From d97b46a64674a267bc41c9e16132ee2a98c3347d Mon Sep 17 00:00:00 2001 From: Cyrill Gorcunov Date: Thu, 31 May 2012 16:26:44 -0700 Subject: syscalls, x86: add __NR_kcmp syscall While doing the checkpoint-restore in the user space one need to determine whether various kernel objects (like mm_struct-s of file_struct-s) are shared between tasks and restore this state. The 2nd step can be solved by using appropriate CLONE_ flags and the unshare syscall, while there's currently no ways for solving the 1st one. One of the ways for checking whether two tasks share e.g. mm_struct is to provide some mm_struct ID of a task to its proc file, but showing such info considered to be not that good for security reasons. Thus after some debates we end up in conclusion that using that named 'comparison' syscall might be the best candidate. So here is it -- __NR_kcmp. It takes up to 5 arguments - the pids of the two tasks (which characteristics should be compared), the comparison type and (in case of comparison of files) two file descriptors. Lookups for pids are done in the caller's PID namespace only. At moment only x86 is supported and tested. [akpm@linux-foundation.org: fix up selftests, warnings] [akpm@linux-foundation.org: include errno.h] [akpm@linux-foundation.org: tweak comment text] Signed-off-by: Cyrill Gorcunov Acked-by: "Eric W. Biederman" Cc: Pavel Emelyanov Cc: Andrey Vagin Cc: KOSAKI Motohiro Cc: Ingo Molnar Cc: H. Peter Anvin Cc: Thomas Gleixner Cc: Glauber Costa Cc: Andi Kleen Cc: Tejun Heo Cc: Matt Helsley Cc: Pekka Enberg Cc: Eric Dumazet Cc: Vasiliy Kulikov Cc: Alexey Dobriyan Cc: Valdis.Kletnieks@vt.edu Cc: Michal Marek Cc: Frederic Weisbecker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/syscalls.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/syscalls.h') diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 3de3acb84a9..19439c75c5b 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -858,4 +858,6 @@ asmlinkage long sys_process_vm_writev(pid_t pid, unsigned long riovcnt, unsigned long flags); +asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type, + unsigned long idx1, unsigned long idx2); #endif -- cgit v1.2.3-70-g09d2