Fix MIPS n32 lseek, lseek64 (bug 21019) [committed]

[Joseph Myers <joseph at codesourcery dot com>]

The lseek consolidation broke lseek64 for MIPS n32, so resulting in
io/test-lfs failing with an incorrect return from ftello64.  This
configuration uses the lseek syscall with a 64-bit return value; as
the C syscall macros return long, they cannot be used in this case and
so an assembly implementation is needed; accordingly, this patch adds
lseek64 back to syscalls.list for this configuration.

lseek was also broken, truncating the result without checking for
overflow.  lseek however was already broken before the consolidation;
it aliased lseek64 so would return an out-of-range value, resulting in
architecturally undefined behavior in the caller if it tried to use a
non-sign-extended value with a 32-bit instruction.  This patch adds a
custom lseek implementation in C for n32, which calls __lseek64 to get
the 64-bit value then checks for overflow.

Because the prior lseek breakage did not show in test results, and the
lseek64 breakage showed only indirectly through tests of ftello64,
test coverage was clearly inadequate.  This patch extends
io/test-lfs.c to test the lseek64 return value (at a point where it
has already seeked over 2GB into a file), and then to test the lseek
return value (with the latter's expectations depending on whether
off_t is smaller than off64_t).

Tested for mips64 n32.  Also tested test-lfs for x86_64 and x86, where
as expected it passes.  Committed.

2017-01-02  Joseph Myers  <joseph@codesourcery.com>

	[BZ #21019]
	* sysdeps/unix/sysv/linux/mips/mips64/n32/syscalls.list (lseek64):
	New syscall entry.
	* sysdeps/unix/sysv/linux/mips/mips64/n32/lseek.c: New file.
	* io/test-lfs.c (do_test): Test offset returned from lseek64 and
	lseek.

diff --git a/io/test-lfs.c b/io/test-lfs.c
index 5d976c7..1477354 100644
--- a/io/test-lfs.c
+++ b/io/test-lfs.c
@@ -163,6 +163,27 @@ do_test (int argc, char *argv[])
       error (0, errno, "lseek64 failed with error");
       exit (EXIT_FAILURE);
     }
+  off64_t offset64 = lseek64 (fd, 0, SEEK_CUR);
+  if (offset64 != TWO_GB + 100)
+    {
+      error (0, 0, "lseek64 did not return expected offset");
+      exit (EXIT_FAILURE);
+    }
+  off_t offset = lseek (fd, 0, SEEK_CUR);
+  if (sizeof (off_t) < sizeof (off64_t))
+    {
+      if (offset != -1 || errno != EOVERFLOW)
+	{
+	  error (0, 0, "lseek did not fail with EOVERFLOW");
+	  exit (EXIT_FAILURE);
+	}
+    }
+  else
+    if (offset != TWO_GB + 100)
+      {
+	error (0, 0, "lseek did not return expected offset");
+	exit (EXIT_FAILURE);
+      }
 
   ret = write (fd, "Hello", 5);
   if (ret == -1 && errno == EFBIG)
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/lseek.c b/sysdeps/unix/sysv/linux/mips/mips64/n32/lseek.c
new file mode 100644
index 0000000..26d2e11
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/lseek.c
@@ -0,0 +1,36 @@
+/* MIPS n32 lseek implementation.
+   Copyright (C) 2017 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/>.  */
+
+#include <unistd.h>
+#include <sys/types.h>
+#include <errno.h>
+
+off_t
+__lseek (int fd, off_t offset, int whence)
+{
+  off64_t res = __lseek64 (fd, offset, whence);
+  if (res != (off_t) res)
+    {
+      __set_errno (EOVERFLOW);
+      return (off_t) -1;
+    }
+  return (off_t) res;
+}
+libc_hidden_def (__lseek)
+weak_alias (__lseek, lseek)
+strong_alias (__lseek, __libc_lseek)
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/syscalls.list b/sysdeps/unix/sysv/linux/mips/mips64/n32/syscalls.list
index 58fd46a..7af317f 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/syscalls.list
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/syscalls.list
@@ -1,5 +1,9 @@
 # File name	Caller	Syscall name	# args	Strong name	Weak names
 
+# C syscall macros cannot be used because this syscall has a 64-bit
+# return value.
+lseek64		-	lseek		i:iii	__lseek64	__libc_lseek64 lseek64 llseek
+
 mmap64		-	mmap		b:aniiii __mmap64	mmap64
 
 readahead	-	readahead	i:iii	__readahead	readahead

-- 
Joseph S. Myers
joseph@codesourcery.com