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-rw-r--r--erts/emulator/beam/external.h17
1 files changed, 13 insertions, 4 deletions
diff --git a/erts/emulator/beam/external.h b/erts/emulator/beam/external.h
index aa124f5197..727333d539 100644
--- a/erts/emulator/beam/external.h
+++ b/erts/emulator/beam/external.h
@@ -98,10 +98,19 @@ typedef struct {
Eterm atom[ERTS_ATOM_CACHE_SIZE];
} ErtsAtomTranslationTable;
-#define ERTS_DIST_EXT_DFLAG_HDR (((Uint32) 1) << 31)
-#define ERTS_DIST_EXT_ATOM_TRANS_TAB (((Uint32) 1) << 30)
-#define ERTS_DIST_EXT_BTT_SAFE (((Uint32) 1) << 29)
-#define ERTS_DIST_EXT_CON_ID_MASK ((Uint32) 0x1fffffff)
+/*
+ * These flags are tagged onto the high bits of a connection ID and stored in
+ * the ErtsDistExternal structure's flags field. They are used to indicate
+ * various bits of state necessary to decode binaries in a variety of
+ * scenarios. The mask ERTS_DIST_EXT_CON_ID_MASK is used later to separate the
+ * connection ID from the flags. Be careful to ensure that the mask does not
+ * overlap any of the bits used for flags, or ERTS will leak flags bits into
+ * connection IDs and leak connection ID bits into the flags.
+ */
+#define ERTS_DIST_EXT_DFLAG_HDR ((Uint32) 0x80000000)
+#define ERTS_DIST_EXT_ATOM_TRANS_TAB ((Uint32) 0x40000000)
+#define ERTS_DIST_EXT_BTT_SAFE ((Uint32) 0x20000000)
+#define ERTS_DIST_EXT_CON_ID_MASK ((Uint32) 0x1fffffff)
#define ERTS_DIST_EXT_CON_ID(DIST_EXTP) \
((DIST_EXTP)->flags & ERTS_DIST_EXT_CON_ID_MASK)