ld.so slight difference Linux and FreeBSD ports/127946

[Maho NAKATA]

Hi Konstantin and Alexander,

in short, your patch is ok.

* applied to 7.2-RELEASE/i386
* small test program works.
* ooo bad transfer error went away (tested with 3.1.0 from ports,
and backout except.cc)

many thanks for your patch!!

Best,

From: Kostik Belousov <kostikbel at gmail.com>
Subject: Re: ld.so slight difference Linux and FreeBSD ports/127946
Date: Tue, 16 Jun 2009 00:08:31 +0300

> On Mon, Jun 15, 2009 at 05:46:54AM +0900, Maho NAKATA wrote:
>> Hi Konstantin,
>> 
>> Your patch rocks! tested on FBSD7/i386 and it works!
>> 
>> * Small test program works.
>> * also PR 127946 and Issue 22253 went away.
>>  
>> Is your patch can be commit to FBSD8 or MFC'ed to 7?
> 
> After discussion with Alexander, who pointed out that handles
> returned from dlopen done over non-NULL name shall not search
> in the namespace of objects opened with RTLD_GLOBAL flag,
> I modified the patch.
> 
> Would be nice if you could retest the change below.
> 
> diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
> index 40ed6ed..54acb8a 100644
> --- a/libexec/rtld-elf/rtld.c
> +++ b/libexec/rtld-elf/rtld.c
> @@ -1048,9 +1048,13 @@ dlcheck(void *handle)
>  {
>      Obj_Entry *obj;
>  
> -    for (obj = obj_list;  obj != NULL;  obj = obj->next)
> -	if (obj == (Obj_Entry *) handle)
> -	    break;
> +    if (handle == RTLD_HANDLE_FROM_NULL)
> +	obj = obj_main;
> +    else {
> +	for (obj = obj_list;  obj != NULL;  obj = obj->next)
> +	    if (obj == (Obj_Entry *) handle)
> +		break;
> +    }
>  
>      if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) {
>  	_rtld_error("Invalid shared object handle %p", handle);
> @@ -2054,6 +2058,8 @@ dlopen(const char *name, int mode)
>      objlist_call_init(&initlist, &lockstate);
>      objlist_clear(&initlist);
>      wlock_release(rtld_bind_lock, lockstate);
> +    if (name == NULL)
> +	obj = RTLD_HANDLE_FROM_NULL;
>      return obj;
>  trace:
>      trace_loaded_objects(obj);
> @@ -2069,7 +2075,7 @@ do_dlsym(void *handle, const char *name, void *retaddr, const Ver_Entry *ve,
>      const Obj_Entry *obj, *defobj;
>      const Elf_Sym *def, *symp;
>      unsigned long hash;
> -    int lockstate;
> +    int lockstate, search_global;
>  
>      hash = elf_hash(name);
>      def = NULL;
> @@ -2079,6 +2085,7 @@ do_dlsym(void *handle, const char *name, void *retaddr, const Ver_Entry *ve,
>      lockstate = rlock_acquire(rtld_bind_lock);
>      if (handle == NULL || handle == RTLD_NEXT ||
>  	handle == RTLD_DEFAULT || handle == RTLD_SELF) {
> +	search_global = true;
>  
>  	if ((obj = obj_from_addr(retaddr)) == NULL) {
>  	    _rtld_error("Cannot determine caller's shared object");
> @@ -2120,6 +2127,7 @@ do_dlsym(void *handle, const char *name, void *retaddr, const Ver_Entry *ve,
>  	    def = symlook_default(name, hash, obj, &defobj, ve, flags);
>  	}
>      } else {
> +	search_global = (handle == RTLD_HANDLE_FROM_NULL);
>  	if ((obj = dlcheck(handle)) == NULL) {
>  	    rlock_release(rtld_bind_lock, lockstate);
>  	    return NULL;
> @@ -2141,6 +2149,11 @@ do_dlsym(void *handle, const char *name, void *retaddr, const Ver_Entry *ve,
>  				 &donelist);
>  	}
>      }
> +    if (def == NULL && search_global) {
> +	donelist_init(&donelist);
> +	def = symlook_list(name, hash, &list_global, &defobj, ve, flags,
> +			   &donelist);
> +    }
>  
>      if (def != NULL) {
>  	rlock_release(rtld_bind_lock, lockstate);
> diff --git a/libexec/rtld-elf/rtld.h b/libexec/rtld-elf/rtld.h
> index 2b3b897..b16e57e 100644
> --- a/libexec/rtld-elf/rtld.h
> +++ b/libexec/rtld-elf/rtld.h
> @@ -238,6 +238,9 @@ typedef struct Struct_Obj_Entry {
>  #define SYMLOOK_DLSYM	0x02	/* Return newes versioned symbol. Used by
>  				   dlsym. */
>  
> +/* Handle returned by dlopen(NULL, flags). */
> +#define	RTLD_HANDLE_FROM_NULL	((void *) -100)
> +
>  /*
>   * Symbol cache entry used during relocation to avoid multiple lookups
>   * of the same symbol.