[RFC][v6][PATCH 7/9]: Define do_fork_with_pids()

[Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>]

Subject: [RFC][v6][PATCH 7/9]: 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[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@linux.vnet.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Reviewed-by: Oren Laadan <orenl@cs.columbia.edu>
---
 include/linux/sched.h |    3 +++
 include/linux/types.h |    5 +++++
 kernel/fork.c         |   16 ++++++++++++++--
 3 files changed, 22 insertions(+), 2 deletions(-)

Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h	2009-09-09 19:06:20.000000000 -0700
+++ linux-2.6/include/linux/sched.h	2009-09-09 19:07:45.000000000 -0700
@@ -2054,6 +2054,9 @@ 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 *,
+				struct pid_set __user *pid_set);
 struct task_struct *fork_idle(int);
 
 extern void set_task_comm(struct task_struct *tsk, char *from);
Index: linux-2.6/include/linux/types.h
===================================================================
--- linux-2.6.orig/include/linux/types.h	2009-09-09 19:06:20.000000000 -0700
+++ linux-2.6/include/linux/types.h	2009-09-09 19:07:45.000000000 -0700
@@ -204,6 +204,11 @@ struct ustat {
 	char			f_fpack[6];
 };
 
+struct pid_set {
+	unsigned int num_pids;
+	pid_t pids[];
+};
+
 #endif	/* __KERNEL__ */
 #endif /*  __ASSEMBLY__ */
 #endif /* _LINUX_TYPES_H */
Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c	2009-09-09 19:07:40.000000000 -0700
+++ linux-2.6/kernel/fork.c	2009-09-09 19:07:45.000000000 -0700
@@ -1332,12 +1332,13 @@ struct task_struct * __cpuinit fork_idle
  * 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,
+	      struct pid_set __user *pid_setp)
 {
 	struct task_struct *p;
 	int trace = 0;
@@ -1440,6 +1441,17 @@ 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, NULL);
+}
+
 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
 #define ARCH_MIN_MMSTRUCT_ALIGN 0
 #endif