Re: enabling caching for dl_iterate_phdr()

[David Mosberger <davidm at napali dot hpl dot hp dot com>]

>>>>> On Thu, 22 Jan 2004 07:29:45 +0100, Jakub Jelinek <jakub@redhat.com> said:

  Jakub> I'd make the counters unsigned long long instead to avoid
  Jakub> wrap around.

Fine by me.

  Jakub> Also, could you write a testcase for it? dl_iterate_phdr,
  Jakub> then dlopen some shlib in elf, then dl_iterate_phdr again,
  Jakub> check the counters, dlclose etc.

Sure.

Attached is an updated patch.  "make check subdirs=elf" passes all
tests (including the new tst-dlmodcount test).  If it looks OK,
please apply.

	--david

ChangeLog

2004-01-23  David Mosberger  <davidm@hpl.hp.com>

	* sysdeps/generic/ldsodefs.h (struct rtld_global): Add members
	_dl_load_adds and _dl_load_subs.
	* elf/dl-support.c (_dl_load_adds): New variable.
	(_dl_load_subs): Likewise.
	* elf/dl-object.c (_dl_new_object): Increment dl_load_adds.
	* elf/dl-close.c (_dl_close): Increment dl_load_subs.

	* elf/link.h (struct dl_phdr_info): Add members dlpi_adds and
	dlpi_subs.
	* include/link.h: Likewise.
	* elf/dl-iteratephdr.c (__dl_iterate_phdr): Initialize dlpi_adds
	and dlpi_subs members.
	(dl_iterate_phdr): Likewise.

	* elf/tst-dlmodcount.c: New file.
	* elf/Makefile (distribute): Mention tst-dlmodcount.c.
	(tests): If build-shared, mention tst-dlmodcount.
	($(objpfx)tst-dlmodcount): If build-shared, build and
	run tst-dlmodcount.

Index: elf/Makefile
--- elf/Makefile
+++ elf/Makefile
@@ -80,7 +80,7 @@
 		   reldep9.c reldep9mod1.c reldep9mod2.c reldep9mod3.c \
 		   tst-array1.exp tst-array2.exp tst-array4.exp \
 		   tst-array2dep.c \
-		   tst-execstack-mod.c \
+		   tst-execstack-mod.c tst-dlmodcount.c \
 		   check-textrel.c dl-sysdep.h
 
 CFLAGS-dl-runtime.c = -fexceptions -fasynchronous-unwind-tables
@@ -151,7 +151,7 @@
 	 restest2 next dblload dblunload reldep5 reldep6 reldep7 reldep8 \
 	 circleload1 tst-tls3 tst-tls4 tst-tls5 tst-tls6 tst-tls7 tst-tls8 \
 	 tst-tls10 tst-tls11 tst-tls12 tst-tls13 tst-tls14 tst-align \
-	 $(tests-execstack-$(have-z-execstack))
+	 $(tests-execstack-$(have-z-execstack)) tst-dlmodcount
 #	 reldep9
 test-srcs = tst-pathopt
 tests-vis-yes = vismain
@@ -713,4 +713,8 @@
 	  $(sort $(wildcard $(common-objpfx)*/lib*.so \
 			    $(common-objpfx)iconvdata/*.so)) > $@
 generated += check-textrel check-textrel.out
+
+$(objpfx)tst-dlmodcount: $(libdl)
+$(objpfx)tst-dlmodcount.out: $(test-modules)
+
 endif
Index: elf/dl-close.c
--- elf/dl-close.c
+++ elf/dl-close.c
@@ -319,6 +319,7 @@
   /* Notify the debugger we are about to remove some loaded objects.  */
   _r_debug.r_state = RT_DELETE;
   _dl_debug_state ();
+  ++GL(dl_load_subs);
 
 #ifdef USE_TLS
   size_t tls_free_start;
Index: elf/dl-iteratephdr.c
--- elf/dl-iteratephdr.c
+++ elf/dl-iteratephdr.c
@@ -48,6 +48,8 @@
       info.dlpi_name = l->l_name;
       info.dlpi_phdr = l->l_phdr;
       info.dlpi_phnum = l->l_phnum;
+      info.dlpi_adds = GL(dl_load_adds);
+      info.dlpi_subs = GL(dl_load_subs);
       ret = callback (&info, sizeof (struct dl_phdr_info), data);
       if (ret)
 	break;
@@ -84,6 +86,8 @@
       info.dlpi_name = "";
       info.dlpi_phdr = _dl_phdr;
       info.dlpi_phnum = _dl_phnum;
+      info.dlpi_adds = GL(dl_load_adds);
+      info.dlpi_subs = GL(dl_load_subs);
       ret = (*callback) (&info, sizeof (struct dl_phdr_info), data);
       if (ret)
 	return ret;
Index: elf/dl-object.c
--- elf/dl-object.c
+++ elf/dl-object.c
@@ -83,6 +83,7 @@
   else
     GL(dl_loaded) = new;
   ++GL(dl_nloaded);
+  ++GL(dl_load_adds);
 
   /* If we have no loader the new object acts as it.  */
   if (loader == NULL)
Index: elf/dl-support.c
--- elf/dl-support.c
+++ elf/dl-support.c
@@ -71,6 +71,11 @@
 /* Number of object in the _dl_loaded list.  */
 unsigned int _dl_nloaded;
 
+/* Incremented whenever something may have been added to dl_loaded. */
+unsigned long long _dl_load_adds;
+/* Incremented whenever something may have been removed from dl_loaded. */
+unsigned long long _dl_load_subs;
+
 /* Fake scope.  In dynamically linked binaries this is the scope of the
    main application but here we don't have something like this.  So
    create a fake scope containing nothing.  */
Index: elf/link.h
--- elf/link.h
+++ elf/link.h
@@ -100,6 +100,12 @@
     const char *dlpi_name;
     const ElfW(Phdr) *dlpi_phdr;
     ElfW(Half) dlpi_phnum;
+
+    /* Note: older versions of libc do not provide the following
+       members.  Check the SIZE argument pass to the dl_iterate_phdr()
+       callback to determine whether or not they areprovided.  */
+    unsigned long long dlpi_adds; /* incr. when phdrs may have been added */
+    unsigned long long dlpi_subs; /* incr. when phdrs may have been removed */
   };
 
 __BEGIN_DECLS
Index: elf/tst-dlmodcount.c
--- /dev/null
+++ elf/tst-dlmodcount.c
@@ -0,0 +1,107 @@
+/* Copyright (C) 2004 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by David Mosberger <davidm@hpl.hp.com>, 2004.
+
+   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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <link.h>
+#include <stdio.h>
+
+#define SET	0
+#define ADD	1
+#define REMOVE	2
+
+#define leq(l,r)	(((r) - (l)) <= ~0ULL/2)
+
+static int
+callback (struct dl_phdr_info *info, size_t size, void *ptr)
+{
+  static int last_adds = 0, last_subs = 0;
+  intptr_t cmd = (intptr_t) ptr;
+
+  printf ("  size = %Zu\n", size);
+  if (size < (offsetof (struct dl_phdr_info, dlpi_subs)
+	      + sizeof (info->dlpi_subs)))
+    {
+      fprintf (stderr, "dl_iterate_phdr failed to pass dlpi_adds/dlpi_subs\n");
+      exit (5);
+    }
+
+  printf ("  dlpi_adds = %Lu dlpi_subs = %Lu\n",
+	  info->dlpi_adds, info->dlpi_subs);
+
+  switch (cmd)
+    {
+    case SET:
+      break;
+
+    case ADD:
+      if (leq (info->dlpi_adds, last_adds))
+	{
+	  fprintf (stderr, "dlpi_adds failed to get incremented!\n");
+	  exit (3);
+	}
+      break;
+
+    case REMOVE:
+      if (leq (info->dlpi_subs, last_subs))
+	{
+	  fprintf (stderr, "dlpi_subs failed to get incremented!\n");
+	  exit (4);
+	}
+      break;
+    }
+  last_adds = info->dlpi_adds;
+  last_subs = info->dlpi_subs;
+  return -1;
+}
+
+static void *
+load (const char *path)
+{
+  void *handle;
+
+  printf ("loading `%s'\n", path);
+  handle = dlopen (path, RTLD_LAZY);
+  if (!handle)
+    exit (1);
+  dl_iterate_phdr (callback, (void *)(intptr_t) ADD);
+  return handle;
+}
+
+static void
+unload (const char *path, void *handle)
+{
+  int ret;
+
+  printf ("unloading `%s'\n", path);
+  if (dlclose (handle) < 0)
+    exit (2);
+  dl_iterate_phdr (callback, (void *)(intptr_t) REMOVE);
+}
+
+int
+main (int argc, char **argv)
+{
+  void *handle1, *handle2;
+
+  dl_iterate_phdr (callback, (void *)(intptr_t) SET);
+  handle1 = load ("firstobj.so");
+  handle2 = load ("globalmod1.so");
+  unload ("firstobj.so", handle1);
+  unload ("globalmod1.so", handle2);
+  return 0;
+}
Index: include/link.h
--- include/link.h
+++ include/link.h
@@ -293,6 +293,12 @@
     const char *dlpi_name;
     const ElfW(Phdr) *dlpi_phdr;
     ElfW(Half) dlpi_phnum;
+
+    /* Note: older versions of libc do not provide the following
+       members.  Check the SIZE argument pass to the dl_iterate_phdr()
+       callback to determine whether or not they areprovided.  */
+    unsigned long long dlpi_adds; /* incr. when phdrs may have been added */
+    unsigned long long dlpi_subs; /* incr. when phdrs may have been removed */
   };
 
 extern int dl_iterate_phdr (int (*callback) (struct dl_phdr_info *info,
Index: sysdeps/generic/ldsodefs.h
--- sysdeps/generic/ldsodefs.h
+++ sysdeps/generic/ldsodefs.h
@@ -265,6 +265,11 @@
   EXTERN const char *_dl_platform;
   EXTERN size_t _dl_platformlen;
 
+  /* Incremented whenever something may have been added to dl_loaded.  */
+  EXTERN unsigned long long _dl_load_adds;
+  /* Incremented whenever something may have been removed from dl_loaded.  */
+  EXTERN unsigned long long _dl_load_subs;
+
 #ifndef MAP_ANON
   /* File descriptor referring to the zero-fill device.  */
   EXTERN int _dl_zerofd;