diff mbox series

[RFC,v6,03/11] trace-cmd: Add TRACE_REQ and TRACE_RESP messages

Message ID 20190214141335.28144-4-kaslevs@vmware.com (mailing list archive)
State Superseded
Headers show
Series Add VM kernel tracing over vsockets and FIFOs | expand

Commit Message

Slavomir Kaslev Feb. 14, 2019, 2:13 p.m. UTC 
Add TRACE_REQ and TRACE_RESP messages which are used for initiating guest VM
tracing.

Signed-off-by: Slavomir Kaslev <kaslevs@vmware.com>
---
 include/trace-cmd/trace-cmd.h |  12 ++
 tracecmd/trace-msg.c          | 208 +++++++++++++++++++++++++++++++++-
 2 files changed, 219 insertions(+), 1 deletion(-)

Comments

Steven Rostedt Feb. 14, 2019, 6:51 p.m. UTC | #1 
On Thu, 14 Feb 2019 16:13:27 +0200
Slavomir Kaslev <kaslevs@vmware.com> wrote:

> + /*
> +  * NOTE: On success, the returned `argv` should be freed with:
> +  *     free(argv[0]);
> +  *     free(argv);
> +  */
> +int tracecmd_msg_recv_trace_req(struct tracecmd_msg_handle *msg_handle,
> +				int *argc, char ***argv)
> +{
> +	struct tracecmd_msg msg;
> +	char *p, *buf_end, **args;
> +	int i, ret, nr_args;
> +	ssize_t buf_len;
> +
> +	ret = tracecmd_msg_recv(msg_handle->fd, &msg);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (ntohl(msg.hdr.cmd) != MSG_TRACE_REQ) {
> +		ret = -ENOTSUP;
> +		goto out;
> +	}
> +
> +	nr_args = ntohl(msg.trace_req.argc);
> +	if (nr_args <= 0) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	buf_len = ntohl(msg.hdr.size) - MSG_HDR_LEN - ntohl(msg.hdr.cmd_size);
> +	buf_end = (char *)msg.buf + buf_len;
> +	if (buf_len <= 0 && ((char *)msg.buf)[buf_len-1] != '\0') {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	args = calloc(nr_args, sizeof(*args));
> +	if (!args) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	p = msg.buf;
> +	for (i = 0; i < nr_args; i++) {
> +		if (p >= buf_end) {
> +			ret = -EINVAL;
> +			goto out_args;
> +		}
> +		args[i] = p;
> +		p = strchr(p, '\0');
> +		if (!p) {
> +			ret = -EINVAL;
> +			goto out_args;
> +		}
> +		p++;
> +	}
> +
> +	/*
> +	 * On success we're passing msg.buf to the caller through argv[0] so we
> +	 * don't msg_free in this case.
> +	 */

This is OK for now, but I'm still wondering if we should just add:

	msg.buf = NULL;
	msg_free(&msg);

For robustness. What happens if for some reason in the future that we
add another allocation to msg? That would cause this to leak memory.

Yeah, yeah, this is highly paranoid, but code like this is exactly how
memory leaks come about and other bugs come about. It's taking advantage
of internals of how msg_free() works to optimize the case. And when the
internals change, things break.

No need to change anything here, I may just add the code on top of this
series.

-- Steve


> +	*argc = nr_args;
> +	*argv = args;
> +	return 0;
> +
> +out_args:
> +	free(args);
> +out:
> +	error_operation(&msg);
> +	if (ret == -EOPNOTSUPP)
> +		handle_unexpected_msg(msg_handle, &msg);
> +	msg_free(&msg);
> +	return ret;
> +}
> +
diff mbox series

Patch

diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
index 5961355..6a21e66 100644
--- a/include/trace-cmd/trace-cmd.h
+++ b/include/trace-cmd/trace-cmd.h
@@ -331,6 +331,18 @@  int tracecmd_msg_collect_data(struct tracecmd_msg_handle *msg_handle, int ofd);
 bool tracecmd_msg_done(struct tracecmd_msg_handle *msg_handle);
 void tracecmd_msg_set_done(struct tracecmd_msg_handle *msg_handle);
 
+int tracecmd_msg_send_trace_req(struct tracecmd_msg_handle *msg_handle,
+				int argc, char **argv);
+int tracecmd_msg_recv_trace_req(struct tracecmd_msg_handle *msg_handle,
+				int *argc, char ***argv);
+
+int tracecmd_msg_send_trace_resp(struct tracecmd_msg_handle *msg_handle,
+				 int nr_cpus, int page_size,
+				 unsigned int *ports);
+int tracecmd_msg_recv_trace_resp(struct tracecmd_msg_handle *msg_handle,
+				 int *nr_cpus, int *page_size,
+				 unsigned int **ports);
+
 /* --- Plugin handling --- */
 extern struct tep_plugin_option trace_ftrace_options[];
 
diff --git a/tracecmd/trace-msg.c b/tracecmd/trace-msg.c
index 51d0ac8..8b0a4e5 100644
--- a/tracecmd/trace-msg.c
+++ b/tracecmd/trace-msg.c
@@ -16,6 +16,7 @@ 
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <string.h>
 #include <unistd.h>
 #include <arpa/inet.h>
 #include <sys/types.h>
@@ -64,6 +65,17 @@  struct tracecmd_msg_rinit {
 	be32 cpus;
 } __attribute__((packed));
 
+struct tracecmd_msg_trace_req {
+	be32 flags;
+	be32 argc;
+} __attribute__((packed));
+
+struct tracecmd_msg_trace_resp {
+	be32 flags;
+	be32 cpus;
+	be32 page_size;
+} __attribute__((packed));
+
 struct tracecmd_msg_header {
 	be32	size;
 	be32	cmd;
@@ -76,7 +88,9 @@  struct tracecmd_msg_header {
 	C(RINIT,	2,	sizeof(struct tracecmd_msg_rinit)),	\
 	C(SEND_DATA,	3,	0),					\
 	C(FIN_DATA,	4,	0),					\
-	C(NOT_SUPP,	5,	0),
+	C(NOT_SUPP,	5,	0),					\
+	C(TRACE_REQ,	6,	sizeof(struct tracecmd_msg_trace_req)),	\
+	C(TRACE_RESP,	7,	sizeof(struct tracecmd_msg_trace_resp)),
 
 #undef C
 #define C(a,b,c)	MSG_##a = b
@@ -108,6 +122,8 @@  struct tracecmd_msg {
 	union {
 		struct tracecmd_msg_tinit	tinit;
 		struct tracecmd_msg_rinit	rinit;
+		struct tracecmd_msg_trace_req	trace_req;
+		struct tracecmd_msg_trace_resp	trace_resp;
 	};
 	union {
 		struct tracecmd_msg_opt		*opt;
@@ -723,3 +739,193 @@  error:
 	msg_free(&msg);
 	return ret;
 }
+
+static int make_trace_req(struct tracecmd_msg *msg, int argc, char **argv)
+{
+	size_t args_size = 0;
+	char *p;
+	int i;
+
+	for (i = 0; i < argc; i++)
+		args_size += strlen(argv[i]) + 1;
+
+	msg->hdr.size = htonl(ntohl(msg->hdr.size) + args_size);
+	msg->trace_req.argc = htonl(argc);
+	msg->buf = calloc(args_size, 1);
+	if (!msg->buf)
+		return -ENOMEM;
+
+	p = msg->buf;
+	for (i = 0; i < argc; i++)
+		p = stpcpy(p, argv[i]) + 1;
+
+	return 0;
+}
+
+int tracecmd_msg_send_trace_req(struct tracecmd_msg_handle *msg_handle,
+				int argc, char **argv)
+{
+	struct tracecmd_msg msg;
+	int ret;
+
+	tracecmd_msg_init(MSG_TRACE_REQ, &msg);
+	ret = make_trace_req(&msg, argc, argv);
+	if (ret < 0)
+		return ret;
+
+	return tracecmd_msg_send(msg_handle->fd, &msg);
+}
+
+ /*
+  * NOTE: On success, the returned `argv` should be freed with:
+  *     free(argv[0]);
+  *     free(argv);
+  */
+int tracecmd_msg_recv_trace_req(struct tracecmd_msg_handle *msg_handle,
+				int *argc, char ***argv)
+{
+	struct tracecmd_msg msg;
+	char *p, *buf_end, **args;
+	int i, ret, nr_args;
+	ssize_t buf_len;
+
+	ret = tracecmd_msg_recv(msg_handle->fd, &msg);
+	if (ret < 0)
+		return ret;
+
+	if (ntohl(msg.hdr.cmd) != MSG_TRACE_REQ) {
+		ret = -ENOTSUP;
+		goto out;
+	}
+
+	nr_args = ntohl(msg.trace_req.argc);
+	if (nr_args <= 0) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	buf_len = ntohl(msg.hdr.size) - MSG_HDR_LEN - ntohl(msg.hdr.cmd_size);
+	buf_end = (char *)msg.buf + buf_len;
+	if (buf_len <= 0 && ((char *)msg.buf)[buf_len-1] != '\0') {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	args = calloc(nr_args, sizeof(*args));
+	if (!args) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	p = msg.buf;
+	for (i = 0; i < nr_args; i++) {
+		if (p >= buf_end) {
+			ret = -EINVAL;
+			goto out_args;
+		}
+		args[i] = p;
+		p = strchr(p, '\0');
+		if (!p) {
+			ret = -EINVAL;
+			goto out_args;
+		}
+		p++;
+	}
+
+	/*
+	 * On success we're passing msg.buf to the caller through argv[0] so we
+	 * don't msg_free in this case.
+	 */
+	*argc = nr_args;
+	*argv = args;
+	return 0;
+
+out_args:
+	free(args);
+out:
+	error_operation(&msg);
+	if (ret == -EOPNOTSUPP)
+		handle_unexpected_msg(msg_handle, &msg);
+	msg_free(&msg);
+	return ret;
+}
+
+static int make_trace_resp(struct tracecmd_msg *msg,
+			   int page_size, int nr_cpus, unsigned int *ports)
+{
+	int ports_size = nr_cpus * sizeof(*msg->port_array);
+	int i;
+
+	msg->hdr.size = htonl(ntohl(msg->hdr.size) + ports_size);
+	msg->trace_resp.cpus = htonl(nr_cpus);
+	msg->trace_resp.page_size = htonl(page_size);
+
+	msg->port_array = malloc(ports_size);
+	if (!msg->port_array)
+		return -ENOMEM;
+
+	for (i = 0; i < nr_cpus; i++)
+		msg->port_array[i] = htonl(ports[i]);
+
+	return 0;
+}
+
+int tracecmd_msg_send_trace_resp(struct tracecmd_msg_handle *msg_handle,
+				 int nr_cpus, int page_size,
+				 unsigned int *ports)
+{
+	struct tracecmd_msg msg;
+	int ret;
+
+	tracecmd_msg_init(MSG_TRACE_RESP, &msg);
+	ret = make_trace_resp(&msg, page_size, nr_cpus, ports);
+	if (ret < 0)
+		return ret;
+
+	return tracecmd_msg_send(msg_handle->fd, &msg);
+}
+
+int tracecmd_msg_recv_trace_resp(struct tracecmd_msg_handle *msg_handle,
+				 int *nr_cpus, int *page_size,
+				 unsigned int **ports)
+{
+	struct tracecmd_msg msg;
+	ssize_t buf_len;
+	int i, ret;
+
+	ret = tracecmd_msg_recv(msg_handle->fd, &msg);
+	if (ret < 0)
+		return ret;
+
+	if (ntohl(msg.hdr.cmd) != MSG_TRACE_RESP) {
+		ret = -ENOTSUP;
+		goto out;
+	}
+
+	buf_len = ntohl(msg.hdr.size) - MSG_HDR_LEN - ntohl(msg.hdr.cmd_size);
+	if (buf_len <= 0 ||
+	    buf_len != sizeof(*msg.port_array) * ntohl(msg.trace_resp.cpus)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	*nr_cpus = ntohl(msg.trace_resp.cpus);
+	*page_size = ntohl(msg.trace_resp.page_size);
+	*ports = calloc(*nr_cpus, sizeof(**ports));
+	if (!*ports) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	for (i = 0; i < *nr_cpus; i++)
+		(*ports)[i] = ntohl(msg.port_array[i]);
+
+	msg_free(&msg);
+	return 0;
+
+out:
+	error_operation(&msg);
+	if (ret == -EOPNOTSUPP)
+		handle_unexpected_msg(msg_handle, &msg);
+	msg_free(&msg);
+	return ret;
+}