1 files changed, 81 insertions, 0 deletions
diff --git a/src/libbasic/include/basic/raw-clone.h b/src/libbasic/include/basic/raw-clone.h
new file mode 100644
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+++ b/src/libbasic/include/basic/raw-clone.h
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+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+  Copyright 2016 Michael Karcher
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sched.h>
+#include <sys/syscall.h>
+
+#include "log.h"
+#include "macro.h"
+
+/**
+ * raw_clone() - uses clone to create a new process with clone flags
+ * @flags: Flags to pass to the clone system call
+ *
+ * Uses the clone system call to create a new process with the cloning
+ * flags and termination signal passed in the flags parameter. Opposed
+ * to glibc's clone funtion, using this function does not set up a
+ * separate stack for the child, but relies on copy-on-write semantics
+ * on the one stack at a common virtual address, just as fork does.
+ *
+ * To obtain copy-on-write semantics, flags must not contain CLONE_VM,
+ * and thus CLONE_THREAD and CLONE_SIGHAND (which require CLONE_VM) are
+ * not usabale.
+ * Additionally, as this function does not pass the ptid, newtls and ctid
+ * parameters to the kernel, flags must not contain CLONE_PARENT_SETTID,
+ * CLONE_CHILD_SETTID, CLONE_CHILD_CLEARTID or CLONE_SETTLS.
+ *
+ * Returns: 0 in the child process and the child process id in the parent.
+ */
+static inline int raw_clone(unsigned long flags) {
+        assert((flags & (CLONE_VM|CLONE_PARENT_SETTID|CLONE_CHILD_SETTID|
+                         CLONE_CHILD_CLEARTID|CLONE_SETTLS)) == 0);
+#if defined(__s390__) || defined(__CRIS__)
+        /* On s390 and cris the order of the first and second arguments
+         * of the raw clone() system call is reversed. */
+        return (int) syscall(__NR_clone, NULL, flags);
+#elif defined(__sparc__) && defined(__arch64__)
+        {
+                /**
+                 * sparc64 always returns the other process id in %o0, and
+                 * a boolean flag whether this is the child or the parent in
+                 * %o1. Inline assembly is needed to get the flag returned
+                 * in %o1.
+                 */
+                int in_child;
+                int child_pid;
+                asm volatile("mov %2, %%g1\n\t"
+                             "mov %3, %%o0\n\t"
+                             "mov 0 , %%o1\n\t"
+                             "t 0x6d\n\t"
+                             "mov %%o1, %0\n\t"
+                             "mov %%o0, %1" :
+                             "=r"(in_child), "=r"(child_pid) :
+                             "i"(__NR_clone), "r"(flags) :
+                             "%o1", "%o0", "%g1" );
+                if (in_child)
+                        return 0;
+                else
+                        return child_pid;
+        }
+#else
+        return (int) syscall(__NR_clone, flags, NULL);
+#endif
+}