Add -falignment-sanitization flag

Here we add a flag to instruct the native code generator to add
alignment checks in all info table dereferences. This is helpful in
catching pointer tagging issues.

Thanks to @jrtc27 for uncovering the tagging issues on Sparc which
inspired this flag.

Test Plan: Validate

Reviewers: simonmar, austin, erikd

Reviewed By: simonmar

Subscribers: rwbarton, trofi, thomie, jrtc27

Differential Revision: https://phabricator.haskell.org/D4101

1 files changed, 10 insertions, 0 deletions

diff --git a/rts/RtsMessages.c b/rts/RtsMessages.c
index ba1f02de29..d976760242 100644
--- a/rts/RtsMessages.c
+++ b/rts/RtsMessages.c
@@ -314,3 +314,13 @@ rtsDebugMsgFn(const char *s, va_list ap)
   _setmode (_fileno(stderr), mode);
 #endif
 }
+
+
+// Used in stg_badAlignment_entry defined in StgStartup.cmm.
+void rtsBadAlignmentBarf(void) GNUC3_ATTRIBUTE(__noreturn__);
+
+void
+rtsBadAlignmentBarf()
+{
+    barf("Encountered incorrectly aligned pointer. This can't be good.");
+}