[PATCH] Honor executables DT_RUNPATH for dlopen

[PATCH] Honor executables DT_RUNPATH for dlopen

[Jakub Jelinek]

Hi!

echo 'void f () {}' | gcc -fpic -shared -xc - -o libbar.so
gcc -Wl,-rpath,.,--enable-new-dtags -xc - -ldl -o bar <<"EOF"
#include <dlfcn.h>

int main () {
  void *p = dlopen ("libbar.so", RTLD_NOW);
  if (!p)
    puts (dlerror ());
  return !p;
}
EOF
./bar

test fails, because for dlopen DT_RUNPATH of the executable is not searched.
Unfortunately the patch does a bunch of tests in the common path, maybe
it should be reordered to check l->l_runpath_dirs.dirs != -1 right before
l->l_type != lt_loaded test.

2002-10-10  Jakub Jelinek  <jakub@redhat.com>

	* elf/dl-load.c (_dl_map_object): Use DT_RUNPATH of the executable
	for dlopen searches.

--- libc/elf/dl-load.c.jj	2002-10-10 13:57:28.000000000 +0200
+++ libc/elf/dl-load.c	2002-10-10 13:59:20.000000000 +0200
@@ -1751,6 +1751,14 @@ _dl_map_object (struct link_map *loader,
 	  break;
 	}
 
+      /* If dynamically linked, try the DT_RUNPATH of the executable
+	 itself.  */
+      l = GL(dl_loaded);
+      if (fd == -1 && l && l->l_type != lt_loaded && l != loader
+	  && l->l_runpath_dirs.dirs != (void *) -1)
+	fd = open_path (name, namelen, preloaded, &l->l_runpath_dirs,
+			&realname, &fb);
+
       if (fd == -1
 	  && (__builtin_expect (! preloaded, 1)
 	      || ! INTUSE(__libc_enable_secure)))

	Jakub

Re: [PATCH] Honor executables DT_RUNPATH for dlopen

[Roland McGrath]

That change is not correct.  The ELF spec says that DT_RUNPATH applies to
"only the immediate dependencies of the executable or shared object
containing the DT_RUNPATH entry."  I'm not aware of anything that specifies
dlopen in enough detail that it couldn't do whatever it likes.  But it
seems consistent with the spec for dlopen not to be affected by any
DT_RUNPATH (except for dependencies being affected by a DT_RUNPATH within a
dlopen'd dependent object).  The application or library can use whatever
prefix it put in its DT_RUNPATH on the strings it passes to dlopen directly.