util, pasta: Add do_clone() wrapper around __clone2() and clone()

Spotted in Debian's buildd logs: on ia64, clone(2) is not available:
the glibc wrapper is named __clone2() and it takes, additionally,
the size of the stack area passed by the caller.

Add a do_clone() wrapper handling the different cases, and also
taking care of pointing the child's stack in the middle of the
allocated area: on PA-RISC (hppa), handled by clone(), the stack
grows up, and on ia64 the stack grows down, but the register backing
store grows up -- and I think it might be actually used here.

Suggested-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/pasta.c b/pasta.c
index db86317..528f02a 100644
--- a/pasta.c
+++ b/pasta.c
@@ -226,11 +226,11 @@ void pasta_start_ns(struct ctx *c, uid_t uid, gid_t gid,
 		arg.argv = sh_argv;
 	}
 
-	pasta_child_pid = clone(pasta_spawn_cmd,
-				ns_fn_stack + sizeof(ns_fn_stack) / 2,
-				CLONE_NEWIPC | CLONE_NEWPID | CLONE_NEWNET |
-				CLONE_NEWUTS,
-				(void *)&arg);
+	pasta_child_pid = do_clone(pasta_spawn_cmd, ns_fn_stack,
+				   sizeof(ns_fn_stack),
+				   CLONE_NEWIPC | CLONE_NEWPID | CLONE_NEWNET |
+				   CLONE_NEWUTS,
+				   (void *)&arg);
 
 	if (pasta_child_pid == -1) {
 		perror("clone");