 +282,9 @@  __debug_calloc (size_t nmemb, size_t size)
 	victim = malloc_mcheck_after (victim, orig_bytes);
       memset (victim, 0, orig_bytes);
     }
+  if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
+    malloc_mtrace_after (victim, orig_bytes, RETURN_ADDRESS (0));
+
   return victim;
 }
 strong_alias (__debug_calloc, calloc)
diff --git a/malloc/mtrace-impl.c b/malloc/mtrace-impl.c
new file mode 100644
index 0000000000..de8e88e4f7
--- /dev/null
+++ b/malloc/mtrace-impl.c
@@ -0,0 +1,224 @@ 
+/* mtrace implementation for `malloc'.
+   Copyright (C) 1991-2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+                 Written April 2, 1991 by John Gilmore of Cygnus Support.
+                 Based on mcheck.c by Mike Haertel.
+
+   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 <malloc.h>
+#include <mcheck.h>
+
+#include <dlfcn.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include <libc-internal.h>
+#include <dso_handle.h>
+
+#include <kernel-features.h>
+
+#define TRACE_BUFFER_SIZE 512
+
+static FILE *mallstream;
+static const char mallenv[] = "MALLOC_TRACE";
+static char *malloc_trace_buffer;
+
+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 *));
+	      char sign;
+	      ptrdiff_t offset =
+		(ptrdiff_t) info->dli_saddr - (ptrdiff_t) caller;
+
+	      if (caller >= (const void *) info->dli_saddr)
+		{
+		  sign = '+';
+		  offset = -offset;
+		}
+	      else
+		  sign = '-';
+
+	      sprintf (buf, "(%s%c%lx)", info->dli_sname, sign, offset);
+            }
+
+	  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;
+
+  flockfile (mallstream);
+
+  return res;
+}
+
+static void
+free_mtrace (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);
+  funlockfile (mallstream);
+}
+
+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 (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
+
+  funlockfile (mallstream);
+}
+
+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 (mallstream, "! %p %#lx\n", oldptr, (unsigned long int) size);
+      else
+        fprintf (mallstream, "- %p\n", oldptr);
+    }
+  else if (oldptr == NULL)
+    fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
+  else
+    {
+      fprintf (mallstream, "< %p\n", oldptr);
+      tr_where (caller, info);
+      fprintf (mallstream, "> %p %#lx\n", block, (unsigned long int) size);
+    }
+
+  funlockfile (mallstream);
+}
+
+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 (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
+
+  funlockfile (mallstream);
+}
+
+/* This function gets called to make sure all memory the library
+   allocates get freed and so does not irritate the user when studying
+   the mtrace output.  */
+static void
+release_libc_mem (void)
+{
+  /* Only call the free function if we still are running in mtrace mode.  */
+  if (mallstream != NULL)
+    __libc_freeres ();
+}
+
+/* We enable tracing if the environment variable MALLOC_TRACE is set.  */
+
+static void
+do_mtrace (void)
+{
+  static int added_atexit_handler;
+  char *mallfile;
+
+  /* Don't panic if we're called more than once.  */
+  if (mallstream != NULL)
+    return;
+
+  mallfile = secure_getenv (mallenv);
+  if (mallfile != NULL)
+    {
+      char *mtb = malloc (TRACE_BUFFER_SIZE);
+      if (mtb == NULL)
+        return;
+
+      mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "wce");
+      if (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");
+          if (!added_atexit_handler)
+            {
+              added_atexit_handler = 1;
+              __cxa_atexit ((void (*)(void *))release_libc_mem, NULL,
+			    __dso_handle);
+            }
+	  __malloc_debug_enable (MALLOC_MTRACE_HOOK);
+        }
+      else
+        free (mtb);
+    }
+}
+
+static void
+do_muntrace (void)
+{
+  __malloc_debug_disable (MALLOC_MTRACE_HOOK);
+  if (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;
+
+  fprintf (f, "= End\n");
+  fclose (f);
+}
diff --git a/malloc/mtrace.c b/malloc/mtrace.c
index 274db3fb47..b632116dd1 100644
--- a/malloc/mtrace.c
+++ b/malloc/mtrace.c
@@ -1,4 +1,4 @@ 
-/* More debugging hooks for `malloc'.
+/* mtrace API for `malloc'.
    Copyright (C) 1991-2021 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
                  Written April 2, 1991 by John Gilmore of Cygnus Support.
@@ -18,40 +18,14 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#ifndef _MALLOC_INTERNAL
-# define _MALLOC_INTERNAL
-# include <malloc.h>
-# include <mcheck.h>
-# include <malloc-internal.h>
-# include <libc-lock.h>
+#if !IS_IN (libc)
+# include "mtrace-impl.c"
+#else
+# include <shlib-compat.h>
+# include <libc-symbols.h>
 #endif
 
-#include <dlfcn.h>
-#include <fcntl.h>
-#include <stdio.h>
-#include <string.h>
-#include <stdlib.h>
-
-#include <_itoa.h>
-
-#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);
-
-#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_34)
+#if IS_IN (libc) && SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_34)
 /* Compatibility symbols that were introduced to help break at allocation sites
    for specific memory allocations.  This is unusable with ASLR, although gdb
    may allow predictable allocation addresses.  Even then, gdb has watchpoint
@@ -71,282 +45,18 @@  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
-   allocates get freed and so does not irritate the user when studying
-   the mtrace output.  */
-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)
-    __libc_freeres ();
-}
-#endif
-
-
-/* We enable tracing if the environment variable MALLOC_TRACE is set.  */
-
 void
 mtrace (void)
 {
-#ifdef _LIBC
-  static int added_atexit_handler;
+#if !IS_IN (libc)
+  do_mtrace ();
 #endif
-  char *mallfile;
-
-  /* Don't panic if we're called more than once.  */
-  if (mallstream != NULL)
-    return;
-
-#ifdef _LIBC
-  /* When compiling the GNU libc we use the secure getenv function
-     which prevents the misuse in case of SUID or SGID enabled
-     programs.  */
-  mallfile = __libc_secure_getenv (mallenv);
-#else
-  mallfile = getenv (mallenv);
-#endif
-  if (mallfile != NULL)
-    {
-      char *mtb = malloc (TRACE_BUFFER_SIZE);
-      if (mtb == NULL)
-        return;
-
-      mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "wce");
-      if (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 ();
-#ifdef _LIBC
-          if (!added_atexit_handler)
-            {
-              added_atexit_handler = 1;
-              __cxa_atexit ((void (*)(void *))release_libc_mem, NULL,
-			    __dso_handle);
-            }
-#endif
-        }
-      else
-        free (mtb);
-    }
 }
 
 void
 muntrace (void)
 {
-  if (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 ();
-
-  fprintf (f, "= End\n");
-  fclose (f);
+#if !IS_IN (libc)
+  do_muntrace ();
+#endif
 }