[lttng-tools.git] / src / bin / lttng / commands / enable_channels.c

/*
 * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 */

#define _LGPL_SOURCE
#include <popt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <inttypes.h>
#include <assert.h>
#include <ctype.h>

#include <common/sessiond-comm/sessiond-comm.h>
#include <common/utils.h>
#include <common/mi-lttng.h>

#include <lttng/domain-internal.h>

#include "../command.h"
#include "../utils.h"


static struct lttng_channel chan_opts;
static char *opt_channels;
static int opt_kernel;
static char *opt_session_name;
static int opt_userspace;
static char *opt_output;
static int opt_buffer_uid;
static int opt_buffer_pid;
static int opt_buffer_global;
static struct {
	bool set;
	uint64_t interval;
} opt_monitor_timer;
static struct {
	bool set;
	int64_t value;
} opt_blocking_timeout;

static struct mi_writer *writer;

#ifdef LTTNG_EMBED_HELP
static const char help_msg[] =
#include <lttng-enable-channel.1.h>
;
#endif

enum {
	OPT_HELP = 1,
	OPT_DISCARD,
	OPT_OVERWRITE,
	OPT_SUBBUF_SIZE,
	OPT_NUM_SUBBUF,
	OPT_SWITCH_TIMER,
	OPT_MONITOR_TIMER,
	OPT_READ_TIMER,
	OPT_USERSPACE,
	OPT_LIST_OPTIONS,
	OPT_TRACEFILE_SIZE,
	OPT_TRACEFILE_COUNT,
	OPT_BLOCKING_TIMEOUT,
};

static struct lttng_handle *handle;

const char *output_mmap = "mmap";
const char *output_splice = "splice";

static struct poptOption long_options[] = {
	/* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
	{"help",           'h', POPT_ARG_NONE, 0, OPT_HELP, 0, 0},
	{"session",        's', POPT_ARG_STRING, &opt_session_name, 0, 0, 0},
	{"kernel",         'k', POPT_ARG_VAL, &opt_kernel, 1, 0, 0},
	{"userspace",      'u', POPT_ARG_NONE, 0, OPT_USERSPACE, 0, 0},
	{"discard",        0,   POPT_ARG_NONE, 0, OPT_DISCARD, 0, 0},
	{"overwrite",      0,   POPT_ARG_NONE, 0, OPT_OVERWRITE, 0, 0},
	{"subbuf-size",    0,   POPT_ARG_STRING, 0, OPT_SUBBUF_SIZE, 0, 0},
	{"num-subbuf",     0,   POPT_ARG_INT, 0, OPT_NUM_SUBBUF, 0, 0},
	{"switch-timer",   0,   POPT_ARG_INT, 0, OPT_SWITCH_TIMER, 0, 0},
	{"monitor-timer",  0,   POPT_ARG_INT, 0, OPT_MONITOR_TIMER, 0, 0},
	{"read-timer",     0,   POPT_ARG_INT, 0, OPT_READ_TIMER, 0, 0},
	{"list-options",   0, POPT_ARG_NONE, NULL, OPT_LIST_OPTIONS, NULL, NULL},
	{"output",         0,   POPT_ARG_STRING, &opt_output, 0, 0, 0},
	{"buffers-uid",    0,	POPT_ARG_VAL, &opt_buffer_uid, 1, 0, 0},
	{"buffers-pid",    0,	POPT_ARG_VAL, &opt_buffer_pid, 1, 0, 0},
	{"buffers-global", 0,	POPT_ARG_VAL, &opt_buffer_global, 1, 0, 0},
	{"tracefile-size", 'C',   POPT_ARG_INT, 0, OPT_TRACEFILE_SIZE, 0, 0},
	{"tracefile-count", 'W',   POPT_ARG_INT, 0, OPT_TRACEFILE_COUNT, 0, 0},
	{"blocking-timeout",     0,   POPT_ARG_INT, 0, OPT_BLOCKING_TIMEOUT, 0, 0},
	{0, 0, 0, 0, 0, 0, 0}
};

/*
 * Set default attributes depending on those already defined from the command
 * line.
 */
static void set_default_attr(struct lttng_domain *dom)
{
	struct lttng_channel_attr default_attr;

	memset(&default_attr, 0, sizeof(default_attr));

	/* Set attributes */
	lttng_channel_set_default_attr(dom, &default_attr);

	if (chan_opts.attr.overwrite == -1) {
		chan_opts.attr.overwrite = default_attr.overwrite;
	}
	if (chan_opts.attr.subbuf_size == -1) {
		chan_opts.attr.subbuf_size = default_attr.subbuf_size;
	}
	if (chan_opts.attr.num_subbuf == -1) {
		chan_opts.attr.num_subbuf = default_attr.num_subbuf;
	}
	if (chan_opts.attr.switch_timer_interval == -1) {
		chan_opts.attr.switch_timer_interval = default_attr.switch_timer_interval;
	}
	if (chan_opts.attr.read_timer_interval == -1) {
		chan_opts.attr.read_timer_interval = default_attr.read_timer_interval;
	}
	if ((int) chan_opts.attr.output == -1) {
		chan_opts.attr.output = default_attr.output;
	}
	if (chan_opts.attr.tracefile_count == -1) {
		chan_opts.attr.tracefile_count = default_attr.tracefile_count;
	}
	if (chan_opts.attr.tracefile_size == -1) {
		chan_opts.attr.tracefile_size = default_attr.tracefile_size;
	}
}

/*
 * Adding channel using the lttng API.
 */
static int enable_channel(char *session_name)
{
	struct lttng_channel *channel = NULL;
	int ret = CMD_SUCCESS, warn = 0, error = 0, success = 0;
	char *channel_name;
	struct lttng_domain dom;

	memset(&dom, 0, sizeof(dom));

	/* Validate options. */
	if (opt_kernel) {
		if (opt_blocking_timeout.set) {
			ERR("Retry timeout option not supported for kernel domain (-k)");
			ret = CMD_ERROR;
			goto error;
		}
	}

	/* Create lttng domain */
	if (opt_kernel) {
		dom.type = LTTNG_DOMAIN_KERNEL;
		dom.buf_type = LTTNG_BUFFER_GLOBAL;
		if (opt_buffer_uid || opt_buffer_pid) {
			ERR("Buffer type not supported for domain -k");
			ret = CMD_ERROR;
			goto error;
		}
	} else if (opt_userspace) {
		dom.type = LTTNG_DOMAIN_UST;
		if (opt_buffer_pid) {
			dom.buf_type = LTTNG_BUFFER_PER_PID;
		} else {
			if (opt_buffer_global) {
				ERR("Buffer type not supported for domain -u");
				ret = CMD_ERROR;
				goto error;
			}
			dom.buf_type = LTTNG_BUFFER_PER_UID;
		}
	} else {
		/* Checked by the caller. */
		assert(0);
	}

	set_default_attr(&dom);

	if (chan_opts.attr.tracefile_size == 0 && chan_opts.attr.tracefile_count) {
		ERR("Missing option --tracefile-size. "
				"A file count without a size won't do anything.");
		ret = CMD_ERROR;
		goto error;
	}

	if ((chan_opts.attr.tracefile_size > 0) &&
			(chan_opts.attr.tracefile_size < chan_opts.attr.subbuf_size)) {
		WARN("Tracefile size rounded up from (%" PRIu64 ") to subbuffer size (%" PRIu64 ")",
				chan_opts.attr.tracefile_size, chan_opts.attr.subbuf_size);
		chan_opts.attr.tracefile_size = chan_opts.attr.subbuf_size;
	}

	/* Setting channel output */
	if (opt_output) {
		if (!strncmp(output_mmap, opt_output, strlen(output_mmap))) {
			chan_opts.attr.output = LTTNG_EVENT_MMAP;
		} else if (!strncmp(output_splice, opt_output, strlen(output_splice))) {
			chan_opts.attr.output = LTTNG_EVENT_SPLICE;
		} else {
			ERR("Unknown output type %s. Possible values are: %s, %s\n",
					opt_output, output_mmap, output_splice);
			ret = CMD_ERROR;
			goto error;
		}
	}

	handle = lttng_create_handle(session_name, &dom);
	if (handle == NULL) {
		ret = -1;
		goto error;
	}

	/* Mi open channels element */
	if (lttng_opt_mi) {
		assert(writer);
		ret = mi_lttng_channels_open(writer);
		if (ret) {
			ret = CMD_ERROR;
			goto error;
		}
	}

	/* Strip channel list (format: chan1,chan2,...) */
	channel_name = strtok(opt_channels, ",");
	while (channel_name != NULL) {
		void *extended_ptr;

		/* Validate channel name's length */
		if (strlen(channel_name) >= sizeof(chan_opts.name)) {
			ERR("Channel name is too long (max. %zu characters)",
					sizeof(chan_opts.name) - 1);
			error = 1;
			goto skip_enable;
		}

		/*
		 * A dynamically-allocated channel is used in order to allow
		 * the configuration of extended attributes (post-2.9).
		 */
		channel = lttng_channel_create(&dom);
		if (!channel) {
			ERR("Unable to create channel object");
			error = 1;
			goto error;
		}

		/* Copy channel name */
		strcpy(channel->name, channel_name);
		channel->enabled = 1;
		extended_ptr = channel->attr.extended.ptr;
		memcpy(&channel->attr, &chan_opts.attr, sizeof(chan_opts.attr));
		channel->attr.extended.ptr = extended_ptr;
		if (opt_monitor_timer.set) {
			ret = lttng_channel_set_monitor_timer_interval(channel,
					opt_monitor_timer.interval);
			if (ret) {
				ERR("Failed to set the channel's monitor timer interval");
				error = 1;
				goto error;
			}
		}
		if (opt_blocking_timeout.set) {
			ret = lttng_channel_set_blocking_timeout(channel,
					opt_blocking_timeout.value);
			if (ret) {
				ERR("Failed to set the channel's blocking timeout");
				error = 1;
				goto error;
			}
		}

		DBG("Enabling channel %s", channel_name);

		ret = lttng_enable_channel(handle, channel);
		if (ret < 0) {
			success = 0;
			switch (-ret) {
			case LTTNG_ERR_KERN_CHAN_EXIST:
			case LTTNG_ERR_UST_CHAN_EXIST:
			case LTTNG_ERR_CHAN_EXIST:
				WARN("Channel %s: %s (session %s)", channel_name,
						lttng_strerror(ret), session_name);
				warn = 1;
				break;
			case LTTNG_ERR_INVALID_CHANNEL_NAME:
				ERR("Invalid channel name: \"%s\". "
				    "Channel names may not start with '.', and "
				    "may not contain '/'.", channel_name);
				error = 1;
				break;
			default:
				ERR("Channel %s: %s (session %s)", channel_name,
						lttng_strerror(ret), session_name);
				error = 1;
				break;
			}
		} else {
			MSG("%s channel %s enabled for session %s",
					lttng_domain_type_str(dom.type),
					channel_name, session_name);
			success = 1;
		}

skip_enable:
		if (lttng_opt_mi) {
			/* Mi print the channel element and leave it open */
			ret = mi_lttng_channel(writer, channel, 1);
			if (ret) {
				ret = CMD_ERROR;
				goto error;
			}

			/* Individual Success ? */
			ret = mi_lttng_writer_write_element_bool(writer,
					mi_lttng_element_command_success, success);
			if (ret) {
				ret = CMD_ERROR;
				goto error;
			}

			/* Close channel element */
			ret = mi_lttng_writer_close_element(writer);
			if (ret) {
				ret = CMD_ERROR;
				goto error;
			}
		}

		/* Next channel */
		channel_name = strtok(NULL, ",");
		lttng_channel_destroy(channel);
		channel = NULL;
	}

	if (lttng_opt_mi) {
		/* Close channels element */
		ret = mi_lttng_writer_close_element(writer);
		if (ret) {
			ret = CMD_ERROR;
			goto error;
		}
	}

	ret = CMD_SUCCESS;

error:
	if (channel) {
		lttng_channel_destroy(channel);
	}
	/* If more important error happen bypass the warning */
	if (!ret && warn) {
		ret = CMD_WARNING;
	}
	/* If more important error happen bypass the warning */
	if (!ret && error) {
		ret = CMD_ERROR;
	}

	lttng_destroy_handle(handle);

	return ret;
}

/*
 * Default value for channel configuration.
 */
static void init_channel_config(void)
{
	/*
	 * Put -1 everywhere so we can identify those set by the command line and
	 * those needed to be set by the default values.
	 */
	memset(&chan_opts.attr, -1, sizeof(chan_opts.attr));
	chan_opts.attr.extended.ptr = NULL;
}

/*
 * Add channel to trace session
 */
int cmd_enable_channels(int argc, const char **argv)
{
	int opt, ret = CMD_SUCCESS, command_ret = CMD_SUCCESS, success = 1;
	static poptContext pc;
	char *session_name = NULL;
	char *opt_arg = NULL;
	const char *leftover = NULL;

	init_channel_config();

	pc = poptGetContext(NULL, argc, argv, long_options, 0);
	poptReadDefaultConfig(pc, 0);

	while ((opt = poptGetNextOpt(pc)) != -1) {
		switch (opt) {
		case OPT_HELP:
			SHOW_HELP();
			goto end;
		case OPT_DISCARD:
			chan_opts.attr.overwrite = 0;
			DBG("Channel set to discard");
			break;
		case OPT_OVERWRITE:
			chan_opts.attr.overwrite = 1;
			DBG("Channel set to overwrite");
			break;
		case OPT_SUBBUF_SIZE:
		{
			uint64_t rounded_size;
			int order;

			/* Parse the size */
			opt_arg = poptGetOptArg(pc);
			if (utils_parse_size_suffix(opt_arg, &chan_opts.attr.subbuf_size) < 0 || !chan_opts.attr.subbuf_size) {
				ERR("Wrong value in --subbuf-size parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}

			order = get_count_order_u64(chan_opts.attr.subbuf_size);
			assert(order >= 0);
			rounded_size = 1ULL << order;
			if (rounded_size < chan_opts.attr.subbuf_size) {
				ERR("The subbuf size (%" PRIu64 ") is rounded and overflows!",
						chan_opts.attr.subbuf_size);
				ret = CMD_ERROR;
				goto end;
			}

			if (rounded_size != chan_opts.attr.subbuf_size) {
				WARN("The subbuf size (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
						chan_opts.attr.subbuf_size, rounded_size);
				chan_opts.attr.subbuf_size = rounded_size;
			}

			/* Should now be power of 2 */
			assert(!((chan_opts.attr.subbuf_size - 1) & chan_opts.attr.subbuf_size));

			DBG("Channel subbuf size set to %" PRIu64, chan_opts.attr.subbuf_size);
			break;
		}
		case OPT_NUM_SUBBUF:
		{
			uint64_t rounded_size;
			int order;

			errno = 0;
			opt_arg = poptGetOptArg(pc);
			chan_opts.attr.num_subbuf = strtoull(opt_arg, NULL, 0);
			if (errno != 0 || !chan_opts.attr.num_subbuf || !isdigit(opt_arg[0])) {
				ERR("Wrong value in --num-subbuf parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}

			order = get_count_order_u64(chan_opts.attr.num_subbuf);
			assert(order >= 0);
			rounded_size = 1ULL << order;
			if (rounded_size < chan_opts.attr.num_subbuf) {
				ERR("The number of subbuffers (%" PRIu64 ") is rounded and overflows!",
						chan_opts.attr.num_subbuf);
				ret = CMD_ERROR;
				goto end;
			}

			if (rounded_size != chan_opts.attr.num_subbuf) {
				WARN("The number of subbuffers (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
						chan_opts.attr.num_subbuf, rounded_size);
				chan_opts.attr.num_subbuf = rounded_size;
			}

			/* Should now be power of 2 */
			assert(!((chan_opts.attr.num_subbuf - 1) & chan_opts.attr.num_subbuf));

			DBG("Channel subbuf num set to %" PRIu64, chan_opts.attr.num_subbuf);
			break;
		}
		case OPT_SWITCH_TIMER:
		{
			uint64_t v;

			errno = 0;
			opt_arg = poptGetOptArg(pc);

			if (utils_parse_time_suffix(opt_arg, &v) < 0) {
				ERR("Wrong value for --switch-timer parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}

			if (v != (uint32_t) v) {
				ERR("32-bit overflow in --switch-timer parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}
			chan_opts.attr.switch_timer_interval = (uint32_t) v;
			DBG("Channel switch timer interval set to %d %s",
					chan_opts.attr.switch_timer_interval,
					USEC_UNIT);
			break;
		}
		case OPT_READ_TIMER:
		{
			uint64_t v;

			errno = 0;
			opt_arg = poptGetOptArg(pc);

			if (utils_parse_time_suffix(opt_arg, &v) < 0) {
				ERR("Wrong value for --read-timer parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}

			if (v != (uint32_t) v) {
				ERR("32-bit overflow in --read-timer parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}
			chan_opts.attr.read_timer_interval = (uint32_t) v;
			DBG("Channel read timer interval set to %d %s",
					chan_opts.attr.read_timer_interval,
					USEC_UNIT);
			break;
		}
		case OPT_MONITOR_TIMER:
		{
			uint64_t v;

			errno = 0;
			opt_arg = poptGetOptArg(pc);

			if (utils_parse_time_suffix(opt_arg, &v) < 0) {
				ERR("Wrong value for --monitor-timer parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}
			opt_monitor_timer.interval = (uint64_t) v;
			opt_monitor_timer.set = true;
			DBG("Channel monitor timer interval set to %" PRIu64 " %s",
					opt_monitor_timer.interval,
					USEC_UNIT);
			break;
		}
		case OPT_BLOCKING_TIMEOUT:
		{
			uint64_t v;
			long long v_msec;

			errno = 0;
			opt_arg = poptGetOptArg(pc);

			if (strcmp(opt_arg, "inf") == 0) {
				opt_blocking_timeout.value = (int64_t) -1;
				opt_blocking_timeout.set = true;
				DBG("Channel blocking timeout set to infinity");
				break;
			}

			if (utils_parse_time_suffix(opt_arg, &v) < 0) {
				ERR("Wrong value for --blocking-timeout parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}

			/*
			 * While LTTng-UST and LTTng-tools will accept a
			 * blocking timeout expressed in µs, the current
			 * tracer implementation relies on poll() which
			 * takes an "int timeout" parameter expressed in
			 * msec.
			 *
			 * Since the error reporting from the tracer is
			 * not precise, we perform this check here to
			 * provide a helpful error message in case of
			 * overflow.
			 *
			 * The setter (liblttng-ctl) also performs an
			 * equivalent check.
			 */
			v_msec = v / 1000;
			if (v_msec != (int32_t) v_msec) {
				ERR("32-bit milliseconds overflow in --blocking-timeout parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}

			opt_blocking_timeout.value = (int64_t) v;
			opt_blocking_timeout.set = true;
			DBG("Channel blocking timeout set to %" PRId64 " %s%s",
					opt_blocking_timeout.value,
					USEC_UNIT,
					opt_blocking_timeout.value == 0 ?
						" (non-blocking)" : "");
			break;
		}
		case OPT_USERSPACE:
			opt_userspace = 1;
			break;
		case OPT_TRACEFILE_SIZE:
			opt_arg = poptGetOptArg(pc);
			if (utils_parse_size_suffix(opt_arg, &chan_opts.attr.tracefile_size) < 0) {
				ERR("Wrong value in --tracefile-size parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}
			DBG("Maximum tracefile size set to %" PRIu64,
					chan_opts.attr.tracefile_size);
			break;
		case OPT_TRACEFILE_COUNT:
		{
			unsigned long v;

			errno = 0;
			opt_arg = poptGetOptArg(pc);
			v = strtoul(opt_arg, NULL, 0);
			if (errno != 0 || !isdigit(opt_arg[0])) {
				ERR("Wrong value in --tracefile-count parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}
			if (v != (uint32_t) v) {
				ERR("32-bit overflow in --tracefile-count parameter: %s", opt_arg);
				ret = CMD_ERROR;
				goto end;
			}
			chan_opts.attr.tracefile_count = (uint32_t) v;
			DBG("Maximum tracefile count set to %" PRIu64,
					chan_opts.attr.tracefile_count);
			break;
		}
		case OPT_LIST_OPTIONS:
			list_cmd_options(stdout, long_options);
			goto end;
		default:
			ret = CMD_UNDEFINED;
			goto end;
		}
	}

	ret = print_missing_or_multiple_domains(
			opt_kernel + opt_userspace, false);
	if (ret) {
		ret = CMD_ERROR;
		goto end;
	}

	if (chan_opts.attr.overwrite == 1 && opt_blocking_timeout.set &&
			opt_blocking_timeout.value != 0) {
		ERR("You cannot specify --overwrite and --blocking-timeout=N, "
			"where N is different than 0");
		ret = CMD_ERROR;
		goto end;
	}

	/* Mi check */
	if (lttng_opt_mi) {
		writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);
		if (!writer) {
			ret = -LTTNG_ERR_NOMEM;
			goto end;
		}

		/* Open command element */
		ret = mi_lttng_writer_command_open(writer,
				mi_lttng_element_command_enable_channels);
		if (ret) {
			ret = CMD_ERROR;
			goto end;
		}

		/* Open output element */
		ret = mi_lttng_writer_open_element(writer,
				mi_lttng_element_command_output);
		if (ret) {
			ret = CMD_ERROR;
			goto end;
		}
	}

	opt_channels = (char*) poptGetArg(pc);
	if (opt_channels == NULL) {
		ERR("Missing channel name.\n");
		ret = CMD_ERROR;
		success = 0;
		goto mi_closing;
	}

	leftover = poptGetArg(pc);
	if (leftover) {
		ERR("Unknown argument: %s", leftover);
		ret = CMD_ERROR;
		success = 0;
		goto mi_closing;
	}

	if (!opt_session_name) {
		session_name = get_session_name();
		if (session_name == NULL) {
			command_ret = CMD_ERROR;
			success = 0;
			goto mi_closing;
		}
	} else {
		session_name = opt_session_name;
	}

	command_ret = enable_channel(session_name);
	if (command_ret) {
		success = 0;
	}

mi_closing:
	/* Mi closing */
	if (lttng_opt_mi) {
		/* Close  output element */
		ret = mi_lttng_writer_close_element(writer);
		if (ret) {
			goto end;
		}

		/* Success ? */
		ret = mi_lttng_writer_write_element_bool(writer,
				mi_lttng_element_command_success, success);
		if (ret) {
			goto end;
		}

		/* Command element close */
		ret = mi_lttng_writer_command_close(writer);
		if (ret) {
			goto end;
		}
	}

end:
	/* Mi clean-up */
	if (writer && mi_lttng_writer_destroy(writer)) {
		/* Preserve original error code */
		ret = ret ? ret : LTTNG_ERR_MI_IO_FAIL;
	}

	if (!opt_session_name && session_name) {
		free(session_name);
	}

	/* Overwrite ret if an error occurred when enable_channel */
	ret = command_ret ? command_ret : ret;
	poptFreeContext(pc);
	return ret;
}
Commit	Line	Data
	1	/*
	2	* Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
	3	*
	4	* SPDX-License-Identifier: GPL-2.0-only
	5	*
	6	*/
	7
	8	#define _LGPL_SOURCE
	9	#include <popt.h>
	10	#include <stdio.h>
	11	#include <stdlib.h>
	12	#include <string.h>
	13	#include <sys/stat.h>
	14	#include <sys/types.h>
	15	#include <unistd.h>
	16	#include <inttypes.h>
	17	#include <assert.h>
	18	#include <ctype.h>
	19
	20	#include <common/sessiond-comm/sessiond-comm.h>
	21	#include <common/utils.h>
	22	#include <common/mi-lttng.h>
	23
	24	#include <lttng/domain-internal.h>
	25
	26	#include "../command.h"
	27	#include "../utils.h"
	28
	29
	30	static struct lttng_channel chan_opts;
	31	static char *opt_channels;
	32	static int opt_kernel;
	33	static char *opt_session_name;
	34	static int opt_userspace;
	35	static char *opt_output;
	36	static int opt_buffer_uid;
	37	static int opt_buffer_pid;
	38	static int opt_buffer_global;
	39	static struct {
	40	bool set;
	41	uint64_t interval;
	42	} opt_monitor_timer;
	43	static struct {
	44	bool set;
	45	int64_t value;
	46	} opt_blocking_timeout;
	47
	48	static struct mi_writer *writer;
	49
	50	#ifdef LTTNG_EMBED_HELP
	51	static const char help_msg[] =
	52	#include <lttng-enable-channel.1.h>
	53	;
	54	#endif
	55
	56	enum {
	57	OPT_HELP = 1,
	58	OPT_DISCARD,
	59	OPT_OVERWRITE,
	60	OPT_SUBBUF_SIZE,
	61	OPT_NUM_SUBBUF,
	62	OPT_SWITCH_TIMER,
	63	OPT_MONITOR_TIMER,
	64	OPT_READ_TIMER,
	65	OPT_USERSPACE,
	66	OPT_LIST_OPTIONS,
	67	OPT_TRACEFILE_SIZE,
	68	OPT_TRACEFILE_COUNT,
	69	OPT_BLOCKING_TIMEOUT,
	70	};
	71
	72	static struct lttng_handle *handle;
	73
	74	const char *output_mmap = "mmap";
	75	const char *output_splice = "splice";
	76
	77	static struct poptOption long_options[] = {
	78	/* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
	79	{"help", 'h', POPT_ARG_NONE, 0, OPT_HELP, 0, 0},
	80	{"session", 's', POPT_ARG_STRING, &opt_session_name, 0, 0, 0},
	81	{"kernel", 'k', POPT_ARG_VAL, &opt_kernel, 1, 0, 0},
	82	{"userspace", 'u', POPT_ARG_NONE, 0, OPT_USERSPACE, 0, 0},
	83	{"discard", 0, POPT_ARG_NONE, 0, OPT_DISCARD, 0, 0},
	84	{"overwrite", 0, POPT_ARG_NONE, 0, OPT_OVERWRITE, 0, 0},
	85	{"subbuf-size", 0, POPT_ARG_STRING, 0, OPT_SUBBUF_SIZE, 0, 0},
	86	{"num-subbuf", 0, POPT_ARG_INT, 0, OPT_NUM_SUBBUF, 0, 0},
	87	{"switch-timer", 0, POPT_ARG_INT, 0, OPT_SWITCH_TIMER, 0, 0},
	88	{"monitor-timer", 0, POPT_ARG_INT, 0, OPT_MONITOR_TIMER, 0, 0},
	89	{"read-timer", 0, POPT_ARG_INT, 0, OPT_READ_TIMER, 0, 0},
	90	{"list-options", 0, POPT_ARG_NONE, NULL, OPT_LIST_OPTIONS, NULL, NULL},
	91	{"output", 0, POPT_ARG_STRING, &opt_output, 0, 0, 0},
	92	{"buffers-uid", 0, POPT_ARG_VAL, &opt_buffer_uid, 1, 0, 0},
	93	{"buffers-pid", 0, POPT_ARG_VAL, &opt_buffer_pid, 1, 0, 0},
	94	{"buffers-global", 0, POPT_ARG_VAL, &opt_buffer_global, 1, 0, 0},
	95	{"tracefile-size", 'C', POPT_ARG_INT, 0, OPT_TRACEFILE_SIZE, 0, 0},
	96	{"tracefile-count", 'W', POPT_ARG_INT, 0, OPT_TRACEFILE_COUNT, 0, 0},
	97	{"blocking-timeout", 0, POPT_ARG_INT, 0, OPT_BLOCKING_TIMEOUT, 0, 0},
	98	{0, 0, 0, 0, 0, 0, 0}
	99	};
	100
	101	/*
	102	* Set default attributes depending on those already defined from the command
	103	* line.
	104	*/
	105	static void set_default_attr(struct lttng_domain *dom)
	106	{
	107	struct lttng_channel_attr default_attr;
	108
	109	memset(&default_attr, 0, sizeof(default_attr));
	110
	111	/* Set attributes */
	112	lttng_channel_set_default_attr(dom, &default_attr);
	113
	114	if (chan_opts.attr.overwrite == -1) {
	115	chan_opts.attr.overwrite = default_attr.overwrite;
	116	}
	117	if (chan_opts.attr.subbuf_size == -1) {
	118	chan_opts.attr.subbuf_size = default_attr.subbuf_size;
	119	}
	120	if (chan_opts.attr.num_subbuf == -1) {
	121	chan_opts.attr.num_subbuf = default_attr.num_subbuf;
	122	}
	123	if (chan_opts.attr.switch_timer_interval == -1) {
	124	chan_opts.attr.switch_timer_interval = default_attr.switch_timer_interval;
	125	}
	126	if (chan_opts.attr.read_timer_interval == -1) {
	127	chan_opts.attr.read_timer_interval = default_attr.read_timer_interval;
	128	}
	129	if ((int) chan_opts.attr.output == -1) {
	130	chan_opts.attr.output = default_attr.output;
	131	}
	132	if (chan_opts.attr.tracefile_count == -1) {
	133	chan_opts.attr.tracefile_count = default_attr.tracefile_count;
	134	}
	135	if (chan_opts.attr.tracefile_size == -1) {
	136	chan_opts.attr.tracefile_size = default_attr.tracefile_size;
	137	}
	138	}
	139
	140	/*
	141	* Adding channel using the lttng API.
	142	*/
	143	static int enable_channel(char *session_name)
	144	{
	145	struct lttng_channel *channel = NULL;
	146	int ret = CMD_SUCCESS, warn = 0, error = 0, success = 0;
	147	char *channel_name;
	148	struct lttng_domain dom;
	149
	150	memset(&dom, 0, sizeof(dom));
	151
	152	/* Validate options. */
	153	if (opt_kernel) {
	154	if (opt_blocking_timeout.set) {
	155	ERR("Retry timeout option not supported for kernel domain (-k)");
	156	ret = CMD_ERROR;
	157	goto error;
	158	}
	159	}
	160
	161	/* Create lttng domain */
	162	if (opt_kernel) {
	163	dom.type = LTTNG_DOMAIN_KERNEL;
	164	dom.buf_type = LTTNG_BUFFER_GLOBAL;
	165	if (opt_buffer_uid \|\| opt_buffer_pid) {
	166	ERR("Buffer type not supported for domain -k");
	167	ret = CMD_ERROR;
	168	goto error;
	169	}
	170	} else if (opt_userspace) {
	171	dom.type = LTTNG_DOMAIN_UST;
	172	if (opt_buffer_pid) {
	173	dom.buf_type = LTTNG_BUFFER_PER_PID;
	174	} else {
	175	if (opt_buffer_global) {
	176	ERR("Buffer type not supported for domain -u");
	177	ret = CMD_ERROR;
	178	goto error;
	179	}
	180	dom.buf_type = LTTNG_BUFFER_PER_UID;
	181	}
	182	} else {
	183	/* Checked by the caller. */
	184	assert(0);
	185	}
	186
	187	set_default_attr(&dom);
	188
	189	if (chan_opts.attr.tracefile_size == 0 && chan_opts.attr.tracefile_count) {
	190	ERR("Missing option --tracefile-size. "
	191	"A file count without a size won't do anything.");
	192	ret = CMD_ERROR;
	193	goto error;
	194	}
	195
	196	if ((chan_opts.attr.tracefile_size > 0) &&
	197	(chan_opts.attr.tracefile_size < chan_opts.attr.subbuf_size)) {
	198	WARN("Tracefile size rounded up from (%" PRIu64 ") to subbuffer size (%" PRIu64 ")",
	199	chan_opts.attr.tracefile_size, chan_opts.attr.subbuf_size);
	200	chan_opts.attr.tracefile_size = chan_opts.attr.subbuf_size;
	201	}
	202
	203	/* Setting channel output */
	204	if (opt_output) {
	205	if (!strncmp(output_mmap, opt_output, strlen(output_mmap))) {
	206	chan_opts.attr.output = LTTNG_EVENT_MMAP;
	207	} else if (!strncmp(output_splice, opt_output, strlen(output_splice))) {
	208	chan_opts.attr.output = LTTNG_EVENT_SPLICE;
	209	} else {
	210	ERR("Unknown output type %s. Possible values are: %s, %s\n",
	211	opt_output, output_mmap, output_splice);
	212	ret = CMD_ERROR;
	213	goto error;
	214	}
	215	}
	216
	217	handle = lttng_create_handle(session_name, &dom);
	218	if (handle == NULL) {
	219	ret = -1;
	220	goto error;
	221	}
	222
	223	/* Mi open channels element */
	224	if (lttng_opt_mi) {
	225	assert(writer);
	226	ret = mi_lttng_channels_open(writer);
	227	if (ret) {
	228	ret = CMD_ERROR;
	229	goto error;
	230	}
	231	}
	232
	233	/* Strip channel list (format: chan1,chan2,...) */
	234	channel_name = strtok(opt_channels, ",");
	235	while (channel_name != NULL) {
	236	void *extended_ptr;
	237
	238	/* Validate channel name's length */
	239	if (strlen(channel_name) >= sizeof(chan_opts.name)) {
	240	ERR("Channel name is too long (max. %zu characters)",
	241	sizeof(chan_opts.name) - 1);
	242	error = 1;
	243	goto skip_enable;
	244	}
	245
	246	/*
	247	* A dynamically-allocated channel is used in order to allow
	248	* the configuration of extended attributes (post-2.9).
	249	*/
	250	channel = lttng_channel_create(&dom);
	251	if (!channel) {
	252	ERR("Unable to create channel object");
	253	error = 1;
	254	goto error;
	255	}
	256
	257	/* Copy channel name */
	258	strcpy(channel->name, channel_name);
	259	channel->enabled = 1;
	260	extended_ptr = channel->attr.extended.ptr;
	261	memcpy(&channel->attr, &chan_opts.attr, sizeof(chan_opts.attr));
	262	channel->attr.extended.ptr = extended_ptr;
	263	if (opt_monitor_timer.set) {
	264	ret = lttng_channel_set_monitor_timer_interval(channel,
	265	opt_monitor_timer.interval);
	266	if (ret) {
	267	ERR("Failed to set the channel's monitor timer interval");
	268	error = 1;
	269	goto error;
	270	}
	271	}
	272	if (opt_blocking_timeout.set) {
	273	ret = lttng_channel_set_blocking_timeout(channel,
	274	opt_blocking_timeout.value);
	275	if (ret) {
	276	ERR("Failed to set the channel's blocking timeout");
	277	error = 1;
	278	goto error;
	279	}
	280	}
	281
	282	DBG("Enabling channel %s", channel_name);
	283
	284	ret = lttng_enable_channel(handle, channel);
	285	if (ret < 0) {
	286	success = 0;
	287	switch (-ret) {
	288	case LTTNG_ERR_KERN_CHAN_EXIST:
	289	case LTTNG_ERR_UST_CHAN_EXIST:
	290	case LTTNG_ERR_CHAN_EXIST:
	291	WARN("Channel %s: %s (session %s)", channel_name,
	292	lttng_strerror(ret), session_name);
	293	warn = 1;
	294	break;
	295	case LTTNG_ERR_INVALID_CHANNEL_NAME:
	296	ERR("Invalid channel name: \"%s\". "
	297	"Channel names may not start with '.', and "
	298	"may not contain '/'.", channel_name);
	299	error = 1;
	300	break;
	301	default:
	302	ERR("Channel %s: %s (session %s)", channel_name,
	303	lttng_strerror(ret), session_name);
	304	error = 1;
	305	break;
	306	}
	307	} else {
	308	MSG("%s channel %s enabled for session %s",
	309	lttng_domain_type_str(dom.type),
	310	channel_name, session_name);
	311	success = 1;
	312	}
	313
	314	skip_enable:
	315	if (lttng_opt_mi) {
	316	/* Mi print the channel element and leave it open */
	317	ret = mi_lttng_channel(writer, channel, 1);
	318	if (ret) {
	319	ret = CMD_ERROR;
	320	goto error;
	321	}
	322
	323	/* Individual Success ? */
	324	ret = mi_lttng_writer_write_element_bool(writer,
	325	mi_lttng_element_command_success, success);
	326	if (ret) {
	327	ret = CMD_ERROR;
	328	goto error;
	329	}
	330
	331	/* Close channel element */
	332	ret = mi_lttng_writer_close_element(writer);
	333	if (ret) {
	334	ret = CMD_ERROR;
	335	goto error;
	336	}
	337	}
	338
	339	/* Next channel */
	340	channel_name = strtok(NULL, ",");
	341	lttng_channel_destroy(channel);
	342	channel = NULL;
	343	}
	344
	345	if (lttng_opt_mi) {
	346	/* Close channels element */
	347	ret = mi_lttng_writer_close_element(writer);
	348	if (ret) {
	349	ret = CMD_ERROR;
	350	goto error;
	351	}
	352	}
	353
	354	ret = CMD_SUCCESS;
	355
	356	error:
	357	if (channel) {
	358	lttng_channel_destroy(channel);
	359	}
	360	/* If more important error happen bypass the warning */
	361	if (!ret && warn) {
	362	ret = CMD_WARNING;
	363	}
	364	/* If more important error happen bypass the warning */
	365	if (!ret && error) {
	366	ret = CMD_ERROR;
	367	}
	368
	369	lttng_destroy_handle(handle);
	370
	371	return ret;
	372	}
	373
	374	/*
	375	* Default value for channel configuration.
	376	*/
	377	static void init_channel_config(void)
	378	{
	379	/*
	380	* Put -1 everywhere so we can identify those set by the command line and
	381	* those needed to be set by the default values.
	382	*/
	383	memset(&chan_opts.attr, -1, sizeof(chan_opts.attr));
	384	chan_opts.attr.extended.ptr = NULL;
	385	}
	386
	387	/*
	388	* Add channel to trace session
	389	*/
	390	int cmd_enable_channels(int argc, const char **argv)
	391	{
	392	int opt, ret = CMD_SUCCESS, command_ret = CMD_SUCCESS, success = 1;
	393	static poptContext pc;
	394	char *session_name = NULL;
	395	char *opt_arg = NULL;
	396	const char *leftover = NULL;
	397
	398	init_channel_config();
	399
	400	pc = poptGetContext(NULL, argc, argv, long_options, 0);
	401	poptReadDefaultConfig(pc, 0);
	402
	403	while ((opt = poptGetNextOpt(pc)) != -1) {
	404	switch (opt) {
	405	case OPT_HELP:
	406	SHOW_HELP();
	407	goto end;
	408	case OPT_DISCARD:
	409	chan_opts.attr.overwrite = 0;
	410	DBG("Channel set to discard");
	411	break;
	412	case OPT_OVERWRITE:
	413	chan_opts.attr.overwrite = 1;
	414	DBG("Channel set to overwrite");
	415	break;
	416	case OPT_SUBBUF_SIZE:
	417	{
	418	uint64_t rounded_size;
	419	int order;
	420
	421	/* Parse the size */
	422	opt_arg = poptGetOptArg(pc);
	423	if (utils_parse_size_suffix(opt_arg, &chan_opts.attr.subbuf_size) < 0 \|\| !chan_opts.attr.subbuf_size) {
	424	ERR("Wrong value in --subbuf-size parameter: %s", opt_arg);
	425	ret = CMD_ERROR;
	426	goto end;
	427	}
	428
	429	order = get_count_order_u64(chan_opts.attr.subbuf_size);
	430	assert(order >= 0);
	431	rounded_size = 1ULL << order;
	432	if (rounded_size < chan_opts.attr.subbuf_size) {
	433	ERR("The subbuf size (%" PRIu64 ") is rounded and overflows!",
	434	chan_opts.attr.subbuf_size);
	435	ret = CMD_ERROR;
	436	goto end;
	437	}
	438
	439	if (rounded_size != chan_opts.attr.subbuf_size) {
	440	WARN("The subbuf size (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
	441	chan_opts.attr.subbuf_size, rounded_size);
	442	chan_opts.attr.subbuf_size = rounded_size;
	443	}
	444
	445	/* Should now be power of 2 */
	446	assert(!((chan_opts.attr.subbuf_size - 1) & chan_opts.attr.subbuf_size));
	447
	448	DBG("Channel subbuf size set to %" PRIu64, chan_opts.attr.subbuf_size);
	449	break;
	450	}
	451	case OPT_NUM_SUBBUF:
	452	{
	453	uint64_t rounded_size;
	454	int order;
	455
	456	errno = 0;
	457	opt_arg = poptGetOptArg(pc);
	458	chan_opts.attr.num_subbuf = strtoull(opt_arg, NULL, 0);
	459	if (errno != 0 \|\| !chan_opts.attr.num_subbuf \|\| !isdigit(opt_arg[0])) {
	460	ERR("Wrong value in --num-subbuf parameter: %s", opt_arg);
	461	ret = CMD_ERROR;
	462	goto end;
	463	}
	464
	465	order = get_count_order_u64(chan_opts.attr.num_subbuf);
	466	assert(order >= 0);
	467	rounded_size = 1ULL << order;
	468	if (rounded_size < chan_opts.attr.num_subbuf) {
	469	ERR("The number of subbuffers (%" PRIu64 ") is rounded and overflows!",
	470	chan_opts.attr.num_subbuf);
	471	ret = CMD_ERROR;
	472	goto end;
	473	}
	474
	475	if (rounded_size != chan_opts.attr.num_subbuf) {
	476	WARN("The number of subbuffers (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
	477	chan_opts.attr.num_subbuf, rounded_size);
	478	chan_opts.attr.num_subbuf = rounded_size;
	479	}
	480
	481	/* Should now be power of 2 */
	482	assert(!((chan_opts.attr.num_subbuf - 1) & chan_opts.attr.num_subbuf));
	483
	484	DBG("Channel subbuf num set to %" PRIu64, chan_opts.attr.num_subbuf);
	485	break;
	486	}
	487	case OPT_SWITCH_TIMER:
	488	{
	489	uint64_t v;
	490
	491	errno = 0;
	492	opt_arg = poptGetOptArg(pc);
	493
	494	if (utils_parse_time_suffix(opt_arg, &v) < 0) {
	495	ERR("Wrong value for --switch-timer parameter: %s", opt_arg);
	496	ret = CMD_ERROR;
	497	goto end;
	498	}
	499
	500	if (v != (uint32_t) v) {
	501	ERR("32-bit overflow in --switch-timer parameter: %s", opt_arg);
	502	ret = CMD_ERROR;
	503	goto end;
	504	}
	505	chan_opts.attr.switch_timer_interval = (uint32_t) v;
	506	DBG("Channel switch timer interval set to %d %s",
	507	chan_opts.attr.switch_timer_interval,
	508	USEC_UNIT);
	509	break;
	510	}
	511	case OPT_READ_TIMER:
	512	{
	513	uint64_t v;
	514
	515	errno = 0;
	516	opt_arg = poptGetOptArg(pc);
	517
	518	if (utils_parse_time_suffix(opt_arg, &v) < 0) {
	519	ERR("Wrong value for --read-timer parameter: %s", opt_arg);
	520	ret = CMD_ERROR;
	521	goto end;
	522	}
	523
	524	if (v != (uint32_t) v) {
	525	ERR("32-bit overflow in --read-timer parameter: %s", opt_arg);
	526	ret = CMD_ERROR;
	527	goto end;
	528	}
	529	chan_opts.attr.read_timer_interval = (uint32_t) v;
	530	DBG("Channel read timer interval set to %d %s",
	531	chan_opts.attr.read_timer_interval,
	532	USEC_UNIT);
	533	break;
	534	}
	535	case OPT_MONITOR_TIMER:
	536	{
	537	uint64_t v;
	538
	539	errno = 0;
	540	opt_arg = poptGetOptArg(pc);
	541
	542	if (utils_parse_time_suffix(opt_arg, &v) < 0) {
	543	ERR("Wrong value for --monitor-timer parameter: %s", opt_arg);
	544	ret = CMD_ERROR;
	545	goto end;
	546	}
	547	opt_monitor_timer.interval = (uint64_t) v;
	548	opt_monitor_timer.set = true;
	549	DBG("Channel monitor timer interval set to %" PRIu64 " %s",
	550	opt_monitor_timer.interval,
	551	USEC_UNIT);
	552	break;
	553	}
	554	case OPT_BLOCKING_TIMEOUT:
	555	{
	556	uint64_t v;
	557	long long v_msec;
	558
	559	errno = 0;
	560	opt_arg = poptGetOptArg(pc);
	561
	562	if (strcmp(opt_arg, "inf") == 0) {
	563	opt_blocking_timeout.value = (int64_t) -1;
	564	opt_blocking_timeout.set = true;
	565	DBG("Channel blocking timeout set to infinity");
	566	break;
	567	}
	568
	569	if (utils_parse_time_suffix(opt_arg, &v) < 0) {
	570	ERR("Wrong value for --blocking-timeout parameter: %s", opt_arg);
	571	ret = CMD_ERROR;
	572	goto end;
	573	}
	574
	575	/*
	576	* While LTTng-UST and LTTng-tools will accept a
	577	* blocking timeout expressed in µs, the current
	578	* tracer implementation relies on poll() which
	579	* takes an "int timeout" parameter expressed in
	580	* msec.
	581	*
	582	* Since the error reporting from the tracer is
	583	* not precise, we perform this check here to
	584	* provide a helpful error message in case of
	585	* overflow.
	586	*
	587	* The setter (liblttng-ctl) also performs an
	588	* equivalent check.
	589	*/
	590	v_msec = v / 1000;
	591	if (v_msec != (int32_t) v_msec) {
	592	ERR("32-bit milliseconds overflow in --blocking-timeout parameter: %s", opt_arg);
	593	ret = CMD_ERROR;
	594	goto end;
	595	}
	596
	597	opt_blocking_timeout.value = (int64_t) v;
	598	opt_blocking_timeout.set = true;
	599	DBG("Channel blocking timeout set to %" PRId64 " %s%s",
	600	opt_blocking_timeout.value,
	601	USEC_UNIT,
	602	opt_blocking_timeout.value == 0 ?
	603	" (non-blocking)" : "");
	604	break;
	605	}
	606	case OPT_USERSPACE:
	607	opt_userspace = 1;
	608	break;
	609	case OPT_TRACEFILE_SIZE:
	610	opt_arg = poptGetOptArg(pc);
	611	if (utils_parse_size_suffix(opt_arg, &chan_opts.attr.tracefile_size) < 0) {
	612	ERR("Wrong value in --tracefile-size parameter: %s", opt_arg);
	613	ret = CMD_ERROR;
	614	goto end;
	615	}
	616	DBG("Maximum tracefile size set to %" PRIu64,
	617	chan_opts.attr.tracefile_size);
	618	break;
	619	case OPT_TRACEFILE_COUNT:
	620	{
	621	unsigned long v;
	622
	623	errno = 0;
	624	opt_arg = poptGetOptArg(pc);
	625	v = strtoul(opt_arg, NULL, 0);
	626	if (errno != 0 \|\| !isdigit(opt_arg[0])) {
	627	ERR("Wrong value in --tracefile-count parameter: %s", opt_arg);
	628	ret = CMD_ERROR;
	629	goto end;
	630	}
	631	if (v != (uint32_t) v) {
	632	ERR("32-bit overflow in --tracefile-count parameter: %s", opt_arg);
	633	ret = CMD_ERROR;
	634	goto end;
	635	}
	636	chan_opts.attr.tracefile_count = (uint32_t) v;
	637	DBG("Maximum tracefile count set to %" PRIu64,
	638	chan_opts.attr.tracefile_count);
	639	break;
	640	}
	641	case OPT_LIST_OPTIONS:
	642	list_cmd_options(stdout, long_options);
	643	goto end;
	644	default:
	645	ret = CMD_UNDEFINED;
	646	goto end;
	647	}
	648	}
	649
	650	ret = print_missing_or_multiple_domains(
	651	opt_kernel + opt_userspace, false);
	652	if (ret) {
	653	ret = CMD_ERROR;
	654	goto end;
	655	}
	656
	657	if (chan_opts.attr.overwrite == 1 && opt_blocking_timeout.set &&
	658	opt_blocking_timeout.value != 0) {
	659	ERR("You cannot specify --overwrite and --blocking-timeout=N, "
	660	"where N is different than 0");
	661	ret = CMD_ERROR;
	662	goto end;
	663	}
	664
	665	/* Mi check */
	666	if (lttng_opt_mi) {
	667	writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);
	668	if (!writer) {
	669	ret = -LTTNG_ERR_NOMEM;
	670	goto end;
	671	}
	672
	673	/* Open command element */
	674	ret = mi_lttng_writer_command_open(writer,
	675	mi_lttng_element_command_enable_channels);
	676	if (ret) {
	677	ret = CMD_ERROR;
	678	goto end;
	679	}
	680
	681	/* Open output element */
	682	ret = mi_lttng_writer_open_element(writer,
	683	mi_lttng_element_command_output);
	684	if (ret) {
	685	ret = CMD_ERROR;
	686	goto end;
	687	}
	688	}
	689
	690	opt_channels = (char*) poptGetArg(pc);
	691	if (opt_channels == NULL) {
	692	ERR("Missing channel name.\n");
	693	ret = CMD_ERROR;
	694	success = 0;
	695	goto mi_closing;
	696	}
	697
	698	leftover = poptGetArg(pc);
	699	if (leftover) {
	700	ERR("Unknown argument: %s", leftover);
	701	ret = CMD_ERROR;
	702	success = 0;
	703	goto mi_closing;
	704	}
	705
	706	if (!opt_session_name) {
	707	session_name = get_session_name();
	708	if (session_name == NULL) {
	709	command_ret = CMD_ERROR;
	710	success = 0;
	711	goto mi_closing;
	712	}
	713	} else {
	714	session_name = opt_session_name;
	715	}
	716
	717	command_ret = enable_channel(session_name);
	718	if (command_ret) {
	719	success = 0;
	720	}
	721
	722	mi_closing:
	723	/* Mi closing */
	724	if (lttng_opt_mi) {
	725	/* Close output element */
	726	ret = mi_lttng_writer_close_element(writer);
	727	if (ret) {
	728	goto end;
	729	}
	730
	731	/* Success ? */
	732	ret = mi_lttng_writer_write_element_bool(writer,
	733	mi_lttng_element_command_success, success);
	734	if (ret) {
	735	goto end;
	736	}
	737
	738	/* Command element close */
	739	ret = mi_lttng_writer_command_close(writer);
	740	if (ret) {
	741	goto end;
	742	}
	743	}
	744
	745	end:
	746	/* Mi clean-up */
	747	if (writer && mi_lttng_writer_destroy(writer)) {
	748	/* Preserve original error code */
	749	ret = ret ? ret : LTTNG_ERR_MI_IO_FAIL;
	750	}
	751
	752	if (!opt_session_name && session_name) {
	753	free(session_name);
	754	}
	755
	756	/* Overwrite ret if an error occurred when enable_channel */
	757	ret = command_ret ? command_ret : ret;
	758	poptFreeContext(pc);
	759	return ret;
	760	}