OpenSolaris Launch

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+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License, Version 1.0 only
+ * (the "License").  You may not use this file except in compliance
+ * with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#ifndef _SYS_DTRACE_IMPL_H
+#define	_SYS_DTRACE_IMPL_H
+
+#pragma ident	"%Z%%M%	%I%	%E% SMI"
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+/*
+ * DTrace Dynamic Tracing Software: Kernel Implementation Interfaces
+ *
+ * Note: The contents of this file are private to the implementation of the
+ * Solaris system and DTrace subsystem and are subject to change at any time
+ * without notice.  Applications and drivers using these interfaces will fail
+ * to run on future releases.  These interfaces should not be used for any
+ * purpose except those expressly outlined in dtrace(7D) and libdtrace(3LIB).
+ * Please refer to the "Solaris Dynamic Tracing Guide" for more information.
+ */
+
+#include <sys/dtrace.h>
+
+/*
+ * DTrace Implementation Constants and Typedefs
+ */
+#define	DTRACE_MAXPROPLEN		128
+#define	DTRACE_DYNVAR_CHUNKSIZE		256
+
+struct dtrace_probe;
+struct dtrace_ecb;
+struct dtrace_predicate;
+struct dtrace_action;
+struct dtrace_provider;
+struct dtrace_state;
+
+typedef struct dtrace_probe dtrace_probe_t;
+typedef struct dtrace_ecb dtrace_ecb_t;
+typedef struct dtrace_predicate dtrace_predicate_t;
+typedef struct dtrace_action dtrace_action_t;
+typedef struct dtrace_provider dtrace_provider_t;
+typedef struct dtrace_meta dtrace_meta_t;
+typedef struct dtrace_state dtrace_state_t;
+typedef uint32_t dtrace_optid_t;
+typedef uint32_t dtrace_specid_t;
+typedef uint64_t dtrace_genid_t;
+
+/*
+ * DTrace Probes
+ *
+ * The probe is the fundamental unit of the DTrace architecture.  Probes are
+ * created by DTrace providers, and managed by the DTrace framework.  A probe
+ * is identified by a unique <provider, module, function, name> tuple, and has
+ * a unique probe identifier assigned to it.  (Some probes are not associated
+ * with a specific point in text; these are called _unanchored probes_ and have
+ * no module or function associated with them.)  Probes are represented as a
+ * dtrace_probe structure.  To allow quick lookups based on each element of the
+ * probe tuple, probes are hashed by each of provider, module, function and
+ * name.  (If a lookup is performed based on a regular expression, a
+ * dtrace_probekey is prepared, and a linear search is performed.) Each probe
+ * is additionally pointed to by a linear array indexed by its identifier.  The
+ * identifier is the provider's mechanism for indicating to the DTrace
+ * framework that a probe has fired:  the identifier is passed as the first
+ * argument to dtrace_probe(), where it is then mapped into the corresponding
+ * dtrace_probe structure.  From the dtrace_probe structure, dtrace_probe() can
+ * iterate over the probe's list of enabling control blocks; see "DTrace
+ * Enabling Control Blocks", below.)
+ */
+struct dtrace_probe {
+	dtrace_id_t dtpr_id;			/* probe identifier */
+	dtrace_ecb_t *dtpr_ecb;			/* ECB list; see below */
+	dtrace_ecb_t *dtpr_ecb_last;		/* last ECB in list */
+	void *dtpr_arg;				/* provider argument */
+	dtrace_cacheid_t dtpr_predcache;	/* predicate cache ID */
+	int dtpr_aframes;			/* artificial frames */
+	dtrace_provider_t *dtpr_provider;	/* pointer to provider */
+	char *dtpr_mod;				/* probe's module name */
+	char *dtpr_func;			/* probe's function name */
+	char *dtpr_name;			/* probe's name */
+	dtrace_probe_t *dtpr_nextmod;		/* next in module hash */
+	dtrace_probe_t *dtpr_prevmod;		/* previous in module hash */
+	dtrace_probe_t *dtpr_nextfunc;		/* next in function hash */
+	dtrace_probe_t *dtpr_prevfunc;		/* previous in function hash */
+	dtrace_probe_t *dtpr_nextname;		/* next in name hash */
+	dtrace_probe_t *dtpr_prevname;		/* previous in name hash */
+	dtrace_genid_t dtpr_gen;		/* probe generation ID */
+};
+
+typedef int dtrace_probekey_f(const char *, const char *, int);
+
+typedef struct dtrace_probekey {
+	const char *dtpk_prov;			/* provider name to match */
+	dtrace_probekey_f *dtpk_pmatch;		/* provider matching function */
+	const char *dtpk_mod;			/* module name to match */
+	dtrace_probekey_f *dtpk_mmatch;		/* module matching function */
+	const char *dtpk_func;			/* func name to match */
+	dtrace_probekey_f *dtpk_fmatch;		/* func matching function */
+	const char *dtpk_name;			/* name to match */
+	dtrace_probekey_f *dtpk_nmatch;		/* name matching function */
+	dtrace_id_t dtpk_id;			/* identifier to match */
+} dtrace_probekey_t;
+
+typedef struct dtrace_hashbucket {
+	struct dtrace_hashbucket *dthb_next;	/* next on hash chain */
+	dtrace_probe_t *dthb_chain;		/* chain of probes */
+	int dthb_len;				/* number of probes here */
+} dtrace_hashbucket_t;
+
+typedef struct dtrace_hash {
+	dtrace_hashbucket_t **dth_tab;		/* hash table */
+	int dth_size;				/* size of hash table */
+	int dth_mask;				/* mask to index into table */
+	int dth_nbuckets;			/* total number of buckets */
+	uintptr_t dth_nextoffs;			/* offset of next in probe */
+	uintptr_t dth_prevoffs;			/* offset of prev in probe */
+	uintptr_t dth_stroffs;			/* offset of str in probe */
+} dtrace_hash_t;
+
+/*
+ * DTrace Enabling Control Blocks
+ *
+ * When a provider wishes to fire a probe, it calls into dtrace_probe(),
+ * passing the probe identifier as the first argument.  As described above,
+ * dtrace_probe() maps the identifier into a pointer to a dtrace_probe_t
+ * structure.  This structure contains information about the probe, and a
+ * pointer to the list of Enabling Control Blocks (ECBs).  Each ECB points to
+ * DTrace consumer state, and contains an optional predicate, and a list of
+ * actions.  (Shown schematically below.)  The ECB abstraction allows a single
+ * probe to be multiplexed across disjoint consumers, or across disjoint
+ * enablings of a single probe within one consumer.
+ *
+ *   Enabling Control Block
+ *        dtrace_ecb_t
+ * +------------------------+
+ * | dtrace_epid_t ---------+--------------> Enabled Probe ID (EPID)
+ * | dtrace_state_t * ------+--------------> State associated with this ECB
+ * | dtrace_predicate_t * --+---------+
+ * | dtrace_action_t * -----+----+    |
+ * | dtrace_ecb_t * ---+    |    |    |       Predicate (if any)
+ * +-------------------+----+    |    |       dtrace_predicate_t
+ *                     |         |    +---> +--------------------+
+ *                     |         |          | dtrace_difo_t * ---+----> DIFO
+ *                     |         |          +--------------------+
+ *                     |         |
+ *            Next ECB |         |           Action
+ *            (if any) |         |       dtrace_action_t
+ *                     :         +--> +-------------------+
+ *                     :              | dtrace_actkind_t -+------> kind
+ *                     v              | dtrace_difo_t * --+------> DIFO (if any)
+ *                                    | dtrace_recdesc_t -+------> record descr.
+ *                                    | dtrace_action_t * +------+
+ *                                    +-------------------+      |
+ *                                                               | Next action
+ *                               +-------------------------------+  (if any)
+ *                               |
+ *                               |           Action
+ *                               |       dtrace_action_t
+ *                               +--> +-------------------+
+ *                                    | dtrace_actkind_t -+------> kind
+ *                                    | dtrace_difo_t * --+------> DIFO (if any)
+ *                                    | dtrace_action_t * +------+
+ *                                    +-------------------+      |
+ *                                                               | Next action
+ *                               +-------------------------------+  (if any)
+ *                               |
+ *                               :
+ *                               v
+ *
+ *
+ * dtrace_probe() iterates over the ECB list.  If the ECB needs less space
+ * than is available in the principal buffer, the ECB is processed:  if the
+ * predicate is non-NULL, the DIF object is executed.  If the result is
+ * non-zero, the action list is processed, with each action being executed
+ * accordingly.  When the action list has been completely executed, processing
+ * advances to the next ECB.  processing advances to the next ECB.  If the
+ * result is non-zero; For each ECB, it first determines the The ECB
+ * abstraction allows disjoint consumers to multiplex on single probes.
+ */
+struct dtrace_ecb {
+	dtrace_epid_t dte_epid;			/* enabled probe ID */
+	uint32_t dte_alignment;			/* required alignment */
+	size_t dte_needed;			/* bytes needed */
+	size_t dte_size;			/* total size of payload */
+	dtrace_predicate_t *dte_predicate;	/* predicate, if any */
+	dtrace_action_t *dte_action;		/* actions, if any */
+	dtrace_ecb_t *dte_next;			/* next ECB on probe */
+	dtrace_state_t *dte_state;		/* pointer to state */
+	uint32_t dte_cond;			/* security condition */
+	dtrace_probe_t *dte_probe;		/* pointer to probe */
+	dtrace_action_t *dte_action_last;	/* last action on ECB */
+	uint64_t dte_uarg;			/* library argument */
+};
+
+struct dtrace_predicate {
+	dtrace_difo_t *dtp_difo;		/* DIF object */
+	dtrace_cacheid_t dtp_cacheid;		/* cache identifier */
+	int dtp_refcnt;				/* reference count */
+};
+
+struct dtrace_action {
+	dtrace_actkind_t dta_kind;		/* kind of action */
+	uint16_t dta_intuple;			/* boolean:  in aggregation */
+	uint32_t dta_refcnt;			/* reference count */
+	dtrace_difo_t *dta_difo;		/* pointer to DIFO */
+	dtrace_recdesc_t dta_rec;		/* record description */
+	dtrace_action_t *dta_prev;		/* previous action */
+	dtrace_action_t *dta_next;		/* next action */
+};
+
+typedef struct dtrace_aggregation {
+	dtrace_action_t dtag_action;		/* action; must be first */
+	dtrace_aggid_t dtag_id;			/* identifier */
+	dtrace_ecb_t *dtag_ecb;			/* corresponding ECB */
+	dtrace_action_t *dtag_first;		/* first action in tuple */
+	uint32_t dtag_base;			/* base of aggregation */
+	uint64_t dtag_initial;			/* initial value */
+	void (*dtag_aggregate)(uint64_t *, uint64_t);
+} dtrace_aggregation_t;
+
+/*
+ * DTrace Buffers
+ *
+ * Principal buffers, aggregation buffers, and speculative buffers are all
+ * managed with the dtrace_buffer structure.  By default, this structure
+ * includes twin data buffers -- dtb_tomax and dtb_xamot -- that serve as the
+ * active and passive buffers, respectively.  For speculative buffers,
+ * dtb_xamot will be NULL; for "ring" and "fill" buffers, dtb_xamot will point
+ * to a scratch buffer.  For all buffer types, the dtrace_buffer structure is
+ * always allocated on a per-CPU basis; a single dtrace_buffer structure is
+ * never shared among CPUs.  (That is, there is never true sharing of the
+ * dtrace_buffer structure; to prevent false sharing of the structure, it must
+ * always be aligned to the coherence granularity -- generally 64 bytes.)
+ *
+ * One of the critical design decisions of DTrace is that a given ECB always
+ * stores the same quantity and type of data.  This is done to assure that the
+ * only metadata required for an ECB's traced data is the EPID.  That is, from
+ * the EPID, the consumer can determine the data layout.  (The data buffer
+ * layout is shown schematically below.)  By assuring that one can determine
+ * data layout from the EPID, the metadata stream can be separated from the
+ * data stream -- simplifying the data stream enormously.
+ *
+ *      base of data buffer --->  +------+--------------------+------+
+ *                                | EPID | data               | EPID |
+ *                                +------+--------+------+----+------+
+ *                                | data          | EPID | data      |
+ *                                +---------------+------+-----------+
+ *                                | data, cont.                      |
+ *                                +------+--------------------+------+
+ *                                | EPID | data               |      |
+ *                                +------+--------------------+      |
+ *                                |                ||                |
+ *                                |                ||                |
+ *                                |                \/                |
+ *                                :                                  :
+ *                                .                                  .
+ *                                .                                  .
+ *                                .                                  .
+ *                                :                                  :
+ *                                |                                  |
+ *     limit of data buffer --->  +----------------------------------+
+ *
+ * When evaluating an ECB, dtrace_probe() determines if the ECB's needs of the
+ * principal buffer (both scratch and payload) exceed the available space.  If
+ * the ECB's needs exceed available space (and if the principal buffer policy
+ * is the default "switch" policy), the ECB is dropped, the buffer's drop count
+ * is incremented, and processing advances to the next ECB.  If the ECB's needs
+ * can be met with the available space, the ECB is processed, but the offset in
+ * the principal buffer is only advanced if the ECB completes processing
+ * without error.
+ *
+ * When a buffer is to be switched (either because the buffer is the principal
+ * buffer with a "switch" policy or because it is an aggregation buffer), a
+ * cross call is issued to the CPU associated with the buffer.  In the cross
+ * call context, interrupts are disabled, and the active and the inactive
+ * buffers are atomically switched.  This involves switching the data pointers,
+ * copying the various state fields (offset, drops, errors, etc.) into their
+ * inactive equivalents, and clearing the state fields.  Because interrupts are
+ * disabled during this procedure, the switch is guaranteed to appear atomic to
+ * dtrace_probe().
+ *
+ * DTrace Ring Buffering
+ *
+ * To process a ring buffer correctly, one must know the oldest valid record.
+ * Processing starts at the oldest record in the buffer and continues until
+ * the end of the buffer is reached.  Processing then resumes starting with
+ * the record stored at offset 0 in the buffer, and continues until the
+ * youngest record is processed.  If trace records are of a fixed-length,
+ * determining the oldest record is trivial:
+ *
+ *   - If the ring buffer has not wrapped, the oldest record is the record
+ *     stored at offset 0.
+ *
+ *   - If the ring buffer has wrapped, the oldest record is the record stored
+ *     at the current offset.
+ *
+ * With variable length records, however, just knowing the current offset
+ * doesn't suffice for determining the oldest valid record:  assuming that one
+ * allows for arbitrary data, one has no way of searching forward from the
+ * current offset to find the oldest valid record.  (That is, one has no way
+ * of separating data from metadata.) It would be possible to simply refuse to
+ * process any data in the ring buffer between the current offset and the
+ * limit, but this leaves (potentially) an enormous amount of otherwise valid
+ * data unprocessed.
+ *
+ * To effect ring buffering, we track two offsets in the buffer:  the current
+ * offset and the _wrapped_ offset.  If a request is made to reserve some
+ * amount of data, and the buffer has wrapped, the wrapped offset is
+ * incremented until the wrapped offset minus the current offset is greater
+ * than or equal to the reserve request.  This is done by repeatedly looking
+ * up the ECB corresponding to the EPID at the current wrapped offset, and
+ * incrementing the wrapped offset by the size of the data payload
+ * corresponding to that ECB.  If this offset is greater than or equal to the
+ * limit of the data buffer, the wrapped offset is set to 0.  Thus, the
+ * current offset effectively "chases" the wrapped offset around the buffer.
+ * Schematically:
+ *
+ *      base of data buffer --->  +------+--------------------+------+
+ *                                | EPID | data               | EPID |
+ *                                +------+--------+------+----+------+
+ *                                | data          | EPID | data      |
+ *                                +---------------+------+-----------+
+ *                                | data, cont.                      |
+ *                                +------+---------------------------+
+ *                                | EPID | data                      |
+ *           current offset --->  +------+---------------------------+
+ *                                | invalid data                     |
+ *           wrapped offset --->  +------+--------------------+------+
+ *                                | EPID | data               | EPID |
+ *                                +------+--------+------+----+------+
+ *                                | data          | EPID | data      |
+ *                                +---------------+------+-----------+
+ *                                :                                  :
+ *                                .                                  .
+ *                                .        ... valid data ...        .
+ *                                .                                  .
+ *                                :                                  :
+ *                                +------+-------------+------+------+
+ *                                | EPID | data        | EPID | data |
+ *                                +------+------------++------+------+
+ *                                | data, cont.       | leftover     |
+ *     limit of data buffer --->  +-------------------+--------------+
+ *
+ * If the amount of requested buffer space exceeds the amount of space
+ * available between the current offset and the end of the buffer:
+ *
+ *  (1)  all words in the data buffer between the current offset and the limit
+ *       of the data buffer (marked "leftover", above) are set to
+ *       DTRACE_EPIDNONE
+ *
+ *  (2)  the wrapped offset is set to zero
+ *
+ *  (3)  the iteration process described above occurs until the wrapped offset
+ *       is greater than the amount of desired space.
+ *
+ * The wrapped offset is implemented by (re-)using the inactive offset.
+ * In a "switch" buffer policy, the inactive offset stores the offset in
+ * the inactive buffer; in a "ring" buffer policy, it stores the wrapped
+ * offset.
+ *
+ * DTrace Scratch Buffering
+ *
+ * Some ECBs may wish to allocate dynamically-sized temporary scratch memory.
+ * To accommodate such requests easily, scratch memory may be allocated in
+ * the buffer beyond the current offset plus the needed memory of the current
+ * ECB.  If there isn't sufficient room in the buffer for the requested amount
+ * of scratch space, the allocation fails and an error is generated.  Scratch
+ * memory is tracked in the dtrace_mstate_t and is automatically freed when
+ * the ECB ceases processing.  Note that ring buffers cannot allocate their
+ * scratch from the principal buffer -- lest they needlessly overwrite older,
+ * valid data.  Ring buffers therefore have their own dedicated scratch buffer
+ * from which scratch is allocated.
+ */
+#define	DTRACEBUF_RING		0x0001		/* bufpolicy set to "ring" */
+#define	DTRACEBUF_FILL		0x0002		/* bufpolicy set to "fill" */
+#define	DTRACEBUF_NOSWITCH	0x0004		/* do not switch buffer */
+#define	DTRACEBUF_WRAPPED	0x0008		/* ring buffer has wrapped */
+#define	DTRACEBUF_DROPPED	0x0010		/* drops occurred */
+#define	DTRACEBUF_ERROR		0x0020		/* errors occurred */
+#define	DTRACEBUF_FULL		0x0040		/* "fill" buffer is full */
+#define	DTRACEBUF_CONSUMED	0x0080		/* buffer has been consumed */
+#define	DTRACEBUF_INACTIVE	0x0100		/* buffer is not yet active */
+
+typedef struct dtrace_buffer {
+	uint64_t dtb_offset;			/* current offset in buffer */
+	uint64_t dtb_size;			/* size of buffer */
+	uint32_t dtb_flags;			/* flags */
+	uint32_t dtb_drops;			/* number of drops */
+	caddr_t dtb_tomax;			/* active buffer */
+	caddr_t dtb_xamot;			/* inactive buffer */
+	uint32_t dtb_xamot_flags;		/* inactive flags */
+	uint32_t dtb_xamot_drops;		/* drops in inactive buffer */
+	uint64_t dtb_xamot_offset;		/* offset in inactive buffer */
+	uint32_t dtb_errors;			/* number of errors */
+	uint32_t dtb_xamot_errors;		/* errors in inactive buffer */
+#ifndef _LP64
+	uint64_t dtb_pad1;
+#endif
+} dtrace_buffer_t;
+
+/*
+ * DTrace Aggregation Buffers
+ *
+ * Aggregation buffers use much of the same mechanism as described above
+ * ("DTrace Buffers").  However, because an aggregation is fundamentally a
+ * hash, there exists dynamic metadata associated with an aggregation buffer
+ * that is not associated with other kinds of buffers.  This aggregation
+ * metadata is _only_ relevant for the in-kernel implementation of
+ * aggregations; it is not actually relevant to user-level consumers.  To do
+ * this, we allocate dynamic aggregation data (hash keys and hash buckets)
+ * starting below the _limit_ of the buffer, and we allocate data from the
+ * _base_ of the buffer.  When the aggregation buffer is copied out, _only_ the
+ * data is copied out; the metadata is simply discarded.  Schematically,
+ * aggregation buffers look like:
+ *
+ *      base of data buffer --->  +-------+------+-----------+-------+
+ *                                | aggid | key  | value     | aggid |
+ *                                +-------+------+-----------+-------+
+ *                                | key                              |
+ *                                +-------+-------+-----+------------+
+ *                                | value | aggid | key | value      |
+ *                                +-------+------++-----+------+-----+
+ *                                | aggid | key  | value       |     |
+ *                                +-------+------+-------------+     |
+ *                                |                ||                |
+ *                                |                ||                |
+ *                                |                \/                |
+ *                                :                                  :
+ *                                .                                  .
+ *                                .                                  .
+ *                                .                                  .
+ *                                :                                  :
+ *                                |                /\                |
+ *                                |                ||   +------------+
+ *                                |                ||   |            |
+ *                                +---------------------+            |
+ *                                | hash keys                        |
+ *                                | (dtrace_aggkey structures)       |
+ *                                |                                  |
+ *                                +----------------------------------+
+ *                                | hash buckets                     |
+ *                                | (dtrace_aggbuffer structure)     |
+ *                                |                                  |
+ *     limit of data buffer --->  +----------------------------------+
+ *
+ *
+ * As implied above, just as we assure that ECBs always store a constant
+ * amount of data, we assure that a given aggregation -- identified by its
+ * aggregation ID -- always stores data of a constant quantity and type.
+ * As with EPIDs, this allows the aggregation ID to serve as the metadata for a
+ * given record.
+ *
+ * Note that the size of the dtrace_aggkey structure must be sizeof (uintptr_t)
+ * aligned.  (If this the structure changes such that this becomes false, an
+ * assertion will fail in dtrace_aggregate().)
+ */
+typedef struct dtrace_aggkey {
+	uint32_t dtak_hashval;			/* hash value */
+	uint32_t dtak_action:4;			/* action -- 4 bits */
+	uint32_t dtak_size:28;			/* size -- 28 bits */
+	caddr_t dtak_data;			/* data pointer */
+	struct dtrace_aggkey *dtak_next;	/* next in hash chain */
+} dtrace_aggkey_t;
+
+typedef struct dtrace_aggbuffer {
+	uintptr_t dtagb_hashsize;		/* number of buckets */
+	uintptr_t dtagb_free;			/* free list of keys */
+	dtrace_aggkey_t **dtagb_hash;		/* hash table */
+} dtrace_aggbuffer_t;
+
+/*
+ * DTrace Speculations
+ *
+ * Speculations have a per-CPU buffer and a global state.  Once a speculation
+ * buffer has been comitted or discarded, it cannot be reused until all CPUs
+ * have taken the same action (commit or discard) on their respective
+ * speculative buffer.  However, because DTrace probes may execute in arbitrary
+ * context, other CPUs cannot simply be cross-called at probe firing time to
+ * perform the necessary commit or discard.  The speculation states thus
+ * optimize for the case that a speculative buffer is only active on one CPU at
+ * the time of a commit() or discard() -- for if this is the case, other CPUs
+ * need not take action, and the speculation is immediately available for
+ * reuse.  If the speculation is active on multiple CPUs, it must be
+ * asynchronously cleaned -- potentially leading to a higher rate of dirty
+ * speculative drops.  The speculation states are as follows:
+ *
+ *  DTRACESPEC_INACTIVE       <= Initial state; inactive speculation
+ *  DTRACESPEC_ACTIVE         <= Allocated, but not yet speculatively traced to
+ *  DTRACESPEC_ACTIVEONE      <= Speculatively traced to on one CPU
+ *  DTRACESPEC_ACTIVEMANY     <= Speculatively traced to on more than one CPU
+ *  DTRACESPEC_COMMITTING     <= Currently being commited on one CPU
+ *  DTRACESPEC_COMMITTINGMANY <= Currently being commited on many CPUs
+ *  DTRACESPEC_DISCARDING     <= Currently being discarded on many CPUs
+ *
+ * The state transition diagram is as follows:
+ *
+ *     +----------------------------------------------------------+
+ *     |                                                          |
+ *     |                      +------------+                      |
+ *     |  +-------------------| COMMITTING |<-----------------+   |
+ *     |  |                   +------------+                  |   |
+ *     |  | copied spec.            ^             commit() on |   | discard() on
+ *     |  | into principal          |              active CPU |   | active CPU
+ *     |  |                         | commit()                |   |
+ *     V  V                         |                         |   |
+ * +----------+                 +--------+                +-----------+
+ * | INACTIVE |---------------->| ACTIVE |--------------->| ACTIVEONE |
+ * +----------+  speculation()  +--------+  speculate()   +-----------+
+ *     ^  ^                         |                         |   |
+ *     |  |                         | discard()               |   |
+ *     |  | asynchronously          |            discard() on |   | speculate()
+ *     |  | cleaned                 V            inactive CPU |   | on inactive
+ *     |  |                   +------------+                  |   | CPU
+ *     |  +-------------------| DISCARDING |<-----------------+   |
+ *     |                      +------------+                      |
+ *     | asynchronously             ^                             |
+ *     | copied spec.               |       discard()             |
+ *     | into principal             +------------------------+    |
+ *     |                                                     |    V
+ *  +----------------+             commit()              +------------+
+ *  | COMMITTINGMANY |<----------------------------------| ACTIVEMANY |
+ *  +----------------+                                   +------------+
+ */
+typedef enum dtrace_speculation_state {
+	DTRACESPEC_INACTIVE = 0,
+	DTRACESPEC_ACTIVE,
+	DTRACESPEC_ACTIVEONE,
+	DTRACESPEC_ACTIVEMANY,
+	DTRACESPEC_COMMITTING,
+	DTRACESPEC_COMMITTINGMANY,
+	DTRACESPEC_DISCARDING
+} dtrace_speculation_state_t;
+
+typedef struct dtrace_speculation {
+	dtrace_speculation_state_t dtsp_state;	/* current speculation state */
+	int dtsp_cleaning;			/* non-zero if being cleaned */
+	dtrace_buffer_t *dtsp_buffer;		/* speculative buffer */
+} dtrace_speculation_t;
+
+/*
+ * DTrace Dynamic Variables
+ *
+ * The dynamic variable problem is obviously decomposed into two subproblems:
+ * allocating new dynamic storage, and freeing old dynamic storage.  The
+ * presence of the second problem makes the first much more complicated -- or
+ * rather, the absence of the second renders the first trivial.  This is the
+ * case with aggregations, for which there is effectively no deallocation of
+ * dynamic storage.  (Or more accurately, all dynamic storage is deallocated
+ * when a snapshot is taken of the aggregation.)  As DTrace dynamic variables
+ * allow for both dynamic allocation and dynamic deallocation, the
+ * implementation of dynamic variables is quite a bit more complicated than
+ * that of their aggregation kin.
+ *
+ * We observe that allocating new dynamic storage is tricky only because the
+ * size can vary -- the allocation problem is much easier if allocation sizes
+ * are uniform.  We further observe that in D, the size of dynamic variables is
+ * actually _not_ dynamic -- dynamic variable sizes may be determined by static
+ * analysis of DIF text.  (This is true even of putatively dynamically-sized
+ * objects like strings and stacks, the sizes of which are dictated by the
+ * "stringsize" and "stackframes" variables, respectively.)  We exploit this by
+ * performing this analysis on all DIF before enabling any probes.  For each
+ * dynamic load or store, we calculate the dynamically-allocated size plus the
+ * size of the dtrace_dynvar structure plus the storage required to key the
+ * data.  For all DIF, we take the largest value and dub it the _chunksize_.
+ * We then divide dynamic memory into two parts:  a hash table that is wide
+ * enough to have every chunk in its own bucket, and a larger region of equal
+ * chunksize units.  Whenever we wish to dynamically allocate a variable, we
+ * always allocate a single chunk of memory.  Depending on the uniformity of
+ * allocation, this will waste some amount of memory -- but it eliminates the
+ * non-determinism inherent in traditional heap fragmentation.
+ *
+ * Dynamic objects are allocated by storing a non-zero value to them; they are
+ * deallocated by storing a zero value to them.  Dynamic variables are
+ * complicated enormously by being shared between CPUs.  In particular,
+ * consider the following scenario:
+ *
+ *                 CPU A                                 CPU B
+ *  +---------------------------------+   +---------------------------------+
+ *  |                                 |   |                                 |
+ *  | allocates dynamic object a[123] |   |                                 |
+ *  | by storing the value 345 to it  |   |                                 |
+ *  |                               --------->                              |
+ *  |                                 |   | wishing to load from object     |
+ *  |                                 |   | a[123], performs lookup in      |
+ *  |                                 |   | dynamic variable space          |
+ *  |                               <---------                              |
+ *  | deallocates object a[123] by    |   |                                 |
+ *  | storing 0 to it                 |   |                                 |
+ *  |                                 |   |                                 |
+ *  | allocates dynamic object b[567] |   | performs load from a[123]       |
+ *  | by storing the value 789 to it  |   |                                 |
+ *  :                                 :   :                                 :
+ *  .                                 .   .                                 .
+ *
+ * This is obviously a race in the D program, but there are nonetheless only
+ * two valid values for CPU B's load from a[123]:  345 or 0.  Most importantly,
+ * CPU B may _not_ see the value 789 for a[123].
+ *
+ * There are essentially two ways to deal with this:
+ *
+ *  (1)  Explicitly spin-lock variables.  That is, if CPU B wishes to load
+ *       from a[123], it needs to lock a[123] and hold the lock for the
+ *       duration that it wishes to manipulate it.
+ *
+ *  (2)  Avoid reusing freed chunks until it is known that no CPU is referring
+ *       to them.
+ *
+ * The implementation of (1) is rife with complexity, because it requires the
+ * user of a dynamic variable to explicitly decree when they are done using it.
+ * Were all variables by value, this perhaps wouldn't be debilitating -- but
+ * dynamic variables of non-scalar types are tracked by reference.  That is, if
+ * a dynamic variable is, say, a string, and that variable is to be traced to,
+ * say, the principal buffer, the DIF emulation code returns to the main
+ * dtrace_probe() loop a pointer to the underlying storage, not the contents of
+ * the storage.  Further, code calling on DIF emulation would have to be aware
+ * that the DIF emulation has returned a reference to a dynamic variable that
+ * has been potentially locked.  The variable would have to be unlocked after
+ * the main dtrace_probe() loop is finished with the variable, and the main
+ * dtrace_probe() loop would have to be careful to not call any further DIF
+ * emulation while the variable is locked to avoid deadlock.  More generally,
+ * if one were to implement (1), DIF emulation code dealing with dynamic
+ * variables could only deal with one dynamic variable at a time (lest deadlock
+ * result).  To sum, (1) exports too much subtlety to the users of dynamic
+ * variables -- increasing maintenance burden and imposing serious constraints
+ * on future DTrace development.
+ *
+ * The implementation of (2) is also complex, but the complexity is more
+ * manageable.  We need to be sure that when a variable is deallocated, it is
+ * not placed on a traditional free list, but rather on a _dirty_ list.  Once a
+ * variable is on a dirty list, it cannot be found by CPUs performing a
+ * subsequent lookup of the variable -- but it may still be in use by other
+ * CPUs.  To assure that all CPUs that may be seeing the old variable have
+ * cleared out of probe context, a dtrace_sync() can be issued.  Once the
+ * dtrace_sync() has completed, it can be known that all CPUs are done
+ * manipulating the dynamic variable -- the dirty list can be atomically
+ * appended to the free list.  Unfortunately, there's a slight hiccup in this
+ * mechanism:  dtrace_sync() may not be issued from probe context.  The
+ * dtrace_sync() must be therefore issued asynchronously from non-probe
+ * context.  For this we rely on the DTrace cleaner, a cyclic that runs at the
+ * "cleanrate" frequency.  To ease this implementation, we define several chunk
+ * lists:
+ *
+ *   - Dirty.  Deallocated chunks, not yet cleaned.  Not available.
+ *
+ *   - Rinsing.  Formerly dirty chunks that are currently being asynchronously
+ *     cleaned.  Not available, but will be shortly.  Dynamic variable
+ *     allocation may not spin or block for availability, however.
+ *
+ *   - Clean.  Clean chunks, ready for allocation -- but not on the free list.
+ *
+ *   - Free.  Available for allocation.
+ *
+ * Moreover, to avoid absurd contention, _each_ of these lists is implemented
+ * on a per-CPU basis.  This is only for performance, not correctness; chunks
+ * may be allocated from another CPU's free list.  The algorithm for allocation
+ * then is this:
+ *
+ *   (1)  Attempt to atomically allocate from current CPU's free list.  If list
+ *        is non-empty and allocation is successful, allocation is complete.
+ *
+ *   (2)  If the clean list is non-empty, atomically move it to the free list,
+ *        and reattempt (1).
+ *
+ *   (3)  If the dynamic variable space is in the CLEAN state, look for free
+ *        and clean lists on other CPUs by setting the current CPU to the next
+ *        CPU, and reattempting (1).  If the next CPU is the current CPU (that
+ *        is, if all CPUs have been checked), atomically switch the state of
+ *        the dynamic variable space based on the following:
+ *
+ *        - If no free chunks were found and no dirty chunks were found,
+ *          atomically set the state to EMPTY.
+ *
+ *        - If dirty chunks were found, atomically set the state to DIRTY.
+ *
+ *        - If rinsing chunks were found, atomically set the state to RINSING.
+ *
+ *   (4)  Based on state of dynamic variable space state, increment appropriate
+ *        counter to indicate dynamic drops (if in EMPTY state) vs. dynamic
+ *        dirty drops (if in DIRTY state) vs. dynamic rinsing drops (if in
+ *        RINSING state).  Fail the allocation.
+ *
+ * The cleaning cyclic operates with the following algorithm:  for all CPUs
+ * with a non-empty dirty list, atomically move the dirty list to the rinsing
+ * list.  Perform a dtrace_sync().  For all CPUs with a non-empty rinsing list,
+ * atomically move the rinsing list to the clean list.  Perform another
+ * dtrace_sync().  By this point, all CPUs have seen the new clean list; the
+ * state of the dynamic variable space can be restored to CLEAN.
+ *
+ * There exist two final races that merit explanation.  The first is a simple
+ * allocation race:
+ *
+ *                 CPU A                                 CPU B
+ *  +---------------------------------+   +---------------------------------+
+ *  |                                 |   |                                 |
+ *  | allocates dynamic object a[123] |   | allocates dynamic object a[123] |
+ *  | by storing the value 345 to it  |   | by storing the value 567 to it  |
+ *  |                                 |   |                                 |
+ *  :                                 :   :                                 :
+ *  .                                 .   .                                 .
+ *
+ * Again, this is a race in the D program.  It can be resolved by having a[123]
+ * hold the value 345 or a[123] hold the value 567 -- but it must be true that
+ * a[123] have only _one_ of these values.  (That is, the racing CPUs may not
+ * put the same element twice on the same hash chain.)  This is resolved
+ * simply:  before the allocation is undertaken, the start of the new chunk's
+ * hash chain is noted.  Later, after the allocation is complete, the hash
+ * chain is atomically switched to point to the new element.  If this fails
+ * (because of either concurrent allocations or an allocation concurrent with a
+ * deletion), the newly allocated chunk is deallocated to the dirty list, and
+ * the whole process of looking up (and potentially allocating) the dynamic
+ * variable is reattempted.
+ *
+ * The final race is a simple deallocation race:
+ *
+ *                 CPU A                                 CPU B
+ *  +---------------------------------+   +---------------------------------+
+ *  |                                 |   |                                 |
+ *  | deallocates dynamic object      |   | deallocates dynamic object      |
+ *  | a[123] by storing the value 0   |   | a[123] by storing the value 0   |
+ *  | to it                           |   | to it                           |
+ *  |                                 |   |                                 |
+ *  :                                 :   :                                 :
+ *  .                                 .   .                                 .
+ *
+ * Once again, this is a race in the D program, but it is one that we must
+ * handle without corrupting the underlying data structures.  Because
+ * deallocations require the deletion of a chunk from the middle of a hash
+ * chain, we cannot use a single-word atomic operation to remove it.  For this,
+ * we add a spin lock to the hash buckets that is _only_ used for deallocations
+ * (allocation races are handled as above).  Further, this spin lock is _only_
+ * held for the duration of the delete; before control is returned to the DIF
+ * emulation code, the hash bucket is unlocked.
+ */
+typedef struct dtrace_key {
+	uint64_t dttk_value;			/* data value or data pointer */
+	uint64_t dttk_size;			/* 0 if by-val, >0 if by-ref */
+} dtrace_key_t;
+
+typedef struct dtrace_tuple {
+	uint32_t dtt_nkeys;			/* number of keys in tuple */
+	uint32_t dtt_pad;			/* padding */
+	dtrace_key_t dtt_key[1];		/* array of tuple keys */
+} dtrace_tuple_t;
+
+typedef struct dtrace_dynvar {
+	uint64_t dtdv_hashval;			/* hash value -- 0 if free */
+	struct dtrace_dynvar *dtdv_next;	/* next on list or hash chain */
+	void *dtdv_data;			/* pointer to data */
+	dtrace_tuple_t dtdv_tuple;		/* tuple key */
+} dtrace_dynvar_t;
+
+typedef enum dtrace_dynvar_op {
+	DTRACE_DYNVAR_ALLOC,
+	DTRACE_DYNVAR_NOALLOC,
+	DTRACE_DYNVAR_DEALLOC
+} dtrace_dynvar_op_t;
+
+typedef struct dtrace_dynhash {
+	dtrace_dynvar_t *dtdh_chain;		/* hash chain for this bucket */
+	uintptr_t dtdh_lock;			/* deallocation lock */
+#ifdef _LP64
+	uintptr_t dtdh_pad[6];			/* pad to avoid false sharing */
+#else
+	uintptr_t dtdh_pad[14];			/* pad to avoid false sharing */
+#endif
+} dtrace_dynhash_t;
+
+typedef struct dtrace_dstate_percpu {
+	dtrace_dynvar_t *dtdsc_free;		/* free list for this CPU */
+	dtrace_dynvar_t *dtdsc_dirty;		/* dirty list for this CPU */
+	dtrace_dynvar_t *dtdsc_rinsing;		/* rinsing list for this CPU */
+	dtrace_dynvar_t *dtdsc_clean;		/* clean list for this CPU */
+	uint64_t dtdsc_drops;			/* number of capacity drops */
+	uint64_t dtdsc_dirty_drops;		/* number of dirty drops */
+	uint64_t dtdsc_rinsing_drops;		/* number of rinsing drops */
+#ifdef _LP64
+	uint64_t dtdsc_pad;			/* pad to avoid false sharing */
+#else
+	uint64_t dtdsc_pad[2];			/* pad to avoid false sharing */
+#endif
+} dtrace_dstate_percpu_t;
+
+typedef enum dtrace_dstate_state {
+	DTRACE_DSTATE_CLEAN = 0,
+	DTRACE_DSTATE_EMPTY,
+	DTRACE_DSTATE_DIRTY,
+	DTRACE_DSTATE_RINSING
+} dtrace_dstate_state_t;
+
+typedef struct dtrace_dstate {
+	void *dtds_base;			/* base of dynamic var. space */
+	size_t dtds_size;			/* size of dynamic var. space */
+	size_t dtds_hashsize;			/* number of buckets in hash */
+	size_t dtds_chunksize;			/* size of each chunk */
+	dtrace_dynhash_t *dtds_hash;		/* pointer to hash table */
+	dtrace_dstate_state_t dtds_state;	/* current dynamic var. state */
+	dtrace_dstate_percpu_t *dtds_percpu;	/* per-CPU dyn. var. state */
+} dtrace_dstate_t;
+
+/*
+ * DTrace Variable State
+ *
+ * The DTrace variable state tracks user-defined variables in its dtrace_vstate
+ * structure.  Each DTrace consumer has exactly one dtrace_vstate structure,
+ * but some dtrace_vstate structures may exist without a corresponding DTrace
+ * consumer (see "DTrace Helpers", below).  As described in <sys/dtrace.h>,
+ * user-defined variables can have one of three scopes:
+ *
+ *  DIFV_SCOPE_GLOBAL  =>  global scope
+ *  DIFV_SCOPE_THREAD  =>  thread-local scope (i.e. "self->" variables)
+ *  DIFV_SCOPE_LOCAL   =>  clause-local scope (i.e. "this->" variables)
+ *
+ * The variable state tracks variables by both their scope and their allocation
+ * type:
+ *
+ *  - The dtvs_globals and dtvs_locals members each point to an array of
+ *    dtrace_statvar structures.  These structures contain both the variable
+ *    metadata (dtrace_difv structures) and the underlying storage for all
+ *    statically allocated variables, including statically allocated
+ *    DIFV_SCOPE_GLOBAL variables and all DIFV_SCOPE_LOCAL variables.
+ *
+ *  - The dtvs_tlocals member points to an array of dtrace_difv structures for
+ *    DIFV_SCOPE_THREAD variables.  As such, this array tracks _only_ the
+ *    variable metadata for DIFV_SCOPE_THREAD variables; the underlying storage
+ *    is allocated out of the dynamic variable space.
+ *
+ *  - The dtvs_dynvars member is the dynamic variable state associated with the
+ *    variable state.  The dynamic variable state (described in "DTrace Dynamic
+ *    Variables", above) tracks all DIFV_SCOPE_THREAD variables and all
+ *    dynamically-allocated DIFV_SCOPE_GLOBAL variables.
+ */
+typedef struct dtrace_statvar {
+	uint64_t dtsv_data;			/* data or pointer to it */
+	size_t dtsv_size;			/* size of pointed-to data */
+	int dtsv_refcnt;			/* reference count */
+	dtrace_difv_t dtsv_var;			/* variable metadata */
+} dtrace_statvar_t;
+
+typedef struct dtrace_vstate {
+	dtrace_state_t *dtvs_state;		/* back pointer to state */
+	dtrace_statvar_t **dtvs_globals;	/* statically-allocated glbls */
+	int dtvs_nglobals;			/* number of globals */
+	dtrace_difv_t *dtvs_tlocals;		/* thread-local metadata */
+	int dtvs_ntlocals;			/* number of thread-locals */
+	dtrace_statvar_t **dtvs_locals;		/* clause-local data */
+	int dtvs_nlocals;			/* number of clause-locals */
+	dtrace_dstate_t dtvs_dynvars;		/* dynamic variable state */
+} dtrace_vstate_t;
+
+/*
+ * DTrace Machine State
+ *
+ * In the process of processing a fired probe, DTrace needs to track and/or
+ * cache some per-CPU state associated with that particular firing.  This is
+ * state that is always discarded after the probe firing has completed, and
+ * much of it is not specific to any DTrace consumer, remaining valid across
+ * all ECBs.  This state is tracked in the dtrace_mstate structure.
+ */
+#define	DTRACE_MSTATE_ARGS		0x00000001
+#define	DTRACE_MSTATE_PROBE		0x00000002
+#define	DTRACE_MSTATE_EPID		0x00000004
+#define	DTRACE_MSTATE_TIMESTAMP		0x00000008
+#define	DTRACE_MSTATE_STACKDEPTH	0x00000010
+#define	DTRACE_MSTATE_CALLER		0x00000020
+#define	DTRACE_MSTATE_IPL		0x00000040
+#define	DTRACE_MSTATE_FLTOFFS		0x00000080
+#define	DTRACE_MSTATE_WALLTIMESTAMP	0x00000100
+
+typedef struct dtrace_mstate {
+	uintptr_t dtms_scratch_base;		/* base of scratch space */
+	uintptr_t dtms_scratch_ptr;		/* current scratch pointer */
+	size_t dtms_scratch_size;		/* scratch size */
+	uint32_t dtms_present;			/* variables that are present */
+	uint64_t dtms_arg[5];			/* cached arguments */
+	dtrace_epid_t dtms_epid;		/* current EPID */
+	uint64_t dtms_timestamp;		/* cached timestamp */
+	hrtime_t dtms_walltimestamp;		/* cached wall timestamp */
+	int dtms_stackdepth;			/* cached stackdepth */
+	struct dtrace_probe *dtms_probe;	/* current probe */
+	uintptr_t dtms_caller;			/* cached caller */
+	int dtms_ipl;				/* cached interrupt pri lev */
+	int dtms_fltoffs;			/* faulting DIFO offset */
+	uintptr_t dtms_strtok;			/* saved strtok() pointer */
+} dtrace_mstate_t;
+
+#define	DTRACE_COND_OWNER	0x1
+#define	DTRACE_COND_USERMODE	0x2
+
+#define	DTRACE_PROBEKEY_MAXDEPTH	8	/* max glob recursion depth */
+
+/*
+ * DTrace Activity
+ *
+ * Each DTrace consumer is in one of several states, which (for purposes of
+ * avoiding yet-another overloading of the noun "state") we call the current
+ * _activity_.  The activity transitions on dtrace_go() (from DTRACIOCGO), on
+ * dtrace_stop() (from DTRACIOCSTOP) and on the exit() action.  Activities may
+ * only transition in one direction; the activity transition diagram is a
+ * directed acyclic graph.  The activity transition diagram is as follows:
+ *
+ *
+ * +----------+                   +--------+                   +--------+
+ * | INACTIVE |------------------>| WARMUP |------------------>| ACTIVE |
+ * +----------+   dtrace_go(),    +--------+   dtrace_go(),    +--------+
+ *                before BEGIN        |        after BEGIN       |  |  |
+ *                                    |                          |  |  |
+ *                      exit() action |                          |  |  |
+ *                     from BEGIN ECB |                          |  |  |
+ *                                    |                          |  |  |
+ *                                    v                          |  |  |
+ *                               +----------+     exit() action  |  |  |
+ *                               | DRAINING |<-------------------+  |  |
+ *                               +----------+                       |  |
+ *                                    |                             |  |
+ *                     dtrace_stop(), |                             |  |
+ *                       before END   |                             |  |
+ *                                    |                             |  |
+ *                                    v                             |  |
+ * +---------+                   +----------+                       |  |
+ * | STOPPED |<------------------| COOLDOWN |<----------------------+  |
+ * +---------+   dtrace_stop(),  +----------+     dtrace_stop(),       |
+ *                 after END                       before END          |
+ *                                                                     |
+ *                                +--------+                           |
+ *                                | KILLED |<--------------------------+
+ *                                +--------+     deadman timeout
+ *
+ * Note that once a DTrace consumer has stopped tracing, there is no way to
+ * restart it; if a DTrace consumer wishes to restart tracing, it must reopen
+ * the DTrace pseudodevice.
+ */
+typedef enum dtrace_activity {
+	DTRACE_ACTIVITY_INACTIVE = 0,		/* not yet running */
+	DTRACE_ACTIVITY_WARMUP,			/* while starting */
+	DTRACE_ACTIVITY_ACTIVE,			/* running */
+	DTRACE_ACTIVITY_DRAINING,		/* before stopping */
+	DTRACE_ACTIVITY_COOLDOWN,		/* while stopping */
+	DTRACE_ACTIVITY_STOPPED,		/* after stopping */
+	DTRACE_ACTIVITY_KILLED			/* killed due to deadman */
+} dtrace_activity_t;
+
+/*
+ * DTrace Helper Implementation
+ *
+ * A description of the helper architecture may be found in <sys/dtrace.h>.
+ * Each process contains a pointer to its helpers in its p_dtrace_helpers
+ * member.  This is a pointer to a dtrace_helpers structure, which contains an
+ * array of pointers to dtrace_helper structures, helper variable state (shared
+ * among a process's helpers) and a generation count.  (The generation count is
+ * used to provide an identifier when a helper is added so that it may be
+ * subsequently removed.)  The dtrace_helper structure is self-explanatory,
+ * containing pointers to the objects needed to execute the helper.  Note that
+ * helpers are _duplicated_ across fork(2), and destroyed on exec(2).  No more
+ * than dtrace_helpers_max are allowed per-process.
+ */
+#define	DTRACE_HELPER_ACTION_USTACK	0
+#define	DTRACE_NHELPER_ACTIONS		1
+
+typedef struct dtrace_helper_action {
+	dtrace_difo_t *dthp_predicate;		/* helper action predicate */
+	int dthp_nactions;			/* number of actions */
+	dtrace_difo_t **dthp_actions;		/* array of actions */
+	int dthp_generation;			/* helper action generation */
+	struct dtrace_helper_action *dthp_next;	/* next helper action */
+} dtrace_helper_action_t;
+
+typedef struct dtrace_helper_provider {
+	dof_helper_t dthp_prov;			/* DOF w/ provider and probes */
+	uint32_t dthp_ref;			/* reference count */
+} dtrace_helper_provider_t;
+
+typedef struct dtrace_helpers {
+	dtrace_helper_action_t **dthps_actions;	/* array of helper actions */
+	dtrace_vstate_t dthps_vstate;		/* helper action var. state */
+	dtrace_helper_provider_t **dthps_provs;	/* array of providers */
+	uint_t dthps_nprovs;			/* count of providers */
+	int dthps_generation;			/* current generation */
+	pid_t dthps_pid;			/* pid of associated proc */
+	struct dtrace_helpers *dthps_next;	/* next pointer */
+	struct dtrace_helpers *dthps_prev;	/* prev pointer */
+} dtrace_helpers_t;
+
+/*
+ * DTrace Helper Action Tracing
+ *
+ * Debugging helper actions can be arduous.  To ease the development and
+ * debugging of helpers, DTrace contains a tracing-framework-within-a-tracing-
+ * framework: helper tracing.  If dtrace_helptrace_enabled is non-zero (which
+ * it is by default on DEBUG kernels), all helper activity will be traced to a
+ * global, in-kernel ring buffer.  Each entry includes a pointer to the specific
+ * helper, the location within the helper, and a trace of all local variables.
+ * The ring buffer may be displayed in a human-readable format with the
+ * ::dtrace_helptrace mdb(1) dcmd.
+ */
+#define	DTRACE_HELPTRACE_NEXT	(-1)
+#define	DTRACE_HELPTRACE_DONE	(-2)
+#define	DTRACE_HELPTRACE_ERR	(-3)
+
+typedef struct dtrace_helptrace {
+	dtrace_helper_action_t	*dtht_helper;	/* helper action */
+	int dtht_where;				/* where in helper action */
+	int dtht_nlocals;			/* number of locals */
+	uint64_t dtht_locals[1];		/* local variables */
+} dtrace_helptrace_t;
+
+/*
+ * DTrace Credentials
+ *
+ * In probe context, we don't have the flexibility to examine the credentials
+ * of the DTrace consumer that created a particular enabling.  Instead, we use
+ * the Least Privilege interfaces to cache the consumer's credentials in a
+ * dtrace_cred_t structure. That structure contains two important sets of
+ * credentials that limit the consumer's breadth of visibility and what
+ * actions the consumer may take.
+ */
+#define	DTRACE_CRV_ALLPROC		0x01
+#define	DTRACE_CRV_KERNEL		0x02
+
+#define	DTRACE_CRV_ALL		(DTRACE_CRV_ALLPROC | DTRACE_CRV_KERNEL)
+
+#define	DTRACE_CRA_PROC			0x0001
+#define	DTRACE_CRA_PROC_DESTRUCTIVE	0x0002
+#define	DTRACE_CRA_PROC_CONTROL		0x0004
+#define	DTRACE_CRA_KERNEL		0x0008
+#define	DTRACE_CRA_KERNEL_DESTRUCTIVE	0x0010
+
+#define	DTRACE_CRA_ALL		(DTRACE_CRA_PROC | \
+	DTRACE_CRA_PROC_DESTRUCTIVE | DTRACE_CRA_PROC_CONTROL | \
+	DTRACE_CRA_KERNEL | DTRACE_CRA_KERNEL_DESTRUCTIVE)
+
+typedef struct dtrace_cred {
+	uid_t			dcr_uid;
+	gid_t			dcr_gid;
+	uint8_t			dcr_destructive;
+	uint8_t			dcr_visible;
+	uint16_t		dcr_action;
+} dtrace_cred_t;
+
+/*
+ * DTrace Consumer State
+ *
+ * Each DTrace consumer has an associated dtrace_state structure that contains
+ * its in-kernel DTrace state -- including options, credentials, statistics and
+ * pointers to ECBs, buffers, speculations and formats.  A dtrace_state
+ * structure is also allocated for anonymous enablings.  When anonymous state
+ * is grabbed, the grabbing consumers dts_anon pointer is set to the grabbed
+ * dtrace_state structure.
+ */
+struct dtrace_state {
+	dev_t dts_dev;				/* device */
+	int dts_necbs;				/* total number of ECBs */
+	dtrace_ecb_t **dts_ecbs;		/* array of ECBs */
+	dtrace_epid_t dts_epid;			/* next EPID to allocate */
+	size_t dts_needed;			/* greatest needed space */
+	struct dtrace_state *dts_anon;		/* anon. state, if grabbed */
+	dtrace_activity_t dts_activity;		/* current activity */
+	dtrace_vstate_t dts_vstate;		/* variable state */
+	dtrace_buffer_t *dts_buffer;		/* principal buffer */
+	dtrace_buffer_t *dts_aggbuffer;		/* aggregation buffer */
+	dtrace_speculation_t *dts_speculations;	/* speculation array */
+	int dts_nspeculations;			/* number of speculations */
+	int dts_naggregations;			/* number of aggregations */
+	dtrace_aggregation_t **dts_aggregations; /* aggregation array */
+	vmem_t *dts_aggid_arena;		/* arena for aggregation IDs */
+	uint32_t dts_speculations_busy;		/* number of spec. busy */
+	uint32_t dts_speculations_unavail;	/* number of spec unavail */
+	uint64_t dts_errors;			/* total number of errors */
+	uint32_t dts_reserve;			/* space reserved for END */
+	hrtime_t dts_laststatus;		/* time of last status */
+	cyclic_id_t dts_cleaner;		/* cleaning cyclic */
+	cyclic_id_t dts_deadman;		/* deadman cyclic */
+	hrtime_t dts_alive;			/* time last alive */
+	char dts_speculates;			/* boolean: has speculations */
+	char dts_destructive;			/* boolean: has dest. actions */
+	int dts_nformats;			/* number of formats */
+	char **dts_formats;			/* format string array */
+	dtrace_optval_t dts_options[DTRACEOPT_MAX]; /* options */
+	dtrace_cred_t dts_cred;			/* credentials */
+	size_t dts_nretained;			/* number of retained enabs */
+};
+
+struct dtrace_provider {
+	dtrace_pattr_t dtpv_attr;		/* provider attributes */
+	dtrace_ppriv_t dtpv_priv;		/* provider privileges */
+	dtrace_pops_t dtpv_pops;		/* provider operations */
+	char *dtpv_name;			/* provider name */
+	void *dtpv_arg;				/* provider argument */
+	uint_t dtpv_defunct;			/* boolean: defunct provider */
+	struct dtrace_provider *dtpv_next;	/* next provider */
+};
+
+struct dtrace_meta {
+	dtrace_mops_t dtm_mops;			/* meta provider operations */
+	char *dtm_name;				/* meta provider name */
+	void *dtm_arg;				/* meta provider user arg */
+	uint64_t dtm_count;			/* no. of associated provs. */
+};
+
+/*
+ * DTrace Enablings
+ *
+ * A dtrace_enabling structure is used to track a collection of ECB
+ * descriptions -- before they have been turned into actual ECBs.  This is
+ * created as a result of DOF processing, and is generally used to generate
+ * ECBs immediately thereafter.  However, enablings are also generally
+ * retained should the probes they describe be created at a later time; as
+ * each new module or provider registers with the framework, the retained
+ * enablings are reevaluated, with any new match resulting in new ECBs.  To
+ * prevent probes from being matched more than once, the enabling tracks the
+ * last probe generation matched, and only matches probes from subsequent
+ * generations.
+ */
+typedef struct dtrace_enabling {
+	dtrace_ecbdesc_t **dten_desc;		/* all ECB descriptions */
+	int dten_ndesc;				/* number of ECB descriptions */
+	int dten_maxdesc;			/* size of ECB array */
+	dtrace_vstate_t *dten_vstate;		/* associated variable state */
+	dtrace_genid_t dten_probegen;		/* matched probe generation */
+	dtrace_ecbdesc_t *dten_current;		/* current ECB description */
+	int dten_error;				/* current error value */
+	int dten_primed;			/* boolean: set if primed */
+	struct dtrace_enabling *dten_prev;	/* previous enabling */
+	struct dtrace_enabling *dten_next;	/* next enabling */
+} dtrace_enabling_t;
+
+/*
+ * DTrace Anonymous Enablings
+ *
+ * Anonymous enablings are DTrace enablings that are not associated with a
+ * controlling process, but rather derive their enabling from DOF stored as
+ * properties in the dtrace.conf file.  If there is an anonymous enabling, a
+ * DTrace consumer state and enabling are created on attach.  The state may be
+ * subsequently grabbed by the first consumer specifying the "grabanon"
+ * option.  As long as an anonymous DTrace enabling exists, dtrace(7D) will
+ * refuse to unload.
+ */
+typedef struct dtrace_anon {
+	dtrace_state_t *dta_state;		/* DTrace consumer state */
+	dtrace_enabling_t *dta_enabling;	/* pointer to enabling */
+	processorid_t dta_beganon;		/* which CPU BEGIN ran on */
+} dtrace_anon_t;
+
+/*
+ * DTrace Error Debugging
+ */
+#ifdef DEBUG
+#define	DTRACE_ERRDEBUG
+#endif
+
+#ifdef DTRACE_ERRDEBUG
+
+typedef struct dtrace_errhash {
+	const char	*dter_msg;	/* error message */
+	int		dter_count;	/* number of times seen */
+} dtrace_errhash_t;
+
+#define	DTRACE_ERRHASHSZ	256	/* must be > number of err msgs */
+
+#endif	/* DTRACE_ERRDEBUG */
+
+/*
+ * DTrace Toxic Ranges
+ *
+ * DTrace supports safe loads from probe context; if the address turns out to
+ * be invalid, a bit will be set by the kernel indicating that DTrace
+ * encountered a memory error, and DTrace will propagate the error to the user
+ * accordingly.  However, there may exist some regions of memory in which an
+ * arbitrary load can change system state, and from which it is impossible to
+ * recover from such a load after it has been attempted.  Examples of this may
+ * include memory in which programmable I/O registers are mapped (for which a
+ * read may have some implications for the device) or (in the specific case of
+ * UltraSPARC-I and -II) the virtual address hole.  The platform is required
+ * to make DTrace aware of these toxic ranges; DTrace will then check that
+ * target addresses are not in a toxic range before attempting to issue a
+ * safe load.
+ */
+typedef struct dtrace_toxrange {
+	uintptr_t	dtt_base;		/* base of toxic range */
+	uintptr_t	dtt_limit;		/* limit of toxic range */
+} dtrace_toxrange_t;
+
+extern uint64_t dtrace_getarg(int, int);
+extern greg_t dtrace_getfp(void);
+extern int dtrace_getipl(void);
+extern uintptr_t dtrace_caller(int);
+extern uint32_t dtrace_cas32(uint32_t *, uint32_t, uint32_t);
+extern void *dtrace_casptr(void *, void *, void *);
+extern void dtrace_copyin(uintptr_t, uintptr_t, size_t);
+extern void dtrace_copyinstr(uintptr_t, uintptr_t, size_t);
+extern void dtrace_copyout(uintptr_t, uintptr_t, size_t);
+extern void dtrace_copyoutstr(uintptr_t, uintptr_t, size_t);
+extern void dtrace_getpcstack(pc_t *, int, int, uint32_t *);
+extern ulong_t dtrace_getreg(struct regs *, uint_t);
+extern int dtrace_getstackdepth(int);
+extern void dtrace_getupcstack(uint64_t *, int);
+extern void dtrace_getufpstack(uint64_t *, uint64_t *, int);
+extern uintptr_t dtrace_fulword(void *);
+extern uint8_t dtrace_fuword8(void *);
+extern uint16_t dtrace_fuword16(void *);
+extern uint32_t dtrace_fuword32(void *);
+extern uint64_t dtrace_fuword64(void *);
+extern void dtrace_probe_error(dtrace_state_t *, dtrace_epid_t, int, int,
+    int, uintptr_t);
+extern int dtrace_assfail(const char *, const char *, int);
+extern int dtrace_attached(void);
+extern hrtime_t dtrace_gethrestime();
+
+#ifdef __sparc
+extern void dtrace_flush_windows(void);
+extern void dtrace_flush_user_windows(void);
+extern uint_t dtrace_getotherwin(void);
+extern uint_t dtrace_getfprs(void);
+#else
+extern void dtrace_copy(uintptr_t, uintptr_t, size_t);
+extern void dtrace_copystr(uintptr_t, uintptr_t, size_t);
+#endif
+
+/*
+ * DTrace Assertions
+ *
+ * DTrace calls ASSERT from probe context.  To assure that a failed ASSERT
+ * does not induce a markedly more catastrophic failure (e.g., one from which
+ * a dump cannot be gleaned), DTrace must define its own ASSERT to be one that
+ * may safely be called from probe context.  This header file must thus be
+ * included by any DTrace component that calls ASSERT from probe context, and
+ * _only_ by those components.  (The only exception to this is kernel
+ * debugging infrastructure at user-level that doesn't depend on calling
+ * ASSERT.)
+ */
+#undef ASSERT
+#ifdef DEBUG
+#define	ASSERT(EX)	((void)((EX) || \
+			dtrace_assfail(#EX, __FILE__, __LINE__)))
+#else
+#define	ASSERT(X)	((void)0)
+#endif
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif /* _SYS_DTRACE_IMPL_H */