signal/signalfd: Add support for SIGSYS

I don't know why signalfd has never grown support for SIGSYS but grow it now.

This corrects an oversight and removes a need for a default in the
switch statement.  Allowing gcc to warn when future members are added
to the enum siginfo_layout, and signalfd does not handle them.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

fs/signalfd.c

@@ -134,7 +134,6 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
 		new.ssi_stime  = kinfo->si_stime;
 		break;
 	case SIL_RT:
-	default:
 		/*
 		 * This case catches also the signals queued by sigqueue().
 		 */
@@ -143,6 +142,11 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
 		new.ssi_ptr = (long) kinfo->si_ptr;
 		new.ssi_int = kinfo->si_int;
 		break;
+	case SIL_SYS:
+		new.ssi_call_addr = (long) kinfo->si_call_addr;
+		new.ssi_syscall   = kinfo->si_syscall;
+		new.ssi_arch      = kinfo->si_arch;
+		break;
 	}
 
 	if (copy_to_user(uinfo, &new, sizeof(struct signalfd_siginfo)))

include/uapi/linux/signalfd.h

@@ -35,6 +35,10 @@ struct signalfd_siginfo {
 	__u64 ssi_stime;
 	__u64 ssi_addr;
 	__u16 ssi_addr_lsb;
+	__u16 __pad2;
+	__s32 ssi_syscall;
+	__u64 ssi_call_addr;
+	__u32 ssi_arch;
 
 	/*
 	 * Pad strcture to 128 bytes. Remember to update the
@@ -45,7 +49,7 @@ struct signalfd_siginfo {
 	 * comes out of a read(2) and we really don't want to have
 	 * a compat on read(2).
 	 */
-	__u8 __pad[46];
+	__u8 __pad[28];
 };