X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;ds=sidebyside;f=src%2Fbin%2Flttng-sessiond%2Fust-metadata.cpp;fp=src%2Fbin%2Flttng-sessiond%2Fust-metadata.cpp;h=abe473f27ce78c6032f4de2b5d1bc869aaa31a0b;hb=7966af5763c4aaca39df9bbfa9277ff15715c720;hp=0000000000000000000000000000000000000000;hpb=3a5f70173aa04d11ccb22694d5d31a702cad33ab;p=lttng-tools.git

diff --git a/src/bin/lttng-sessiond/ust-metadata.cpp b/src/bin/lttng-sessiond/ust-metadata.cpp
new file mode 100644
index 000000000..abe473f27
--- /dev/null
+++ b/src/bin/lttng-sessiond/ust-metadata.cpp
@@ -0,0 +1,1344 @@
+/*
+ * Copyright (C) 2010-2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ *
+ */
+
+#define _LGPL_SOURCE
+#include <stdint.h>
+#include <string.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <limits.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <common/common.h>
+#include <common/time.h>
+
+#include "ust-registry.h"
+#include "ust-clock.h"
+#include "ust-app.h"
+
+#ifndef max_t
+#define max_t(type, a, b)	((type) ((a) > (b) ? (a) : (b)))
+#endif
+
+#define NR_CLOCK_OFFSET_SAMPLES		10
+
+struct offset_sample {
+	int64_t offset;			/* correlation offset */
+	uint64_t measure_delta;		/* lower is better */
+};
+
+static
+int _lttng_field_statedump(struct ust_registry_session *session,
+		const struct lttng_ust_ctl_field *fields, size_t nr_fields,
+		size_t *iter_field, size_t nesting);
+
+static inline
+int get_count_order(unsigned int count)
+{
+	int order;
+
+	order = lttng_fls(count) - 1;
+	if (count & (count - 1)) {
+		order++;
+	}
+	LTTNG_ASSERT(order >= 0);
+	return order;
+}
+
+/*
+ * Returns offset where to write in metadata array, or negative error value on error.
+ */
+static
+ssize_t metadata_reserve(struct ust_registry_session *session, size_t len)
+{
+	size_t new_len = session->metadata_len + len;
+	size_t new_alloc_len = new_len;
+	size_t old_alloc_len = session->metadata_alloc_len;
+	ssize_t ret;
+
+	if (new_alloc_len > (UINT32_MAX >> 1))
+		return -EINVAL;
+	if ((old_alloc_len << 1) > (UINT32_MAX >> 1))
+		return -EINVAL;
+
+	if (new_alloc_len > old_alloc_len) {
+		char *newptr;
+
+		new_alloc_len =
+			max_t(size_t, 1U << get_count_order(new_alloc_len), old_alloc_len << 1);
+		newptr = (char *) realloc(session->metadata, new_alloc_len);
+		if (!newptr)
+			return -ENOMEM;
+		session->metadata = newptr;
+		/* We zero directly the memory from start of allocation. */
+		memset(&session->metadata[old_alloc_len], 0, new_alloc_len - old_alloc_len);
+		session->metadata_alloc_len = new_alloc_len;
+	}
+	ret = session->metadata_len;
+	session->metadata_len += len;
+	return ret;
+}
+
+static
+int metadata_file_append(struct ust_registry_session *session,
+		const char *str, size_t len)
+{
+	ssize_t written;
+
+	if (session->metadata_fd < 0) {
+		return 0;
+	}
+	/* Write to metadata file */
+	written = lttng_write(session->metadata_fd, str, len);
+	if (written != len) {
+		return -1;
+	}
+	return 0;
+}
+
+/*
+ * We have exclusive access to our metadata buffer (protected by the
+ * ust_lock), so we can do racy operations such as looking for
+ * remaining space left in packet and write, since mutual exclusion
+ * protects us from concurrent writes.
+ */
+static
+int lttng_metadata_printf(struct ust_registry_session *session,
+		const char *fmt, ...)
+{
+	char *str = NULL;
+	size_t len;
+	va_list ap;
+	ssize_t offset;
+	int ret;
+
+	va_start(ap, fmt);
+	ret = vasprintf(&str, fmt, ap);
+	va_end(ap);
+	if (ret < 0)
+		return -ENOMEM;
+
+	len = strlen(str);
+	offset = metadata_reserve(session, len);
+	if (offset < 0) {
+		ret = offset;
+		goto end;
+	}
+	memcpy(&session->metadata[offset], str, len);
+	ret = metadata_file_append(session, str, len);
+	if (ret) {
+		PERROR("Error appending to metadata file");
+		goto end;
+	}
+	DBG3("Append to metadata: \"%s\"", str);
+	ret = 0;
+
+end:
+	free(str);
+	return ret;
+}
+
+static
+int print_tabs(struct ust_registry_session *session, size_t nesting)
+{
+	size_t i;
+
+	for (i = 0; i < nesting; i++) {
+		int ret;
+
+		ret = lttng_metadata_printf(session, "	");
+		if (ret) {
+			return ret;
+		}
+	}
+	return 0;
+}
+
+static
+void sanitize_ctf_identifier(char *out, const char *in)
+{
+	size_t i;
+
+	for (i = 0; i < LTTNG_UST_ABI_SYM_NAME_LEN; i++) {
+		switch (in[i]) {
+		case '.':
+		case '$':
+		case ':':
+			out[i] = '_';
+			break;
+		default:
+			out[i] = in[i];
+		}
+	}
+}
+
+static
+int print_escaped_ctf_string(struct ust_registry_session *session, const char *string)
+{
+	int ret = 0;
+	size_t i;
+	char cur;
+
+	i = 0;
+	cur = string[i];
+	while (cur != '\0') {
+		switch (cur) {
+		case '\n':
+			ret = lttng_metadata_printf(session, "%s", "\\n");
+			break;
+		case '\\':
+		case '"':
+			ret = lttng_metadata_printf(session, "%c", '\\');
+			if (ret) {
+				goto error;
+			}
+			/* We still print the current char */
+			/* Fallthrough */
+		default:
+			ret = lttng_metadata_printf(session, "%c", cur);
+			break;
+		}
+
+		if (ret) {
+			goto error;
+		}
+
+		cur = string[++i];
+	}
+error:
+	return ret;
+}
+
+/* Called with session registry mutex held. */
+static
+int ust_metadata_enum_statedump(struct ust_registry_session *session,
+		const char *enum_name,
+		uint64_t enum_id,
+		const struct lttng_ust_ctl_integer_type *container_type,
+		const char *field_name, size_t *iter_field, size_t nesting)
+{
+	struct ust_registry_enum *reg_enum;
+	const struct lttng_ust_ctl_enum_entry *entries;
+	size_t nr_entries;
+	int ret = 0;
+	size_t i;
+	char identifier[LTTNG_UST_ABI_SYM_NAME_LEN];
+
+	rcu_read_lock();
+	reg_enum = ust_registry_lookup_enum_by_id(session, enum_name, enum_id);
+	rcu_read_unlock();
+	/* reg_enum can still be used because session registry mutex is held. */
+	if (!reg_enum) {
+		ret = -ENOENT;
+		goto end;
+	}
+	entries = reg_enum->entries;
+	nr_entries = reg_enum->nr_entries;
+
+	ret = print_tabs(session, nesting);
+	if (ret) {
+		goto end;
+	}
+	ret = lttng_metadata_printf(session,
+		"enum : integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u; } {\n",
+		container_type->size,
+		container_type->alignment,
+		container_type->signedness,
+		(container_type->encoding == lttng_ust_ctl_encode_none)
+			? "none"
+			: (container_type->encoding == lttng_ust_ctl_encode_UTF8)
+				? "UTF8"
+				: "ASCII",
+		container_type->base);
+	if (ret) {
+	        goto end;
+	}
+	nesting++;
+	/* Dump all entries */
+	for (i = 0; i < nr_entries; i++) {
+		const struct lttng_ust_ctl_enum_entry *entry = &entries[i];
+		int j, len;
+
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		ret = lttng_metadata_printf(session,
+				"\"");
+		if (ret) {
+			goto end;
+		}
+		len = strlen(entry->string);
+		/* Escape the character '"' */
+		for (j = 0; j < len; j++) {
+			char c = entry->string[j];
+
+			switch (c) {
+			case '"':
+				ret = lttng_metadata_printf(session,
+						"\\\"");
+				break;
+			case '\\':
+				ret = lttng_metadata_printf(session,
+						"\\\\");
+				break;
+			default:
+				ret = lttng_metadata_printf(session,
+						"%c", c);
+				break;
+			}
+			if (ret) {
+				goto end;
+			}
+		}
+		ret = lttng_metadata_printf(session, "\"");
+		if (ret) {
+			goto end;
+		}
+
+		if (entry->u.extra.options &
+				LTTNG_UST_CTL_UST_ENUM_ENTRY_OPTION_IS_AUTO) {
+			ret = lttng_metadata_printf(session, ",\n");
+			if (ret) {
+				goto end;
+			}
+		} else {
+			ret = lttng_metadata_printf(session,
+					" = ");
+			if (ret) {
+				goto end;
+			}
+
+			if (entry->start.signedness) {
+				ret = lttng_metadata_printf(session,
+					"%lld", (long long) entry->start.value);
+			} else {
+				ret = lttng_metadata_printf(session,
+					"%llu", entry->start.value);
+			}
+			if (ret) {
+				goto end;
+			}
+
+			if (entry->start.signedness == entry->end.signedness &&
+					entry->start.value ==
+						entry->end.value) {
+				ret = lttng_metadata_printf(session, ",\n");
+			} else {
+				if (entry->end.signedness) {
+					ret = lttng_metadata_printf(session,
+						" ... %lld,\n",
+						(long long) entry->end.value);
+				} else {
+					ret = lttng_metadata_printf(session,
+						" ... %llu,\n",
+						entry->end.value);
+				}
+			}
+			if (ret) {
+				goto end;
+			}
+		}
+	}
+	nesting--;
+	sanitize_ctf_identifier(identifier, field_name);
+	ret = print_tabs(session, nesting);
+	if (ret) {
+		goto end;
+	}
+	ret = lttng_metadata_printf(session, "} _%s;\n",
+			identifier);
+end:
+	(*iter_field)++;
+	return ret;
+}
+
+static
+int _lttng_variant_statedump(struct ust_registry_session *session,
+		uint32_t nr_choices, const char *tag_name,
+		uint32_t alignment,
+		const struct lttng_ust_ctl_field *fields, size_t nr_fields,
+		size_t *iter_field, size_t nesting)
+{
+	const struct lttng_ust_ctl_field *variant = &fields[*iter_field];
+	uint32_t i;
+	int ret;
+	char identifier[LTTNG_UST_ABI_SYM_NAME_LEN];
+
+	if (variant->type.atype != lttng_ust_ctl_atype_variant) {
+		ret = -EINVAL;
+		goto end;
+	}
+	(*iter_field)++;
+	sanitize_ctf_identifier(identifier, tag_name);
+	if (alignment) {
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		ret = lttng_metadata_printf(session,
+		"struct { } align(%u) _%s_padding;\n",
+				alignment * CHAR_BIT,
+				variant->name);
+		if (ret) {
+			goto end;
+		}
+	}
+	ret = print_tabs(session, nesting);
+	if (ret) {
+		goto end;
+	}
+	ret = lttng_metadata_printf(session,
+			"variant <_%s> {\n",
+			identifier);
+	if (ret) {
+		goto end;
+	}
+
+	for (i = 0; i < nr_choices; i++) {
+		if (*iter_field >= nr_fields) {
+			ret = -EOVERFLOW;
+			goto end;
+		}
+		ret = _lttng_field_statedump(session,
+				fields, nr_fields,
+				iter_field, nesting + 1);
+		if (ret) {
+			goto end;
+		}
+	}
+	sanitize_ctf_identifier(identifier, variant->name);
+	ret = print_tabs(session, nesting);
+	if (ret) {
+		goto end;
+	}
+	ret = lttng_metadata_printf(session,
+			"} _%s;\n",
+			identifier);
+	if (ret) {
+		goto end;
+	}
+end:
+	return ret;
+}
+
+static
+int _lttng_field_statedump(struct ust_registry_session *session,
+		const struct lttng_ust_ctl_field *fields, size_t nr_fields,
+		size_t *iter_field, size_t nesting)
+{
+	int ret = 0;
+	const char *bo_be = " byte_order = be;";
+	const char *bo_le = " byte_order = le;";
+	const char *bo_native = "";
+	const char *bo_reverse;
+	const struct lttng_ust_ctl_field *field;
+
+	if (*iter_field >= nr_fields) {
+		ret = -EOVERFLOW;
+		goto end;
+	}
+	field = &fields[*iter_field];
+
+	if (session->byte_order == BIG_ENDIAN) {
+		bo_reverse = bo_le;
+	} else {
+		bo_reverse = bo_be;
+	}
+
+	switch (field->type.atype) {
+	case lttng_ust_ctl_atype_integer:
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		ret = lttng_metadata_printf(session,
+			"integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s;\n",
+			field->type.u.integer.size,
+			field->type.u.integer.alignment,
+			field->type.u.integer.signedness,
+			(field->type.u.integer.encoding == lttng_ust_ctl_encode_none)
+				? "none"
+				: (field->type.u.integer.encoding == lttng_ust_ctl_encode_UTF8)
+					? "UTF8"
+					: "ASCII",
+			field->type.u.integer.base,
+			field->type.u.integer.reverse_byte_order ? bo_reverse : bo_native,
+			field->name);
+		(*iter_field)++;
+		break;
+	case lttng_ust_ctl_atype_enum:
+		ret = ust_metadata_enum_statedump(session,
+			field->type.u.legacy.basic.enumeration.name,
+			field->type.u.legacy.basic.enumeration.id,
+			&field->type.u.legacy.basic.enumeration.container_type,
+			field->name, iter_field, nesting);
+		break;
+	case lttng_ust_ctl_atype_float:
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		ret = lttng_metadata_printf(session,
+			"floating_point { exp_dig = %u; mant_dig = %u; align = %u;%s } _%s;\n",
+			field->type.u._float.exp_dig,
+			field->type.u._float.mant_dig,
+			field->type.u._float.alignment,
+			field->type.u._float.reverse_byte_order ? bo_reverse : bo_native,
+			field->name);
+		(*iter_field)++;
+		break;
+	case lttng_ust_ctl_atype_array:
+	{
+		const struct lttng_ust_ctl_basic_type *elem_type;
+
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		elem_type = &field->type.u.legacy.array.elem_type;
+		/* Only integers are currently supported in arrays. */
+		if (elem_type->atype != lttng_ust_ctl_atype_integer) {
+			ret = -EINVAL;
+			goto end;
+		}
+		ret = lttng_metadata_printf(session,
+			"integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[%u];\n",
+			elem_type->u.basic.integer.size,
+			elem_type->u.basic.integer.alignment,
+			elem_type->u.basic.integer.signedness,
+			(elem_type->u.basic.integer.encoding == lttng_ust_ctl_encode_none)
+				? "none"
+				: (elem_type->u.basic.integer.encoding == lttng_ust_ctl_encode_UTF8)
+					? "UTF8"
+					: "ASCII",
+			elem_type->u.basic.integer.base,
+			elem_type->u.basic.integer.reverse_byte_order ? bo_reverse : bo_native,
+			field->name, field->type.u.legacy.array.length);
+		(*iter_field)++;
+		break;
+	}
+	case lttng_ust_ctl_atype_array_nestable:
+	{
+		uint32_t array_length;
+		const struct lttng_ust_ctl_field *array_nestable;
+		const struct lttng_ust_ctl_type *elem_type;
+
+		array_length = field->type.u.array_nestable.length;
+		(*iter_field)++;
+
+		if (*iter_field >= nr_fields) {
+			ret = -EOVERFLOW;
+			goto end;
+		}
+		array_nestable = &fields[*iter_field];
+		elem_type = &array_nestable->type;
+
+		/* Only integers are currently supported in arrays. */
+		if (elem_type->atype != lttng_ust_ctl_atype_integer) {
+			ret = -EINVAL;
+			goto end;
+		}
+
+		if (field->type.u.array_nestable.alignment) {
+			ret = print_tabs(session, nesting);
+			if (ret) {
+				goto end;
+			}
+			ret = lttng_metadata_printf(session,
+				"struct { } align(%u) _%s_padding;\n",
+				field->type.u.array_nestable.alignment * CHAR_BIT,
+				field->name);
+			if (ret) {
+				goto end;
+			}
+		}
+
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		ret = lttng_metadata_printf(session,
+			"integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[%u];\n",
+			elem_type->u.integer.size,
+			elem_type->u.integer.alignment,
+			elem_type->u.integer.signedness,
+			(elem_type->u.integer.encoding == lttng_ust_ctl_encode_none)
+				? "none"
+				: (elem_type->u.integer.encoding == lttng_ust_ctl_encode_UTF8)
+					? "UTF8"
+					: "ASCII",
+			elem_type->u.integer.base,
+			elem_type->u.integer.reverse_byte_order ? bo_reverse : bo_native,
+			field->name, array_length);
+		(*iter_field)++;
+		break;
+	}
+	case lttng_ust_ctl_atype_sequence:
+	{
+		const struct lttng_ust_ctl_basic_type *elem_type;
+		const struct lttng_ust_ctl_basic_type *length_type;
+
+		elem_type = &field->type.u.legacy.sequence.elem_type;
+		length_type = &field->type.u.legacy.sequence.length_type;
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+
+		/* Only integers are currently supported in sequences. */
+		if (elem_type->atype != lttng_ust_ctl_atype_integer) {
+			ret = -EINVAL;
+			goto end;
+		}
+
+		ret = lttng_metadata_printf(session,
+			"integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } __%s_length;\n",
+			length_type->u.basic.integer.size,
+			(unsigned int) length_type->u.basic.integer.alignment,
+			length_type->u.basic.integer.signedness,
+			(length_type->u.basic.integer.encoding == lttng_ust_ctl_encode_none)
+				? "none"
+				: ((length_type->u.basic.integer.encoding == lttng_ust_ctl_encode_UTF8)
+					? "UTF8"
+					: "ASCII"),
+			length_type->u.basic.integer.base,
+			length_type->u.basic.integer.reverse_byte_order ? bo_reverse : bo_native,
+			field->name);
+		if (ret) {
+			goto end;
+		}
+
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		ret = lttng_metadata_printf(session,
+			"integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[ __%s_length ];\n",
+			elem_type->u.basic.integer.size,
+			(unsigned int) elem_type->u.basic.integer.alignment,
+			elem_type->u.basic.integer.signedness,
+			(elem_type->u.basic.integer.encoding == lttng_ust_ctl_encode_none)
+				? "none"
+				: ((elem_type->u.basic.integer.encoding == lttng_ust_ctl_encode_UTF8)
+					? "UTF8"
+					: "ASCII"),
+			elem_type->u.basic.integer.base,
+			elem_type->u.basic.integer.reverse_byte_order ? bo_reverse : bo_native,
+			field->name,
+			field->name);
+		(*iter_field)++;
+		break;
+	}
+	case lttng_ust_ctl_atype_sequence_nestable:
+	{
+		const struct lttng_ust_ctl_field *sequence_nestable;
+		const struct lttng_ust_ctl_type *elem_type;
+
+		(*iter_field)++;
+		if (*iter_field >= nr_fields) {
+			ret = -EOVERFLOW;
+			goto end;
+		}
+		sequence_nestable = &fields[*iter_field];
+		elem_type = &sequence_nestable->type;
+
+		/* Only integers are currently supported in sequences. */
+		if (elem_type->atype != lttng_ust_ctl_atype_integer) {
+			ret = -EINVAL;
+			goto end;
+		}
+
+		if (field->type.u.sequence_nestable.alignment) {
+			ret = print_tabs(session, nesting);
+			if (ret) {
+				goto end;
+			}
+			ret = lttng_metadata_printf(session,
+				"struct { } align(%u) _%s_padding;\n",
+				field->type.u.sequence_nestable.alignment * CHAR_BIT,
+				field->name);
+			if (ret) {
+				goto end;
+			}
+		}
+
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		ret = lttng_metadata_printf(session,
+			"integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[ _%s ];\n",
+			elem_type->u.integer.size,
+			(unsigned int) elem_type->u.integer.alignment,
+			elem_type->u.integer.signedness,
+			(elem_type->u.integer.encoding == lttng_ust_ctl_encode_none)
+				? "none"
+				: ((elem_type->u.integer.encoding == lttng_ust_ctl_encode_UTF8)
+					? "UTF8"
+					: "ASCII"),
+			elem_type->u.integer.base,
+			elem_type->u.integer.reverse_byte_order ? bo_reverse : bo_native,
+			field->name,
+			field->type.u.sequence_nestable.length_name);
+		(*iter_field)++;
+		break;
+	}
+	case lttng_ust_ctl_atype_string:
+		/* Default encoding is UTF8 */
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		ret = lttng_metadata_printf(session,
+			"string%s _%s;\n",
+			field->type.u.string.encoding == lttng_ust_ctl_encode_ASCII ?
+				" { encoding = ASCII; }" : "",
+			field->name);
+		(*iter_field)++;
+		break;
+	case lttng_ust_ctl_atype_variant:
+		ret = _lttng_variant_statedump(session,
+				field->type.u.legacy.variant.nr_choices,
+				field->type.u.legacy.variant.tag_name,
+				0,
+				fields, nr_fields, iter_field, nesting);
+		if (ret) {
+			goto end;
+		}
+		break;
+	case lttng_ust_ctl_atype_variant_nestable:
+		ret = _lttng_variant_statedump(session,
+				field->type.u.variant_nestable.nr_choices,
+				field->type.u.variant_nestable.tag_name,
+				field->type.u.variant_nestable.alignment,
+				fields, nr_fields, iter_field, nesting);
+		if (ret) {
+			goto end;
+		}
+		break;
+	case lttng_ust_ctl_atype_struct:
+		if (field->type.u.legacy._struct.nr_fields != 0) {
+			/* Currently only 0-length structures are supported. */
+			ret = -EINVAL;
+			goto end;
+		}
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		ret = lttng_metadata_printf(session,
+			"struct {} _%s;\n",
+			field->name);
+		(*iter_field)++;
+		break;
+	case lttng_ust_ctl_atype_struct_nestable:
+		if (field->type.u.struct_nestable.nr_fields != 0) {
+			/* Currently only 0-length structures are supported. */
+			ret = -EINVAL;
+			goto end;
+		}
+		ret = print_tabs(session, nesting);
+		if (ret) {
+			goto end;
+		}
+		if (field->type.u.struct_nestable.alignment) {
+			ret = lttng_metadata_printf(session,
+				"struct {} align(%u) _%s;\n",
+				field->type.u.struct_nestable.alignment * CHAR_BIT,
+				field->name);
+			if (ret) {
+				goto end;
+			}
+		} else {
+			ret = lttng_metadata_printf(session,
+				"struct {} _%s;\n",
+				field->name);
+		}
+		(*iter_field)++;
+		break;
+	case lttng_ust_ctl_atype_enum_nestable:
+	{
+		const struct lttng_ust_ctl_field *container_field;
+		const struct lttng_ust_ctl_type *container_type;
+
+		(*iter_field)++;
+		if (*iter_field >= nr_fields) {
+			ret = -EOVERFLOW;
+			goto end;
+		}
+		container_field = &fields[*iter_field];
+		container_type = &container_field->type;
+
+		/* Only integers are supported as container types. */
+		if (container_type->atype != lttng_ust_ctl_atype_integer) {
+			ret = -EINVAL;
+			goto end;
+		}
+		ret = ust_metadata_enum_statedump(session,
+			field->type.u.enum_nestable.name,
+			field->type.u.enum_nestable.id,
+			&container_type->u.integer,
+			field->name, iter_field, nesting);
+		break;
+	}
+	default:
+		ret = -EINVAL;
+	}
+end:
+	return ret;
+}
+
+static
+int _lttng_context_metadata_statedump(struct ust_registry_session *session,
+		size_t nr_ctx_fields,
+		struct lttng_ust_ctl_field *ctx)
+{
+	int ret = 0;
+	size_t i = 0;
+
+	if (!ctx)
+		return 0;
+	for (;;) {
+		if (i >= nr_ctx_fields) {
+			break;
+		}
+		ret = _lttng_field_statedump(session, ctx,
+				nr_ctx_fields, &i, 2);
+		if (ret) {
+			break;
+		}
+	}
+	return ret;
+}
+
+static
+int _lttng_fields_metadata_statedump(struct ust_registry_session *session,
+		struct ust_registry_event *event)
+{
+	int ret = 0;
+	size_t i = 0;
+
+	for (;;) {
+		if (i >= event->nr_fields) {
+			break;
+		}
+		ret = _lttng_field_statedump(session, event->fields,
+				event->nr_fields, &i, 2);
+		if (ret) {
+			break;
+		}
+	}
+	return ret;
+}
+
+/*
+ * Should be called with session registry mutex held.
+ */
+int ust_metadata_event_statedump(struct ust_registry_session *session,
+		struct ust_registry_channel *chan,
+		struct ust_registry_event *event)
+{
+	int ret = 0;
+
+	/* Don't dump metadata events */
+	if (chan->chan_id == -1U)
+		return 0;
+
+	ret = lttng_metadata_printf(session,
+		"event {\n"
+		"	name = \"%s\";\n"
+		"	id = %u;\n"
+		"	stream_id = %u;\n",
+		event->name,
+		event->id,
+		chan->chan_id);
+	if (ret) {
+		goto end;
+	}
+
+	ret = lttng_metadata_printf(session,
+		"	loglevel = %d;\n",
+		event->loglevel_value);
+	if (ret) {
+		goto end;
+	}
+
+	if (event->model_emf_uri) {
+		ret = lttng_metadata_printf(session,
+			"	model.emf.uri = \"%s\";\n",
+			event->model_emf_uri);
+		if (ret) {
+			goto end;
+		}
+	}
+
+	ret = lttng_metadata_printf(session,
+		"	fields := struct {\n"
+		);
+	if (ret) {
+		goto end;
+	}
+
+	ret = _lttng_fields_metadata_statedump(session, event);
+	if (ret) {
+		goto end;
+	}
+
+	ret = lttng_metadata_printf(session,
+		"	};\n"
+		"};\n\n");
+	if (ret) {
+		goto end;
+	}
+	event->metadata_dumped = 1;
+
+end:
+	return ret;
+}
+
+/*
+ * Should be called with session registry mutex held.
+ */
+int ust_metadata_channel_statedump(struct ust_registry_session *session,
+		struct ust_registry_channel *chan)
+{
+	int ret = 0;
+
+	/* Don't dump metadata events */
+	if (chan->chan_id == -1U)
+		return 0;
+
+	if (!chan->header_type)
+		return -EINVAL;
+
+	ret = lttng_metadata_printf(session,
+		"stream {\n"
+		"	id = %u;\n"
+		"	event.header := %s;\n"
+		"	packet.context := struct packet_context;\n",
+		chan->chan_id,
+		chan->header_type == LTTNG_UST_CTL_CHANNEL_HEADER_COMPACT ?
+			"struct event_header_compact" :
+			"struct event_header_large");
+	if (ret) {
+		goto end;
+	}
+
+	if (chan->ctx_fields) {
+		ret = lttng_metadata_printf(session,
+			"	event.context := struct {\n");
+		if (ret) {
+			goto end;
+		}
+	}
+	ret = _lttng_context_metadata_statedump(session,
+		chan->nr_ctx_fields,
+		chan->ctx_fields);
+	if (ret) {
+		goto end;
+	}
+	if (chan->ctx_fields) {
+		ret = lttng_metadata_printf(session,
+			"	};\n");
+		if (ret) {
+			goto end;
+		}
+	}
+
+	ret = lttng_metadata_printf(session,
+		"};\n\n");
+	/* Flag success of metadata dump. */
+	chan->metadata_dumped = 1;
+
+end:
+	return ret;
+}
+
+static
+int _lttng_stream_packet_context_declare(struct ust_registry_session *session)
+{
+	return lttng_metadata_printf(session,
+		"struct packet_context {\n"
+		"	uint64_clock_monotonic_t timestamp_begin;\n"
+		"	uint64_clock_monotonic_t timestamp_end;\n"
+		"	uint64_t content_size;\n"
+		"	uint64_t packet_size;\n"
+		"	uint64_t packet_seq_num;\n"
+		"	unsigned long events_discarded;\n"
+		"	uint32_t cpu_id;\n"
+		"};\n\n"
+		);
+}
+
+/*
+ * Compact header:
+ * id: range: 0 - 30.
+ * id 31 is reserved to indicate an extended header.
+ *
+ * Large header:
+ * id: range: 0 - 65534.
+ * id 65535 is reserved to indicate an extended header.
+ */
+static
+int _lttng_event_header_declare(struct ust_registry_session *session)
+{
+	return lttng_metadata_printf(session,
+	"struct event_header_compact {\n"
+	"	enum : uint5_t { compact = 0 ... 30, extended = 31 } id;\n"
+	"	variant <id> {\n"
+	"		struct {\n"
+	"			uint27_clock_monotonic_t timestamp;\n"
+	"		} compact;\n"
+	"		struct {\n"
+	"			uint32_t id;\n"
+	"			uint64_clock_monotonic_t timestamp;\n"
+	"		} extended;\n"
+	"	} v;\n"
+	"} align(%u);\n"
+	"\n"
+	"struct event_header_large {\n"
+	"	enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;\n"
+	"	variant <id> {\n"
+	"		struct {\n"
+	"			uint32_clock_monotonic_t timestamp;\n"
+	"		} compact;\n"
+	"		struct {\n"
+	"			uint32_t id;\n"
+	"			uint64_clock_monotonic_t timestamp;\n"
+	"		} extended;\n"
+	"	} v;\n"
+	"} align(%u);\n\n",
+	session->uint32_t_alignment,
+	session->uint16_t_alignment
+	);
+}
+
+/*
+ * The offset between monotonic and realtime clock can be negative if
+ * the system sets the REALTIME clock to 0 after boot.
+ */
+static
+int measure_single_clock_offset(struct offset_sample *sample)
+{
+	uint64_t monotonic_avg, monotonic[2], measure_delta, realtime;
+	uint64_t tcf = trace_clock_freq();
+	struct timespec rts = { 0, 0 };
+	int ret;
+
+	monotonic[0] = trace_clock_read64();
+	ret = lttng_clock_gettime(CLOCK_REALTIME, &rts);
+	if (ret < 0) {
+		return ret;
+	}
+	monotonic[1] = trace_clock_read64();
+	measure_delta = monotonic[1] - monotonic[0];
+	if (measure_delta > sample->measure_delta) {
+		/*
+		 * Discard value if it took longer to read than the best
+		 * sample so far.
+		 */
+		return 0;
+	}
+	monotonic_avg = (monotonic[0] + monotonic[1]) >> 1;
+	realtime = (uint64_t) rts.tv_sec * tcf;
+	if (tcf == NSEC_PER_SEC) {
+		realtime += rts.tv_nsec;
+	} else {
+		realtime += (uint64_t) rts.tv_nsec * tcf / NSEC_PER_SEC;
+	}
+	sample->offset = (int64_t) realtime - monotonic_avg;
+	sample->measure_delta = measure_delta;
+	return 0;
+}
+
+/*
+ * Approximation of NTP time of day to clock monotonic correlation,
+ * taken at start of trace. Keep the measurement that took the less time
+ * to complete, thus removing imprecision caused by preemption.
+ * May return a negative offset.
+ */
+static
+int64_t measure_clock_offset(void)
+{
+	int i;
+	struct offset_sample offset_best_sample = {
+		.offset = 0,
+		.measure_delta = UINT64_MAX,
+	};
+
+	for (i = 0; i < NR_CLOCK_OFFSET_SAMPLES; i++) {
+		if (measure_single_clock_offset(&offset_best_sample)) {
+			return 0;
+		}
+	}
+	return offset_best_sample.offset;
+}
+
+static
+int print_metadata_session_information(struct ust_registry_session *registry)
+{
+	int ret;
+	struct ltt_session *session = NULL;
+	char creation_datetime[ISO8601_STR_LEN];
+
+	rcu_read_lock();
+	session = session_find_by_id(registry->tracing_id);
+	if (!session) {
+		ret = -1;
+		goto error;
+	}
+
+	/* Print the trace name */
+	ret = lttng_metadata_printf(registry, "	trace_name = \"");
+	if (ret) {
+		goto error;
+	}
+
+	/*
+	 * This is necessary since the creation time is present in the session
+	 * name when it is generated.
+	 */
+	if (session->has_auto_generated_name) {
+		ret = print_escaped_ctf_string(registry, DEFAULT_SESSION_NAME);
+	} else {
+		ret = print_escaped_ctf_string(registry, session->name);
+	}
+	if (ret) {
+		goto error;
+	}
+
+	ret = lttng_metadata_printf(registry, "\";\n");
+	if (ret) {
+		goto error;
+	}
+
+	/* Prepare creation time */
+	ret = time_to_iso8601_str(session->creation_time, creation_datetime,
+			sizeof(creation_datetime));
+	if (ret) {
+		goto error;
+	}
+
+	/* Output the reste of the information */
+	ret = lttng_metadata_printf(registry,
+			"	trace_creation_datetime = \"%s\";\n"
+			"	hostname = \"%s\";\n",
+			creation_datetime, session->hostname);
+	if (ret) {
+		goto error;
+	}
+
+error:
+	if (session) {
+		session_put(session);
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
+static
+int print_metadata_app_information(struct ust_registry_session *registry,
+		struct ust_app *app)
+{
+	int ret;
+	char datetime[ISO8601_STR_LEN];
+
+	if (!app) {
+		ret = 0;
+		goto end;
+	}
+
+	ret = time_to_iso8601_str(
+			app->registration_time, datetime, sizeof(datetime));
+	if (ret) {
+		goto end;
+	}
+
+	ret = lttng_metadata_printf(registry,
+			"	tracer_patchlevel = %u;\n"
+			"	vpid = %d;\n"
+			"	procname = \"%s\";\n"
+			"	vpid_datetime = \"%s\";\n",
+			app->version.patchlevel, (int) app->pid, app->name,
+			datetime);
+
+end:
+	return ret;
+}
+
+/*
+ * Should be called with session registry mutex held.
+ */
+int ust_metadata_session_statedump(struct ust_registry_session *session,
+		struct ust_app *app,
+		uint32_t major,
+		uint32_t minor)
+{
+	char uuid_s[LTTNG_UUID_STR_LEN],
+		clock_uuid_s[LTTNG_UUID_STR_LEN];
+	int ret = 0;
+
+	LTTNG_ASSERT(session);
+
+	lttng_uuid_to_str(session->uuid, uuid_s);
+
+	/* For crash ABI */
+	ret = lttng_metadata_printf(session,
+		"/* CTF %u.%u */\n\n",
+		CTF_SPEC_MAJOR,
+		CTF_SPEC_MINOR);
+	if (ret) {
+		goto end;
+	}
+
+	ret = lttng_metadata_printf(session,
+		"typealias integer { size = 8; align = %u; signed = false; } := uint8_t;\n"
+		"typealias integer { size = 16; align = %u; signed = false; } := uint16_t;\n"
+		"typealias integer { size = 32; align = %u; signed = false; } := uint32_t;\n"
+		"typealias integer { size = 64; align = %u; signed = false; } := uint64_t;\n"
+		"typealias integer { size = %u; align = %u; signed = false; } := unsigned long;\n"
+		"typealias integer { size = 5; align = 1; signed = false; } := uint5_t;\n"
+		"typealias integer { size = 27; align = 1; signed = false; } := uint27_t;\n"
+		"\n"
+		"trace {\n"
+		"	major = %u;\n"
+		"	minor = %u;\n"
+		"	uuid = \"%s\";\n"
+		"	byte_order = %s;\n"
+		"	packet.header := struct {\n"
+		"		uint32_t magic;\n"
+		"		uint8_t  uuid[16];\n"
+		"		uint32_t stream_id;\n"
+		"		uint64_t stream_instance_id;\n"
+		"	};\n"
+		"};\n\n",
+		session->uint8_t_alignment,
+		session->uint16_t_alignment,
+		session->uint32_t_alignment,
+		session->uint64_t_alignment,
+		session->bits_per_long,
+		session->long_alignment,
+		CTF_SPEC_MAJOR,
+		CTF_SPEC_MINOR,
+		uuid_s,
+		session->byte_order == BIG_ENDIAN ? "be" : "le"
+		);
+	if (ret) {
+		goto end;
+	}
+
+	ret = lttng_metadata_printf(session,
+		"env {\n"
+		"	domain = \"ust\";\n"
+		"	tracer_name = \"lttng-ust\";\n"
+		"	tracer_major = %u;\n"
+		"	tracer_minor = %u;\n"
+		"	tracer_buffering_scheme = \"%s\";\n"
+		"	tracer_buffering_id = %u;\n"
+		"	architecture_bit_width = %u;\n",
+		major,
+		minor,
+		app ? "pid" : "uid",
+		app ? (int) app->pid : (int) session->tracing_uid,
+		session->bits_per_long);
+	if (ret) {
+		goto end;
+	}
+
+	ret = print_metadata_session_information(session);
+	if (ret) {
+		goto end;
+	}
+
+	/*
+	 * If per-application registry, we can output extra information
+	 * about the application.
+	 */
+	ret = print_metadata_app_information(session, app);
+	if (ret) {
+		goto end;
+	}
+
+	ret = lttng_metadata_printf(session,
+		"};\n\n"
+		);
+	if (ret) {
+		goto end;
+	}
+
+	ret = lttng_metadata_printf(session,
+		"clock {\n"
+		"	name = \"%s\";\n",
+		trace_clock_name()
+		);
+	if (ret) {
+		goto end;
+	}
+
+	if (!trace_clock_uuid(clock_uuid_s)) {
+		ret = lttng_metadata_printf(session,
+			"	uuid = \"%s\";\n",
+			clock_uuid_s
+			);
+		if (ret) {
+			goto end;
+		}
+	}
+
+	ret = lttng_metadata_printf(session,
+		"	description = \"%s\";\n"
+		"	freq = %" PRIu64 "; /* Frequency, in Hz */\n"
+		"	/* clock value offset from Epoch is: offset * (1/freq) */\n"
+		"	offset = %" PRId64 ";\n"
+		"};\n\n",
+		trace_clock_description(),
+		trace_clock_freq(),
+		measure_clock_offset()
+		);
+	if (ret) {
+		goto end;
+	}
+
+	ret = lttng_metadata_printf(session,
+		"typealias integer {\n"
+		"	size = 27; align = 1; signed = false;\n"
+		"	map = clock.%s.value;\n"
+		"} := uint27_clock_monotonic_t;\n"
+		"\n"
+		"typealias integer {\n"
+		"	size = 32; align = %u; signed = false;\n"
+		"	map = clock.%s.value;\n"
+		"} := uint32_clock_monotonic_t;\n"
+		"\n"
+		"typealias integer {\n"
+		"	size = 64; align = %u; signed = false;\n"
+		"	map = clock.%s.value;\n"
+		"} := uint64_clock_monotonic_t;\n\n",
+		trace_clock_name(),
+		session->uint32_t_alignment,
+		trace_clock_name(),
+		session->uint64_t_alignment,
+		trace_clock_name()
+		);
+	if (ret) {
+		goto end;
+	}
+
+	ret = _lttng_stream_packet_context_declare(session);
+	if (ret) {
+		goto end;
+	}
+
+	ret = _lttng_event_header_declare(session);
+	if (ret) {
+		goto end;
+	}
+
+end:
+	return ret;
+}