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-rw-r--r--src/basic/raw-clone.h79
1 files changed, 79 insertions, 0 deletions
diff --git a/src/basic/raw-clone.h b/src/basic/raw-clone.h
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+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+/***
+ Copyright © 2016 Michael Karcher
+***/
+
+#include <errno.h>
+#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 usable.
+ *
+ * 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 pid_t raw_clone(unsigned long flags) {
+ pid_t ret;
+
+ assert((flags & (CLONE_VM|CLONE_PARENT_SETTID|CLONE_CHILD_SETTID|
+ CLONE_CHILD_CLEARTID|CLONE_SETTLS)) == 0);
+#if defined(__s390x__) || defined(__s390__) || defined(__CRIS__)
+ /* On s390/s390x and cris the order of the first and second arguments
+ * of the raw clone() system call is reversed. */
+ ret = (pid_t) syscall(__NR_clone, NULL, flags);
+#elif defined(__sparc__)
+ {
+ /**
+ * sparc 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, child_pid, error;
+
+ asm volatile("mov %3, %%g1\n\t"
+ "mov %4, %%o0\n\t"
+ "mov 0 , %%o1\n\t"
+#if defined(__arch64__)
+ "t 0x6d\n\t"
+#else
+ "t 0x10\n\t"
+#endif
+ "addx %%g0, 0, %2\n\t"
+ "mov %%o1, %0\n\t"
+ "mov %%o0, %1" :
+ "=r"(in_child), "=r"(child_pid), "=r"(error) :
+ "i"(__NR_clone), "r"(flags) :
+ "%o1", "%o0", "%g1", "cc" );
+
+ if (error) {
+ errno = child_pid;
+ ret = -1;
+ } else
+ ret = in_child ? 0 : child_pid;
+ }
+#else
+ ret = (pid_t) syscall(__NR_clone, flags, NULL);
+#endif
+
+ if (ret == 0)
+ reset_cached_pid();
+
+ return ret;
+}