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authorCyrill Gorcunov <gorcunov@openvz.org>2012-05-31 16:26:44 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-31 17:49:32 -0700
commitd97b46a64674a267bc41c9e16132ee2a98c3347d (patch)
tree316f77d212c84aef226684eb05d5d33f40743ac9 /arch
parent818411616baf46ceba0cff6f05af3a9b294734f7 (diff)
downloadlinux-d97b46a64674a267bc41c9e16132ee2a98c3347d.tar.gz
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 <gorcunov@openvz.org> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Andrey Vagin <avagin@openvz.org> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Glauber Costa <glommer@parallels.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Tejun Heo <tj@kernel.org> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Vasiliy Kulikov <segoon@openwall.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Valdis.Kletnieks@vt.edu Cc: Michal Marek <mmarek@suse.cz> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/syscalls/syscall_32.tbl1
-rw-r--r--arch/x86/syscalls/syscall_64.tbl2
2 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
index 29f9f0554f7..7a35a6e71d4 100644
--- a/arch/x86/syscalls/syscall_32.tbl
+++ b/arch/x86/syscalls/syscall_32.tbl
@@ -355,3 +355,4 @@
346 i386 setns sys_setns
347 i386 process_vm_readv sys_process_vm_readv compat_sys_process_vm_readv
348 i386 process_vm_writev sys_process_vm_writev compat_sys_process_vm_writev
+349 i386 kcmp sys_kcmp
diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
index dd29a9ea27c..51171aeff0d 100644
--- a/arch/x86/syscalls/syscall_64.tbl
+++ b/arch/x86/syscalls/syscall_64.tbl
@@ -318,6 +318,8 @@
309 common getcpu sys_getcpu
310 64 process_vm_readv sys_process_vm_readv
311 64 process_vm_writev sys_process_vm_writev
+312 64 kcmp sys_kcmp
+
#
# x32-specific system call numbers start at 512 to avoid cache impact
# for native 64-bit operation.