From fd537e535fe9f4d2b0286cf7a7242ef1e6775e67 Mon Sep 17 00:00:00 2001
From: Ulrich Drepper <drepper@redhat.com>
Date: Thu, 29 Jan 2009 00:17:57 +0000
Subject: [PATCH] [BZ #9750]

	* nscd/mem.c (gc): Use alloca_count to get the real stack usage.
	* include/alloca.h (alloca_account): Define.
	* sysdeps/x86_64/stackinfo.h (stackinfo_get_sp): Define.
	(stackinfo_sub_sp): Define.
---
 ChangeLog                  |  6 ++++++
 include/alloca.h           | 13 +++++++++++++
 nscd/mem.c                 | 21 ++++++++-------------
 sysdeps/x86_64/stackinfo.h | 12 +++++++++++-
 4 files changed, 38 insertions(+), 14 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 257d1e8..36d09f7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2009-01-28  Ulrich Drepper  <drepper@redhat.com>
 
+	[BZ #9750]
+	* nscd/mem.c (gc): Use alloca_count to get the real stack usage.
+	* include/alloca.h (alloca_account): Define.
+	* sysdeps/x86_64/stackinfo.h (stackinfo_get_sp): Define.
+	(stackinfo_sub_sp): Define.
+
 	* nscd/connections.c (nscd_init): If database file access be
 	opened check whether this is due to permission problems and bail
 	in that case.
diff --git a/include/alloca.h b/include/alloca.h
index 563d786..7d243fd 100644
--- a/include/alloca.h
+++ b/include/alloca.h
@@ -46,4 +46,17 @@ extern int __libc_alloca_cutoff (size_t size) __attribute__ ((const));
   __alloca (((len) = (newlen)))
 #endif
 
+#if defined stackinfo_get_sp && defined stackinfo_sub_sp
+# define alloca_account(size, avar) \
+  ({ void *old__ = stackinfo_get_sp ();			\
+     void *m__ = __alloca (size);			\
+     avar += stackinfo_sub_sp (old__);			\
+     m__; })
+#else
+# define alloca_account(size, avar) \
+  ({ size_t s__ = (size);		    \
+     avar += size__;			    \
+     __alloca (size__); })
+#endif
+
 #endif
diff --git a/nscd/mem.c b/nscd/mem.c
index 5f4c4dd..7f3ea06 100644
--- a/nscd/mem.c
+++ b/nscd/mem.c
@@ -134,12 +134,11 @@ gc (struct database_dyn *db)
     stack_used = 0;
   size_t nmark = (db->head->first_free / BLOCK_ALIGN + BITS - 1) / BITS;
   size_t memory_needed = nmark * sizeof (BITMAP_T);
-  if (stack_used + memory_needed <= MAX_STACK_USE)
+  if (__builtin_expect (stack_used + memory_needed <= MAX_STACK_USE, 1))
     {
-      mark = (BITMAP_T *) alloca (memory_needed);
+      mark = (BITMAP_T *) alloca_account (memory_needed, stack_used);
       mark_use_malloc = false;
       memset (mark, '\0', memory_needed);
-      stack_used += memory_needed;
     }
   else
     {
@@ -153,19 +152,17 @@ gc (struct database_dyn *db)
   struct hashentry **he;
   struct hashentry **he_data;
   bool he_use_malloc;
-  if (stack_used + memory_needed <= MAX_STACK_USE)
+  if (__builtin_expect (stack_used + memory_needed <= MAX_STACK_USE, 1))
     {
-      he = alloca (db->head->nentries * sizeof (struct hashentry *));
-      he_data = alloca (db->head->nentries * sizeof (struct hashentry *));
+      he = alloca_account (memory_needed, stack_used);
       he_use_malloc = false;
-      stack_used += memory_needed;
     }
   else
     {
       he = xmalloc (memory_needed);
-      he_data = &he[db->head->nentries];
       he_use_malloc = true;
     }
+  he_data = &he[db->head->nentries];
 
   size_t cnt = 0;
   for (size_t idx = 0; idx < db->head->module; ++idx)
@@ -373,11 +370,9 @@ gc (struct database_dyn *db)
       ref_t disp = off_alloc - off_free;
 
       struct moveinfo *new_move;
-      if (stack_used + sizeof (*new_move) <= MAX_STACK_USE)
-	{
-	  new_move = alloca (sizeof (*new_move));
-	  stack_used += sizeof (*new_move);
-	}
+      if (__builtin_expect (stack_used + sizeof (*new_move) <= MAX_STACK_USE,
+			    1))
+	new_move = alloca_account (sizeof (*new_move), stack_used);
       else
 	new_move = obstack_alloc (&ob, sizeof (*new_move));
       new_move->from = db->data + off_alloc;
diff --git a/sysdeps/x86_64/stackinfo.h b/sysdeps/x86_64/stackinfo.h
index 60668d1..b11849d 100644
--- a/sysdeps/x86_64/stackinfo.h
+++ b/sysdeps/x86_64/stackinfo.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009 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
@@ -25,4 +25,14 @@
 /* On x86_64 the stack grows down.  */
 #define _STACK_GROWS_DOWN	1
 
+/* Access to the stack pointer.  The macros are used in alloca_account
+   for which they need to act as barriers as well, hence the additional
+   (unnecessary) parameters.  */
+#define stackinfo_get_sp() \
+  ({ void *p__; asm volatile ("mov %%rsp, %0" : "=r" (p__)); p__; })
+#define stackinfo_sub_sp(ptr) \
+  ({ ptrdiff_t d__;						\
+     asm volatile ("sub %%rsp, %0" : "=r" (d__) : "0" (ptr));	\
+     d__; })
+
 #endif	/* stackinfo.h */
-- 
2.7.4