[RFC PATCH v5 07/11] trace-cmd: Add `trace-cmd setup-guest` command

[Slavomir Kaslev <kaslevs@vmware.com>]

Add `trace-cmd setup-guest` command that creates the necessary FIFOs for tracing
a guest over FIFOs instead of vsockets.

Signed-off-by: Slavomir Kaslev <kaslevs@vmware.com>
---
 tracecmd/Makefile              |   1 +
 tracecmd/include/trace-local.h |   6 ++
 tracecmd/trace-cmd.c           |   1 +
 tracecmd/trace-setup-guest.c   | 181 +++++++++++++++++++++++++++++++++
 tracecmd/trace-usage.c         |   8 ++
 5 files changed, 197 insertions(+)
 create mode 100644 tracecmd/trace-setup-guest.c

diff --git a/tracecmd/Makefile b/tracecmd/Makefile
index 865b1c6..d3e3080 100644
--- a/tracecmd/Makefile
+++ b/tracecmd/Makefile
@@ -35,6 +35,7 @@ TRACE_CMD_OBJS += trace-msg.o
 
 ifeq ($(VSOCK_DEFINED), 1)
 TRACE_CMD_OBJS += trace-agent.o
+TRACE_CMD_OBJS += trace-setup-guest.o
 endif
 
 ALL_OBJS := $(TRACE_CMD_OBJS:%.o=$(bdir)/%.o)
diff --git a/tracecmd/include/trace-local.h b/tracecmd/include/trace-local.h
index 823d323..b23130e 100644
--- a/tracecmd/include/trace-local.h
+++ b/tracecmd/include/trace-local.h
@@ -14,6 +14,10 @@
 
 #define TRACE_AGENT_DEFAULT_PORT	823
 
+#define GUEST_PIPE_NAME		"trace-pipe-cpu"
+#define GUEST_DIR_FMT		"/var/lib/trace-cmd/virt/%s"
+#define GUEST_FIFO_FMT		GUEST_DIR_FMT "/" GUEST_PIPE_NAME "%d"
+
 extern int debug;
 extern int quiet;
 
@@ -68,6 +72,8 @@ void trace_listen(int argc, char **argv);
 
 void trace_agent(int argc, char **argv);
 
+void trace_setup_guest(int argc, char **argv);
+
 void trace_restore(int argc, char **argv);
 
 void trace_clear(int argc, char **argv);
diff --git a/tracecmd/trace-cmd.c b/tracecmd/trace-cmd.c
index 3ae5e2e..4da82b4 100644
--- a/tracecmd/trace-cmd.c
+++ b/tracecmd/trace-cmd.c
@@ -85,6 +85,7 @@ struct command commands[] = {
 	{"listen", trace_listen},
 #ifdef VSOCK
 	{"agent", trace_agent},
+	{"setup-guest", trace_setup_guest},
 #endif
 	{"split", trace_split},
 	{"restore", trace_restore},
diff --git a/tracecmd/trace-setup-guest.c b/tracecmd/trace-setup-guest.c
new file mode 100644
index 0000000..1a2c8d4
--- /dev/null
+++ b/tracecmd/trace-setup-guest.c
@@ -0,0 +1,181 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 VMware Inc, Slavomir Kaslev <kaslevs@vmware.com>
+ *
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <grp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "trace-local.h"
+#include "trace-msg.h"
+
+static int make_dir(const char *path, mode_t mode)
+{
+	char *buf, *end, *p;
+	int ret = 0;
+
+	buf = strdup(path);
+	end = buf + strlen(buf);
+
+	for (p = buf; p < end; p++) {
+		for (; p < end && *p == '/'; p++);
+		for (; p < end && *p != '/'; p++);
+
+		*p = '\0';
+		ret = mkdir(buf, mode);
+		if (ret < 0) {
+			if (errno != EEXIST)
+				break;
+			ret = 0;
+		}
+		*p = '/';
+	}
+
+	free(buf);
+	return ret;
+}
+
+static int make_fifo(const char *path, mode_t mode)
+{
+	struct stat st;
+	int ret;
+
+	ret = stat(path, &st);
+	if (ret == 0) {
+		if (S_ISFIFO(st.st_mode))
+			return 0;
+		errno = EEXIST;
+		return -1;
+	}
+
+	return mkfifo(path, mode);
+}
+
+static int make_guest_dir(const char *guest)
+{
+	char path[PATH_MAX];
+
+	snprintf(path, sizeof(path), GUEST_DIR_FMT, guest);
+	return make_dir(path, 0750);
+}
+
+static int make_guest_fifo(const char *guest, int cpu, mode_t mode)
+{
+	static const char *exts[] = {".in", ".out"};
+	char path[PATH_MAX];
+	int i, ret = 0;
+
+	for (i = 0; i < ARRAY_SIZE(exts); i++) {
+		snprintf(path, sizeof(path), GUEST_FIFO_FMT "%s",
+			 guest, cpu, exts[i]);
+		ret = make_fifo(path, mode);
+		if (ret < 0)
+			break;
+	}
+
+	return ret;
+}
+
+static int make_guest_fifos(const char *guest, int nr_cpus, mode_t mode)
+{
+	int i, ret = 0;
+	mode_t mask;
+
+	mask = umask(0);
+	for (i = 0; i < nr_cpus; i++) {
+		ret = make_guest_fifo(guest, i, mode);
+		if (ret < 0)
+			break;
+	}
+	umask(mask);
+
+	return ret;
+}
+
+static void do_setup_guest(const char *guest, int nr_cpus, mode_t mode, gid_t gid)
+{
+	gid_t save_egid;
+	int ret;
+
+	save_egid = getegid();
+	ret = setegid(gid);
+	if (ret < 0)
+		pdie("failed to set effective group ID");
+
+	ret = make_guest_dir(guest);
+	if (ret < 0)
+		pdie("failed to create guest directory for %s", guest);
+
+	ret = make_guest_fifos(guest, nr_cpus, mode);
+	if (ret < 0)
+		pdie("failed to create FIFOs for %s", guest);
+
+	ret = setegid(save_egid);
+	if (ret < 0)
+		pdie("failed to restore effective group ID");
+}
+
+void trace_setup_guest(int argc, char **argv)
+{
+	struct group *group;
+	mode_t mode = 0660;
+	int nr_cpus = -1;
+	gid_t gid = -1;
+	char *guest;
+
+	if (argc < 2)
+		usage(argv);
+
+	if (strcmp(argv[1], "setup-guest") != 0)
+		usage(argv);
+
+	for (;;) {
+		int c, option_index = 0;
+		static struct option long_options[] = {
+			{"help", no_argument, NULL, '?'},
+			{NULL, 0, NULL, 0}
+		};
+
+		c = getopt_long(argc-1, argv+1, "+hc:p:g:",
+				long_options, &option_index);
+		if (c == -1)
+			break;
+		switch (c) {
+		case 'h':
+			usage(argv);
+			break;
+		case 'c':
+			nr_cpus = atoi(optarg);
+			break;
+		case 'p':
+			mode = strtol(optarg, NULL, 8);
+			break;
+		case 'g':
+			group = getgrnam(optarg);
+			if (!group)
+				pdie("group %s does not exist", optarg);
+			gid = group->gr_gid;
+			break;
+		default:
+			usage(argv);
+		}
+	}
+
+	if (optind != argc-2)
+		usage(argv);
+
+	guest = argv[optind+1];
+
+	if (nr_cpus <= 0)
+		pdie("invalid number of cpus for guest %s", guest);
+
+	do_setup_guest(guest, nr_cpus, mode, gid);
+}
diff --git a/tracecmd/trace-usage.c b/tracecmd/trace-usage.c
index e845f50..7a8002f 100644
--- a/tracecmd/trace-usage.c
+++ b/tracecmd/trace-usage.c
@@ -246,6 +246,14 @@ static struct usage_help usage_help[] = {
 		"          -p port number to listen on.\n"
 		"          -D run in daemon mode.\n"
 	},
+	{
+		"setup-guest",
+		"create FIFOs for tracing guest VMs",
+		" %s setup-guest -c cpus[-p perm][-g group] guest\n"
+		"          -c number of guest virtual CPUs\n"
+		"          -p FIFOs permissions (default: 0660)\n"
+		"          -g FIFOs group owner\n"
+	},
 #endif
 	{
 		"list",
-- 
2.19.1