[v13][PATCH 00/12] Implement eclone() system call

[v13][PATCH 00/12] Implement eclone() system call

[Sukadev Bhattiprolu]

Andrew,

(Sorry to spam, but I failed to cc LKML on my previous post and want to
make sure I addressed all comments).

We also ported the eclone() syscall to x86_64, powerpc and s390.
Can you please merge or let me know if there are other comments ?

---

Subject: [v13][PATCH 00/12] Implement eclone() system call

To support application checkpoint/restart, a task must have the same pid it
had when it was checkpointed.  When containers are nested, the tasks within
the containers exist in multiple pid namespaces and hence have multiple pids
to specify during restart.

This patchset implements a new system call, eclone() that lets a process
specify the pids of the child process.

Patches 1 through 7 are helper patches needed for choosing a pid for the
child process.

Patches 8 through 11 implement the eclone() system call on x86, x86_64, s390
and powerpc.

Patch 12 documents the new system call, some/all of which will eventually
go into a man page.

Changelog[v13]:
	- Implement sys_eclone() on x86_64, s390 and powerpc architectures
	- Reorg x86 implementation to enable sharing code with x86_64
	- [Arnd Bergmann] Remove the ->reserved1 field we now have args_size
	- [Nathan Lynch, Serge Hallyn]: Rename ->child_stack_base to
	  ->child_stack and ensure ->child_stack_size is 0 on architectures
	  that don't need the stack size.
	- Modify exmaple in Documentation to avoid unnecessary register copy.

Changelog[v12]:
	- Ignore ->child_stack_size when ->child_stack_base is NULL (PATCH 8)
	- Cleanup/simplify example in Documentation/eclone (PATCH 9).
	- Rename sys call to a shorter name, eclone()

Changelog[v11]:
	- [Dave Hansen] Move clone_args validation checks to arch-indpeendent
	  code.
	- [Oren Laadan] Make args_size a parameter to system call and remove
	  it from 'struct clone_args'

Changelog[v10]:
	- [Linus Torvalds] Use PTREGSCALL() implementation for clone rather
	  than the generic system call
	- Rename clone3() to clone_with_pids()
	- Update Documentation/clone_with_pids() to show example usage with
	  the PTREGSCALL implementation.

Changelog[v9]:
	- [Pavel Emelyanov] Drop the patch that made 'pid_max' a property
	  of struct pid_namespace
	- [Roland McGrath, H. Peter Anvin and earlier on, Serge Hallyn] To
	  avoid inadvertent truncation clone_flags, preserve the first
	  parameter of clone3() as 'u32 clone_flags' and specify newer
	  flags in clone_args.flags_high (PATCH 8/9 and PATCH 9/9)
	- [Eric Biederman] Generalize alloc_pidmap() code to simplify and
	  remove duplication (see PATCH 3/9].
	  
Changelog[v8]:
	- [Oren Laadan, Louis Rilling, KOSAKI Motohiro]
	  The name 'clone2()' is in use - renamed new syscall to clone3().
	- [Oren Laadan] ->parent_tidptr and ->child_tidptr need to be 64bit.
	- [Oren Laadan] Ensure that unused fields/flags in clone_struct are 0.
	  (Added [PATCH 7/10] to the patchset).

Changelog[v7]:
	- [Peter Zijlstra, Arnd Bergmann]
	  Group the arguments to clone2() into a 'struct clone_arg' to
	  workaround the issue of exceeding 6 arguments to the system call.
	  Also define clone-flags as u64 to allow additional clone-flags.

Changelog[v6]:
	- [Nathan Lynch, Arnd Bergmann, H. Peter Anvin, Linus Torvalds]
	  Change 'pid_set.pids' to 'pid_t pids[]' so sizeof(struct pid_set) is
	  constant across architectures (Patches 7, 8).
	- (Nathan Lynch) Change pid_set.num_pids to unsigned and remove
	  'unum_pids < 0' check (Patches 7,8)
	- (Pavel Machek) New patch (Patch 9) to add some documentation.

Changelog[v5]:
	- Make 'pid_max' a property of pid_ns (Integrated Serge Hallyn's patch
	  into this set)
	- (Eric Biederman): Avoid the new function, set_pidmap() - added
	  couple of checks on 'target_pid' in alloc_pidmap() itself.

=== IMPORTANT NOTE:

clone() system call has another limitation - all but one bits in clone-flags
are in use and if more new clone-flags are needed, we will need a variant of
the clone() system call. 

It appears to make sense to try and extend this new system call to address
this limitation as well. The requirements of a new clone system call could
then be summarized as:

	- do everything clone() does today, and
	- give application an ability to choose pids for the child process
	  in all ancestor pid namespaces, and
	- allow more clone_flags

Contstraints:

	- system-calls are restricted to 6 parameters and clone() already
	  takes 5 parameters, any extension to clone() interface would require
	  one or more copy_from_user().  (Not sure if copy_from_user() of ~40
	  bytes would have a significant impact on performance of clone()).

Based on these requirements and constraints, we explored a couple of system
call interfaces (in earlier versions of this patchset). Based on input from
Arnd Bergmann and others, the new interface of the system call is: 

	struct clone_args {
		u64 clone_flags_high;
		u64 child_stack_base;
		u64 child_stack_size;
		u64 parent_tid_ptr;
		u64 child_tid_ptr;
		u32 nr_pids;
		u32 reserved0;
	};

	sys_eclone(u32 flags_low, struct clone_args *cargs, int args_size,
			pid_t *pids)

Details of the struct clone_args and the usage are explained in the
documentation (PATCH 12/12).

NOTE:
	While this patchset enables support for more clone-flags, actual
	implementation for additional clone-flags is best implemented as
	a separate patchset (PATCH 8/9 identifies some TODOs)

Signed-off-by: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>

[v13][PATCH 01/12] Factor out code to allocate pidmap page

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Subject: [v13][PATCH 01/12] Factor out code to allocate pidmap page

To simplify alloc_pidmap(), move code to allocate a pid map page to a
separate function.

Changelog[v3]:
	- Earlier version of patchset called alloc_pidmap_page() from two
	  places. But now its called from only one place. Even so, moving
	  this code out into a separate function simplifies alloc_pidmap().
Changelog[v2]:
	- (Matt Helsley, Dave Hansen) Have alloc_pidmap_page() return
	  -ENOMEM on error instead of -1.

Signed-off-by: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Reviewed-by: Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
---
 kernel/pid.c |   45 ++++++++++++++++++++++++++++++---------------
 1 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/kernel/pid.c b/kernel/pid.c
index d3f722d..7d4bb6e 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -122,9 +122,35 @@ static void free_pidmap(struct upid *upid)
 	atomic_inc(&map->nr_free);
 }
 
+static int alloc_pidmap_page(struct pidmap *map)
+{
+	void *page;
+
+	if (likely(map->page))
+		return 0;
+
+	page = kzalloc(PAGE_SIZE, GFP_KERNEL);
+
+	/*
+	 * Free the page if someone raced with us installing it:
+	 */
+	spin_lock_irq(&pidmap_lock);
+	if (map->page)
+		kfree(page);
+	else
+		map->page = page;
+	spin_unlock_irq(&pidmap_lock);
+
+	if (unlikely(!map->page))
+		return -ENOMEM;
+
+	return 0;
+}
+
 static int alloc_pidmap(struct pid_namespace *pid_ns)
 {
 	int i, offset, max_scan, pid, last = pid_ns->last_pid;
+	int rc;
 	struct pidmap *map;
 
 	pid = last + 1;
@@ -134,21 +160,10 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
 	map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
 	max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset;
 	for (i = 0; i <= max_scan; ++i) {
-		if (unlikely(!map->page)) {
-			void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
-			/*
-			 * Free the page if someone raced with us
-			 * installing it:
-			 */
-			spin_lock_irq(&pidmap_lock);
-			if (map->page)
-				kfree(page);
-			else
-				map->page = page;
-			spin_unlock_irq(&pidmap_lock);
-			if (unlikely(!map->page))
-				break;
-		}
+		rc = alloc_pidmap_page(map);
+		if (rc)
+			break;
+
 		if (likely(atomic_read(&map->nr_free))) {
 			do {
 				if (!test_and_set_bit(offset, map->page)) {
-- 
1.6.0.4

[v13][PATCH 02/12] Have alloc_pidmap() return actual error code

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Subject: [v13][PATCH 02/12] Have alloc_pidmap() return actual error code

alloc_pidmap() can fail either because all pid numbers are in use or
because memory allocation failed.  With support for setting a specific
pid number, alloc_pidmap() would also fail if either the given pid
number is invalid or in use.

Rather than have callers assume -ENOMEM, have alloc_pidmap() return
the actual error.

Signed-off-by: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Reviewed-by: Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
---
 kernel/fork.c |    5 +++--
 kernel/pid.c  |   14 +++++++++-----
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 166b8c4..8053c10 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1156,10 +1156,11 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 		goto bad_fork_cleanup_io;
 
 	if (pid != &init_struct_pid) {
-		retval = -ENOMEM;
 		pid = alloc_pid(p->nsproxy->pid_ns);
-		if (!pid)
+		if (IS_ERR(pid)) {
+			retval = PTR_ERR(pid);
 			goto bad_fork_cleanup_io;
+		}
 
 		if (clone_flags & CLONE_NEWPID) {
 			retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
diff --git a/kernel/pid.c b/kernel/pid.c
index 7d4bb6e..c4d9914 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -150,7 +150,7 @@ static int alloc_pidmap_page(struct pidmap *map)
 static int alloc_pidmap(struct pid_namespace *pid_ns)
 {
 	int i, offset, max_scan, pid, last = pid_ns->last_pid;
-	int rc;
+	int rc = -EAGAIN;
 	struct pidmap *map;
 
 	pid = last + 1;
@@ -189,12 +189,14 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
 		} else {
 			map = &pid_ns->pidmap[0];
 			offset = RESERVED_PIDS;
-			if (unlikely(last == offset))
+			if (unlikely(last == offset)) {
+				rc = -EAGAIN;
 				break;
+			}
 		}
 		pid = mk_pid(pid_ns, map, offset);
 	}
-	return -1;
+	return rc;
 }
 
 int next_pidmap(struct pid_namespace *pid_ns, int last)
@@ -263,8 +265,10 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 	struct upid *upid;
 
 	pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
-	if (!pid)
+	if (!pid) {
+		pid = ERR_PTR(-ENOMEM);
 		goto out;
+	}
 
 	tmp = ns;
 	for (i = ns->level; i >= 0; i--) {
@@ -299,7 +303,7 @@ out_free:
 		free_pidmap(pid->numbers + i);
 
 	kmem_cache_free(ns->pid_cachep, pid);
-	pid = NULL;
+	pid = ERR_PTR(nr);
 	goto out;
 }
 
-- 
1.6.0.4

[v13][PATCH 03/12] Define set_pidmap() function

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Subject: [v13][PATCH 03/12] Define set_pidmap() function

Define a set_pidmap() interface which is like alloc_pidmap() only that
caller specifies the pid number to be assigned.

Changelog[v13]:
	- Don't let do_alloc_pidmap return 0 if it failed to find a pid.
Changelog[v9]:
	- Completely rewrote this patch based on Eric Biederman's code.
Changelog[v7]:
        - [Eric Biederman] Generalize alloc_pidmap() to take a range of pids.
Changelog[v6]:
        - Separate target_pid > 0 case to minimize the number of checks needed.
Changelog[v3]:
        - (Eric Biederman): Avoid set_pidmap() function. Added couple of
          checks for target_pid in alloc_pidmap() itself.
Changelog[v2]:
        - (Serge Hallyn) Check for 'pid < 0' in set_pidmap().(Code
          actually checks for 'pid <= 0' for completeness).

Signed-off-by: Sukadev Bhattiprolu <sukadev-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Serge E. Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 kernel/pid.c |   46 +++++++++++++++++++++++++++++++++++-----------
 1 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/kernel/pid.c b/kernel/pid.c
index c4d9914..c50a711 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -147,28 +147,29 @@ static int alloc_pidmap_page(struct pidmap *map)
 	return 0;
 }
 
-static int alloc_pidmap(struct pid_namespace *pid_ns)
+static int do_alloc_pidmap(struct pid_namespace *pid_ns, int last, int min,
+		int max)
 {
-	int i, offset, max_scan, pid, last = pid_ns->last_pid;
+	int i, offset, max_scan, pid;
 	int rc = -EAGAIN;
 	struct pidmap *map;
 
 	pid = last + 1;
 	if (pid >= pid_max)
-		pid = RESERVED_PIDS;
+		pid = min;
 	offset = pid & BITS_PER_PAGE_MASK;
 	map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
-	max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset;
+	max_scan = (max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset;
 	for (i = 0; i <= max_scan; ++i) {
 		rc = alloc_pidmap_page(map);
 		if (rc)
 			break;
 
+		rc = -EAGAIN;
 		if (likely(atomic_read(&map->nr_free))) {
 			do {
 				if (!test_and_set_bit(offset, map->page)) {
 					atomic_dec(&map->nr_free);
-					pid_ns->last_pid = pid;
 					return pid;
 				}
 				offset = find_next_offset(map, offset);
@@ -179,26 +180,49 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
 			 * bitmap block and the final block was the same
 			 * as the starting point, pid is before last_pid.
 			 */
-			} while (offset < BITS_PER_PAGE && pid < pid_max &&
+			} while (offset < BITS_PER_PAGE && pid < max &&
 					(i != max_scan || pid < last ||
 					    !((last+1) & BITS_PER_PAGE_MASK)));
 		}
-		if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) {
+		if (map < &pid_ns->pidmap[(max-1)/BITS_PER_PAGE]) {
 			++map;
 			offset = 0;
 		} else {
 			map = &pid_ns->pidmap[0];
-			offset = RESERVED_PIDS;
-			if (unlikely(last == offset)) {
-				rc = -EAGAIN;
+			offset = min;
+			if (unlikely(last == offset))
 				break;
-			}
 		}
 		pid = mk_pid(pid_ns, map, offset);
 	}
 	return rc;
 }
 
+static int alloc_pidmap(struct pid_namespace *pid_ns)
+{
+	int nr;
+
+	nr = do_alloc_pidmap(pid_ns, pid_ns->last_pid, RESERVED_PIDS, pid_max);
+	if (nr >= 0)
+		pid_ns->last_pid = nr;
+	return nr;
+}
+
+static int set_pidmap(struct pid_namespace *pid_ns, int target)
+{
+	if (!target)
+		return alloc_pidmap(pid_ns);
+
+	if (target >= pid_max)
+		return -EINVAL;
+
+	if ((target < 0) || (target < RESERVED_PIDS &&
+				pid_ns->last_pid >= RESERVED_PIDS))
+		return -EINVAL;
+
+	return do_alloc_pidmap(pid_ns, target - 1, target, target + 1);
+}
+
 int next_pidmap(struct pid_namespace *pid_ns, int last)
 {
 	int offset;
-- 
1.6.0.4

[v13][PATCH 06/12] Check invalid clone flags

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Subject: [v13][PATCH 06/12] Check invalid clone flags

As pointed out by Oren Laadan, we want to ensure that unused bits in the
clone-flags remain unused and available for future. To ensure this, define
a mask of clone-flags and check the flags in the clone() system calls.

Changelog[v9]:
	- Include the unused clone-flag (CLONE_UNUSED) to VALID_CLONE_FLAGS
	  to avoid breaking any applications that may have set it. IOW, this
	  patch/check only applies to clone-flags bits 33 and higher.

Changelog[v8]:
	- New patch in set

Signed-off-by: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
---
 include/linux/sched.h |   12 ++++++++++++
 kernel/fork.c         |    3 +++
 2 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 75e6e60..a4d2c23 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -29,6 +29,18 @@
 #define CLONE_NEWNET		0x40000000	/* New network namespace */
 #define CLONE_IO		0x80000000	/* Clone io context */
 
+#define CLONE_UNUSED        	0x00001000	/* Can be reused ? */
+
+#define VALID_CLONE_FLAGS	(CSIGNAL | CLONE_VM | CLONE_FS | CLONE_FILES |\
+				 CLONE_SIGHAND | CLONE_UNUSED | CLONE_PTRACE |\
+				 CLONE_VFORK  | CLONE_PARENT | CLONE_THREAD  |\
+				 CLONE_NEWNS  | CLONE_SYSVSEM | CLONE_SETTLS |\
+				 CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID  |\
+				 CLONE_DETACHED | CLONE_UNTRACED             |\
+				 CLONE_CHILD_SETTID | CLONE_STOPPED          |\
+				 CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWUSER |\
+				 CLONE_NEWPID | CLONE_NEWNET | CLONE_IO)
+
 /*
  * Scheduling policies
  */
diff --git a/kernel/fork.c b/kernel/fork.c
index 72c76a1..317adcf 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -982,6 +982,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	struct task_struct *p;
 	int cgroup_callbacks_done = 0;
 
+	if (clone_flags & ~VALID_CLONE_FLAGS)
+		return ERR_PTR(-EINVAL);
+
 	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 		return ERR_PTR(-EINVAL);
 
-- 
1.6.0.4

[v13][PATCH 07/12] Define do_fork_with_pids()

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Subject: [v13][PATCH 07/12] Define do_fork_with_pids()

do_fork_with_pids() is same as do_fork(), except that it takes an
additional, 'pid_set', parameter. This parameter, currently unused,
specifies the set of target pids of the process in each of its pid
namespaces.

Changelog[v7]:
	- Drop 'struct pid_set' object and pass in 'pid_t *target_pids'
	  instead of 'struct pid_set *'.

Changelog[v6]:
	- (Nathan Lynch, Arnd Bergmann, H. Peter Anvin, Linus Torvalds)
	  Change 'pid_set.pids' to a 'pid_t pids[]' so size of 'struct pid_set'
	  is constant across architectures.
	- (Nathan Lynch) Change 'pid_set.num_pids' to 'unsigned int'.

Changelog[v4]:
	- Rename 'struct target_pid_set' to 'struct pid_set' since it may
	  be useful in other contexts.

Changelog[v3]:
	- Fix "long-line" warning from checkpatch.pl

Changelog[v2]:
	- To facilitate moving architecture-inpdendent code to kernel/fork.c
	  pass in 'struct target_pid_set __user *' to do_fork_with_pids()
	  rather than 'pid_t *' (next patch moves the arch-independent
	  code to kernel/fork.c)

Signed-off-by: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Reviewed-by: Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
---
 include/linux/sched.h |    3 +++
 kernel/fork.c         |   17 +++++++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index a4d2c23..85e971a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2153,6 +2153,9 @@ extern int disallow_signal(int);
 
 extern int do_execve(char *, char __user * __user *, char __user * __user *, struct pt_regs *);
 extern long do_fork(unsigned long, unsigned long, struct pt_regs *, unsigned long, int __user *, int __user *);
+extern long do_fork_with_pids(unsigned long, unsigned long, struct pt_regs *,
+				unsigned long, int __user *, int __user *,
+				unsigned int, pid_t __user *);
 struct task_struct *fork_idle(int);
 
 extern void set_task_comm(struct task_struct *tsk, char *from);
diff --git a/kernel/fork.c b/kernel/fork.c
index 317adcf..2610a64 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1377,12 +1377,14 @@ struct task_struct * __cpuinit fork_idle(int cpu)
  * It copies the process, and if successful kick-starts
  * it and waits for it to finish using the VM if required.
  */
-long do_fork(unsigned long clone_flags,
+long do_fork_with_pids(unsigned long clone_flags,
 	      unsigned long stack_start,
 	      struct pt_regs *regs,
 	      unsigned long stack_size,
 	      int __user *parent_tidptr,
-	      int __user *child_tidptr)
+	      int __user *child_tidptr,
+	      unsigned int num_pids,
+	      pid_t __user *upids)
 {
 	struct task_struct *p;
 	int trace = 0;
@@ -1485,6 +1487,17 @@ long do_fork(unsigned long clone_flags,
 	return nr;
 }
 
+long do_fork(unsigned long clone_flags,
+	      unsigned long stack_start,
+	      struct pt_regs *regs,
+	      unsigned long stack_size,
+	      int __user *parent_tidptr,
+	      int __user *child_tidptr)
+{
+	return do_fork_with_pids(clone_flags, stack_start, regs, stack_size,
+			parent_tidptr, child_tidptr, 0, NULL);
+}
+
 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
 #define ARCH_MIN_MMSTRUCT_ALIGN 0
 #endif
-- 
1.6.0.4

[v13][PATCH 09/12] Implement sys_eclone for x86_64

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Subject: [v13][PATCH 09/12] Implement sys_eclone for x86_64

Implement sys_eclone() system call for x86_64.

This is based on earlier code from Dave Hansen. Modified to share code
between x86 and x86_64 kernels.

Signed-off-by: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
---
 arch/x86/include/asm/unistd_64.h |    3 +++
 arch/x86/kernel/entry_64.S       |    1 +
 arch/x86/kernel/process_64.c     |    7 +++++++
 3 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/unistd_64.h b/arch/x86/include/asm/unistd_64.h
index 8d3ad0a..d2ffc89 100644
--- a/arch/x86/include/asm/unistd_64.h
+++ b/arch/x86/include/asm/unistd_64.h
@@ -661,6 +661,9 @@ __SYSCALL(__NR_pwritev, sys_pwritev)
 __SYSCALL(__NR_rt_tgsigqueueinfo, sys_rt_tgsigqueueinfo)
 #define __NR_perf_event_open			298
 __SYSCALL(__NR_perf_event_open, sys_perf_event_open)
+#define __NR_eclone                   		299
+__SYSCALL(__NR_eclone, stub_eclone)
+
 
 #ifndef __NO_STUBS
 #define __ARCH_WANT_OLD_READDIR
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index b5c061f..6d60cd1 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -698,6 +698,7 @@ END(\label)
 	PTREGSCALL stub_vfork, sys_vfork, %rdi
 	PTREGSCALL stub_sigaltstack, sys_sigaltstack, %rdx
 	PTREGSCALL stub_iopl, sys_iopl, %rsi
+	PTREGSCALL stub_eclone, sys_eclone, %r8
 
 ENTRY(ptregscall_common)
 	DEFAULT_FRAME 1 8	/* offset 8: return address */
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index eb62cbc..2c306b9 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -540,6 +540,13 @@ sys_clone(unsigned long clone_flags, unsigned long newsp,
 	return do_fork(clone_flags, newsp, regs, 0, parent_tid, child_tid);
 }
 
+asmlinkage long
+sys_eclone(unsigned int flags_low, struct clone_args * __user uca,
+		int args_size, pid_t * __user pids, struct pt_regs *regs)
+{
+	return do_eclone_common(regs, flags_low, uca, args_size, pids);
+}
+
 unsigned long get_wchan(struct task_struct *p)
 {
 	unsigned long stack;
-- 
1.6.0.4

[v13][PATCH 11/12] Implement sys_eclone for powerpc

[Sukadev Bhattiprolu]

From: Nathan Lynch <ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
Subject: [v13][PATCH 11/12] Implement sys_eclone for powerpc

Wired up for both ppc32 and ppc64, but tested only with the latter.

Changelog:
	Nov 17:  (serge) remove redundant flags_high check, and
		don't fold it into flags.

Signed-off-by: Nathan Lynch <ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Serge E. Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 arch/powerpc/include/asm/syscalls.h |    6 ++++
 arch/powerpc/include/asm/systbl.h   |    1 +
 arch/powerpc/include/asm/unistd.h   |    3 +-
 arch/powerpc/kernel/entry_32.S      |    8 +++++
 arch/powerpc/kernel/entry_64.S      |    5 +++
 arch/powerpc/kernel/process.c       |   52 +++++++++++++++++++++++++++++++++++
 6 files changed, 74 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index eb8eb40..1674544 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -24,6 +24,12 @@ asmlinkage int sys_execve(unsigned long a0, unsigned long a1,
 asmlinkage int sys_clone(unsigned long clone_flags, unsigned long usp,
 		int __user *parent_tidp, void __user *child_threadptr,
 		int __user *child_tidp, int p6, struct pt_regs *regs);
+asmlinkage int sys_eclone(unsigned long flags_low,
+			  struct clone_args __user *args,
+			  size_t args_size,
+			  pid_t __user *pids,
+			  unsigned long p5, unsigned long p6,
+			  struct pt_regs *regs);
 asmlinkage int sys_fork(unsigned long p1, unsigned long p2,
 		unsigned long p3, unsigned long p4, unsigned long p5,
 		unsigned long p6, struct pt_regs *regs);
diff --git a/arch/powerpc/include/asm/systbl.h b/arch/powerpc/include/asm/systbl.h
index c7d671a..a7f67ee 100644
--- a/arch/powerpc/include/asm/systbl.h
+++ b/arch/powerpc/include/asm/systbl.h
@@ -326,3 +326,4 @@ SYSCALL_SPU(perf_event_open)
 COMPAT_SYS_SPU(preadv)
 COMPAT_SYS_SPU(pwritev)
 COMPAT_SYS(rt_tgsigqueueinfo)
+PPC_SYS(eclone)
diff --git a/arch/powerpc/include/asm/unistd.h b/arch/powerpc/include/asm/unistd.h
index f6ca761..37357a2 100644
--- a/arch/powerpc/include/asm/unistd.h
+++ b/arch/powerpc/include/asm/unistd.h
@@ -345,10 +345,11 @@
 #define __NR_preadv		320
 #define __NR_pwritev		321
 #define __NR_rt_tgsigqueueinfo	322
+#define __NR_eclone		323
 
 #ifdef __KERNEL__
 
-#define __NR_syscalls		323
+#define __NR_syscalls		324
 
 #define __NR__exit __NR_exit
 #define NR_syscalls	__NR_syscalls
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 1175a85..579f1da 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -586,6 +586,14 @@ ppc_clone:
 	stw	r0,_TRAP(r1)		/* register set saved */
 	b	sys_clone
 
+	.globl	ppc_eclone
+ppc_eclone:
+	SAVE_NVGPRS(r1)
+	lwz	r0,_TRAP(r1)
+	rlwinm	r0,r0,0,0,30		/* clear LSB to indicate full */
+	stw	r0,_TRAP(r1)		/* register set saved */
+	b	sys_eclone
+
 	.globl	ppc_swapcontext
 ppc_swapcontext:
 	SAVE_NVGPRS(r1)
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 9763267..febdca1 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -344,6 +344,11 @@ _GLOBAL(ppc_clone)
 	bl	.sys_clone
 	b	syscall_exit
 
+_GLOBAL(ppc_eclone)
+	bl	.save_nvgprs
+	bl	.sys_eclone
+	b	syscall_exit
+
 _GLOBAL(ppc32_swapcontext)
 	bl	.save_nvgprs
 	bl	.compat_sys_swapcontext
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index c930ac3..3874477 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -900,6 +900,58 @@ int sys_clone(unsigned long clone_flags, unsigned long usp,
  	return do_fork(clone_flags, usp, regs, 0, parent_tidp, child_tidp);
 }
 
+int sys_eclone(unsigned long clone_flags_low,
+	       struct clone_args __user *uclone_args,
+	       size_t size,
+	       pid_t __user *upids,
+	       unsigned long p5, unsigned long p6,
+	       struct pt_regs *regs)
+{
+	struct clone_args kclone_args;
+	unsigned long stack_base;
+	int __user *parent_tidp;
+	int __user *child_tidp;
+	unsigned long stack_sz;
+	unsigned int nr_pids;
+	unsigned long flags;
+	unsigned long usp;
+	int rc;
+
+	CHECK_FULL_REGS(regs);
+
+	rc = fetch_clone_args_from_user(uclone_args, size, &kclone_args);
+	if (rc)
+		return rc;
+
+	stack_sz = kclone_args.child_stack_size;
+	stack_base = kclone_args.child_stack;
+
+	/* powerpc doesn't do anything useful with the stack size */
+	if (stack_sz)
+		return -EINVAL;
+
+	/* Interpret stack_base as the child sp if it is set. */
+	usp = regs->gpr[1];
+	if (stack_base)
+		usp = stack_base;
+
+	flags = clone_flags_low;
+
+	nr_pids = kclone_args.nr_pids;
+
+	parent_tidp = (int __user *)kclone_args.parent_tid_ptr;
+	child_tidp = (int __user *)kclone_args.child_tid_ptr;
+
+#ifdef CONFIG_PPC64
+	if (test_thread_flag(TIF_32BIT)) {
+		parent_tidp = TRUNC_PTR(parent_tidp);
+		child_tidp = TRUNC_PTR(child_tidp);
+	}
+#endif
+	return do_fork_with_pids(flags, stack_base, regs, stack_sz,
+				 parent_tidp, child_tidp, nr_pids, upids);
+}
+
 int sys_fork(unsigned long p1, unsigned long p2, unsigned long p3,
 	     unsigned long p4, unsigned long p5, unsigned long p6,
 	     struct pt_regs *regs)
-- 
1.6.0.4

[v13][PATCH 12/12] Document sys_eclone

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Subject: [v13][PATCH 12/12] Document sys_eclone

This gives a brief overview of the eclone() system call.  We should
eventually describe more details in existing clone(2) man page or in
a new man page.

Changelog[v13]:
	- [Nathan Lynch, Serge Hallyn] Rename ->child_stack_base to
	  ->child_stack and ensure ->child_stack_size is 0 on architectures
	  that don't need it.
	- [Arnd Bergmann] Remove ->reserved1 field
	- [Louis Rilling, Dave Hansen] Combine the two asm statements in the
	  example into one and use memory constraint to avoid unncessary copies.
Changelog[v12]:
	- [Serge Hallyn] Fix/simplify stack-setup in the example code
	- [Serge Hallyn, Oren Laadan] Rename syscall to eclone()

Changelog[v11]:
	- [Dave Hansen] Move clone_args validation checks to arch-indpendent
	  code.
	- [Oren Laadan] Make args_size a parameter to system call and remove
	  it from 'struct clone_args'
	- [Oren Laadan] Fix some typos and clarify the order of pids in the
	  @pids parameter.

Changelog[v10]:
	- Rename clone3() to clone_with_pids() and fix some typos.
	- Modify example to show usage with the ptregs implementation.
Changelog[v9]:
	- [Pavel Machek]: Fix an inconsistency and rename new file to
	  Documentation/clone3.
	- [Roland McGrath, H. Peter Anvin] Updates to description and
	  example to reflect new prototype of clone3() and the updated/
	  renamed 'struct clone_args'.

Changelog[v8]:
	- clone2() is already in use in IA64. Rename syscall to clone3()
	- Add notes to say that we return -EINVAL if invalid clone flags
	  are specified or if the reserved fields are not 0.
Changelog[v7]:
	- Rename clone_with_pids() to clone2()
	- Changes to reflect new prototype of clone2() (using clone_struct).

Signed-off-by: Sukadev Bhattiprolu <sukadev-8jLBTbqmX/OZamtmwQBW5tBPR1lH4CV8@public.gmane.org>
Acked-by: Oren Laadan  <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
---
 Documentation/eclone |  348 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 348 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/eclone

diff --git a/Documentation/eclone b/Documentation/eclone
new file mode 100644
index 0000000..c2f1b4b
--- /dev/null
+++ b/Documentation/eclone
@@ -0,0 +1,348 @@
+
+struct clone_args {
+	u64 clone_flags_high;
+	u64 child_stack;
+	u64 child_stack_size;
+	u64 parent_tid_ptr;
+	u64 child_tid_ptr;
+	u32 nr_pids;
+	u32 reserved0;
+};
+
+
+sys_eclone(u32 flags_low, struct clone_args * __user cargs, int cargs_size,
+		pid_t * __user pids)
+
+	In addition to doing everything that clone() system call does, the
+	eclone() system call:
+
+		- allows additional clone flags (31 of 32 bits in the flags
+		  parameter to clone() are in use)
+
+		- allows user to specify a pid for the child process in its
+		  active and ancestor pid namespaces.
+
+	This system call is meant to be used when restarting an application
+	from a checkpoint. Such restart requires that the processes in the
+	application have the same pids they had when the application was
+	checkpointed. When containers are nested, the processes within the
+	containers exist in multiple pid namespaces and hence have multiple
+	pids to specify during restart.
+
+	The @flags_low parameter is identical to the 'clone_flags' parameter
+	in existing clone() system call.
+
+	The fields in 'struct clone_args' are meant to be used as follows:
+
+	u64 clone_flags_high:
+
+		When eclone() supports more than 32 flags, the additional bits
+		in the clone_flags should be specified in this field. This
+		field is currently unused and must be set to 0.
+
+	u64 child_stack;
+	u64 child_stack_size;
+
+		These two fields correspond to the 'child_stack' fields in
+		clone() and clone2() (on IA64) system calls. The usage of
+		these two fields depends on the processor architecture.
+
+		Most architectures use ->child_stack to pass-in a stack-pointer
+		itself and don't need the ->child_stack_size field. On these
+		architectures the ->child_stack_size field must be 0.
+
+		Some architectures, eg IA64, use ->child_stack to pass-in the
+		base of the region allocated for stack. These architectures
+		must pass in the size of the stack-region in ->child_stack_size.
+
+	u64 parent_tid_ptr;
+	u64 child_tid_ptr;
+
+		These two fields correspond to the 'parent_tid_ptr' and
+		'child_tid_ptr' fields in the clone() system call
+
+	u32 nr_pids;
+
+		nr_pids specifies the number of pids in the @pids array
+		parameter to eclone() (see below). nr_pids should not exceed
+		the current nesting level of the calling process (i.e if the
+		process is in init_pid_ns, nr_pids must be 1, if process is
+		in a pid namespace that is a child of init-pid-ns, nr_pids
+		cannot exceed 2, and so on).
+
+	u32 reserved0;
+	u64 reserved1;
+
+		These fields are intended to extend the functionality of the
+		eclone() in the future, while preserving backward compatibility.
+		They must be set to 0 for now.
+
+	The @cargs_size parameter specifes the sizeof(struct clone_args) and
+	is intended to enable extending this structure in the future, while
+	preserving backward compatibility.  For now, this field must be set
+	to the sizeof(struct clone_args) and this size must match the kernel's
+	view of the structure.
+
+	The @pids parameter defines the set of pids that should be assigned to
+	the child process in its active and ancestor pid namespaces. The
+	descendant pid namespaces do not matter since a process does not have a
+	pid in descendant namespaces, unless the process is in a new pid
+	namespace in which case the process is a container-init (and must have
+	the pid 1 in that namespace).
+
+	See CLONE_NEWPID section of clone(2) man page for details about pid
+	namespaces.
+
+	If a pid in the @pids list is 0, the kernel will assign the next
+	available pid in the pid namespace.
+
+	If a pid in the @pids list is non-zero, the kernel tries to assign
+	the specified pid in that namespace.  If that pid is already in use
+	by another process, the system call fails (see EBUSY below).
+
+	The order of pids in @pids is oldest in pids[0] to youngest pid
+	namespace in pids[nr_pids-1]. If the number of pids specified in the
+	@pids list is fewer than the nesting level of the process, the pids
+	are applied from youngest namespace. i.e if the process is nested in
+	a level-6 pid namespace and @pids only specifies 3 pids, the 3 pids
+	are applied to levels 6, 5 and 4. Levels 0 through 3 are assumed to
+	have a pid of '0' (the kernel will assign a pid in those namespaces).
+
+	On success, the system call returns the pid of the child process in
+	the parent's active pid namespace.
+
+	On failure, eclone() returns -1 and sets 'errno' to one of following
+	values (the child process is not created).
+
+	EPERM	Caller does not have the CAP_SYS_ADMIN privilege needed to
+		specify the pids in this call (if pids are not specifed
+		CAP_SYS_ADMIN is not required).
+
+	EINVAL	The number of pids specified in 'clone_args.nr_pids' exceeds
+		the current nesting level of parent process
+
+	EINVAL	Not all specified clone-flags are valid.
+
+	EINVAL	The reserved fields in the clone_args argument are not 0.
+
+	EINVAL	The child_stack_size field is not 0 (on architectures that
+		pass in a stack pointer in ->child_stack field)
+
+	EBUSY	A requested pid is in use by another process in that namespace.
+
+---
+/*
+ * Example eclone() usage - Create a child process with pid CHILD_TID1 in
+ * the current pid namespace. The child gets the usual "random" pid in any
+ * ancestor pid namespaces.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <signal.h>
+#include <errno.h>
+#include <unistd.h>
+#include <wait.h>
+#include <sys/syscall.h>
+
+#define __NR_eclone		337
+#define CLONE_NEWPID            0x20000000
+#define CLONE_CHILD_SETTID      0x01000000
+#define CLONE_PARENT_SETTID     0x00100000
+#define CLONE_UNUSED		0x00001000
+
+#define STACKSIZE		8192
+
+typedef unsigned long long u64;
+typedef unsigned int u32;
+typedef int pid_t;
+struct clone_args {
+	u64 clone_flags_high;
+	u64 child_stack;
+	u64 child_stack_size;
+
+	u64 parent_tid_ptr;
+	u64 child_tid_ptr;
+
+	u32 nr_pids;
+
+	u32 reserved0;
+};
+
+#define exit		_exit
+
+/*
+ * Following eclone() is based on code posted by Oren Laadan at:
+ * https://lists.linux-foundation.org/pipermail/containers/2009-June/018463.html
+ */
+#if defined(__i386__) && defined(__NR_eclone)
+
+int eclone(u32 flags_low, struct clone_args *clone_args, int args_size,
+		int *pids)
+{
+	long retval;
+
+	__asm__ __volatile__(
+		 "movl %3, %%ebx\n\t"	/* flags_low -> 1st (ebx) */
+		 "movl %4, %%ecx\n\t"	/* clone_args -> 2nd (ecx)*/
+		 "movl %5, %%edx\n\t"	/* args_size -> 3rd (edx) */
+		 "movl %6, %%edi\n\t"	/* pids -> 4th (edi)*/
+
+		 "pushl %%ebp\n\t"	/* save value of ebp */
+		 "int $0x80\n\t"	/* Linux/i386 system call */
+		 "testl %0,%0\n\t"	/* check return value */
+		 "jne 1f\n\t"		/* jump if parent */
+
+		 "popl %%esi\n\t"	/* get subthread function */
+		 "call *%%esi\n\t"	/* start subthread function */
+		 "movl %2,%0\n\t"
+		 "int $0x80\n"		/* exit system call: exit subthread */
+		 "1:\n\t"
+		 "popl %%ebp\t"		/* restore parent's ebp */
+
+		:"=a" (retval)
+
+		:"0" (__NR_eclone),
+		 "i" (__NR_exit),
+		 "m" (flags_low),
+		 "m" (clone_args),
+		 "m" (args_size),
+		 "m" (pids)
+		);
+
+	if (retval < 0) {
+		errno = -retval;
+		retval = -1;
+	}
+	return retval;
+}
+
+/*
+ * Allocate a stack for the clone-child and arrange to have the child
+ * execute @child_fn with @child_arg as the argument.
+ */
+void *setup_stack(int (*child_fn)(void *), void *child_arg, int size)
+{
+	void *stack_base;
+	void **stack_top;
+
+	stack_base = malloc(size + size);
+	if (!stack_base) {
+		perror("malloc()");
+		exit(1);
+	}
+
+	stack_top = (void **)((char *)stack_base + (size - 4));
+	*--stack_top = child_arg;
+	*--stack_top = child_fn;
+
+	return stack_top;
+}
+#endif
+
+/* gettid() is a bit more useful than getpid() when messing with clone() */
+int gettid()
+{
+	int rc;
+
+	rc = syscall(__NR_gettid, 0, 0, 0);
+	if (rc < 0) {
+		printf("rc %d, errno %d\n", rc, errno);
+		exit(1);
+	}
+	return rc;
+}
+
+#define CHILD_TID1	377
+#define CHILD_TID2	1177
+#define CHILD_TID3	2799
+
+struct clone_args clone_args;
+void *child_arg = &clone_args;
+int child_tid;
+
+int do_child(void *arg)
+{
+	struct clone_args *cs = (struct clone_args *)arg;
+	int ctid;
+
+	/* Verify we pushed the arguments correctly on the stack... */
+	if (arg != child_arg)  {
+		printf("Child: Incorrect child arg pointer, expected %p,"
+				"actual %p\n", child_arg, arg);
+		exit(1);
+	}
+
+	/* ... and that we got the thread-id we expected */
+	ctid = *((int *)(unsigned long)cs->child_tid_ptr);
+	if (ctid != CHILD_TID1) {
+		printf("Child: Incorrect child tid, expected %d, actual %d\n",
+				CHILD_TID1, ctid);
+		exit(1);
+	} else {
+		printf("Child got the expected tid, %d\n", gettid());
+	}
+	sleep(2);
+
+	printf("[%d, %d]: Child exiting\n", getpid(), ctid);
+	exit(0);
+}
+
+static int do_clone(int (*child_fn)(void *), void *child_arg,
+		unsigned int flags_low, int nr_pids, pid_t *pids_list)
+{
+	int rc;
+	void *stack;
+	struct clone_args *ca = &clone_args;
+	int args_size;
+
+	stack = setup_stack(child_fn, child_arg, STACKSIZE);
+
+	memset(ca, 0, sizeof(*ca));
+
+	ca->child_stack		= (u64)(unsigned long)stack;
+	ca->child_stack_size	= (u64)0;
+	ca->child_tid_ptr	= (u64)(unsigned long)&child_tid;
+	ca->nr_pids		= nr_pids;
+
+	args_size = sizeof(struct clone_args);
+	rc = eclone(flags_low, ca, args_size, pids_list);
+
+	printf("[%d, %d]: eclone() returned %d, error %d\n", getpid(), gettid(),
+				rc, errno);
+	return rc;
+}
+
+/*
+ * Multiple pid_t pid_t values in pids_list[] here are just for illustration.
+ * The test case creates a child in the current pid namespace and uses only
+ * the first value, CHILD_TID1.
+ */
+pid_t pids_list[] = { CHILD_TID1, CHILD_TID2, CHILD_TID3 };
+int main()
+{
+	int rc, pid, status;
+	unsigned long flags;
+	int nr_pids = 1;
+
+	flags = SIGCHLD|CLONE_CHILD_SETTID;
+
+	pid = do_clone(do_child, &clone_args, flags, nr_pids, pids_list);
+
+	printf("[%d, %d]: Parent waiting for %d\n", getpid(), gettid(), pid);
+
+	rc = waitpid(pid, &status, __WALL);
+	if (rc < 0) {
+		printf("waitpid(): rc %d, error %d\n", rc, errno);
+	} else {
+		printf("[%d, %d]: child %d:\n\t wait-status 0x%x\n", getpid(),
+			 gettid(), rc, status);
+
+		if (WIFEXITED(status)) {
+			printf("\t EXITED, %d\n", WEXITSTATUS(status));
+		} else if (WIFSIGNALED(status)) {
+			printf("\t SIGNALED, %d\n", WTERMSIG(status));
+		}
+	}
+	return 0;
+}
-- 
1.6.0.4

[v13][PATCH 04/12] Add target_pids parameter to alloc_pid()

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Subject: [v13][PATCH 04/12] Add target_pids parameter to alloc_pid()

This parameter is currently NULL, but will be used in a follow-on patch.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Reviewed-by: Oren Laadan <orenl@cs.columbia.edu>
---
 include/linux/pid.h |    2 +-
 kernel/fork.c       |    3 ++-
 kernel/pid.c        |    9 +++++++--
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/include/linux/pid.h b/include/linux/pid.h
index 49f1c2f..914185d 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -119,7 +119,7 @@ extern struct pid *find_get_pid(int nr);
 extern struct pid *find_ge_pid(int nr, struct pid_namespace *);
 int next_pidmap(struct pid_namespace *pid_ns, int last);
 
-extern struct pid *alloc_pid(struct pid_namespace *ns);
+extern struct pid *alloc_pid(struct pid_namespace *ns, pid_t *target_pids);
 extern void free_pid(struct pid *pid);
 
 /*
diff --git a/kernel/fork.c b/kernel/fork.c
index 8053c10..00adf9f 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -980,6 +980,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	int retval;
 	struct task_struct *p;
 	int cgroup_callbacks_done = 0;
+	pid_t *target_pids = NULL;
 
 	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 		return ERR_PTR(-EINVAL);
@@ -1156,7 +1157,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 		goto bad_fork_cleanup_io;
 
 	if (pid != &init_struct_pid) {
-		pid = alloc_pid(p->nsproxy->pid_ns);
+		pid = alloc_pid(p->nsproxy->pid_ns, target_pids);
 		if (IS_ERR(pid)) {
 			retval = PTR_ERR(pid);
 			goto bad_fork_cleanup_io;
diff --git a/kernel/pid.c b/kernel/pid.c
index c50a711..ad3408b 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -280,13 +280,14 @@ void free_pid(struct pid *pid)
 	call_rcu(&pid->rcu, delayed_put_pid);
 }
 
-struct pid *alloc_pid(struct pid_namespace *ns)
+struct pid *alloc_pid(struct pid_namespace *ns, pid_t *target_pids)
 {
 	struct pid *pid;
 	enum pid_type type;
 	int i, nr;
 	struct pid_namespace *tmp;
 	struct upid *upid;
+	pid_t tpid;
 
 	pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
 	if (!pid) {
@@ -296,7 +297,11 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 
 	tmp = ns;
 	for (i = ns->level; i >= 0; i--) {
-		nr = alloc_pidmap(tmp);
+		tpid = 0;
+		if (target_pids)
+			tpid = target_pids[i];
+
+		nr = set_pidmap(tmp, tpid);
 		if (nr < 0)
 			goto out_free;
 
-- 
1.6.0.4

[v13][PATCH 05/12] Add target_pids parameter to copy_process()

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Subject: [v13][PATCH 05/12] Add target_pids parameter to copy_process()

Add a 'target_pids' parameter to copy_process().  The new parameter will be
used in a follow-on patch when eclone() is implemented.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Reviewed-by: Oren Laadan <orenl@cs.columbia.edu>
---
 kernel/fork.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 00adf9f..72c76a1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -975,12 +975,12 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 					unsigned long stack_size,
 					int __user *child_tidptr,
 					struct pid *pid,
+					pid_t *target_pids,
 					int trace)
 {
 	int retval;
 	struct task_struct *p;
 	int cgroup_callbacks_done = 0;
-	pid_t *target_pids = NULL;
 
 	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 		return ERR_PTR(-EINVAL);
@@ -1361,7 +1361,7 @@ struct task_struct * __cpuinit fork_idle(int cpu)
 	struct pt_regs regs;
 
 	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
-			    &init_struct_pid, 0);
+			    &init_struct_pid, NULL, 0);
 	if (!IS_ERR(task))
 		init_idle(task, cpu);
 
@@ -1384,6 +1384,7 @@ long do_fork(unsigned long clone_flags,
 	struct task_struct *p;
 	int trace = 0;
 	long nr;
+	pid_t *target_pids = NULL;
 
 	/*
 	 * Do some preliminary argument and permissions checking before we
@@ -1424,7 +1425,7 @@ long do_fork(unsigned long clone_flags,
 		trace = tracehook_prepare_clone(clone_flags);
 
 	p = copy_process(clone_flags, stack_start, regs, stack_size,
-			 child_tidptr, NULL, trace);
+			 child_tidptr, NULL, target_pids, trace);
 	/*
 	 * Do this prior waking up the new thread - the thread pointer
 	 * might get invalid after that point, if the thread exits quickly.
-- 
1.6.0.4

[v13][PATCH 08/12] Implement sys_eclone for x86

[Sukadev Bhattiprolu]

From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Subject: [v13][PATCH 08/12] Implement sys_eclone for x86

Container restart requires that a task have the same pid it had when it was
checkpointed. When containers are nested the tasks within the containers
exist in multiple pid namespaces and hence have multiple pids to specify
during restart.

eclone(), intended for use during restart, is the same as
clone(), except that it takes a 'pids' paramter. This parameter lets
caller choose specific pid numbers for the child process, in the
process's active and ancestor pid namespaces. (Descendant pid namespaces
in general don't matter since processes don't have pids in them anyway,
but see comments in copy_target_pids() regarding CLONE_NEWPID).

eclone() also attempts to address a second limitation of the
clone() system call. clone() is restricted to 32 clone flags and all but
one of these are in use. If more new clone flags are needed, we will be
forced to define a new variant of the clone() system call. To address
this, eclone() allows at least 64 clone flags with some room
for more if necessary.

To prevent unprivileged processes from misusing this interface,
eclone() currently needs CAP_SYS_ADMIN, when the 'pids' parameter
is non-NULL.

See Documentation/eclone in next patch for more details and an
example of its usage.

NOTE:
	- System calls are restricted to 6 parameters and the number and sizes
	  of parameters needed for eclone() exceed 6 integers. The new
	  prototype works around this restriction while providing some
	  flexibility if eclone() needs to be further extended in the
	  future.
TODO:
	- We should convert clone-flags to 64-bit value in all architectures.
	  Its probably best to do that as a separate patchset since clone_flags
	  touches several functions and that patchset seems independent of this
	  new system call.

Changelog[v13]:
	- [Dave Hansen]: Reorg to enable sharing code between x86 and x86-64.
	- [Arnd Bergmann]: With args_size parameter, ->reserved1 is redundant
	  and can be removed.
	- [Nathan Lynch]: stop warnings about assigning u64 to a (32-bit) int*.
	- [Nathan Lynch, Serge Hallyn] Rename ->child_stack_base to
	  ->child_stack and ensure ->child_stack_size is 0 on architectures
	  that don't need it (see comments in types.h for details).

Changelog[v12]:
	- [Serge Hallyn] Ignore ->child_stack_size if ->child_stack_base
	  is NULL.
	- [Oren Laadan, Serge Hallyn] Rename clone_with_pids() to eclone()
Changelog[v11]:
	- [Dave Hansen] Move clone_args validation checks to arch-indpeendent
	  code.
	- [Oren Laadan] Make args_size a parameter to system call and remove
	  it from 'struct clone_args'

Changelog[v10]:
	- Rename clone3() to clone_with_pids()
	- [Linus Torvalds] Use PTREGSCALL() rather than the generic syscall
	  implementation

Changelog[v9]:
	- [Roland McGrath, H. Peter Anvin] To avoid confusion on 64-bit
	  architectures split the new clone-flags into 'low' and 'high'
	  words and pass in the 'lower' flags as the first argument.
	  This would maintain similarity of the clone3() with clone()/
	  clone2(). Also has the side-effect of the name matching the
	  number of parameters :-)
	- [Roland McGrath] Rename structure to 'clone_args' and add a
	  'child_stack_size' field

Changelog[v8]
	- [Oren Laadan] parent_tid and child_tid fields in 'struct clone_arg'
	  must be 64-bit.
	- clone2() is in use in IA64. Rename system call to clone3().

Changelog[v7]:
	- [Peter Zijlstra, Arnd Bergmann] Rename system call to clone2()
	  and group parameters into a new 'struct clone_struct' object.

Changelog[v6]:
	- (Nathan Lynch, Arnd Bergmann, H. Peter Anvin, Linus Torvalds)
	  Change 'pid_set.pids' to a 'pid_t pids[]' so size of 'struct pid_set'
	  is constant across architectures.
	- (Nathan Lynch) Change pid_set.num_pids to unsigned and remove
	  'unum_pids < 0' check.

Changelog[v4]:
	- (Oren Laadan) rename 'struct target_pid_set' to 'struct pid_set'

Changelog[v3]:
	- (Oren Laadan) Allow CLONE_NEWPID flag (by allocating an extra pid
	  in the target_pids[] list and setting it 0. See copy_target_pids()).
	- (Oren Laadan) Specified target pids should apply only to youngest
	  pid-namespaces (see copy_target_pids())
	- (Matt Helsley) Update patch description.

Changelog[v2]:
	- Remove unnecessary printk and add a note to callers of
	  copy_target_pids() to free target_pids.
	- (Serge Hallyn) Mention CAP_SYS_ADMIN restriction in patch description.
	- (Oren Laadan) Add checks for 'num_pids < 0' (return -EINVAL) and
	  'num_pids == 0' (fall back to normal clone()).
	- Move arch-independent code (sanity checks and copy-in of target-pids)
	  into kernel/fork.c and simplify sys_clone_with_pids()

Changelog[v1]:
	- Fixed some compile errors (had fixed these errors earlier in my
	  git tree but had not refreshed patches before emailing them)

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
---
 arch/x86/include/asm/processor.h   |    4 +
 arch/x86/include/asm/syscalls.h    |    1 +
 arch/x86/include/asm/unistd_32.h   |    3 +-
 arch/x86/kernel/entry_32.S         |    1 +
 arch/x86/kernel/process.c          |   40 ++++++++++++
 arch/x86/kernel/process_32.c       |   15 ++++
 arch/x86/kernel/syscall_table_32.S |    1 +
 include/linux/sched.h              |    2 +
 include/linux/types.h              |   16 +++++
 kernel/fork.c                      |  124 +++++++++++++++++++++++++++++++++++-
 10 files changed, 205 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index c978648..af6edd4 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -1052,4 +1052,8 @@ unsigned long calc_aperfmperf_ratio(struct aperfmperf *old,
 	return ratio;
 }
 
+extern int do_eclone_common(struct pt_regs *regs, unsigned flags_low,
+				struct clone_args __user *uca, int args_size,
+				pid_t __user *pids);
+
 #endif /* _ASM_X86_PROCESSOR_H */
diff --git a/arch/x86/include/asm/syscalls.h b/arch/x86/include/asm/syscalls.h
index 372b76e..2cadb8e 100644
--- a/arch/x86/include/asm/syscalls.h
+++ b/arch/x86/include/asm/syscalls.h
@@ -40,6 +40,7 @@ long sys_iopl(struct pt_regs *);
 
 /* kernel/process_32.c */
 int sys_clone(struct pt_regs *);
+int sys_eclone(struct pt_regs *);
 int sys_execve(struct pt_regs *);
 
 /* kernel/signal.c */
diff --git a/arch/x86/include/asm/unistd_32.h b/arch/x86/include/asm/unistd_32.h
index 6fb3c20..d2ffbf7 100644
--- a/arch/x86/include/asm/unistd_32.h
+++ b/arch/x86/include/asm/unistd_32.h
@@ -342,10 +342,11 @@
 #define __NR_pwritev		334
 #define __NR_rt_tgsigqueueinfo	335
 #define __NR_perf_event_open	336
+#define __NR_eclone		337
 
 #ifdef __KERNEL__
 
-#define NR_syscalls 337
+#define NR_syscalls 338
 
 #define __ARCH_WANT_IPC_PARSE_VERSION
 #define __ARCH_WANT_OLD_READDIR
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index c097e7d..7e7f3c8 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -718,6 +718,7 @@ ptregs_##name: \
 PTREGSCALL(iopl)
 PTREGSCALL(fork)
 PTREGSCALL(clone)
+PTREGSCALL(eclone)
 PTREGSCALL(vfork)
 PTREGSCALL(execve)
 PTREGSCALL(sigaltstack)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 5284cd2..4f5ddc8 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -610,3 +610,43 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
 	return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
 }
 
+int do_eclone_common(struct pt_regs *regs, unsigned flags_low,
+			struct clone_args __user *uca, int args_size,
+			pid_t __user *pids)
+{
+	int rc;
+	struct clone_args kca;
+	unsigned long flags;
+	int __user *parent_tidp;
+	int __user *child_tidp;
+	unsigned long __user stack;
+	unsigned long stack_size;
+
+	rc = fetch_clone_args_from_user(uca, args_size, &kca);
+	if (rc)
+		return rc;
+
+	/*
+	 * TODO: Convert 'clone-flags' to 64-bits on all architectures.
+	 * TODO: When ->clone_flags_high is non-zero, copy it in to the
+	 * 	 higher word(s) of 'flags':
+	 *
+	 * 		flags = (kca.clone_flags_high << 32) | flags_low;
+	 */
+	flags = flags_low;
+	parent_tidp = (int *)(unsigned long)kca.parent_tid_ptr;
+	child_tidp = (int *)(unsigned long)kca.child_tid_ptr;
+
+	stack_size = (unsigned long)kca.child_stack_size;
+	if (stack_size)
+		return -EINVAL;
+
+	stack = (unsigned long)kca.child_stack;
+	if (!stack)
+		stack = regs->sp;
+
+	return do_fork_with_pids(flags, stack, regs, stack_size, parent_tidp,
+				child_tidp, kca.nr_pids, pids);
+}
+
+
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 4cf7956..ed8b53c 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -445,6 +445,21 @@ int sys_clone(struct pt_regs *regs)
 	return do_fork(clone_flags, newsp, regs, 0, parent_tidptr, child_tidptr);
 }
 
+int sys_eclone(struct pt_regs *regs)
+{
+	int args_size;
+	unsigned int flags_low;
+	struct clone_args __user *uca;
+	pid_t __user *pids;
+
+	flags_low = regs->bx;
+	uca = (struct clone_args __user *)regs->cx;
+	args_size = regs->dx;
+	pids = (pid_t __user *)regs->di;
+
+	return do_eclone_common(regs, flags_low, uca, args_size, pids);
+}
+
 /*
  * sys_execve() executes a new program.
  */
diff --git a/arch/x86/kernel/syscall_table_32.S b/arch/x86/kernel/syscall_table_32.S
index 0157cd2..2b6394c 100644
--- a/arch/x86/kernel/syscall_table_32.S
+++ b/arch/x86/kernel/syscall_table_32.S
@@ -336,3 +336,4 @@ ENTRY(sys_call_table)
 	.long sys_pwritev
 	.long sys_rt_tgsigqueueinfo	/* 335 */
 	.long sys_perf_event_open
+	.long ptregs_eclone
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 85e971a..b2a881d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2153,6 +2153,8 @@ extern int disallow_signal(int);
 
 extern int do_execve(char *, char __user * __user *, char __user * __user *, struct pt_regs *);
 extern long do_fork(unsigned long, unsigned long, struct pt_regs *, unsigned long, int __user *, int __user *);
+extern int fetch_clone_args_from_user(struct clone_args __user *, int,
+				struct clone_args *);
 extern long do_fork_with_pids(unsigned long, unsigned long, struct pt_regs *,
 				unsigned long, int __user *, int __user *,
 				unsigned int, pid_t __user *);
diff --git a/include/linux/types.h b/include/linux/types.h
index c42724f..d8bfd6b 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -204,6 +204,22 @@ struct ustat {
 	char			f_fpack[6];
 };
 
+struct clone_args {
+	u64 clone_flags_high;
+	/*
+	 * Architectures can use child_stack for either the stack pointer or
+	 * the base of of stack. If child_stack is used as the stack pointer,
+	 * child_stack_size must be 0. Otherwise child_stack_size must be
+	 * set to size of allocated stack.
+	 */
+	u64 child_stack;
+	u64 child_stack_size;
+	u64 parent_tid_ptr;
+	u64 child_tid_ptr;
+	u32 nr_pids;
+	u32 reserved0;
+};
+
 #endif	/* __KERNEL__ */
 #endif /*  __ASSEMBLY__ */
 #endif /* _LINUX_TYPES_H */
diff --git a/kernel/fork.c b/kernel/fork.c
index 2610a64..5838754 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1372,6 +1372,114 @@ struct task_struct * __cpuinit fork_idle(int cpu)
 }
 
 /*
+ * If user specified any 'target-pids' in @upid_setp, copy them from
+ * user and return a pointer to a local copy of the list of pids. The
+ * caller must free the list, when they are done using it.
+ *
+ * If user did not specify any target pids, return NULL (caller should
+ * treat this like normal clone).
+ *
+ * On any errors, return the error code
+ */
+static pid_t *copy_target_pids(int unum_pids, pid_t __user *upids)
+{
+	int j;
+	int rc;
+	int size;
+	int knum_pids;		/* # of pids needed in kernel */
+	pid_t *target_pids;
+
+	if (!unum_pids)
+		return NULL;
+
+	knum_pids = task_pid(current)->level + 1;
+	if (unum_pids > knum_pids)
+		return ERR_PTR(-EINVAL);
+
+	/*
+	 * To keep alloc_pid() simple, allocate an extra pid_t in target_pids[]
+	 * and set it to 0. This last entry in target_pids[] corresponds to the
+	 * (yet-to-be-created) descendant pid-namespace if CLONE_NEWPID was
+	 * specified. If CLONE_NEWPID was not specified, this last entry will
+	 * simply be ignored.
+	 */
+	target_pids = kzalloc((knum_pids + 1) * sizeof(pid_t), GFP_KERNEL);
+	if (!target_pids)
+		return ERR_PTR(-ENOMEM);
+
+	/*
+	 * A process running in a level 2 pid namespace has three pid namespaces
+	 * and hence three pid numbers. If this process is checkpointed,
+	 * information about these three namespaces are saved. We refer to these
+	 * namespaces as 'known namespaces'.
+	 *
+	 * If this checkpointed process is however restarted in a level 3 pid
+	 * namespace, the restarted process has an extra ancestor pid namespace
+	 * (i.e 'unknown namespace') and 'knum_pids' exceeds 'unum_pids'.
+	 *
+	 * During restart, the process requests specific pids for its 'known
+	 * namespaces' and lets kernel assign pids to its 'unknown namespaces'.
+	 *
+	 * Since the requested-pids correspond to 'known namespaces' and since
+	 * 'known-namespaces' are younger than (i.e descendants of) 'unknown-
+	 * namespaces', copy requested pids to the back-end of target_pids[]
+	 * (i.e before the last entry for CLONE_NEWPID mentioned above).
+	 * Any entries in target_pids[] not corresponding to a requested pid
+	 * will be set to zero and kernel assigns a pid in those namespaces.
+	 *
+	 * NOTE: The order of pids in target_pids[] is oldest pid namespace to
+	 * 	 youngest (target_pids[0] corresponds to init_pid_ns). i.e.
+	 * 	 the order is:
+	 *
+	 * 		- pids for 'unknown-namespaces' (if any)
+	 * 		- pids for 'known-namespaces' (requested pids)
+	 * 		- 0 in the last entry (for CLONE_NEWPID).
+	 */
+	j = knum_pids - unum_pids;
+	size = unum_pids * sizeof(pid_t);
+
+	rc = copy_from_user(&target_pids[j], upids, size);
+	if (rc) {
+		rc = -EFAULT;
+		goto out_free;
+	}
+
+	return target_pids;
+
+out_free:
+	kfree(target_pids);
+	return ERR_PTR(rc);
+}
+
+int
+fetch_clone_args_from_user(struct clone_args __user *uca, int args_size,
+			struct clone_args *kca)
+{
+	int rc;
+
+	/*
+	 * TODO: If size of clone_args is not what the kernel expects, it
+	 * 	 could be that kernel is newer and has an extended structure.
+	 * 	 When that happens, this check needs to be smarter.  For now,
+	 * 	 assume exact match.
+	 */
+	if (args_size != sizeof(struct clone_args))
+		return -EINVAL;
+
+	rc = copy_from_user(kca, uca, args_size);
+	if (rc)
+		return -EFAULT;
+
+	/*
+	 * To avoid future compatibility issues, ensure unused fields are 0.
+	 */
+	if (kca->reserved0 || kca->clone_flags_high)
+		return -EINVAL;
+
+	return 0;
+}
+
+/*
  *  Ok, this is the main fork-routine.
  *
  * It copies the process, and if successful kick-starts
@@ -1389,7 +1497,7 @@ long do_fork_with_pids(unsigned long clone_flags,
 	struct task_struct *p;
 	int trace = 0;
 	long nr;
-	pid_t *target_pids = NULL;
+	pid_t *target_pids;
 
 	/*
 	 * Do some preliminary argument and permissions checking before we
@@ -1423,6 +1531,16 @@ long do_fork_with_pids(unsigned long clone_flags,
 		}
 	}
 
+	target_pids = copy_target_pids(num_pids, upids);
+	if (target_pids) {
+		if (IS_ERR(target_pids))
+			return PTR_ERR(target_pids);
+
+		nr = -EPERM;
+		if (!capable(CAP_SYS_ADMIN))
+			goto out_free;
+	}
+
 	/*
 	 * When called from kernel_thread, don't do user tracing stuff.
 	 */
@@ -1484,6 +1602,10 @@ long do_fork_with_pids(unsigned long clone_flags,
 	} else {
 		nr = PTR_ERR(p);
 	}
+
+out_free:
+	kfree(target_pids);
+
 	return nr;
 }
 
-- 
1.6.0.4

[v13][PATCH 10/12] Implement sys_eclone for s390

[Sukadev Bhattiprolu]

From: Serge E. Hallyn <serue@us.ibm.com>
Subject: [v13][PATCH 10/12] Implement sys_eclone for s390

Implement the s390 hook for sys_eclone().

Changelog:
	Nov 24: Removed user-space code from commit log. See user-cr git tree.
	Nov 17: remove redundant flags_high check
	Nov 13: As suggested by Heiko, convert eclone to take its
		parameters via registers.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
---
 arch/s390/include/asm/unistd.h    |    3 ++-
 arch/s390/kernel/compat_wrapper.S |    8 ++++++++
 arch/s390/kernel/process.c        |   37 +++++++++++++++++++++++++++++++++++++
 arch/s390/kernel/syscalls.S       |    1 +
 4 files changed, 48 insertions(+), 1 deletions(-)

diff --git a/arch/s390/include/asm/unistd.h b/arch/s390/include/asm/unistd.h
index cb5232d..cbf6c7c 100644
--- a/arch/s390/include/asm/unistd.h
+++ b/arch/s390/include/asm/unistd.h
@@ -269,7 +269,8 @@
 #define	__NR_pwritev		329
 #define __NR_rt_tgsigqueueinfo	330
 #define __NR_perf_event_open	331
-#define NR_syscalls 332
+#define __NR_eclone		332
+#define NR_syscalls 333
 
 /* 
  * There are some system calls that are not present on 64 bit, some
diff --git a/arch/s390/kernel/compat_wrapper.S b/arch/s390/kernel/compat_wrapper.S
index cbd9901..816ae61 100644
--- a/arch/s390/kernel/compat_wrapper.S
+++ b/arch/s390/kernel/compat_wrapper.S
@@ -1849,6 +1849,14 @@ sys_clone_wrapper:
 	llgtr	%r5,%r5			# int *
 	jg	sys_clone		# branch to system call
 
+	.globl	sys_eclone_wrapper
+sys_eclone_wrapper:
+	llgfr	%r2,%r2			# unsigned int
+	llgtr	%r3,%r3			# struct clone_args *
+	lgfr	%r4,%r4			# int
+	llgtr	%r5,%r5			# pid_t *
+	jg	sys_eclone		# branch to system call
+
 	.globl	sys32_execve_wrapper
 sys32_execve_wrapper:
 	llgtr	%r2,%r2			# char *
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 5417eb5..0a59317 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -241,6 +241,43 @@ SYSCALL_DEFINE4(clone, unsigned long, newsp, unsigned long, clone_flags,
 		       parent_tidptr, child_tidptr);
 }
 
+SYSCALL_DEFINE4(eclone, unsigned int, flags_low, struct clone_args __user *,
+		uca, int, args_size, pid_t __user *, pids)
+{
+	int rc;
+	struct pt_regs *regs = task_pt_regs(current);
+	struct clone_args kca;
+	int __user *parent_tid_ptr;
+	int __user *child_tid_ptr;
+	unsigned long flags;
+	unsigned long __user child_stack;
+	unsigned long stack_size;
+
+	rc = fetch_clone_args_from_user(uca, args_size, &kca);
+	if (rc)
+		return rc;
+
+	flags = flags_low;
+	parent_tid_ptr = (int __user *) kca.parent_tid_ptr;
+	child_tid_ptr =  (int __user *) kca.child_tid_ptr;
+
+	stack_size = (unsigned long) kca.child_stack_size;
+	if (stack_size)
+		return -EINVAL;
+
+	child_stack = (unsigned long) kca.child_stack;
+	if (!child_stack)
+		child_stack = regs->gprs[15];
+
+	/*
+	 * TODO: On 32-bit systems, clone_flags is passed in as 32-bit value
+	 * 	 to several functions. Need to convert clone_flags to 64-bit.
+	 */
+	return do_fork_with_pids(flags, child_stack, regs, stack_size,
+				parent_tid_ptr, child_tid_ptr, kca.nr_pids,
+				pids);
+}
+
 /*
  * This is trivial, and on the face of it looks like it
  * could equally well be done in user mode.
diff --git a/arch/s390/kernel/syscalls.S b/arch/s390/kernel/syscalls.S
index 30eca07..fb8708d 100644
--- a/arch/s390/kernel/syscalls.S
+++ b/arch/s390/kernel/syscalls.S
@@ -340,3 +340,4 @@ SYSCALL(sys_preadv,sys_preadv,compat_sys_preadv_wrapper)
 SYSCALL(sys_pwritev,sys_pwritev,compat_sys_pwritev_wrapper)
 SYSCALL(sys_rt_tgsigqueueinfo,sys_rt_tgsigqueueinfo,compat_sys_rt_tgsigqueueinfo_wrapper) /* 330 */
 SYSCALL(sys_perf_event_open,sys_perf_event_open,sys_perf_event_open_wrapper)
+SYSCALL(sys_eclone,sys_eclone,sys_eclone_wrapper)
-- 
1.6.0.4

[v13][PATCH 00/12] Implement eclone() system call

[Sukadev Bhattiprolu]

Andrew,

We ported the syscall to x86_64, powerpc and s390 and in the process hashed
out couple of minor issues in the interface.

Can you please merge or let me know if there are other comments ?

---

Subject: [v13][PATCH 00/12] Implement eclone() system call

To support application checkpoint/restart, a task must have the same pid it
had when it was checkpointed.  When containers are nested, the tasks within
the containers exist in multiple pid namespaces and hence have multiple pids
to specify during restart.

This patchset implements a new system call, eclone() that lets a process
specify the pids of the child process.

Patches 1 through 7 are helper patches needed for choosing a pid for the
child process.

Patches 8 through 11 implement the eclone() system call on x86, x86_64, s390
and powerpc.

Patch 12 documents the new system call, some/all of which will eventually
go into a man page.

Changelog[v13]:
	- Implement sys_eclone() on x86_64, s390 and powerpc architectures
	- Reorg x86 implementation to enable sharing code with x86_64
	- [Arnd Bergmann] Remove the ->reserved1 field we now have args_size
	- [Nathan Lynch, Serge Hallyn]: Rename ->child_stack_base to
	  ->child_stack and ensure ->child_stack_size is 0 on architectures
	  that don't need the stack size.
	- Modify exmaple in Documentation to avoid unnecessary register copy.

Changelog[v12]:
	- Ignore ->child_stack_size when ->child_stack_base is NULL (PATCH 8)
	- Cleanup/simplify example in Documentation/eclone (PATCH 9).
	- Rename sys call to a shorter name, eclone()

Changelog[v11]:
	- [Dave Hansen] Move clone_args validation checks to arch-indpeendent
	  code.
	- [Oren Laadan] Make args_size a parameter to system call and remove
	  it from 'struct clone_args'

Changelog[v10]:
	- [Linus Torvalds] Use PTREGSCALL() implementation for clone rather
	  than the generic system call
	- Rename clone3() to clone_with_pids()
	- Update Documentation/clone_with_pids() to show example usage with
	  the PTREGSCALL implementation.

Changelog[v9]:
	- [Pavel Emelyanov] Drop the patch that made 'pid_max' a property
	  of struct pid_namespace
	- [Roland McGrath, H. Peter Anvin and earlier on, Serge Hallyn] To
	  avoid inadvertent truncation clone_flags, preserve the first
	  parameter of clone3() as 'u32 clone_flags' and specify newer
	  flags in clone_args.flags_high (PATCH 8/9 and PATCH 9/9)
	- [Eric Biederman] Generalize alloc_pidmap() code to simplify and
	  remove duplication (see PATCH 3/9].
	  
Changelog[v8]:
	- [Oren Laadan, Louis Rilling, KOSAKI Motohiro]
	  The name 'clone2()' is in use - renamed new syscall to clone3().
	- [Oren Laadan] ->parent_tidptr and ->child_tidptr need to be 64bit.
	- [Oren Laadan] Ensure that unused fields/flags in clone_struct are 0.
	  (Added [PATCH 7/10] to the patchset).

Changelog[v7]:
	- [Peter Zijlstra, Arnd Bergmann]
	  Group the arguments to clone2() into a 'struct clone_arg' to
	  workaround the issue of exceeding 6 arguments to the system call.
	  Also define clone-flags as u64 to allow additional clone-flags.

Changelog[v6]:
	- [Nathan Lynch, Arnd Bergmann, H. Peter Anvin, Linus Torvalds]
	  Change 'pid_set.pids' to 'pid_t pids[]' so sizeof(struct pid_set) is
	  constant across architectures (Patches 7, 8).
	- (Nathan Lynch) Change pid_set.num_pids to unsigned and remove
	  'unum_pids < 0' check (Patches 7,8)
	- (Pavel Machek) New patch (Patch 9) to add some documentation.

Changelog[v5]:
	- Make 'pid_max' a property of pid_ns (Integrated Serge Hallyn's patch
	  into this set)
	- (Eric Biederman): Avoid the new function, set_pidmap() - added
	  couple of checks on 'target_pid' in alloc_pidmap() itself.

=== IMPORTANT NOTE:

clone() system call has another limitation - all but one bits in clone-flags
are in use and if more new clone-flags are needed, we will need a variant of
the clone() system call. 

It appears to make sense to try and extend this new system call to address
this limitation as well. The requirements of a new clone system call could
then be summarized as:

	- do everything clone() does today, and
	- give application an ability to choose pids for the child process
	  in all ancestor pid namespaces, and
	- allow more clone_flags

Contstraints:

	- system-calls are restricted to 6 parameters and clone() already
	  takes 5 parameters, any extension to clone() interface would require
	  one or more copy_from_user().  (Not sure if copy_from_user() of ~40
	  bytes would have a significant impact on performance of clone()).

Based on these requirements and constraints, we explored a couple of system
call interfaces (in earlier versions of this patchset). Based on input from
Arnd Bergmann and others, the new interface of the system call is: 

	struct clone_args {
		u64 clone_flags_high;
		u64 child_stack_base;
		u64 child_stack_size;
		u64 parent_tid_ptr;
		u64 child_tid_ptr;
		u32 nr_pids;
		u32 reserved0;
	};

	sys_eclone(u32 flags_low, struct clone_args *cargs, int args_size,
			pid_t *pids)

Details of the struct clone_args and the usage are explained in the
documentation (PATCH 12/12).

NOTE:
	While this patchset enables support for more clone-flags, actual
	implementation for additional clone-flags is best implemented as
	a separate patchset (PATCH 8/9 identifies some TODOs)

Signed-off-by: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>