Add a "dumpable" bit to the extent state.

Currently, this is unused (i.e. all extents are always marked dumpable).  In the
future, we'll begin using this functionality.

2 files changed, 44 insertions, 8 deletions

diff --git a/include/jemalloc/internal/extent_inlines.h b/include/jemalloc/internal/extent_inlines.h
index bb2bd699..610072eb 100644
--- a/include/jemalloc/internal/extent_inlines.h
+++ b/include/jemalloc/internal/extent_inlines.h
@@ -94,6 +94,12 @@ extent_committed_get(const extent_t *extent) {
 }
 
 static inline bool
+extent_dumpable_get(const extent_t *extent) {
+	return (bool)((extent->e_bits & EXTENT_BITS_DUMPABLE_MASK) >>
+	    EXTENT_BITS_DUMPABLE_SHIFT);
+}
+
+static inline bool
 extent_slab_get(const extent_t *extent) {
 	return (bool)((extent->e_bits & EXTENT_BITS_SLAB_MASK) >>
 	    EXTENT_BITS_SLAB_SHIFT);
@@ -270,6 +276,12 @@ extent_committed_set(extent_t *extent, bool committed) {
 }
 
 static inline void
+extent_dumpable_set(extent_t *extent, bool dumpable) {
+	extent->e_bits = (extent->e_bits & ~EXTENT_BITS_DUMPABLE_MASK) |
+	    ((uint64_t)dumpable << EXTENT_BITS_DUMPABLE_SHIFT);
+}
+
+static inline void
 extent_slab_set(extent_t *extent, bool slab) {
 	extent->e_bits = (extent->e_bits & ~EXTENT_BITS_SLAB_MASK) |
 	    ((uint64_t)slab << EXTENT_BITS_SLAB_SHIFT);
@@ -283,7 +295,7 @@ extent_prof_tctx_set(extent_t *extent, prof_tctx_t *tctx) {
 static inline void
 extent_init(extent_t *extent, arena_t *arena, void *addr, size_t size,
     bool slab, szind_t szind, size_t sn, extent_state_t state, bool zeroed,
-    bool committed) {
+    bool committed, bool dumpable) {
 	assert(addr == PAGE_ADDR2BASE(addr) || !slab);
 
 	extent_arena_set(extent, arena);
@@ -295,6 +307,7 @@ extent_init(extent_t *extent, arena_t *arena, void *addr, size_t size,
 	extent_state_set(extent, state);
 	extent_zeroed_set(extent, zeroed);
 	extent_committed_set(extent, committed);
+	extent_dumpable_set(extent, dumpable);
 	ql_elm_new(extent, ql_link);
 	if (config_prof) {
 		extent_prof_tctx_set(extent, NULL);
@@ -312,6 +325,7 @@ extent_binit(extent_t *extent, void *addr, size_t bsize, size_t sn) {
 	extent_state_set(extent, extent_state_active);
 	extent_zeroed_set(extent, true);
 	extent_committed_set(extent, true);
+	extent_dumpable_set(extent, true);
 }
 
 static inline void
diff --git a/include/jemalloc/internal/extent_structs.h b/include/jemalloc/internal/extent_structs.h
index 641a6325..722963b5 100644
--- a/include/jemalloc/internal/extent_structs.h
+++ b/include/jemalloc/internal/extent_structs.h
@@ -23,13 +23,14 @@ struct extent_s {
 	 * a: arena_ind
 	 * b: slab
 	 * c: committed
+	 * d: dumpable
 	 * z: zeroed
 	 * t: state
 	 * i: szind
 	 * f: nfree
 	 * n: sn
 	 *
-	 * nnnnnnnn ... nnnnnfff fffffffi iiiiiiit tzcbaaaa aaaaaaaa
+	 * nnnnnnnn ... nnnnffff ffffffii iiiiiitt zdcbaaaa aaaaaaaa
 	 *
 	 * arena_ind: Arena from which this extent came, or all 1 bits if
 	 *            unassociated.
@@ -44,6 +45,23 @@ struct extent_s {
 	 *            as on a system that overcommits and satisfies physical
 	 *            memory needs on demand via soft page faults.
 	 *
+	 * dumpable: The dumpable flag indicates whether or not we've set the
+	 *           memory in question to be dumpable.  Note that this
+	 *           interacts somewhat subtly with user-specified extent hooks,
+	 *           since we don't know if *they* are fiddling with
+	 *           dumpability (in which case, we don't want to undo whatever
+	 *           they're doing).  To deal with this scenario, we:
+	 *             - Make dumpable false only for memory allocated with the
+	 *               default hooks.
+	 *             - Only allow memory to go from non-dumpable to dumpable,
+	 *               and only once.
+	 *             - Never make the OS call to allow dumping when the
+	 *               dumpable bit is already set.
+	 *           These three constraints mean that we will never
+	 *           accidentally dump user memory that the user meant to set
+	 *           nondumpable with their extent hooks.
+	 *
+	 *
 	 * zeroed: The zeroed flag is used by extent recycling code to track
 	 *         whether memory is zero-filled.
 	 *
@@ -80,25 +98,29 @@ struct extent_s {
 #define EXTENT_BITS_COMMITTED_MASK \
     ((uint64_t)0x1U << EXTENT_BITS_COMMITTED_SHIFT)
 
-#define EXTENT_BITS_ZEROED_SHIFT	(MALLOCX_ARENA_BITS + 2)
+#define EXTENT_BITS_DUMPABLE_SHIFT	(MALLOCX_ARENA_BITS + 2)
+#define EXTENT_BITS_DUMPABLE_MASK \
+    ((uint64_t)0x1U << EXTENT_BITS_DUMPABLE_SHIFT)
+
+#define EXTENT_BITS_ZEROED_SHIFT	(MALLOCX_ARENA_BITS + 3)
 #define EXTENT_BITS_ZEROED_MASK \
     ((uint64_t)0x1U << EXTENT_BITS_ZEROED_SHIFT)
 
-#define EXTENT_BITS_STATE_SHIFT		(MALLOCX_ARENA_BITS + 3)
+#define EXTENT_BITS_STATE_SHIFT		(MALLOCX_ARENA_BITS + 4)
 #define EXTENT_BITS_STATE_MASK \
     ((uint64_t)0x3U << EXTENT_BITS_STATE_SHIFT)
 
-#define EXTENT_BITS_SZIND_SHIFT		(MALLOCX_ARENA_BITS + 5)
+#define EXTENT_BITS_SZIND_SHIFT		(MALLOCX_ARENA_BITS + 6)
 #define EXTENT_BITS_SZIND_MASK \
     (((uint64_t)(1U << LG_CEIL_NSIZES) - 1) << EXTENT_BITS_SZIND_SHIFT)
 
 #define EXTENT_BITS_NFREE_SHIFT \
-    (MALLOCX_ARENA_BITS + 5 + LG_CEIL_NSIZES)
+    (MALLOCX_ARENA_BITS + 6 + LG_CEIL_NSIZES)
 #define EXTENT_BITS_NFREE_MASK \
     ((uint64_t)((1U << (LG_SLAB_MAXREGS + 1)) - 1) << EXTENT_BITS_NFREE_SHIFT)
 
 #define EXTENT_BITS_SN_SHIFT \
-    (MALLOCX_ARENA_BITS + 5 + LG_CEIL_NSIZES + (LG_SLAB_MAXREGS + 1))
+    (MALLOCX_ARENA_BITS + 6 + LG_CEIL_NSIZES + (LG_SLAB_MAXREGS + 1))
 #define EXTENT_BITS_SN_MASK		(UINT64_MAX << EXTENT_BITS_SN_SHIFT)
 
 	/* Pointer to the extent that this structure is responsible for. */
@@ -128,7 +150,7 @@ struct extent_s {
 	 */
 	ql_elm(extent_t)	ql_link;
 
-	/* 
+	/*
 	 * Linkage for per size class sn/address-ordered heaps, and
 	 * for extent_avail
 	 */