linux-user: prefer glibc over direct syscalls

The openat/*at syscalls are incredibly common with modern coreutils,
calling them directly via syscalls breaks for example fakeroot. Use
glibc stubs whenever directly available and provide old syscall
calling for people still using older libc.

Patch originally from Mika Westerberg, Adapted to
apply to current trunk and cleaned up by Riku Voipio.

Signed-off-by: Riku Voipio <riku.voipio@iki.fi>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7118 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 53 insertions, 0 deletions

diff --git a/configure b/configure
index 0ca6a3ed5d..7cefb062b4 100755
--- a/configure
+++ b/configure
@@ -1156,6 +1156,53 @@ EOF
   fi
 fi
 
+#
+# Check for xxxat() functions when we are building linux-user
+# emulator.  This is done because older glibc versions don't
+# have syscall stubs for these implemented.
+#
+atfile=no
+if [ "$linux_user" = "yes" ] ; then
+  cat > $TMPC << EOF
+#define _ATFILE_SOURCE
+#include <sys/types.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+int
+main(void)
+{
+	/* try to unlink nonexisting file */
+	return (unlinkat(AT_FDCWD, "nonexistent_file", 0));
+}
+EOF
+  if $cc $ARCH_CFLAGS -o $TMPE $TMPC 2> /dev/null ; then
+    atfile=yes
+  fi
+fi
+
+# Check for initofy functions when we are building linux-user
+# emulator.  This is done because older glibc versions don't
+# have syscall stubs for these implemented.  In that case we
+# don't provide them even if kernel supports them.
+#
+inotify=no
+if [ "$linux_user" = "yes" ] ; then
+  cat > $TMPC << EOF
+#include <sys/inotify.h>
+
+int
+main(void)
+{
+	/* try to start inotify */
+	return inotify_init(void);
+}
+EOF
+  if $cc $ARCH_CFLAGS -o $TMPE $TMPC 2> /dev/null ; then
+    inotify=yes
+  fi
+fi
+
 # Check if tools are available to build documentation.
 if [ -x "`which texi2html 2>/dev/null`" ] && \
    [ -x "`which pod2man 2>/dev/null`" ]; then
@@ -1544,6 +1591,12 @@ if test "$curses" = "yes" ; then
   echo "CONFIG_CURSES=yes" >> $config_mak
   echo "CURSES_LIBS=-lcurses" >> $config_mak
 fi
+if test "$atfile" = "yes" ; then
+  echo "#define CONFIG_ATFILE 1" >> $config_h
+fi
+if test "$inotify" = "yes" ; then
+  echo "#define CONFIG_INOTIFY 1" >> $config_h
+fi
 if test "$brlapi" = "yes" ; then
   echo "CONFIG_BRLAPI=yes" >> $config_mak
   echo "#define CONFIG_BRLAPI 1" >> $config_h