trace-recorder.c

/*
 * Copyright (C) 2009, 2010 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License (not later!)
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not,  see <http://www.gnu.org/licenses>
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */
#define _LARGEFILE64_SOURCE
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <pthread.h>
#include <fcntl.h>
#include <unistd.h>
#include <ctype.h>
#include <errno.h>

#include "trace-cmd.h"
#include "event-utils.h"

struct tracecmd_recorder {
	int		fd;
	int		fd1;
	int		fd2;
	int		trace_fd;
	int		brass[2];
	int		page_size;
	int		cpu;
	int		stop;
	int		max;
	int		pages;
	int		count;
	unsigned	fd_flags;
	unsigned	flags;
};

static int append_file(int size, int dst, int src)
{
	char buf[size];
	int r;

	lseek64(src, 0, SEEK_SET);

	/* If there's an error, then we are pretty much screwed :-p */
	do {
		r = read(src, buf, size);
		if (r < 0)
			return r;
		r = write(dst, buf, r);
		if (r < 0)
			return r;
	} while (r);
	return 0;
}

void tracecmd_free_recorder(struct tracecmd_recorder *recorder)
{
	if (!recorder)
		return;

	if (recorder->max) {
		/* Need to put everything into fd1 */
		if (recorder->fd == recorder->fd1) {
			int ret;
			/*
			 * Crap, the older data is in fd2, and we need
			 * to append fd1 onto it, and then copy over to fd1
			 */
			ret = append_file(recorder->page_size,
					  recorder->fd2, recorder->fd1);
			/* Error on copying, then just keep fd1 */
			if (ret) {
				lseek64(recorder->fd1, 0, SEEK_END);
				goto close;
			}
			lseek64(recorder->fd1, 0, SEEK_SET);
			ftruncate(recorder->fd1, 0);
		}
		append_file(recorder->page_size, recorder->fd1, recorder->fd2);
	}
 close:
	if (recorder->trace_fd >= 0)
		close(recorder->trace_fd);

	if (recorder->fd1 >= 0)
		close(recorder->fd1);

	if (recorder->fd2 >= 0)
		close(recorder->fd2);

	free(recorder);
}

struct tracecmd_recorder *
tracecmd_create_buffer_recorder_fd2(int fd, int fd2, int cpu, unsigned flags,
				    const char *buffer, int maxkb)
{
	struct tracecmd_recorder *recorder;
	char *path = NULL;
	int ret;

	recorder = malloc(sizeof(*recorder));
	if (!recorder)
		return NULL;

	recorder->cpu = cpu;
	recorder->flags = flags;

	recorder->fd_flags = 1; /* SPLICE_F_MOVE */

	if (!(recorder->flags & TRACECMD_RECORD_BLOCK))
		recorder->fd_flags |= 2; /* and NON_BLOCK */

	/* Init to know what to free and release */
	recorder->trace_fd = -1;
	recorder->brass[0] = -1;
	recorder->brass[1] = -1;

	recorder->page_size = getpagesize();
	if (maxkb) {
		int kb_per_page = recorder->page_size >> 10;

		if (!kb_per_page)
			kb_per_page = 1;
		recorder->max = maxkb / kb_per_page;
		/* keep max half */
		recorder->max >>= 1;
		if (!recorder->max)
			recorder->max = 1;
	} else
		recorder->max = 0;

	recorder->count = 0;
	recorder->pages = 0;

	/* fd always points to what to write to */
	recorder->fd = fd;
	recorder->fd1 = fd;
	recorder->fd2 = fd2;

	path = malloc(strlen(buffer) + 40);
	if (!path)
		goto out_free;

	if (flags & TRACECMD_RECORD_SNAPSHOT)
		sprintf(path, "%s/per_cpu/cpu%d/snapshot_raw", buffer, cpu);
	else
		sprintf(path, "%s/per_cpu/cpu%d/trace_pipe_raw", buffer, cpu);
	recorder->trace_fd = open(path, O_RDONLY);
	if (recorder->trace_fd < 0)
		goto out_free;

	if ((recorder->flags & TRACECMD_RECORD_NOSPLICE) == 0) {
		ret = pipe(recorder->brass);
		if (ret < 0)
			goto out_free;
	}

	free(path);

	return recorder;

 out_free:
	free(path);

	tracecmd_free_recorder(recorder);
	return NULL;
}

struct tracecmd_recorder *
tracecmd_create_buffer_recorder_fd(int fd, int cpu, unsigned flags, const char *buffer)
{
	return tracecmd_create_buffer_recorder_fd2(fd, -1, cpu, flags, buffer, 0);
}

struct tracecmd_recorder *
tracecmd_create_buffer_recorder(const char *file, int cpu, unsigned flags, const char *buffer)
{
	struct tracecmd_recorder *recorder;
	int fd;

	fd = open(file, O_WRONLY | O_CREAT | O_TRUNC | O_LARGEFILE, 0644);
	if (fd < 0)
		return NULL;

	recorder = tracecmd_create_buffer_recorder_fd(fd, cpu, flags, buffer);
	if (!recorder) {
		close(fd);
		unlink(file);
	}

	return recorder;
}

struct tracecmd_recorder *
tracecmd_create_buffer_recorder_maxkb(const char *file, int cpu, unsigned flags,
				      const char *buffer, int maxkb)
{
	struct tracecmd_recorder *recorder = NULL;
	char *file2;
	int len;
	int fd;
	int fd2;

	if (!maxkb)
		return tracecmd_create_buffer_recorder(file, cpu, flags, buffer);

	len = strlen(file);
	file2 = malloc(len + 3);
	if (!file2)
		return NULL;

	sprintf(file2, "%s.1", file);

	fd = open(file, O_RDWR | O_CREAT | O_TRUNC | O_LARGEFILE, 0644);
	if (fd < 0)
		goto out;

	fd2 = open(file2, O_RDWR | O_CREAT | O_TRUNC | O_LARGEFILE, 0644);
	if (fd < 0)
		goto err;

	recorder = tracecmd_create_buffer_recorder_fd2(fd, fd2, cpu, flags, buffer, maxkb);
	if (!recorder)
		goto err2;
 out:
	/* Unlink file2, we need to add everything to file at the end */
	unlink(file2);
	free(file2);

	return recorder;
 err2:
	close(fd2);
 err:
	close(fd);
	unlink(file);
	goto out;
}

struct tracecmd_recorder *tracecmd_create_recorder_fd(int fd, int cpu, unsigned flags)
{
	const char *tracing;

	tracing = tracecmd_get_tracing_dir();
	if (!tracing) {
		errno = ENODEV;
		return NULL;
	}

	return tracecmd_create_buffer_recorder_fd(fd, cpu, flags, tracing);
}

struct tracecmd_recorder *tracecmd_create_recorder(const char *file, int cpu, unsigned flags)
{
	const char *tracing;

	tracing = tracecmd_get_tracing_dir();
	if (!tracing) {
		errno = ENODEV;
		return NULL;
	}

	return tracecmd_create_buffer_recorder(file, cpu, flags, tracing);
}

struct tracecmd_recorder *
tracecmd_create_recorder_maxkb(const char *file, int cpu, unsigned flags, int maxkb)
{
	const char *tracing;

	tracing = tracecmd_get_tracing_dir();
	if (!tracing) {
		errno = ENODEV;
		return NULL;
	}

	return tracecmd_create_buffer_recorder_maxkb(file, cpu, flags, tracing, maxkb);
}

static inline void update_fd(struct tracecmd_recorder *recorder, int size)
{
	int fd;

	if (!recorder->max)
		return;

	recorder->count += size;

	if (recorder->count >= recorder->page_size) {
		recorder->count = 0;
		recorder->pages++;
	}

	if (recorder->pages < recorder->max)
		return;

	recorder->pages = 0;

	fd = recorder->fd;

	/* Swap fd to next file. */
	if (fd == recorder->fd1)
		fd = recorder->fd2;
	else
		fd = recorder->fd1;

	/* Zero out the new file we are writing to */
	lseek64(fd, 0, SEEK_SET);
	ftruncate(fd, 0);

	recorder->fd = fd;
}

/*
 * Returns -1 on error.
 *          or bytes of data read.
 */
static long splice_data(struct tracecmd_recorder *recorder)
{
	long ret;

	ret = splice(recorder->trace_fd, NULL, recorder->brass[1], NULL,
		     recorder->page_size, 1 /* SPLICE_F_MOVE */);
	if (ret < 0) {
		if (errno != EAGAIN && errno != EINTR) {
			warning("recorder error in splice input");
			return -1;
		}
		if (errno == EINTR)
			return 0;
	} else if (ret == 0)
		return 0;

	ret = splice(recorder->brass[0], NULL, recorder->fd, NULL,
		     recorder->page_size, recorder->fd_flags);
	if (ret < 0) {
		if (errno != EAGAIN && errno != EINTR) {
			warning("recorder error in splice output");
			return -1;
		}
		ret = 0;
	} else
		update_fd(recorder, ret);

	return ret;
}

/*
 * Returns -1 on error.
 *          or bytes of data read.
 */
static long read_data(struct tracecmd_recorder *recorder)
{
	char buf[recorder->page_size];
	long ret;

	ret = read(recorder->trace_fd, buf, recorder->page_size);
	if (ret < 0) {
		if (errno != EAGAIN && errno != EINTR) {
			warning("recorder error in read output");
			return -1;
		}
		ret = 0;
	}
	if (ret > 0) {
		write(recorder->fd, buf, ret);
		update_fd(recorder, ret);
	}

	return ret;
}

static void set_nonblock(struct tracecmd_recorder *recorder)
{
	long flags;

	/* Do not block on reads for flushing */
	flags = fcntl(recorder->trace_fd, F_GETFL);
	fcntl(recorder->trace_fd, F_SETFL, flags | O_NONBLOCK);

	/* Do not block on streams for write */
	recorder->fd_flags |= 2; /* NON_BLOCK */
}

long tracecmd_flush_recording(struct tracecmd_recorder *recorder)
{
	char buf[recorder->page_size];
	long total = 0;
	long wrote = 0;
	long ret;

	set_nonblock(recorder);

	do {
		if (recorder->flags & TRACECMD_RECORD_NOSPLICE)
			ret = read_data(recorder);
		else
			ret = splice_data(recorder);
		if (ret < 0)
			return ret;
		total += ret;
	} while (ret);

	/* splice only reads full pages */
	do {
		ret = read(recorder->trace_fd, buf, recorder->page_size);
		if (ret > 0) {
			write(recorder->fd, buf, ret);
			wrote += ret;
		}

	} while (ret > 0);

	/* Make sure we finish off with a page size boundary */
	wrote &= recorder->page_size - 1;
	if (wrote) {
		memset(buf, 0, recorder->page_size);
		write(recorder->fd, buf, recorder->page_size - wrote);
		total += recorder->page_size;
	}

	return total;
}

int tracecmd_start_recording(struct tracecmd_recorder *recorder, unsigned long sleep)
{
	struct timespec req;
	long read = 1;
	long ret;

	recorder->stop = 0;

	do {
		/* Only sleep if we did not read anything last time */
		if (!read && sleep) {
			req.tv_sec = sleep / 1000000;
			req.tv_nsec = (sleep % 1000000) * 1000;
			nanosleep(&req, NULL);
		}
		read = 0;
		do {
			if (recorder->flags & TRACECMD_RECORD_NOSPLICE)
				ret = read_data(recorder);
			else
				ret = splice_data(recorder);
			if (ret < 0)
				return ret;
			read += ret;
		} while (ret);
	} while (!recorder->stop);

	/* Flush out the rest */
	ret = tracecmd_flush_recording(recorder);

	if (ret < 0)
		return ret;

	return 0;
}

void tracecmd_stop_recording(struct tracecmd_recorder *recorder)
{
	if (!recorder)
		return;

	set_nonblock(recorder);

	recorder->stop = 1;
}