build: Check that mlockall() exists

Instead of assuming that all POSIX platforms provide mlockall(),
test for it in configure. If the host doesn't provide this platform
then os_mlock() will fail -ENOSYS, as it does already on Windows.

This is necessary for Haiku, which does not have mlockall().

Signed-off-by: David Carlier <devnexen@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20200703145614.16684-4-peter.maydell@linaro.org
[PMM: Expanded commit message; rename to HAVE_MLOCKALL]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

configure

@@ -2408,6 +2408,18 @@ else
   pty_h=no
 fi
 
+cat > $TMPC <<EOF
+#include <sys/mman.h>
+int main(int argc, char *argv[]) {
+    return mlockall(MCL_FUTURE);
+}
+EOF
+if compile_prog "" "" ; then
+  have_mlockall=yes
+else
+  have_mlockall=no
+fi
+
 #########################################
 # vhost interdependencies and host support
 
@@ -7902,6 +7914,9 @@ fi
 if test "$pty_h" = "yes" ; then
   echo "HAVE_PTY_H=y" >> $config_host_mak
 fi
+if test "$have_mlockall" = "yes" ; then
+  echo "HAVE_MLOCKALL=y" >> $config_host_mak
+fi
 if test "$fuzzing" = "yes" ; then
   if test "$have_fuzzer" = "yes"; then
     FUZZ_LDFLAGS=" -fsanitize=address,fuzzer"

os-posix.c

@@ -337,6 +337,7 @@ bool is_daemonized(void)
 
 int os_mlock(void)
 {
+#ifdef HAVE_MLOCKALL
     int ret = 0;
 
     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
@@ -345,4 +346,7 @@ int os_mlock(void)
     }
 
     return ret;
+#else
+    return -ENOSYS;
+#endif
 }