Re: [PATCH] elf/dl-load.c: Remove local_strdup.

["Carlos O'Donell" <carlos at redhat dot com>]

On 10/23/2014 11:07 PM, Carlos O'Donell wrote:
> This patch removes the apparently superfluous local_strdup.
> I can find no reason for it to be here and the reason for
> it being there is not documented.
> 
> It has been present since 1996-08-15 in a patch that simply
> refactored strlen/malloc/memcpy code into local_strdup without
> changing anything. Probably a conservative change. Why strdup
> was not called is not clear.
> 
> I have verified that building dl-load.c uses the __strdup
> alias so the loader is self-consistent.
> 
> Tested on x86_64 with no regressions.
> 
> OK to commit?

v2
- Call __strdup

I checked this in.


elf/dl-load.c: Use __strdup.
    
During a refactoring pass several repeated blocks of code in dl-load.c
were turned into a call to a local function named local_strdup.  There
is no need for local_strdup, and the routines should instead call
__strdup.  This change does just that.  We call the internal symbol
__strdup because calling strdup is unsafe.  The user might be
using a standard that doesn't include strdup and may have defined this
symbol in their application. During a static link we might reference
the user defined symbol and crash if it doesn't implement a standards
conforming strdup. The resulting code is simpler to understand, and
makes it easier to debug.
    
No regressions on x86_64.
    
2014-10-28  Carlos O'Donell  <carlos@redhat.com>
    
	* dl-load.c (local_strdup): Remove.
	(expand_dynamic_string_token): Use __strdup.
	(decompose_rpath): Likewise.
	(_dl_map_object): Likewise.

a/ChangeLog b/ChangeLog
index 5c7bef3..6874e54 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2014-10-28  Carlos O'Donell  <carlos@redhat.com>
+
+	* dl-load.c (local_strdup): Remove.
+	(expand_dynamic_string_token): Use __strdup.
+	(decompose_rpath): Likewise.
+	(_dl_map_object): Likewise.
+
 2014-10-28  Joseph Myers  <joseph@codesourcery.com>
 
 	[BZ #14132]
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 9dd40e3..ce5b626 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -112,20 +112,6 @@ static const size_t system_dirs_len[] =
   (sizeof (system_dirs_len) / sizeof (system_dirs_len[0]))
 
 
-/* Local version of `strdup' function.  */
-static char *
-local_strdup (const char *s)
-{
-  size_t len = strlen (s) + 1;
-  void *new = malloc (len);
-
-  if (new == NULL)
-    return NULL;
-
-  return (char *) memcpy (new, s, len);
-}
-
-
 static bool
 is_trusted_path (const char *path, size_t len)
 {
@@ -384,7 +370,7 @@ expand_dynamic_string_token (struct link_map *l, const char *s, int is_path)
 
   /* If we do not have to replace anything simply copy the string.  */
   if (__glibc_likely (cnt == 0))
-    return local_strdup (s);
+    return __strdup (s);
 
   /* Determine the length of the substituted string.  */
   total = DL_DST_REQUIRED (l, s, strlen (s), cnt);
@@ -593,7 +579,7 @@ decompose_rpath (struct r_search_path_struct *sps,
     }
 
   /* Make a writable copy.  */
-  copy = local_strdup (rpath);
+  copy = __strdup (rpath);
   if (copy == NULL)
     {
       errstring = N_("cannot create RUNPATH/RPATH copy");
@@ -2101,7 +2087,7 @@ _dl_map_object (struct link_map *loader, const char *name,
 				    false);
 		  if (__glibc_likely (fd != -1))
 		    {
-		      realname = local_strdup (cached);
+		      realname = __strdup (cached);
 		      if (realname == NULL)
 			{
 			  __close (fd);
@@ -2130,7 +2116,7 @@ _dl_map_object (struct link_map *loader, const char *name,
       /* The path may contain dynamic string tokens.  */
       realname = (loader
 		  ? expand_dynamic_string_token (loader, name, 0)
-		  : local_strdup (name));
+		  : __strdup (name));
       if (realname == NULL)
 	fd = -1;
       else
@@ -2164,7 +2150,7 @@ _dl_map_object (struct link_map *loader, const char *name,
 	  static const Elf_Symndx dummy_bucket = STN_UNDEF;
 
 	  /* Allocate a new object map.  */
-	  if ((name_copy = local_strdup (name)) == NULL
+	  if ((name_copy = __strdup (name)) == NULL
 	      || (l = _dl_new_object (name_copy, name, type, loader,
 				      mode, nsid)) == NULL)
 	    {
---

Cheers,
Carlos.