signal: Extend siginfo_layout with SIL_FAULT_{MCEERR|BNDERR|PKUERR}

Update the siginfo_layout function and enum siginfo_layout to represent
all of the possible field layouts of struct siginfo.

This allows the uses of siginfo_layout in um and arm64 where they are testing
for SIL_FAULT to be more accurate as this rules out the other cases.

Further this allows the switch statements on siginfo_layout to be simpler
if perhaps a little more wordy.  Making it easier to understand what is
actually going on.

As SIL_FAULT_BNDERR and SIL_FAULT_PKUERR are never expected to appear
in signalfd just treat them as SIL_FAULT.  To include them would take
20 extra bytes an pretty much fill up what is left of
signalfd_siginfo.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 16 insertions, 8 deletions

diff --git a/fs/signalfd.c b/fs/signalfd.c
index f652249f59f9..cbb42f77a2bd 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -112,19 +112,27 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
 		new.ssi_band = kinfo->si_band;
 		new.ssi_fd   = kinfo->si_fd;
 		break;
+	case SIL_FAULT_BNDERR:
+	case SIL_FAULT_PKUERR:
+		/*
+		 * Fall through to the SIL_FAULT case.  Both SIL_FAULT_BNDERR
+		 * and SIL_FAULT_PKUERR are only generated by faults that
+		 * deliver them synchronously to userspace.  In case someone
+		 * injects one of these signals and signalfd catches it treat
+		 * it as SIL_FAULT.
+		 */
 	case SIL_FAULT:
 		new.ssi_addr = (long) kinfo->si_addr;
 #ifdef __ARCH_SI_TRAPNO
 		new.ssi_trapno = kinfo->si_trapno;
 #endif
-		/*
-		 * Other callers might not initialize the si_lsb field,
-		 * so check explicitly for the right codes here.
-		 */
-		if (kinfo->si_signo == SIGBUS &&
-		    ((kinfo->si_code == BUS_MCEERR_AR) ||
-		     (kinfo->si_code == BUS_MCEERR_AO)))
-			new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
+		break;
+	case SIL_FAULT_MCEERR:
+		new.ssi_addr = (long) kinfo->si_addr;
+#ifdef __ARCH_SI_TRAPNO
+		new.ssi_trapno = kinfo->si_trapno;
+#endif
+		new.ssi_addr_lsb = (short) kinfo->si_addr_lsb;
 		break;
 	case SIL_CHLD:
 		new.ssi_pid    = kinfo->si_pid;