1 files changed, 809 insertions, 0 deletions

diff --git a/tools/lib/traceevent/kbuffer-parse.c b/tools/lib/traceevent/kbuffer-parse.c
new file mode 100644
index 000000000..f1640d651
--- /dev/null
+++ b/tools/lib/traceevent/kbuffer-parse.c
@@ -0,0 +1,809 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ * Copyright (C) 2009, 2010 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
+ *
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "kbuffer.h"
+
+#define MISSING_EVENTS (1UL << 31)
+#define MISSING_STORED (1UL << 30)
+
+#define COMMIT_MASK ((1 << 27) - 1)
+
+enum {
+	KBUFFER_FL_HOST_BIG_ENDIAN	= (1<<0),
+	KBUFFER_FL_BIG_ENDIAN		= (1<<1),
+	KBUFFER_FL_LONG_8		= (1<<2),
+	KBUFFER_FL_OLD_FORMAT		= (1<<3),
+};
+
+#define ENDIAN_MASK (KBUFFER_FL_HOST_BIG_ENDIAN | KBUFFER_FL_BIG_ENDIAN)
+
+/** kbuffer
+ * @timestamp		- timestamp of current event
+ * @lost_events		- # of lost events between this subbuffer and previous
+ * @flags		- special flags of the kbuffer
+ * @subbuffer		- pointer to the sub-buffer page
+ * @data		- pointer to the start of data on the sub-buffer page
+ * @index		- index from @data to the @curr event data
+ * @curr		- offset from @data to the start of current event
+ *			   (includes metadata)
+ * @next		- offset from @data to the start of next event
+ * @size		- The size of data on @data
+ * @start		- The offset from @subbuffer where @data lives
+ *
+ * @read_4		- Function to read 4 raw bytes (may swap)
+ * @read_8		- Function to read 8 raw bytes (may swap)
+ * @read_long		- Function to read a long word (4 or 8 bytes with needed swap)
+ */
+struct kbuffer {
+	unsigned long long 	timestamp;
+	long long		lost_events;
+	unsigned long		flags;
+	void			*subbuffer;
+	void			*data;
+	unsigned int		index;
+	unsigned int		curr;
+	unsigned int		next;
+	unsigned int		size;
+	unsigned int		start;
+
+	unsigned int (*read_4)(void *ptr);
+	unsigned long long (*read_8)(void *ptr);
+	unsigned long long (*read_long)(struct kbuffer *kbuf, void *ptr);
+	int (*next_event)(struct kbuffer *kbuf);
+};
+
+static void *zmalloc(size_t size)
+{
+	return calloc(1, size);
+}
+
+static int host_is_bigendian(void)
+{
+	unsigned char str[] = { 0x1, 0x2, 0x3, 0x4 };
+	unsigned int *ptr;
+
+	ptr = (unsigned int *)str;
+	return *ptr == 0x01020304;
+}
+
+static int do_swap(struct kbuffer *kbuf)
+{
+	return ((kbuf->flags & KBUFFER_FL_HOST_BIG_ENDIAN) + kbuf->flags) &
+		ENDIAN_MASK;
+}
+
+static unsigned long long __read_8(void *ptr)
+{
+	unsigned long long data = *(unsigned long long *)ptr;
+
+	return data;
+}
+
+static unsigned long long __read_8_sw(void *ptr)
+{
+	unsigned long long data = *(unsigned long long *)ptr;
+	unsigned long long swap;
+
+	swap = ((data & 0xffULL) << 56) |
+		((data & (0xffULL << 8)) << 40) |
+		((data & (0xffULL << 16)) << 24) |
+		((data & (0xffULL << 24)) << 8) |
+		((data & (0xffULL << 32)) >> 8) |
+		((data & (0xffULL << 40)) >> 24) |
+		((data & (0xffULL << 48)) >> 40) |
+		((data & (0xffULL << 56)) >> 56);
+
+	return swap;
+}
+
+static unsigned int __read_4(void *ptr)
+{
+	unsigned int data = *(unsigned int *)ptr;
+
+	return data;
+}
+
+static unsigned int __read_4_sw(void *ptr)
+{
+	unsigned int data = *(unsigned int *)ptr;
+	unsigned int swap;
+
+	swap = ((data & 0xffULL) << 24) |
+		((data & (0xffULL << 8)) << 8) |
+		((data & (0xffULL << 16)) >> 8) |
+		((data & (0xffULL << 24)) >> 24);
+
+	return swap;
+}
+
+static unsigned long long read_8(struct kbuffer *kbuf, void *ptr)
+{
+	return kbuf->read_8(ptr);
+}
+
+static unsigned int read_4(struct kbuffer *kbuf, void *ptr)
+{
+	return kbuf->read_4(ptr);
+}
+
+static unsigned long long __read_long_8(struct kbuffer *kbuf, void *ptr)
+{
+	return kbuf->read_8(ptr);
+}
+
+static unsigned long long __read_long_4(struct kbuffer *kbuf, void *ptr)
+{
+	return kbuf->read_4(ptr);
+}
+
+static unsigned long long read_long(struct kbuffer *kbuf, void *ptr)
+{
+	return kbuf->read_long(kbuf, ptr);
+}
+
+static int calc_index(struct kbuffer *kbuf, void *ptr)
+{
+	return (unsigned long)ptr - (unsigned long)kbuf->data;
+}
+
+static int __next_event(struct kbuffer *kbuf);
+
+/**
+ * kbuffer_alloc - allocat a new kbuffer
+ * @size;	enum to denote size of word
+ * @endian:	enum to denote endianness
+ *
+ * Allocates and returns a new kbuffer.
+ */
+struct kbuffer *
+kbuffer_alloc(enum kbuffer_long_size size, enum kbuffer_endian endian)
+{
+	struct kbuffer *kbuf;
+	int flags = 0;
+
+	switch (size) {
+	case KBUFFER_LSIZE_4:
+		break;
+	case KBUFFER_LSIZE_8:
+		flags |= KBUFFER_FL_LONG_8;
+		break;
+	default:
+		return NULL;
+	}
+
+	switch (endian) {
+	case KBUFFER_ENDIAN_LITTLE:
+		break;
+	case KBUFFER_ENDIAN_BIG:
+		flags |= KBUFFER_FL_BIG_ENDIAN;
+		break;
+	default:
+		return NULL;
+	}
+
+	kbuf = zmalloc(sizeof(*kbuf));
+	if (!kbuf)
+		return NULL;
+
+	kbuf->flags = flags;
+
+	if (host_is_bigendian())
+		kbuf->flags |= KBUFFER_FL_HOST_BIG_ENDIAN;
+
+	if (do_swap(kbuf)) {
+		kbuf->read_8 = __read_8_sw;
+		kbuf->read_4 = __read_4_sw;
+	} else {
+		kbuf->read_8 = __read_8;
+		kbuf->read_4 = __read_4;
+	}
+
+	if (kbuf->flags & KBUFFER_FL_LONG_8)
+		kbuf->read_long = __read_long_8;
+	else
+		kbuf->read_long = __read_long_4;
+
+	/* May be changed by kbuffer_set_old_format() */
+	kbuf->next_event = __next_event;
+
+	return kbuf;
+}
+
+/** kbuffer_free - free an allocated kbuffer
+ * @kbuf:	The kbuffer to free
+ *
+ * Can take NULL as a parameter.
+ */
+void kbuffer_free(struct kbuffer *kbuf)
+{
+	free(kbuf);
+}
+
+static unsigned int type4host(struct kbuffer *kbuf,
+			      unsigned int type_len_ts)
+{
+	if (kbuf->flags & KBUFFER_FL_BIG_ENDIAN)
+		return (type_len_ts >> 29) & 3;
+	else
+		return type_len_ts & 3;
+}
+
+static unsigned int len4host(struct kbuffer *kbuf,
+			     unsigned int type_len_ts)
+{
+	if (kbuf->flags & KBUFFER_FL_BIG_ENDIAN)
+		return (type_len_ts >> 27) & 7;
+	else
+		return (type_len_ts >> 2) & 7;
+}
+
+static unsigned int type_len4host(struct kbuffer *kbuf,
+				  unsigned int type_len_ts)
+{
+	if (kbuf->flags & KBUFFER_FL_BIG_ENDIAN)
+		return (type_len_ts >> 27) & ((1 << 5) - 1);
+	else
+		return type_len_ts & ((1 << 5) - 1);
+}
+
+static unsigned int ts4host(struct kbuffer *kbuf,
+			    unsigned int type_len_ts)
+{
+	if (kbuf->flags & KBUFFER_FL_BIG_ENDIAN)
+		return type_len_ts & ((1 << 27) - 1);
+	else
+		return type_len_ts >> 5;
+}
+
+/*
+ * Linux 2.6.30 and earlier (not much ealier) had a different
+ * ring buffer format. It should be obsolete, but we handle it anyway.
+ */
+enum old_ring_buffer_type {
+	OLD_RINGBUF_TYPE_PADDING,
+	OLD_RINGBUF_TYPE_TIME_EXTEND,
+	OLD_RINGBUF_TYPE_TIME_STAMP,
+	OLD_RINGBUF_TYPE_DATA,
+};
+
+static unsigned int old_update_pointers(struct kbuffer *kbuf)
+{
+	unsigned long long extend;
+	unsigned int type_len_ts;
+	unsigned int type;
+	unsigned int len;
+	unsigned int delta;
+	unsigned int length;
+	void *ptr = kbuf->data + kbuf->curr;
+
+	type_len_ts = read_4(kbuf, ptr);
+	ptr += 4;
+
+	type = type4host(kbuf, type_len_ts);
+	len = len4host(kbuf, type_len_ts);
+	delta = ts4host(kbuf, type_len_ts);
+
+	switch (type) {
+	case OLD_RINGBUF_TYPE_PADDING:
+		kbuf->next = kbuf->size;
+		return 0;
+
+	case OLD_RINGBUF_TYPE_TIME_EXTEND:
+		extend = read_4(kbuf, ptr);
+		extend <<= TS_SHIFT;
+		extend += delta;
+		delta = extend;
+		ptr += 4;
+		length = 0;
+		break;
+
+	case OLD_RINGBUF_TYPE_TIME_STAMP:
+		/* should never happen! */
+		kbuf->curr = kbuf->size;
+		kbuf->next = kbuf->size;
+		kbuf->index = kbuf->size;
+		return -1;
+	default:
+		if (len)
+			length = len * 4;
+		else {
+			length = read_4(kbuf, ptr);
+			length -= 4;
+			ptr += 4;
+		}
+		break;
+	}
+
+	kbuf->timestamp += delta;
+	kbuf->index = calc_index(kbuf, ptr);
+	kbuf->next = kbuf->index + length;
+
+	return type;
+}
+
+static int __old_next_event(struct kbuffer *kbuf)
+{
+	int type;
+
+	do {
+		kbuf->curr = kbuf->next;
+		if (kbuf->next >= kbuf->size)
+			return -1;
+		type = old_update_pointers(kbuf);
+	} while (type == OLD_RINGBUF_TYPE_TIME_EXTEND || type == OLD_RINGBUF_TYPE_PADDING);
+
+	return 0;
+}
+
+static unsigned int
+translate_data(struct kbuffer *kbuf, void *data, void **rptr,
+	       unsigned long long *delta, int *length)
+{
+	unsigned long long extend;
+	unsigned int type_len_ts;
+	unsigned int type_len;
+
+	type_len_ts = read_4(kbuf, data);
+	data += 4;
+
+	type_len = type_len4host(kbuf, type_len_ts);
+	*delta = ts4host(kbuf, type_len_ts);
+
+	switch (type_len) {
+	case KBUFFER_TYPE_PADDING:
+		*length = read_4(kbuf, data);
+		break;
+
+	case KBUFFER_TYPE_TIME_EXTEND:
+	case KBUFFER_TYPE_TIME_STAMP:
+		extend = read_4(kbuf, data);
+		data += 4;
+		extend <<= TS_SHIFT;
+		extend += *delta;
+		*delta = extend;
+		*length = 0;
+		break;
+
+	case 0:
+		*length = read_4(kbuf, data) - 4;
+		*length = (*length + 3) & ~3;
+		data += 4;
+		break;
+	default:
+		*length = type_len * 4;
+		break;
+	}
+
+	*rptr = data;
+
+	return type_len;
+}
+
+static unsigned int update_pointers(struct kbuffer *kbuf)
+{
+	unsigned long long delta;
+	unsigned int type_len;
+	int length;
+	void *ptr = kbuf->data + kbuf->curr;
+
+	type_len = translate_data(kbuf, ptr, &ptr, &delta, &length);
+
+	if (type_len == KBUFFER_TYPE_TIME_STAMP)
+		kbuf->timestamp = delta;
+	else
+		kbuf->timestamp += delta;
+
+	kbuf->index = calc_index(kbuf, ptr);
+	kbuf->next = kbuf->index + length;
+
+	return type_len;
+}
+
+/**
+ * kbuffer_translate_data - read raw data to get a record
+ * @swap:	Set to 1 if bytes in words need to be swapped when read
+ * @data:	The raw data to read
+ * @size:	Address to store the size of the event data.
+ *
+ * Returns a pointer to the event data. To determine the entire
+ * record size (record metadata + data) just add the difference between
+ * @data and the returned value to @size.
+ */
+void *kbuffer_translate_data(int swap, void *data, unsigned int *size)
+{
+	unsigned long long delta;
+	struct kbuffer kbuf;
+	int type_len;
+	int length;
+	void *ptr;
+
+	if (swap) {
+		kbuf.read_8 = __read_8_sw;
+		kbuf.read_4 = __read_4_sw;
+		kbuf.flags = host_is_bigendian() ? 0 : KBUFFER_FL_BIG_ENDIAN;
+	} else {
+		kbuf.read_8 = __read_8;
+		kbuf.read_4 = __read_4;
+		kbuf.flags = host_is_bigendian() ? KBUFFER_FL_BIG_ENDIAN: 0;
+	}
+
+	type_len = translate_data(&kbuf, data, &ptr, &delta, &length);
+	switch (type_len) {
+	case KBUFFER_TYPE_PADDING:
+	case KBUFFER_TYPE_TIME_EXTEND:
+	case KBUFFER_TYPE_TIME_STAMP:
+		return NULL;
+	}
+
+	*size = length;
+
+	return ptr;
+}
+
+static int __next_event(struct kbuffer *kbuf)
+{
+	int type;
+
+	do {
+		kbuf->curr = kbuf->next;
+		if (kbuf->next >= kbuf->size)
+			return -1;
+		type = update_pointers(kbuf);
+	} while (type == KBUFFER_TYPE_TIME_EXTEND ||
+		 type == KBUFFER_TYPE_TIME_STAMP ||
+		 type == KBUFFER_TYPE_PADDING);
+
+	return 0;
+}
+
+static int next_event(struct kbuffer *kbuf)
+{
+	return kbuf->next_event(kbuf);
+}
+
+/**
+ * kbuffer_next_event - increment the current pointer
+ * @kbuf:	The kbuffer to read
+ * @ts:		Address to store the next record's timestamp (may be NULL to ignore)
+ *
+ * Increments the pointers into the subbuffer of the kbuffer to point to the
+ * next event so that the next kbuffer_read_event() will return a
+ * new event.
+ *
+ * Returns the data of the next event if a new event exists on the subbuffer,
+ * NULL otherwise.
+ */
+void *kbuffer_next_event(struct kbuffer *kbuf, unsigned long long *ts)
+{
+	int ret;
+
+	if (!kbuf || !kbuf->subbuffer)
+		return NULL;
+
+	ret = next_event(kbuf);
+	if (ret < 0)
+		return NULL;
+
+	if (ts)
+		*ts = kbuf->timestamp;
+
+	return kbuf->data + kbuf->index;
+}
+
+/**
+ * kbuffer_load_subbuffer - load a new subbuffer into the kbuffer
+ * @kbuf:	The kbuffer to load
+ * @subbuffer:	The subbuffer to load into @kbuf.
+ *
+ * Load a new subbuffer (page) into @kbuf. This will reset all
+ * the pointers and update the @kbuf timestamp. The next read will
+ * return the first event on @subbuffer.
+ *
+ * Returns 0 on succes, -1 otherwise.
+ */
+int kbuffer_load_subbuffer(struct kbuffer *kbuf, void *subbuffer)
+{
+	unsigned long long flags;
+	void *ptr = subbuffer;
+
+	if (!kbuf || !subbuffer)
+		return -1;
+
+	kbuf->subbuffer = subbuffer;
+
+	kbuf->timestamp = read_8(kbuf, ptr);
+	ptr += 8;
+
+	kbuf->curr = 0;
+
+	if (kbuf->flags & KBUFFER_FL_LONG_8)
+		kbuf->start = 16;
+	else
+		kbuf->start = 12;
+
+	kbuf->data = subbuffer + kbuf->start;
+
+	flags = read_long(kbuf, ptr);
+	kbuf->size = (unsigned int)flags & COMMIT_MASK;
+
+	if (flags & MISSING_EVENTS) {
+		if (flags & MISSING_STORED) {
+			ptr = kbuf->data + kbuf->size;
+			kbuf->lost_events = read_long(kbuf, ptr);
+		} else
+			kbuf->lost_events = -1;
+	} else
+		kbuf->lost_events = 0;
+
+	kbuf->index = 0;
+	kbuf->next = 0;
+
+	next_event(kbuf);
+
+	return 0;
+}
+
+/**
+ * kbuffer_subbuf_timestamp - read the timestamp from a sub buffer
+ * @kbuf:      The kbuffer to load
+ * @subbuf:    The subbuffer to read from.
+ *
+ * Return the timestamp from a subbuffer.
+ */
+unsigned long long kbuffer_subbuf_timestamp(struct kbuffer *kbuf, void *subbuf)
+{
+	return kbuf->read_8(subbuf);
+}
+
+/**
+ * kbuffer_ptr_delta - read the delta field from a record
+ * @kbuf:      The kbuffer to load
+ * @ptr:       The record in the buffe.
+ *
+ * Return the timestamp delta from a record
+ */
+unsigned int kbuffer_ptr_delta(struct kbuffer *kbuf, void *ptr)
+{
+	unsigned int type_len_ts;
+
+	type_len_ts = read_4(kbuf, ptr);
+	return ts4host(kbuf, type_len_ts);
+}
+
+
+/**
+ * kbuffer_read_event - read the next event in the kbuffer subbuffer
+ * @kbuf:	The kbuffer to read from
+ * @ts:		The address to store the timestamp of the event (may be NULL to ignore)
+ *
+ * Returns a pointer to the data part of the current event.
+ * NULL if no event is left on the subbuffer.
+ */
+void *kbuffer_read_event(struct kbuffer *kbuf, unsigned long long *ts)
+{
+	if (!kbuf || !kbuf->subbuffer)
+		return NULL;
+
+	if (kbuf->curr >= kbuf->size)
+		return NULL;
+
+	if (ts)
+		*ts = kbuf->timestamp;
+	return kbuf->data + kbuf->index;
+}
+
+/**
+ * kbuffer_timestamp - Return the timestamp of the current event
+ * @kbuf:	The kbuffer to read from
+ *
+ * Returns the timestamp of the current (next) event.
+ */
+unsigned long long kbuffer_timestamp(struct kbuffer *kbuf)
+{
+	return kbuf->timestamp;
+}
+
+/**
+ * kbuffer_read_at_offset - read the event that is at offset
+ * @kbuf:	The kbuffer to read from
+ * @offset:	The offset into the subbuffer
+ * @ts:		The address to store the timestamp of the event (may be NULL to ignore)
+ *
+ * The @offset must be an index from the @kbuf subbuffer beginning.
+ * If @offset is bigger than the stored subbuffer, NULL will be returned.
+ *
+ * Returns the data of the record that is at @offset. Note, @offset does
+ * not need to be the start of the record, the offset just needs to be
+ * in the record (or beginning of it).
+ *
+ * Note, the kbuf timestamp and pointers are updated to the
+ * returned record. That is, kbuffer_read_event() will return the same
+ * data and timestamp, and kbuffer_next_event() will increment from
+ * this record.
+ */
+void *kbuffer_read_at_offset(struct kbuffer *kbuf, int offset,
+			     unsigned long long *ts)
+{
+	void *data;
+
+	if (offset < kbuf->start)
+		offset = 0;
+	else
+		offset -= kbuf->start;
+
+	/* Reset the buffer */
+	kbuffer_load_subbuffer(kbuf, kbuf->subbuffer);
+	data = kbuffer_read_event(kbuf, ts);
+
+	while (kbuf->curr < offset) {
+		data = kbuffer_next_event(kbuf, ts);
+		if (!data)
+			break;
+	}
+
+	return data;
+}
+
+/**
+ * kbuffer_subbuffer_size - the size of the loaded subbuffer
+ * @kbuf:	The kbuffer to read from
+ *
+ * Returns the size of the subbuffer. Note, this size is
+ * where the last event resides. The stored subbuffer may actually be
+ * bigger due to padding and such.
+ */
+int kbuffer_subbuffer_size(struct kbuffer *kbuf)
+{
+	return kbuf->size;
+}
+
+/**
+ * kbuffer_curr_index - Return the index of the record
+ * @kbuf:	The kbuffer to read from
+ *
+ * Returns the index from the start of the data part of
+ * the subbuffer to the current location. Note this is not
+ * from the start of the subbuffer. An index of zero will
+ * point to the first record. Use kbuffer_curr_offset() for
+ * the actually offset (that can be used by kbuffer_read_at_offset())
+ */
+int kbuffer_curr_index(struct kbuffer *kbuf)
+{
+	return kbuf->curr;
+}
+
+/**
+ * kbuffer_curr_offset - Return the offset of the record
+ * @kbuf:	The kbuffer to read from
+ *
+ * Returns the offset from the start of the subbuffer to the
+ * current location.
+ */
+int kbuffer_curr_offset(struct kbuffer *kbuf)
+{
+	return kbuf->curr + kbuf->start;
+}
+
+/**
+ * kbuffer_event_size - return the size of the event data
+ * @kbuf:	The kbuffer to read
+ *
+ * Returns the size of the event data (the payload not counting
+ * the meta data of the record) of the current event.
+ */
+int kbuffer_event_size(struct kbuffer *kbuf)
+{
+	return kbuf->next - kbuf->index;
+}
+
+/**
+ * kbuffer_curr_size - return the size of the entire record
+ * @kbuf:	The kbuffer to read
+ *
+ * Returns the size of the entire record (meta data and payload)
+ * of the current event.
+ */
+int kbuffer_curr_size(struct kbuffer *kbuf)
+{
+	return kbuf->next - kbuf->curr;
+}
+
+/**
+ * kbuffer_missed_events - return the # of missed events from last event.
+ * @kbuf: 	The kbuffer to read from
+ *
+ * Returns the # of missed events (if recorded) before the current
+ * event. Note, only events on the beginning of a subbuffer can
+ * have missed events, all other events within the buffer will be
+ * zero.
+ */
+int kbuffer_missed_events(struct kbuffer *kbuf)
+{
+	/* Only the first event can have missed events */
+	if (kbuf->curr)
+		return 0;
+
+	return kbuf->lost_events;
+}
+
+/**
+ * kbuffer_set_old_forma - set the kbuffer to use the old format parsing
+ * @kbuf:	The kbuffer to set
+ *
+ * This is obsolete (or should be). The first kernels to use the
+ * new ring buffer had a slightly different ring buffer format
+ * (2.6.30 and earlier). It is still somewhat supported by kbuffer,
+ * but should not be counted on in the future.
+ */
+void kbuffer_set_old_format(struct kbuffer *kbuf)
+{
+	kbuf->flags |= KBUFFER_FL_OLD_FORMAT;
+
+	kbuf->next_event = __old_next_event;
+}
+
+/**
+ * kbuffer_start_of_data - return offset of where data starts on subbuffer
+ * @kbuf:	The kbuffer
+ *
+ * Returns the location on the subbuffer where the data starts.
+ */
+int kbuffer_start_of_data(struct kbuffer *kbuf)
+{
+	return kbuf->start;
+}
+
+/**
+ * kbuffer_raw_get - get raw buffer info
+ * @kbuf:	The kbuffer
+ * @subbuf:	Start of mapped subbuffer
+ * @info:	Info descriptor to fill in
+ *
+ * For debugging. This can return internals of the ring buffer.
+ * Expects to have info->next set to what it will read.
+ * The type, length and timestamp delta will be filled in, and
+ * @info->next will be updated to the next element.
+ * The @subbuf is used to know if the info is passed the end of
+ * data and NULL will be returned if it is.
+ */
+struct kbuffer_raw_info *
+kbuffer_raw_get(struct kbuffer *kbuf, void *subbuf, struct kbuffer_raw_info *info)
+{
+	unsigned long long flags;
+	unsigned long long delta;
+	unsigned int type_len;
+	unsigned int size;
+	int start;
+	int length;
+	void *ptr = info->next;
+
+	if (!kbuf || !subbuf)
+		return NULL;
+
+	if (kbuf->flags & KBUFFER_FL_LONG_8)
+		start = 16;
+	else
+		start = 12;
+
+	flags = read_long(kbuf, subbuf + 8);
+	size = (unsigned int)flags & COMMIT_MASK;
+
+	if (ptr < subbuf || ptr >= subbuf + start + size)
+		return NULL;
+
+	type_len = translate_data(kbuf, ptr, &ptr, &delta, &length);
+
+	info->next = ptr + length;
+
+	info->type = type_len;
+	info->delta = delta;
+	info->length = length;
+
+	return info;
+}