[RFC patch 17/41] LTTng - serialization

[Mathieu Desnoyers]

Generic serialization mechanism : takes the variable argument list and
serializes it them in the trace buffers.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
---
 ltt/ltt-serialize.c |  685 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 685 insertions(+)

Index: linux-2.6-lttng/ltt/ltt-serialize.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6-lttng/ltt/ltt-serialize.c	2009-03-04 14:07:58.000000000 -0500
@@ -0,0 +1,685 @@
+/*
+ * LTTng serializing code.
+ *
+ * Copyright Mathieu Desnoyers, March 2007.
+ *
+ * Licensed under the GPLv2.
+ *
+ * See this discussion about weirdness about passing va_list and then va_list to
+ * functions. (related to array argument passing). va_list seems to be
+ * implemented as an array on x86_64, but not on i386... This is why we pass a
+ * va_list * to ltt_vtrace.
+ */
+
+#include <stdarg.h>
+#include <linux/ctype.h>
+#include <linux/string.h>
+#include <linux/module.h>
+#include <linux/ltt-tracer.h>
+
+enum ltt_type {
+	LTT_TYPE_SIGNED_INT,
+	LTT_TYPE_UNSIGNED_INT,
+	LTT_TYPE_STRING,
+	LTT_TYPE_NONE,
+};
+
+#define LTT_ATTRIBUTE_NETWORK_BYTE_ORDER (1<<1)
+
+/*
+ * Inspired from vsnprintf
+ *
+ * The serialization format string supports the basic printf format strings.
+ * In addition, it defines new formats that can be used to serialize more
+ * complex/non portable data structures.
+ *
+ * Typical use:
+ *
+ * field_name %ctype
+ * field_name #tracetype %ctype
+ * field_name #tracetype %ctype1 %ctype2 ...
+ *
+ * A conversion is performed between format string types supported by GCC and
+ * the trace type requested. GCC type is used to perform type checking on format
+ * strings. Trace type is used to specify the exact binary representation
+ * in the trace. A mapping is done between one or more GCC types to one trace
+ * type. Sign extension, if required by the conversion, is performed following
+ * the trace type.
+ *
+ * If a gcc format is not declared with a trace format, the gcc format is
+ * also used as binary representation in the trace.
+ *
+ * Strings are supported with %s.
+ * A single tracetype (sequence) can take multiple c types as parameter.
+ *
+ * c types:
+ *
+ * see printf(3).
+ *
+ * Note: to write a uint32_t in a trace, the following expression is recommended
+ * si it can be portable:
+ *
+ * ("#4u%lu", (unsigned long)var)
+ *
+ * trace types:
+ *
+ * Serialization specific formats :
+ *
+ * Fixed size integers
+ * #1u     writes uint8_t
+ * #2u     writes uint16_t
+ * #4u     writes uint32_t
+ * #8u     writes uint64_t
+ * #1d     writes int8_t
+ * #2d     writes int16_t
+ * #4d     writes int32_t
+ * #8d     writes int64_t
+ * i.e.:
+ * #1u%lu #2u%lu #4d%lu #8d%lu #llu%hu #d%lu
+ *
+ * * Attributes:
+ *
+ * n:  (for network byte order)
+ * #ntracetype%ctype
+ *            is written in the trace in network byte order.
+ *
+ * i.e.: #bn4u%lu, #n%lu, #b%u
+ *
+ * TODO (eventually)
+ * Variable length sequence
+ * #a #tracetype1 #tracetype2 %array_ptr %elem_size %num_elems
+ *            In the trace:
+ *            #a specifies that this is a sequence
+ *            #tracetype1 is the type of elements in the sequence
+ *            #tracetype2 is the type of the element count
+ *            GCC input:
+ *            array_ptr is a pointer to an array that contains members of size
+ *            elem_size.
+ *            num_elems is the number of elements in the array.
+ * i.e.: #a #lu #lu %p %lu %u
+ *
+ * Callback
+ * #k         callback (taken from the probe data)
+ *            The following % arguments are exepected by the callback
+ *
+ * i.e.: #a #lu #lu #k %p
+ *
+ * Note: No conversion is done from floats to integers, nor from integers to
+ * floats between c types and trace types. float conversion from double to float
+ * or from float to double is also not supported.
+ *
+ * REMOVE
+ * %*b     expects sizeof(data), data
+ *         where sizeof(data) is 1, 2, 4 or 8
+ *
+ * Fixed length struct, union or array.
+ * FIXME: unable to extract those sizes statically.
+ * %*r     expects sizeof(*ptr), ptr
+ * %*.*r   expects sizeof(*ptr), __alignof__(*ptr), ptr
+ * struct and unions removed.
+ * Fixed length array:
+ * [%p]#a[len #tracetype]
+ * i.e.: [%p]#a[12 #lu]
+ *
+ * Variable length sequence
+ * %*.*:*v expects sizeof(*ptr), __alignof__(*ptr), elem_num, ptr
+ *         where elem_num is the number of elements in the sequence
+ */
+static inline const char *parse_trace_type(const char *fmt,
+		char *trace_size, enum ltt_type *trace_type,
+		unsigned long *attributes)
+{
+	int qualifier;		/* 'h', 'l', or 'L' for integer fields */
+				/* 'z' support added 23/7/1999 S.H.    */
+				/* 'z' changed to 'Z' --davidm 1/25/99 */
+				/* 't' added for ptrdiff_t */
+
+	/* parse attributes. */
+repeat:
+	switch (*fmt) {
+	case 'n':
+		*attributes |= LTT_ATTRIBUTE_NETWORK_BYTE_ORDER;
+		++fmt;
+		goto repeat;
+	}
+
+	/* get the conversion qualifier */
+	qualifier = -1;
+	if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L' ||
+	    *fmt == 'Z' || *fmt == 'z' || *fmt == 't' ||
+	    *fmt == 'S' || *fmt == '1' || *fmt == '2' ||
+	    *fmt == '4' || *fmt == 8) {
+		qualifier = *fmt;
+		++fmt;
+		if (qualifier == 'l' && *fmt == 'l') {
+			qualifier = 'L';
+			++fmt;
+		}
+	}
+
+	switch (*fmt) {
+	case 'c':
+		*trace_type = LTT_TYPE_UNSIGNED_INT;
+		*trace_size = sizeof(unsigned char);
+		goto parse_end;
+	case 's':
+		*trace_type = LTT_TYPE_STRING;
+		goto parse_end;
+	case 'p':
+		*trace_type = LTT_TYPE_UNSIGNED_INT;
+		*trace_size = sizeof(void *);
+		goto parse_end;
+	case 'd':
+	case 'i':
+		*trace_type = LTT_TYPE_SIGNED_INT;
+		break;
+	case 'o':
+	case 'u':
+	case 'x':
+	case 'X':
+		*trace_type = LTT_TYPE_UNSIGNED_INT;
+		break;
+	default:
+		if (!*fmt)
+			--fmt;
+		goto parse_end;
+	}
+	switch (qualifier) {
+	case 'L':
+		*trace_size = sizeof(long long);
+		break;
+	case 'l':
+		*trace_size = sizeof(long);
+		break;
+	case 'Z':
+	case 'z':
+		*trace_size = sizeof(size_t);
+		break;
+	case 't':
+		*trace_size = sizeof(ptrdiff_t);
+		break;
+	case 'h':
+		*trace_size = sizeof(short);
+		break;
+	case '1':
+		*trace_size = sizeof(uint8_t);
+		break;
+	case '2':
+		*trace_size = sizeof(uint16_t);
+		break;
+	case '4':
+		*trace_size = sizeof(uint32_t);
+		break;
+	case '8':
+		*trace_size = sizeof(uint64_t);
+		break;
+	default:
+		*trace_size = sizeof(int);
+	}
+
+parse_end:
+	return fmt;
+}
+
+/*
+ * Restrictions:
+ * Field width and precision are *not* supported.
+ * %n not supported.
+ */
+static inline const char *parse_c_type(const char *fmt,
+		char *c_size, enum ltt_type *c_type)
+{
+	int qualifier;		/* 'h', 'l', or 'L' for integer fields */
+				/* 'z' support added 23/7/1999 S.H.    */
+				/* 'z' changed to 'Z' --davidm 1/25/99 */
+				/* 't' added for ptrdiff_t */
+
+	/* process flags : ignore standard print formats for now. */
+repeat:
+	switch (*fmt) {
+	case '-':
+	case '+':
+	case ' ':
+	case '#':
+	case '0':
+		++fmt;
+		goto repeat;
+	}
+
+	/* get the conversion qualifier */
+	qualifier = -1;
+	if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L' ||
+	    *fmt == 'Z' || *fmt == 'z' || *fmt == 't' ||
+	    *fmt == 'S') {
+		qualifier = *fmt;
+		++fmt;
+		if (qualifier == 'l' && *fmt == 'l') {
+			qualifier = 'L';
+			++fmt;
+		}
+	}
+
+	switch (*fmt) {
+	case 'c':
+		*c_type = LTT_TYPE_UNSIGNED_INT;
+		*c_size = sizeof(unsigned char);
+		goto parse_end;
+	case 's':
+		*c_type = LTT_TYPE_STRING;
+		goto parse_end;
+	case 'p':
+		*c_type = LTT_TYPE_UNSIGNED_INT;
+		*c_size = sizeof(void *);
+		goto parse_end;
+	case 'd':
+	case 'i':
+		*c_type = LTT_TYPE_SIGNED_INT;
+		break;
+	case 'o':
+	case 'u':
+	case 'x':
+	case 'X':
+		*c_type = LTT_TYPE_UNSIGNED_INT;
+		break;
+	default:
+		if (!*fmt)
+			--fmt;
+		goto parse_end;
+	}
+	switch (qualifier) {
+	case 'L':
+		*c_size = sizeof(long long);
+		break;
+	case 'l':
+		*c_size = sizeof(long);
+		break;
+	case 'Z':
+	case 'z':
+		*c_size = sizeof(size_t);
+		break;
+	case 't':
+		*c_size = sizeof(ptrdiff_t);
+		break;
+	case 'h':
+		*c_size = sizeof(short);
+		break;
+	default:
+		*c_size = sizeof(int);
+	}
+
+parse_end:
+	return fmt;
+}
+
+static inline size_t serialize_trace_data(struct rchan_buf *buf,
+		size_t buf_offset,
+		char trace_size, enum ltt_type trace_type,
+		char c_size, enum ltt_type c_type,
+		int *largest_align, va_list *args)
+{
+	union {
+		unsigned long v_ulong;
+		uint64_t v_uint64;
+		struct {
+			const char *s;
+			size_t len;
+		} v_string;
+	} tmp;
+
+	/*
+	 * Be careful about sign extension here.
+	 * Sign extension is done with the destination (trace) type.
+	 */
+	switch (trace_type) {
+	case LTT_TYPE_SIGNED_INT:
+		switch (c_size) {
+		case 1:
+			tmp.v_ulong = (long)(int8_t)va_arg(*args, int);
+			break;
+		case 2:
+			tmp.v_ulong = (long)(int16_t)va_arg(*args, int);
+			break;
+		case 4:
+			tmp.v_ulong = (long)(int32_t)va_arg(*args, int);
+			break;
+		case 8:
+			tmp.v_uint64 = va_arg(*args, int64_t);
+			break;
+		default:
+			BUG();
+		}
+		break;
+	case LTT_TYPE_UNSIGNED_INT:
+		switch (c_size) {
+		case 1:
+			tmp.v_ulong = (unsigned long)(uint8_t)
+					va_arg(*args, unsigned int);
+			break;
+		case 2:
+			tmp.v_ulong = (unsigned long)(uint16_t)
+					va_arg(*args, unsigned int);
+			break;
+		case 4:
+			tmp.v_ulong = (unsigned long)(uint32_t)
+					va_arg(*args, unsigned int);
+			break;
+		case 8:
+			tmp.v_uint64 = va_arg(*args, uint64_t);
+			break;
+		default:
+			BUG();
+		}
+		break;
+	case LTT_TYPE_STRING:
+		tmp.v_string.s = va_arg(*args, const char *);
+		if ((unsigned long)tmp.v_string.s < PAGE_SIZE)
+			tmp.v_string.s = "<NULL>";
+		tmp.v_string.len = strlen(tmp.v_string.s)+1;
+		if (buf)
+			ltt_relay_write(buf, buf_offset, tmp.v_string.s,
+				tmp.v_string.len);
+		buf_offset += tmp.v_string.len;
+		goto copydone;
+	default:
+		BUG();
+	}
+
+	/*
+	 * If trace_size is lower or equal to 4 bytes, there is no sign
+	 * extension to do because we are already encoded in a long. Therefore,
+	 * we can combine signed and unsigned ops. 4 bytes float also works
+	 * with this, because we do a simple copy of 4 bytes into 4 bytes
+	 * without manipulation (and we do not support conversion from integers
+	 * to floats).
+	 * It is also the case if c_size is 8 bytes, which is the largest
+	 * possible integer.
+	 */
+	if (ltt_get_alignment()) {
+		buf_offset += ltt_align(buf_offset, trace_size);
+		if (largest_align)
+			*largest_align = max_t(int, *largest_align, trace_size);
+	}
+	if (trace_size <= 4 || c_size == 8) {
+		if (buf) {
+			switch (trace_size) {
+			case 1:
+				if (c_size == 8)
+					ltt_relay_write(buf, buf_offset,
+					(uint8_t[]){ (uint8_t)tmp.v_uint64 },
+					sizeof(uint8_t));
+				else
+					ltt_relay_write(buf, buf_offset,
+					(uint8_t[]){ (uint8_t)tmp.v_ulong },
+					sizeof(uint8_t));
+				break;
+			case 2:
+				if (c_size == 8)
+					ltt_relay_write(buf, buf_offset,
+					(uint16_t[]){ (uint16_t)tmp.v_uint64 },
+					sizeof(uint16_t));
+				else
+					ltt_relay_write(buf, buf_offset,
+					(uint16_t[]){ (uint16_t)tmp.v_ulong },
+					sizeof(uint16_t));
+				break;
+			case 4:
+				if (c_size == 8)
+					ltt_relay_write(buf, buf_offset,
+					(uint32_t[]){ (uint32_t)tmp.v_uint64 },
+					sizeof(uint32_t));
+				else
+					ltt_relay_write(buf, buf_offset,
+					(uint32_t[]){ (uint32_t)tmp.v_ulong },
+					sizeof(uint32_t));
+				break;
+			case 8:
+				/*
+				 * c_size cannot be other than 8 here because
+				 * trace_size > 4.
+				 */
+				ltt_relay_write(buf, buf_offset,
+				(uint64_t[]){ (uint64_t)tmp.v_uint64 },
+				sizeof(uint64_t));
+				break;
+			default:
+				BUG();
+			}
+		}
+		buf_offset += trace_size;
+		goto copydone;
+	} else {
+		/*
+		 * Perform sign extension.
+		 */
+		if (buf) {
+			switch (trace_type) {
+			case LTT_TYPE_SIGNED_INT:
+				ltt_relay_write(buf, buf_offset,
+					(int64_t[]){ (int64_t)tmp.v_ulong },
+					sizeof(int64_t));
+				break;
+			case LTT_TYPE_UNSIGNED_INT:
+				ltt_relay_write(buf, buf_offset,
+					(uint64_t[]){ (uint64_t)tmp.v_ulong },
+					sizeof(uint64_t));
+				break;
+			default:
+				BUG();
+			}
+		}
+		buf_offset += trace_size;
+		goto copydone;
+	}
+
+copydone:
+	return buf_offset;
+}
+
+notrace size_t ltt_serialize_data(struct rchan_buf *buf, size_t buf_offset,
+			struct ltt_serialize_closure *closure,
+			void *serialize_private, int *largest_align,
+			const char *fmt, va_list *args)
+{
+	char trace_size = 0, c_size = 0;	/*
+						 * 0 (unset), 1, 2, 4, 8 bytes.
+						 */
+	enum ltt_type trace_type = LTT_TYPE_NONE, c_type = LTT_TYPE_NONE;
+	unsigned long attributes = 0;
+
+	for (; *fmt ; ++fmt) {
+		switch (*fmt) {
+		case '#':
+			/* tracetypes (#) */
+			++fmt;			/* skip first '#' */
+			if (*fmt == '#')	/* Escaped ## */
+				break;
+			attributes = 0;
+			fmt = parse_trace_type(fmt, &trace_size, &trace_type,
+				&attributes);
+			break;
+		case '%':
+			/* c types (%) */
+			++fmt;			/* skip first '%' */
+			if (*fmt == '%')	/* Escaped %% */
+				break;
+			fmt = parse_c_type(fmt, &c_size, &c_type);
+			/*
+			 * Output c types if no trace types has been
+			 * specified.
+			 */
+			if (!trace_size)
+				trace_size = c_size;
+			if (trace_type == LTT_TYPE_NONE)
+				trace_type = c_type;
+			if (c_type == LTT_TYPE_STRING)
+				trace_type = LTT_TYPE_STRING;
+			/* perform trace write */
+			buf_offset = serialize_trace_data(buf,
+						buf_offset, trace_size,
+						trace_type, c_size, c_type,
+						largest_align, args);
+			trace_size = 0;
+			c_size = 0;
+			trace_type = LTT_TYPE_NONE;
+			c_size = LTT_TYPE_NONE;
+			attributes = 0;
+			break;
+			/* default is to skip the text, doing nothing */
+		}
+	}
+	return buf_offset;
+}
+EXPORT_SYMBOL_GPL(ltt_serialize_data);
+
+/*
+ * Calculate data size
+ * Assume that the padding for alignment starts at a sizeof(void *) address.
+ */
+static notrace size_t ltt_get_data_size(struct ltt_serialize_closure *closure,
+				void *serialize_private, int *largest_align,
+				const char *fmt, va_list *args)
+{
+	ltt_serialize_cb cb = closure->callbacks[0];
+	closure->cb_idx = 0;
+	return (size_t)cb(NULL, 0, closure, serialize_private,
+				largest_align, fmt, args);
+}
+
+static notrace
+void ltt_write_event_data(struct rchan_buf *buf, size_t buf_offset,
+				struct ltt_serialize_closure *closure,
+				void *serialize_private, int largest_align,
+				const char *fmt, va_list *args)
+{
+	ltt_serialize_cb cb = closure->callbacks[0];
+	closure->cb_idx = 0;
+	buf_offset += ltt_align(buf_offset, largest_align);
+	cb(buf, buf_offset, closure, serialize_private, NULL, fmt, args);
+}
+
+
+notrace void ltt_vtrace(const struct marker *mdata, void *probe_data,
+			void *call_data, const char *fmt, va_list *args)
+{
+	int largest_align, ret;
+	struct ltt_active_marker *pdata;
+	uint16_t eID;
+	size_t data_size, slot_size;
+	unsigned int chan_index;
+	struct ltt_channel_struct *channel;
+	struct ltt_trace_struct *trace, *dest_trace = NULL;
+	struct rchan_buf *buf;
+	void *transport_data;
+	uint64_t tsc;
+	long buf_offset;
+	va_list args_copy;
+	struct ltt_serialize_closure closure;
+	struct ltt_probe_private_data *private_data = call_data;
+	void *serialize_private = NULL;
+	int cpu;
+	unsigned int rflags;
+
+	/*
+	 * This test is useful for quickly exiting static tracing when no trace
+	 * is active. We expect to have an active trace when we get here.
+	 */
+	if (unlikely(ltt_traces.num_active_traces == 0))
+		return;
+
+	rcu_read_lock_sched_notrace();
+	cpu = smp_processor_id();
+	__get_cpu_var(ltt_nesting)++;
+
+	pdata = (struct ltt_active_marker *)probe_data;
+	eID = mdata->event_id;
+	chan_index = mdata->channel_id;
+	closure.callbacks = pdata->probe->callbacks;
+
+	if (unlikely(private_data)) {
+		dest_trace = private_data->trace;
+		if (private_data->serializer)
+			closure.callbacks = &private_data->serializer;
+		serialize_private = private_data->serialize_private;
+	}
+
+	va_copy(args_copy, *args);
+	/*
+	 * Assumes event payload to start on largest_align alignment.
+	 */
+	largest_align = 1;	/* must be non-zero for ltt_align */
+	data_size = ltt_get_data_size(&closure, serialize_private,
+					&largest_align, fmt, &args_copy);
+	largest_align = min_t(int, largest_align, sizeof(void *));
+	va_end(args_copy);
+
+	/* Iterate on each trace */
+	list_for_each_entry_rcu(trace, &ltt_traces.head, list) {
+		/*
+		 * Expect the filter to filter out events. If we get here,
+		 * we went through tracepoint activation as a first step.
+		 */
+		if (unlikely(dest_trace && trace != dest_trace))
+			continue;
+		if (unlikely(!trace->active))
+			continue;
+		if (unlikely(!ltt_run_filter(trace, eID)))
+			continue;
+#ifdef CONFIG_LTT_DEBUG_EVENT_SIZE
+		rflags = LTT_RFLAG_ID_SIZE;
+#else
+		if (unlikely(eID >= LTT_FREE_EVENTS))
+			rflags = LTT_RFLAG_ID;
+		else
+			rflags = 0;
+#endif
+		/*
+		 * Skip channels added after trace creation.
+		 */
+		if (unlikely(chan_index >= trace->nr_channels))
+			continue;
+		channel = &trace->channels[chan_index];
+		if (!channel->active)
+			continue;
+
+		/* reserve space : header and data */
+		ret = ltt_reserve_slot(trace, channel, &transport_data,
+					data_size, &slot_size, &buf_offset,
+					&tsc, &rflags,
+					largest_align, cpu);
+		if (unlikely(ret < 0))
+			continue; /* buffer full */
+
+		va_copy(args_copy, *args);
+		/* FIXME : could probably encapsulate transport better. */
+		buf = ((struct rchan *)channel->trans_channel_data)->buf[cpu];
+		/* Out-of-order write : header and data */
+		buf_offset = ltt_write_event_header(trace,
+					channel, buf, buf_offset,
+					eID, data_size, tsc, rflags);
+		ltt_write_event_data(buf, buf_offset, &closure,
+					serialize_private,
+					largest_align, fmt, &args_copy);
+		va_end(args_copy);
+		/* Out-of-order commit */
+		ltt_commit_slot(channel, &transport_data, buf_offset,
+				slot_size);
+	}
+	__get_cpu_var(ltt_nesting)--;
+	rcu_read_unlock_sched_notrace();
+}
+EXPORT_SYMBOL_GPL(ltt_vtrace);
+
+notrace void ltt_trace(const struct marker *mdata, void *probe_data,
+		       void *call_data, const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	ltt_vtrace(mdata, probe_data, call_data, fmt, &args);
+	va_end(args);
+}
+EXPORT_SYMBOL_GPL(ltt_trace);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Linux Trace Toolkit Next Generation Serializer");

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/