[PATCH 2/6] New internal function __access_noerrno

[Siddhesh Poyarekar <siddhesh at sourceware dot org>]

Implement an internal version of __access called __access_noerrno that
avoids setting errno.  This is useful to check accessibility of files
very early on in process startup i.e. before TLS setup.  This allows
tunables to replace MALLOC_CHECK_ safely (i.e. check existence of
/etc/suid-debug to enable/disable MALLOC_CHECK) and at the same time
initialize very early so that it can override IFUNCs.

	* include/unistd.h [IS_IN (rtld) || !defined SHARED]: Declare
	__access_noerrno.
	* io/Makefile (routines): Add access_noerrno.
	* io/access.c (__ACCESS)[!__ACCESS]: Define as __access.
	(__access): Rename to __ACCESS.
	[!NOERRNO]: Retain default __access logic.
	* io/access_noerrno.c: New file.
	* sysdeps/mach/hurd/access.c (__ACCESS)[!__ACCESS]: Define as
	__access.
	(__HURD_FAIL): New macro.
	(__access): Rename to __ACCESS.  Use __HURD_FAIL instead of
	__hurd_fail.
	[!NOERRNO]: Set weak alias to access.
	* sysdeps/nacl/access.c (__ACCESS)[!__ACCESS]: Define as
	__access.
	(DO_NACL_CALL): New macro.
	(__access): Rename to __ACCESS.  Use DO_NACL_CALL instead of
	NACL_CALL.
	[!NOERRNO]: Set weak alias to access.
	* sysdeps/nacl/nacl-interfaces.h (NACL_CALL_NOERRNO): New
	macro.
	* sysdeps/unix/access_noerrno.c: New file.
	* sysdeps/unix/sysv/linux/generic/access.c: Include sysdep.h.
	(__ACCESS)[!__ACCESS]: Define as __access.
	(__access): Rename to __ACCESS.
	[NOERRNO]: Call faccessat syscall without setting errno.
---
 include/unistd.h                         |  6 +++++
 io/Makefile                              |  1 +
 io/access.c                              | 10 ++++++++-
 io/access_noerrno.c                      | 21 ++++++++++++++++++
 sysdeps/mach/hurd/access.c               | 20 +++++++++++++----
 sysdeps/nacl/access.c                    | 16 ++++++++++++--
 sysdeps/nacl/nacl-interfaces.h           |  4 ++++
 sysdeps/unix/access_noerrno.c            | 38 ++++++++++++++++++++++++++++++++
 sysdeps/unix/sysv/linux/generic/access.c | 19 +++++++++++++++-
 9 files changed, 127 insertions(+), 8 deletions(-)
 create mode 100644 io/access_noerrno.c
 create mode 100644 sysdeps/unix/access_noerrno.c

diff --git a/include/unistd.h b/include/unistd.h
index d2802b2..6144f41 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -181,6 +181,12 @@ extern int __getlogin_r_loginuid (char *name, size_t namesize)
 #   include <dl-unistd.h>
 #  endif
 
+#  if IS_IN (rtld) || !defined SHARED
+/* __access variant that does not set errno.  Used in very early initialization
+   code in libc.a and ld.so.  */
+extern __typeof (__access) __access_noerrno attribute_hidden;
+#  endif
+
 __END_DECLS
 # endif
 
diff --git a/io/Makefile b/io/Makefile
index e5493b3..1ebb0d0 100644
--- a/io/Makefile
+++ b/io/Makefile
@@ -40,6 +40,7 @@ routines :=								\
 	mkdir mkdirat							\
 	open open_2 open64 open64_2 openat openat_2 openat64 openat64_2	\
 	read write lseek lseek64 access euidaccess faccessat		\
+	access_noerrno							\
 	fcntl flock lockf lockf64					\
 	close dup dup2 dup3 pipe pipe2					\
 	creat creat64							\
diff --git a/io/access.c b/io/access.c
index 4534704..80cfa98 100644
--- a/io/access.c
+++ b/io/access.c
@@ -19,10 +19,15 @@
 #include <stddef.h>
 #include <unistd.h>
 
+#ifndef __ACCESS
+# define __ACCESS __access
+#endif
+
 /* Test for access to FILE.  */
 int
-__access (const char *file, int type)
+__ACCESS (const char *file, int type)
 {
+#ifndef NOERRNO
   if (file == NULL || (type & ~(R_OK|W_OK|X_OK|F_OK)) != 0)
     {
       __set_errno (EINVAL);
@@ -30,8 +35,11 @@ __access (const char *file, int type)
     }
 
   __set_errno (ENOSYS);
+#endif
   return -1;
 }
+#ifndef NOERRNO
 stub_warning (access)
 
 weak_alias (__access, access)
+#endif
diff --git a/io/access_noerrno.c b/io/access_noerrno.c
new file mode 100644
index 0000000..4bd531f
--- /dev/null
+++ b/io/access_noerrno.c
@@ -0,0 +1,21 @@
+/* Test for access to a file but do not set errno on error.
+   Copyright (C) 2016 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/>.  */
+
+#define NOERRNO 1
+#define __ACCESS __access_noerrno
+#include <access.c>
diff --git a/sysdeps/mach/hurd/access.c b/sysdeps/mach/hurd/access.c
index c308340..189fefe 100644
--- a/sysdeps/mach/hurd/access.c
+++ b/sysdeps/mach/hurd/access.c
@@ -22,9 +22,19 @@
 #include <hurd/lookup.h>
 #include <fcntl.h>
 
+#ifndef __ACCESS
+# define __ACCESS __access
+#endif
+
+#ifndef NOERRNO
+# define __HURD_FAIL(e) __hurd_fail (e)
+#else
+# define __HURD_FAIL(e) (e)
+#endif
+
 /* Test for access to FILE by our real user and group IDs.  */
 int
-__access (const char *file, int type)
+__ACCESS (const char *file, int type)
 {
   error_t err;
   file_t rcrdir, rcwdir, io;
@@ -120,13 +130,13 @@ __access (const char *file, int type)
   if (rcwdir != MACH_PORT_NULL)
     __mach_port_deallocate (__mach_task_self (), rcwdir);
   if (err)
-    return __hurd_fail (err);
+    return __HURD_FAIL (err);
 
   /* Find out what types of access we are allowed to this file.  */
   err = __file_check_access (io, &allowed);
   __mach_port_deallocate (__mach_task_self (), io);
   if (err)
-    return __hurd_fail (err);
+    return __HURD_FAIL (err);
 
   flags = 0;
   if (type & R_OK)
@@ -138,9 +148,11 @@ __access (const char *file, int type)
 
   if (flags & ~allowed)
     /* We are not allowed all the requested types of access.  */
-    return __hurd_fail (EACCES);
+    return __HURD_FAIL (EACCES);
 
   return 0;
 }
 
+#ifndef NOERRNO
 weak_alias (__access, access)
+#endif
diff --git a/sysdeps/nacl/access.c b/sysdeps/nacl/access.c
index 95a0fb7..b7339e7 100644
--- a/sysdeps/nacl/access.c
+++ b/sysdeps/nacl/access.c
@@ -19,10 +19,22 @@
 #include <unistd.h>
 #include <nacl-interfaces.h>
 
+#ifndef __ACCESS
+# define __ACCESS __access
+#endif
+
+#ifndef NOERRNO
+# define DO_NACL_CALL NACL_CALL
+#else
+# define DO_NACL_CALL NACL_CALL_NOERRNO
+#endif
+
 /* Test for access to FILE.  */
 int
-__access (const char *file, int type)
+__ACCESS (const char *file, int type)
 {
-  return NACL_CALL (__nacl_irt_dev_filename.access (file, type), 0);
+  return DO_NACL_CALL (__nacl_irt_dev_filename.access (file, type), 0);
 }
+#ifndef NOERRNO
 weak_alias (__access, access)
+#endif
diff --git a/sysdeps/nacl/nacl-interfaces.h b/sysdeps/nacl/nacl-interfaces.h
index b7b45bb..fd8d580 100644
--- a/sysdeps/nacl/nacl-interfaces.h
+++ b/sysdeps/nacl/nacl-interfaces.h
@@ -113,4 +113,8 @@ __nacl_fail (int err)
 #define NACL_CALL(err, val) \
   ({ int _err = (err); _err ? __nacl_fail (_err) : (val); })
 
+/* Don't set errno.  */
+#define NACL_CALL_NOERRNO(err, val) \
+  ({ int _err = (err); _err ? _err : (val); })
+
 #endif  /* nacl-interfaces.h */
diff --git a/sysdeps/unix/access_noerrno.c b/sysdeps/unix/access_noerrno.c
new file mode 100644
index 0000000..1ff90a2
--- /dev/null
+++ b/sysdeps/unix/access_noerrno.c
@@ -0,0 +1,38 @@
+/* Test for access to a file but do not set errno on error.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
+
+   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/>.  */
+
+#include <errno.h>
+#include <stddef.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sysdep-cancel.h>
+#include <sysdep.h>
+
+/* Test for access to FILE.  */
+int
+__access_noerrno (const char *file, int type)
+{
+  INTERNAL_SYSCALL_DECL (err);
+  int res;
+  res = INTERNAL_SYSCALL (access, err, 2, file, type);
+  if (INTERNAL_SYSCALL_ERROR_P (res, err))
+    return INTERNAL_SYSCALL_ERRNO (res, err);
+  else
+    return 0;
+}
diff --git a/sysdeps/unix/sysv/linux/generic/access.c b/sysdeps/unix/sysv/linux/generic/access.c
index 586aa93..5bafc06 100644
--- a/sysdeps/unix/sysv/linux/generic/access.c
+++ b/sysdeps/unix/sysv/linux/generic/access.c
@@ -21,11 +21,28 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <sysdep-cancel.h>
+#include <sysdep.h>
+
+#ifndef __ACCESS
+# define __ACCESS __access
+#endif
 
 /* Test for access to FILE.  */
 int
-__access (const char *file, int type)
+__ACCESS (const char *file, int type)
 {
+#ifndef NOERRNO
   return INLINE_SYSCALL (faccessat, 3, AT_FDCWD, file, type);
+#else
+  INTERNAL_SYSCALL_DECL (err);
+  int res;
+  res = INTERNAL_SYSCALL (faccessat, err, 3, AT_FDCWD, file, type);
+  if (INTERNAL_SYSCALL_ERROR_P (res, err))
+    return INTERNAL_SYSCALL_ERRNO (res, err);
+  else
+    return 0;
+#endif
 }
+#ifndef NOERRNO
 weak_alias (__access, access)
+#endif
-- 
2.7.4