tools: Add guest trace agent as a user tool

This patch adds a user tool, "trace agent" for sending trace data of a guest to
a Host in low overhead. This agent has the following functions:
 - splice a page of ring-buffer to read_pipe without memory copying
 - splice the page from write_pipe to virtio-console without memory copying
 - write trace data to stdout by using -o option
 - controlled by start/stop orders from a Host

Changes in v2:
 - Cleanup (change fprintf() to pr_err() and an include guard)

Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Acked-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 270 insertions, 0 deletions

diff --git a/tools/virtio/virtio-trace/trace-agent.c b/tools/virtio/virtio-trace/trace-agent.c
new file mode 100644
index 000000000000..0a0a7dd4eff7
--- /dev/null
+++ b/tools/virtio/virtio-trace/trace-agent.c
@@ -0,0 +1,270 @@
+/*
+ * Guest agent for virtio-trace
+ *
+ * Copyright (C) 2012 Hitachi, Ltd.
+ * Created by Yoshihiro Yunomae <yoshihiro.yunomae.ez@hitachi.com>
+ *            Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
+ *
+ * Licensed under GPL version 2 only.
+ *
+ */
+
+#define _GNU_SOURCE
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "trace-agent.h"
+
+#define PAGE_SIZE               (sysconf(_SC_PAGE_SIZE))
+#define PIPE_DEF_BUFS           16
+#define PIPE_MIN_SIZE           (PAGE_SIZE*PIPE_DEF_BUFS)
+#define PIPE_MAX_SIZE           (1024*1024)
+#define READ_PATH_FMT   \
+                "/sys/kernel/debug/tracing/per_cpu/cpu%d/trace_pipe_raw"
+#define WRITE_PATH_FMT          "/dev/virtio-ports/trace-path-cpu%d"
+#define CTL_PATH                "/dev/virtio-ports/agent-ctl-path"
+
+pthread_mutex_t mutex_notify = PTHREAD_MUTEX_INITIALIZER;
+pthread_cond_t cond_wakeup = PTHREAD_COND_INITIALIZER;
+
+static int get_total_cpus(void)
+{
+        int nr_cpus = (int)sysconf(_SC_NPROCESSORS_CONF);
+
+        if (nr_cpus <= 0) {
+                pr_err("Could not read cpus\n");
+                goto error;
+        } else if (nr_cpus > MAX_CPUS) {
+                pr_err("Exceed max cpus(%d)\n", (int)MAX_CPUS);
+                goto error;
+        }
+
+        return nr_cpus;
+
+error:
+        exit(EXIT_FAILURE);
+}
+
+static void *agent_info_new(void)
+{
+        struct agent_info *s;
+        int i;
+
+        s = zalloc(sizeof(struct agent_info));
+        if (s == NULL) {
+                pr_err("agent_info zalloc error\n");
+                exit(EXIT_FAILURE);
+        }
+
+        s->pipe_size = PIPE_INIT;
+        s->use_stdout = false;
+        s->cpus = get_total_cpus();
+        s->ctl_fd = -1;
+
+        /* read/write threads init */
+        for (i = 0; i < s->cpus; i++)
+                s->rw_ti[i] = rw_thread_info_new();
+
+        return s;
+}
+
+static unsigned long parse_size(const char *arg)
+{
+        unsigned long value, round;
+        char *ptr;
+
+        value = strtoul(arg, &ptr, 10);
+        switch (*ptr) {
+        case 'K': case 'k':
+                value <<= 10;
+                break;
+        case 'M': case 'm':
+                value <<= 20;
+                break;
+        default:
+                break;
+        }
+
+        if (value > PIPE_MAX_SIZE) {
+                pr_err("Pipe size must be less than 1MB\n");
+                goto error;
+        } else if (value < PIPE_MIN_SIZE) {
+                pr_err("Pipe size must be over 64KB\n");
+                goto error;
+        }
+
+        /* Align buffer size with page unit */
+        round = value & (PAGE_SIZE - 1);
+        value = value - round;
+
+        return value;
+error:
+        return 0;
+}
+
+static void usage(char const *prg)
+{
+        pr_err("usage: %s [-h] [-o] [-s <size of pipe>]\n", prg);
+}
+
+static const char *make_path(int cpu_num, bool this_is_write_path)
+{
+        int ret;
+        char *buf;
+
+        buf = zalloc(PATH_MAX);
+        if (buf == NULL) {
+                pr_err("Could not allocate buffer\n");
+                goto error;
+        }
+
+        if (this_is_write_path)
+                /* write(output) path */
+                ret = snprintf(buf, PATH_MAX, WRITE_PATH_FMT, cpu_num);
+        else
+                /* read(input) path */
+                ret = snprintf(buf, PATH_MAX, READ_PATH_FMT, cpu_num);
+
+        if (ret <= 0) {
+                pr_err("Failed to generate %s path(CPU#%d):%d\n",
+                        this_is_write_path ? "read" : "write", cpu_num, ret);
+                goto error;
+        }
+
+        return buf;
+
+error:
+        free(buf);
+        return NULL;
+}
+
+static const char *make_input_path(int cpu_num)
+{
+        return make_path(cpu_num, false);
+}
+
+static const char *make_output_path(int cpu_num)
+{
+        return make_path(cpu_num, true);
+}
+
+static void *agent_info_init(struct agent_info *s)
+{
+        int cpu;
+        const char *in_path = NULL;
+        const char *out_path = NULL;
+
+        /* init read/write threads */
+        for (cpu = 0; cpu < s->cpus; cpu++) {
+                /* set read(input) path per read/write thread */
+                in_path = make_input_path(cpu);
+                if (in_path == NULL)
+                        goto error;
+
+                /* set write(output) path per read/write thread*/
+                if (!s->use_stdout) {
+                        out_path = make_output_path(cpu);
+                        if (out_path == NULL)
+                                goto error;
+                } else
+                        /* stdout mode */
+                        pr_debug("stdout mode\n");
+
+                rw_thread_init(cpu, in_path, out_path, s->use_stdout,
+                                                s->pipe_size, s->rw_ti[cpu]);
+        }
+
+        /* init controller of read/write threads */
+        s->ctl_fd = rw_ctl_init((const char *)CTL_PATH);
+
+        return NULL;
+
+error:
+        exit(EXIT_FAILURE);
+}
+
+static void *parse_args(int argc, char *argv[], struct agent_info *s)
+{
+        int cmd;
+        unsigned long size;
+
+        while ((cmd = getopt(argc, argv, "hos:")) != -1) {
+                switch (cmd) {
+                /* stdout mode */
+                case 'o':
+                        s->use_stdout = true;
+                        break;
+                /* size of pipe */
+                case 's':
+                        size = parse_size(optarg);
+                        if (size == 0)
+                                goto error;
+                        s->pipe_size = size;
+                        break;
+                case 'h':
+                default:
+                        usage(argv[0]);
+                        goto error;
+                }
+        }
+
+        agent_info_init(s);
+
+        return NULL;
+
+error:
+        exit(EXIT_FAILURE);
+}
+
+static void agent_main_loop(struct agent_info *s)
+{
+        int cpu;
+        pthread_t rw_thread_per_cpu[MAX_CPUS];
+
+        /* Start all read/write threads */
+        for (cpu = 0; cpu < s->cpus; cpu++)
+                rw_thread_per_cpu[cpu] = rw_thread_run(s->rw_ti[cpu]);
+
+        rw_ctl_loop(s->ctl_fd);
+
+        /* Finish all read/write threads */
+        for (cpu = 0; cpu < s->cpus; cpu++) {
+                int ret;
+
+                ret = pthread_join(rw_thread_per_cpu[cpu], NULL);
+                if (ret != 0) {
+                        pr_err("pthread_join() error:%d (cpu %d)\n", ret, cpu);
+                        exit(EXIT_FAILURE);
+                }
+        }
+}
+
+static void agent_info_free(struct agent_info *s)
+{
+        int i;
+
+        close(s->ctl_fd);
+        for (i = 0; i < s->cpus; i++) {
+                close(s->rw_ti[i]->in_fd);
+                close(s->rw_ti[i]->out_fd);
+                close(s->rw_ti[i]->read_pipe);
+                close(s->rw_ti[i]->write_pipe);
+                free(s->rw_ti[i]);
+        }
+        free(s);
+}
+
+int main(int argc, char *argv[])
+{
+        struct agent_info *s = NULL;
+
+        s = agent_info_new();
+        parse_args(argc, argv, s);
+
+        agent_main_loop(s);
+
+        agent_info_free(s);
+
+        return 0;
+}