trace-record.c

#define _LARGEFILE64_SOURCE
#define _GNU_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"

struct tracecmd_recorder {
	int		fd;
	int		trace_fd;
	int		brass[2];
	int		page_size;
	int		cpu;
	int		stop;
};

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

	if (recorder->fd)
		close(recorder->fd);

	free(recorder);
}

struct tracecmd_recorder *tracecmd_create_recorder(const char *file, int cpu)
{
	struct tracecmd_recorder *recorder;
	char *tracing = NULL;
	char *path = NULL;
	int ret;

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

	recorder->cpu = cpu;

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

	recorder->page_size = getpagesize();

	recorder->fd = open(file, O_WRONLY | O_CREAT | O_TRUNC | O_LARGEFILE, 0644);
	if (recorder->fd < 0)
		goto out_free;

	tracing = tracecmd_find_tracing_dir();
	if (!tracing) {
		errno = ENODEV;
		goto out_free;
	}

	path = malloc_or_die(strlen(tracing) + 40);
	if (!path)
		goto out_free;

	sprintf(path, "%s/per_cpu/cpu%d/trace_pipe_raw", tracing, cpu);
	recorder->trace_fd = open(path, O_RDONLY);
	if (recorder->trace_fd < 0)
		goto out_free;

	free(tracing);
	free(path);

	ret = pipe(recorder->brass);
	if (ret < 0)
		goto out_free;

	return recorder;

 out_free:
	free(tracing);
	free(path);

	tracecmd_free_recorder(recorder);
	return NULL;
}

int tracecmd_start_recording(struct tracecmd_recorder *recorder)
{
	char *buf[recorder->page_size];
	int ret;

	recorder->stop = 0;

	do {
		ret = splice(recorder->trace_fd, NULL, recorder->brass[1], NULL,
			     recorder->page_size, 1 /* SPLICE_F_MOVE */);
		if (ret < 0) {
			warning("recorder error in splice input");
			return -1;
		}
		ret = splice(recorder->brass[0], NULL, recorder->fd, NULL,
			     recorder->page_size, 3 /* and NON_BLOCK */);
		if (ret < 0 && errno != EAGAIN) {
			warning("recorder error in splice output");
			return -1;
		}
	} while (!recorder->stop);

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

	return 0;
}

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

	recorder->stop = 1;
}