[PATCH] On linux require the libc to have large file support

[Felix Janda <felix.janda@posteo.de>]

With this, support code in grub-core/osdep/unix/hostdisk.c
for old glibc releases could be removed.
---
This patch tries to address the issues raised in

http://lists.gnu.org/archive/html/grub-devel/2014-12/msg00030.html
---
 INSTALL                         |  1 +
 configure.ac                    |  5 +++++
 grub-core/osdep/unix/hostdisk.c | 25 -------------------------
 3 files changed, 6 insertions(+), 25 deletions(-)

diff --git a/INSTALL b/INSTALL
index b67cd7f..ac7c2aa 100644
--- a/INSTALL
+++ b/INSTALL
@@ -39,6 +39,7 @@ configuring the GRUB.
 On GNU/Linux, you also need:
 
 * libdevmapper 1.02.34 or later (recommended)
+* a libc with large file support (e.g. glibc 2.1 or later)
 
 For optional grub-emu features, you need:
 
diff --git a/configure.ac b/configure.ac
index 31d2b0b..bdaebb8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -346,6 +346,11 @@ AC_GNU_SOURCE
 AM_GNU_GETTEXT([external])
 AC_SYS_LARGEFILE
 
+if test x"$host_kernel" = xlinux ; then
+  AC_CHECK_SIZEOF(off_t)
+  test x"$ac_cv_sizeof_off_t" = x8 || AC_MSG_ERROR([Large file support is required])
+fi
+
 # Identify characteristics of the host architecture.
 unset ac_cv_c_bigendian
 
diff --git a/grub-core/osdep/unix/hostdisk.c b/grub-core/osdep/unix/hostdisk.c
index 43b56ff..14cab1c 100644
--- a/grub-core/osdep/unix/hostdisk.c
+++ b/grub-core/osdep/unix/hostdisk.c
@@ -48,11 +48,6 @@
 #ifdef __linux__
 # include <sys/ioctl.h>         /* ioctl */
 # include <sys/mount.h>
-# if !defined(__GLIBC__) || \
-        ((__GLIBC__ < 2) || ((__GLIBC__ == 2) && (__GLIBC_MINOR__ < 1)))
-/* Maybe libc doesn't have large file support.  */
-#  include <linux/unistd.h>     /* _llseek */
-# endif /* (GLIBC < 2) || ((__GLIBC__ == 2) && (__GLIBC_MINOR < 1)) */
 #endif /* __linux__ */
 
 grub_uint64_t
@@ -79,24 +74,6 @@ grub_util_get_fd_size (grub_util_fd_t fd, const char *name, unsigned *log_secsiz
   return st.st_size;
 }
 
-#if defined(__linux__) && (!defined(__GLIBC__) || \
-        ((__GLIBC__ < 2) || ((__GLIBC__ == 2) && (__GLIBC_MINOR__ < 1))))
-  /* Maybe libc doesn't have large file support.  */
-int
-grub_util_fd_seek (grub_util_fd_t fd, grub_uint64_t off)
-{
-  loff_t offset, result;
-  static int _llseek (uint filedes, ulong hi, ulong lo,
-		      loff_t *res, uint wh);
-  _syscall5 (int, _llseek, uint, filedes, ulong, hi, ulong, lo,
-	     loff_t *, res, uint, wh);
-
-  offset = (loff_t) off;
-  if (_llseek (fd, offset >> 32, offset & 0xffffffff, &result, SEEK_SET))
-    return -1;
-  return GRUB_ERR_NONE;
-}
-#else
 int
 grub_util_fd_seek (grub_util_fd_t fd, grub_uint64_t off)
 {
@@ -107,8 +84,6 @@ grub_util_fd_seek (grub_util_fd_t fd, grub_uint64_t off)
 
   return 0;
 }
-#endif
-
 
 /* Read LEN bytes from FD in BUF. Return less than or equal to zero if an
    error occurs, otherwise return LEN.  */
-- 
2.0.5