[roland/nacl-open-resource] NaCl: Use open_resource API for shared objects
diff mbox

Message ID 20151110002043.CB3782C3B1E@topped-with-meat.com
State New
Headers show

Commit Message

Roland McGrath Nov. 10, 2015, 12:20 a.m. UTC
This is necessary for arm-nacl applications to load their libraries in the
normal NaCl deployment model in the web browser.  It's user-visible in the
sense that this didn't work before, but there is no bugzilla item because
no NaCl users actually encountered the problem yet (nobody really tried
using arm-nacl glibc in the browser before now).

I've verified on x86_64-linux-gnu that this does not change the compiled
code meaningfully.  (In fact, the code itself is wholly unchanged, though
the local symbols are substantially different because the compiler did a
lot of fancy optimization to turn this change back into a no-op.)

If there are no objections, I'll put this on both trunk and 2.22 on Tuesday.


Thanks,
Roland



2015-11-09  Roland McGrath  <roland@hack.frob.com>

	* elf/dl-load.c (open_verify): Take new argument FD.
	Skip __open call if passed FD is not -1.
	(_dl_map_object, open_path): Update callers.
	* elf/dl-sysdep-open.h: New file.
	* elf/dl-load.c: Include it.
	(_dl_map_object): Try _dl_sysdep_open_object before ldconfig cache.
	* sysdeps/nacl/dl-sysdep.c (_dl_sysdep_open_object): New function.
	* sysdeps/nacl/dl-sysdep-open.h: New file.
	* sysdeps/nacl/nacl-interface-list.h: Move nacl_irt_resource_open
	from libc to rtld.

Patch
diff mbox

diff --git a/elf/dl-load.c b/elf/dl-load.c
index c5e948e..6fb615e 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -43,6 +43,7 @@ 
 #include <dl-map-segments.h>
 #include <dl-unmap-segments.h>
 #include <dl-machine-reject-phdr.h>
+#include <dl-sysdep-open.h>
 
 
 #include <endian.h>
@@ -1483,9 +1484,13 @@  print_search_path (struct r_search_path_elem **list,
    ignore only ELF files for other architectures.  Non-ELF files and
    ELF files with different header information cause fatal errors since
    this could mean there is something wrong in the installation and the
-   user might want to know about this.  */
+   user might want to know about this.
+
+   If FD is not -1, then the file is already open and FD refers to it.
+   In that case, FD is consumed for both successful and error returns.  */
 static int
-open_verify (const char *name, struct filebuf *fbp, struct link_map *loader,
+open_verify (const char *name, int fd,
+             struct filebuf *fbp, struct link_map *loader,
 	     int whatcode, int mode, bool *found_other_class, bool free_name)
 {
   /* This is the expected ELF header.  */
@@ -1526,6 +1531,7 @@  open_verify (const char *name, struct filebuf *fbp, struct link_map *loader,
   if (__glibc_unlikely (GLRO(dl_naudit) > 0) && whatcode != 0
       && loader->l_auditing == 0)
     {
+      const char *original_name = name;
       struct audit_ifaces *afct = GLRO(dl_audit);
       for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 	{
@@ -1540,11 +1546,21 @@  open_verify (const char *name, struct filebuf *fbp, struct link_map *loader,
 
 	  afct = afct->next;
 	}
+
+      if (fd != -1 && name != original_name && strcmp (name, original_name))
+        {
+          /* An audit library changed what we're supposed to open,
+             so FD no longer matches it.  */
+          __close (fd);
+          fd = -1;
+        }
     }
 #endif
 
-  /* Open the file.  We always open files read-only.  */
-  int fd = __open (name, O_RDONLY | O_CLOEXEC);
+  if (fd == -1)
+    /* Open the file.  We always open files read-only.  */
+    fd = __open (name, O_RDONLY | O_CLOEXEC);
+
   if (fd != -1)
     {
       ElfW(Ehdr) *ehdr;
@@ -1813,7 +1829,7 @@  open_path (const char *name, size_t namelen, int mode,
 	  if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_LIBS))
 	    _dl_debug_printf ("  trying file=%s\n", buf);
 
-	  fd = open_verify (buf, fbp, loader, whatcode, mode,
+	  fd = open_verify (buf, -1, fbp, loader, whatcode, mode,
 			    found_other_class, false);
 	  if (this_dir->status[cnt] == unknown)
 	    {
@@ -2064,6 +2080,20 @@  _dl_map_object (struct link_map *loader, const char *name,
 			&loader->l_runpath_dirs, &realname, &fb, loader,
 			LA_SER_RUNPATH, &found_other_class);
 
+      if (fd == -1)
+        {
+          realname = _dl_sysdep_open_object (name, namelen, &fd);
+          if (realname != NULL)
+            {
+              fd = open_verify (realname, fd,
+                                &fb, loader ?: GL(dl_ns)[nsid]._ns_loaded,
+                                LA_SER_CONFIG, mode, &found_other_class,
+                                false);
+              if (fd == -1)
+                free (realname);
+            }
+        }
+
 #ifdef USE_LDCONFIG
       if (fd == -1
 	  && (__glibc_likely ((mode & __RTLD_SECURE) == 0)
@@ -2109,7 +2139,7 @@  _dl_map_object (struct link_map *loader, const char *name,
 
 	      if (cached != NULL)
 		{
-		  fd = open_verify (cached,
+		  fd = open_verify (cached, -1,
 				    &fb, loader ?: GL(dl_ns)[nsid]._ns_loaded,
 				    LA_SER_CONFIG, mode, &found_other_class,
 				    false);
@@ -2144,7 +2174,7 @@  _dl_map_object (struct link_map *loader, const char *name,
 	fd = -1;
       else
 	{
-	  fd = open_verify (realname, &fb,
+	  fd = open_verify (realname, -1, &fb,
 			    loader ?: GL(dl_ns)[nsid]._ns_loaded, 0, mode,
 			    &found_other_class, true);
 	  if (__glibc_unlikely (fd == -1))
diff --git a/elf/dl-sysdep-open.h b/elf/dl-sysdep-open.h
new file mode 100644
index 0000000..a63d9f5
--- /dev/null
+++ b/elf/dl-sysdep-open.h
@@ -0,0 +1,45 @@ 
+/* System-specific call to open a shared object by name.  Stub version.
+   Copyright (C) 2015 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
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _DL_SYSDEP_OPEN_H
+#define _DL_SYSDEP_OPEN_H	1
+
+#include <assert.h>
+#include <stddef.h>
+
+/* NAME is a name without slashes, as it appears in a DT_NEEDED entry
+   or a dlopen call's argument or suchlike.  NAMELEN is (strlen (NAME) + 1).
+
+   Find NAME in an OS-dependent fashion, and return its "real" name.
+   Optionally fill in *FD with a file descriptor open on that file (or
+   else leave its initial value of -1).  The return value is a new
+   malloc'd string, which will be free'd by the caller.  If NAME is
+   resolved to an actual file that can be opened, then the return
+   value should name that file (and if *FD was not set, then a normal
+   __open call on that string will be made).  If *FD was set by some
+   other means than a normal open and there is no "real" name to use,
+   then __strdup (NAME) is fine (modulo error checking).  */
+
+static inline char *
+_dl_sysdep_open_object (const char *name, size_t namelen, int *fd)
+{
+  assert (*fd == -1);
+  return NULL;
+}
+
+#endif  /* dl-sysdep-open.h */
diff --git a/sysdeps/nacl/dl-sysdep-open.h b/sysdeps/nacl/dl-sysdep-open.h
new file mode 100644
index 0000000..38b0f9e
--- /dev/null
+++ b/sysdeps/nacl/dl-sysdep-open.h
@@ -0,0 +1,40 @@ 
+/* System-specific call to open a shared object by name.  NaCl version.
+   Copyright (C) 2015 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
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _DL_SYSDEP_OPEN_H
+#define _DL_SYSDEP_OPEN_H	1
+
+#include <stddef.h>
+
+/* NAME is a name without slashes, as it appears in a DT_NEEDED entry
+   or a dlopen call's argument or suchlike.  NAMELEN is (strlen (NAME) + 1).
+
+   Find NAME in an OS-dependent fashion, and return its "real" name.
+   Optionally fill in *FD with a file descriptor open on that file (or
+   else leave its initial value of -1).  The return value is a new
+   malloc'd string, which will be free'd by the caller.  If NAME is
+   resolved to an actual file that can be opened, then the return
+   value should name that file (and if *FD was not set, then a normal
+   __open call on that string will be made).  If *FD was set by some
+   other means than a normal open and there is no "real" name to use,
+   then __strdup (NAME) is fine (modulo error checking).  */
+
+extern char *_dl_sysdep_open_object (const char *name, size_t namelen, int *fd)
+  internal_function attribute_hidden;
+
+#endif  /* dl-sysdep-open.h */
diff --git a/sysdeps/nacl/dl-sysdep.c b/sysdeps/nacl/dl-sysdep.c
index 3e902c2..3a04aa1 100644
--- a/sysdeps/nacl/dl-sysdep.c
+++ b/sysdeps/nacl/dl-sysdep.c
@@ -87,3 +87,26 @@  _dl_start_user (void (*user_entry) (uint32_t info[]), uint32_t info[])
 #endif  /* SHARED */
 
 #include <elf/dl-sysdep.c>
+
+#include <dl-sysdep-open.h>
+#include <nacl-interfaces.h>
+#include <assert.h>
+#include <string.h>
+#include <unistd.h>
+
+char *
+internal_function
+_dl_sysdep_open_object (const char *name, size_t namelen, int *fd)
+{
+  int error = __nacl_irt_resource_open.open_resource (name, fd);
+  if (error)
+    return NULL;
+  assert (*fd != -1);
+  char *realname = __strdup (name);
+  if (__glibc_unlikely (realname == NULL))
+    {
+      __close (*fd);
+      *fd = -1;
+    }
+  return realname;
+}
diff --git a/sysdeps/nacl/nacl-interface-list.h b/sysdeps/nacl/nacl-interface-list.h
index cb33751..c68faed 100644
--- a/sysdeps/nacl/nacl-interface-list.h
+++ b/sysdeps/nacl/nacl-interface-list.h
@@ -28,7 +28,7 @@  NACL_MANDATORY_INTERFACE (rtld,
 			  NACL_IRT_FUTEX_v0_1, nacl_irt_futex)
 NACL_MANDATORY_INTERFACE (rtld,
 			  NACL_IRT_TLS_v0_1, nacl_irt_tls)
-NACL_MANDATORY_INTERFACE (libc,
+NACL_MANDATORY_INTERFACE (rtld,
 			  NACL_IRT_RESOURCE_OPEN_v0_1, nacl_irt_resource_open)
 NACL_MANDATORY_INTERFACE (rtld,
 			  NACL_IRT_CODE_DATA_ALLOC_v0_1,