For Google b/8315591, experimental implementation of dlopen_with_offset.

5 files changed, 108 insertions, 25 deletions

diff --git a/dlfcn/Versions b/dlfcn/Versions
index 97902f0..77b0cf0 100644
--- a/dlfcn/Versions
+++ b/dlfcn/Versions
@@ -11,6 +11,9 @@ libdl {
   GLIBC_2.3.4 {
     dlmopen;
   }
+  GLIBC_2.15 {
+    __google_dlopen_with_offset; __google_dlmopen_with_offset;
+  }
   GLIBC_PRIVATE {
     _dlfcn_hook;
   }
diff --git a/dlfcn/dlfcn.h b/dlfcn/dlfcn.h
index 0921fd7..caa92e6 100644
--- a/dlfcn/dlfcn.h
+++ b/dlfcn/dlfcn.h
@@ -22,6 +22,7 @@
 #include <features.h>
 #define __need_size_t
 #include <stddef.h>
+#include <sys/types.h>
 
 /* Collect various system dependent definitions and declarations.  */
 #include <bits/dlfcn.h>
@@ -55,6 +56,11 @@ __BEGIN_DECLS
    passed to `dlsym' to get symbol values from it.  */
 extern void *dlopen (const char *__file, int __mode) __THROWNL;
 
+/* Same as above, but ELF header is at OFF from the start of file.  */
+extern void *__google_dlopen_with_offset (__const char *__file,
+					  off_t offset,
+					  int __mode) __THROW;
+
 /* Unmap and close a shared object opened by `dlopen'.
    The handle cannot be used again after calling `dlclose'.  */
 extern int dlclose (void *__handle) __THROWNL __nonnull ((1));
@@ -68,6 +74,12 @@ extern void *dlsym (void *__restrict __handle,
 /* Like `dlopen', but request object to be allocated in a new namespace.  */
 extern void *dlmopen (Lmid_t __nsid, const char *__file, int __mode) __THROWNL;
 
+/* Same as above, but ELF header is at OFF from the start of file.  */
+extern void *__google_dlmopen_with_offset (Lmid_t __nsid,
+					   __const char *__file,
+					   off_t offset,
+					   int __mode) __THROW;
+
 /* Find the run-time address in the shared object HANDLE refers to
    of the symbol called NAME with VERSION.  */
 extern void *dlvsym (void *__restrict __handle,
diff --git a/dlfcn/dlmopen.c b/dlfcn/dlmopen.c
index 2be1319..fb665ed 100644
--- a/dlfcn/dlmopen.c
+++ b/dlfcn/dlmopen.c
@@ -40,6 +40,8 @@ struct dlmopen_args
 {
   /* Namespace ID.  */
   Lmid_t nsid;
+  /* ELF header at offset in file.  */
+  off_t offset;
   /* The arguments for dlopen_doit.  */
   const char *file;
   int mode;
@@ -70,13 +72,52 @@ dlmopen_doit (void *a)
 	_dl_signal_error (EINVAL, NULL, NULL, N_("invalid mode"));
     }
 
-  args->new = GLRO(dl_open) (args->file ?: "", args->mode | __RTLD_DLOPEN,
+  args->new = GLRO(dl_open) (args->file ?: "", args->offset, args->mode | __RTLD_DLOPEN,
 			     args->caller,
 			     args->nsid, __dlfcn_argc, __dlfcn_argv,
 			     __environ);
 }
 
 
+static void *
+__dlmopen_common (struct dlmopen_args *args)
+{
+
+# ifdef SHARED
+  return _dlerror_run (dlmopen_doit, args) ? NULL : args->new;
+# else
+  if (_dlerror_run (dlmopen_doit, args))
+    return NULL;
+
+  __libc_register_dl_open_hook ((struct link_map *) args->new);
+  __libc_register_dlfcn_hook ((struct link_map *) args->new);
+
+  return args->new;
+# endif
+}
+
+void *
+__dlmopen_with_offset (Lmid_t nsid, const char *file, off_t offset,
+		       int mode DL_CALLER_DECL)
+{
+# ifdef SHARED
+  if (!rtld_active ())
+    return _dlfcn_hook->dlmopen_with_offset (nsid, file, offset, mode, RETURN_ADDRESS (0));
+# endif
+
+  struct dlmopen_args oargs;
+  oargs.nsid = nsid;
+  oargs.file = file;
+  oargs.offset = offset;
+  oargs.mode = mode;
+  oargs.caller = DL_CALLER;
+
+  return __dlmopen_common (&oargs);
+}
+# ifdef SHARED
+strong_alias (__dlmopen_with_offset, __google_dlmopen_with_offset)
+# endif
+
 void *
 __dlmopen (Lmid_t nsid, const char *file, int mode DL_CALLER_DECL)
 {
@@ -88,20 +129,11 @@ __dlmopen (Lmid_t nsid, const char *file, int mode DL_CALLER_DECL)
   struct dlmopen_args args;
   args.nsid = nsid;
   args.file = file;
+  args.offset = 0;
   args.mode = mode;
   args.caller = DL_CALLER;
 
-# ifdef SHARED
-  return _dlerror_run (dlmopen_doit, &args) ? NULL : args.new;
-# else
-  if (_dlerror_run (dlmopen_doit, &args))
-    return NULL;
-
-  __libc_register_dl_open_hook ((struct link_map *) args.new);
-  __libc_register_dlfcn_hook ((struct link_map *) args.new);
-
-  return args.new;
-# endif
+  return __dlmopen_common (&args);
 }
 # ifdef SHARED
 strong_alias (__dlmopen, dlmopen)
diff --git a/dlfcn/dlopen.c b/dlfcn/dlopen.c
index c62ca23..319ae6e 100644
--- a/dlfcn/dlopen.c
+++ b/dlfcn/dlopen.c
@@ -33,12 +33,21 @@ dlopen (const char *file, int mode)
 static_link_warning (dlopen)
 #endif
 
+void *
+dlopen_with_offset (const char *file, off_t offset, int mode)
+{
+  return __dlopen_with_offset (file, offset, mode, RETURN_ADDRESS (0));
+}
+static_link_warning (dlopen_with_offset)
+
 #else
 
 struct dlopen_args
 {
   /* The arguments for dlopen_doit.  */
   const char *file;
+  /* ELF header at offset in file.  */
+  off_t offset;
   int mode;
   /* The return value of dlopen_doit.  */
   void *new;
@@ -65,13 +74,49 @@ dlopen_doit (void *a)
 		     | __RTLD_SPROF))
     _dl_signal_error (0, NULL, NULL, _("invalid mode parameter"));
 
-  args->new = GLRO(dl_open) (args->file ?: "", args->mode | __RTLD_DLOPEN,
+  args->new = GLRO(dl_open) (args->file ?: "", args->offset, args->mode | __RTLD_DLOPEN,
 			     args->caller,
 			     args->file == NULL ? LM_ID_BASE : NS,
 			     __dlfcn_argc, __dlfcn_argv, __environ);
 }
 
 
+static void *
+__dlopen_common (struct dlopen_args *args)
+{
+# ifdef SHARED
+  return _dlerror_run (dlopen_doit, args) ? NULL : args->new;
+# else
+  if (_dlerror_run (dlopen_doit, args))
+    return NULL;
+
+  __libc_register_dl_open_hook ((struct link_map *) args->new);
+  __libc_register_dlfcn_hook ((struct link_map *) args->new);
+
+  return args->new;
+# endif
+}
+
+void *
+__dlopen_with_offset (const char *file, off_t offset, int mode DL_CALLER_DECL)
+{
+# ifdef SHARED
+  if (!rtld_active ())
+    return _dlfcn_hook->dlopen_with_offset (file, offset, mode, DL_CALLER);
+# endif
+
+  struct dlopen_args oargs;
+  oargs.file = file;
+  oargs.offset = offset;
+  oargs.mode = mode;
+  oargs.caller = DL_CALLER;
+
+  return __dlopen_common (&oargs);
+}
+# ifdef SHARED
+strong_alias (__dlopen_with_offset, __google_dlopen_with_offset)
+# endif
+
 void *
 __dlopen (const char *file, int mode DL_CALLER_DECL)
 {
@@ -82,20 +127,11 @@ __dlopen (const char *file, int mode DL_CALLER_DECL)
 
   struct dlopen_args args;
   args.file = file;
+  args.offset = 0;
   args.mode = mode;
   args.caller = DL_CALLER;
 
-# ifdef SHARED
-  return _dlerror_run (dlopen_doit, &args) ? NULL : args.new;
-# else
-  if (_dlerror_run (dlopen_doit, &args))
-    return NULL;
-
-  __libc_register_dl_open_hook ((struct link_map *) args.new);
-  __libc_register_dlfcn_hook ((struct link_map *) args.new);
-
-  return args.new;
-# endif
+  return __dlopen_common (&args);
 }
 # ifdef SHARED
 #  include <shlib-compat.h>
diff --git a/dlfcn/dlopenold.c b/dlfcn/dlopenold.c
index d3b6a6c..d9ca12d 100644
--- a/dlfcn/dlopenold.c
+++ b/dlfcn/dlopenold.c
@@ -51,7 +51,7 @@ dlopen_doit (void *a)
 {
   struct dlopen_args *args = (struct dlopen_args *) a;
 
-  args->new = GLRO(dl_open) (args->file ?: "", args->mode | __RTLD_DLOPEN,
+  args->new = GLRO(dl_open) (args->file ?: "", 0, args->mode | __RTLD_DLOPEN,
 			     args->caller,
 			     args->file == NULL ? LM_ID_BASE : NS,
 			     __dlfcn_argc, __dlfcn_argv, __environ);