diff mbox series

[v8,10/12] user_events: Add sample code for typical usage

Message ID 20211216173511.10390-11-beaub@linux.microsoft.com (mailing list archive)
State Superseded
Headers show
Series user_events: Enable user processes to create and write to trace events | expand

Commit Message

Beau Belgrave Dec. 16, 2021, 5:35 p.m. UTC 
Add sample code for user_events typical usage to show how to register
and monitor status, as well as to write out data.

Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
---
 samples/user_events/Makefile  |  5 ++
 samples/user_events/example.c | 91 +++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 samples/user_events/Makefile
 create mode 100644 samples/user_events/example.c

Comments

Masami Hiramatsu (Google) Dec. 22, 2021, 11:18 p.m. UTC | #1 
On Thu, 16 Dec 2021 09:35:09 -0800
Beau Belgrave <beaub@linux.microsoft.com> wrote:

> Add sample code for user_events typical usage to show how to register
> and monitor status, as well as to write out data.

Ah, here is the sample code. OK.

Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>

Thanks!

> 
> Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
> ---
>  samples/user_events/Makefile  |  5 ++
>  samples/user_events/example.c | 91 +++++++++++++++++++++++++++++++++++
>  2 files changed, 96 insertions(+)
>  create mode 100644 samples/user_events/Makefile
>  create mode 100644 samples/user_events/example.c
> 
> diff --git a/samples/user_events/Makefile b/samples/user_events/Makefile
> new file mode 100644
> index 000000000000..7252b589db57
> --- /dev/null
> +++ b/samples/user_events/Makefile
> @@ -0,0 +1,5 @@
> +# SPDX-License-Identifier: GPL-2.0
> +CFLAGS += -Wl,-no-as-needed -Wall -I../../usr/include
> +
> +example: example.o
> +example.o: example.c
> diff --git a/samples/user_events/example.c b/samples/user_events/example.c
> new file mode 100644
> index 000000000000..4f5778e441c0
> --- /dev/null
> +++ b/samples/user_events/example.c
> @@ -0,0 +1,91 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2021, Microsoft Corporation.
> + *
> + * Authors:
> + *   Beau Belgrave <beaub@linux.microsoft.com>
> + */
> +
> +#include <errno.h>
> +#include <sys/ioctl.h>
> +#include <sys/mman.h>
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <linux/user_events.h>
> +
> +/* Assumes debugfs is mounted */
> +const char *data_file = "/sys/kernel/debug/tracing/user_events_data";
> +const char *status_file = "/sys/kernel/debug/tracing/user_events_status";
> +
> +static int event_status(char **status)
> +{
> +	int fd = open(status_file, O_RDONLY);
> +
> +	*status = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ,
> +		       MAP_SHARED, fd, 0);
> +
> +	close(fd);
> +
> +	if (*status == MAP_FAILED)
> +		return -1;
> +
> +	return 0;
> +}
> +
> +static int event_reg(int fd, const char *command, int *status, int *write)
> +{
> +	struct user_reg reg = {0};
> +
> +	reg.size = sizeof(reg);
> +	reg.name_args = (__u64)command;
> +
> +	if (ioctl(fd, DIAG_IOCSREG, &reg) == -1)
> +		return -1;
> +
> +	*status = reg.status_index;
> +	*write = reg.write_index;
> +
> +	return 0;
> +}
> +
> +int main(int argc, char **argv)
> +{
> +	int data_fd, status, write;
> +	char *status_page;
> +	struct iovec io[2];
> +	__u32 count = 0;
> +
> +	if (event_status(&status_page) == -1)
> +		return errno;
> +
> +	data_fd = open(data_file, O_RDWR);
> +
> +	if (event_reg(data_fd, "test u32 count", &status, &write) == -1)
> +		return errno;
> +
> +	/* Setup iovec */
> +	io[0].iov_base = &write;
> +	io[0].iov_len = sizeof(write);
> +	io[1].iov_base = &count;
> +	io[1].iov_len = sizeof(count);
> +
> +ask:
> +	printf("Press enter to check status...\n");
> +	getchar();
> +
> +	/* Check if anyone is listening */
> +	if (status_page[status]) {
> +		/* Yep, trace out our data */
> +		writev(data_fd, (const struct iovec *)io, 2);
> +
> +		/* Increase the count */
> +		count++;
> +
> +		printf("Something was attached, wrote data\n");
> +	}
> +
> +	goto ask;
> +
> +	return 0;
> +}
> -- 
> 2.17.1
>
Steven Rostedt Jan. 6, 2022, 10:09 p.m. UTC | #2 
On Thu, 23 Dec 2021 08:18:14 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> On Thu, 16 Dec 2021 09:35:09 -0800
> Beau Belgrave <beaub@linux.microsoft.com> wrote:
> 
> > Add sample code for user_events typical usage to show how to register
> > and monitor status, as well as to write out data.  
> 
> Ah, here is the sample code. OK.
> 
> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>

Ah, probably should swap the patches around (makes it easier on the
reviewers ;-)

That is, 10 should come before 9, so that the reference to samples exists
when the document is added.

-- Steve
Beau Belgrave Jan. 6, 2022, 11:06 p.m. UTC | #3 
On Thu, Jan 06, 2022 at 05:09:07PM -0500, Steven Rostedt wrote:
> On Thu, 23 Dec 2021 08:18:14 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
> 
> > On Thu, 16 Dec 2021 09:35:09 -0800
> > Beau Belgrave <beaub@linux.microsoft.com> wrote:
> > 
> > > Add sample code for user_events typical usage to show how to register
> > > and monitor status, as well as to write out data.  
> > 
> > Ah, here is the sample code. OK.
> > 
> > Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
> 
> Ah, probably should swap the patches around (makes it easier on the
> reviewers ;-)
> 
> That is, 10 should come before 9, so that the reference to samples exists
> when the document is added.
> 
> -- Steve

Sure thing.

Thanks,
-Beau
diff mbox series

Patch

diff --git a/samples/user_events/Makefile b/samples/user_events/Makefile
new file mode 100644
index 000000000000..7252b589db57
--- /dev/null
+++ b/samples/user_events/Makefile
@@ -0,0 +1,5 @@ 
+# SPDX-License-Identifier: GPL-2.0
+CFLAGS += -Wl,-no-as-needed -Wall -I../../usr/include
+
+example: example.o
+example.o: example.c
diff --git a/samples/user_events/example.c b/samples/user_events/example.c
new file mode 100644
index 000000000000..4f5778e441c0
--- /dev/null
+++ b/samples/user_events/example.c
@@ -0,0 +1,91 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2021, Microsoft Corporation.
+ *
+ * Authors:
+ *   Beau Belgrave <beaub@linux.microsoft.com>
+ */
+
+#include <errno.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <linux/user_events.h>
+
+/* Assumes debugfs is mounted */
+const char *data_file = "/sys/kernel/debug/tracing/user_events_data";
+const char *status_file = "/sys/kernel/debug/tracing/user_events_status";
+
+static int event_status(char **status)
+{
+	int fd = open(status_file, O_RDONLY);
+
+	*status = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ,
+		       MAP_SHARED, fd, 0);
+
+	close(fd);
+
+	if (*status == MAP_FAILED)
+		return -1;
+
+	return 0;
+}
+
+static int event_reg(int fd, const char *command, int *status, int *write)
+{
+	struct user_reg reg = {0};
+
+	reg.size = sizeof(reg);
+	reg.name_args = (__u64)command;
+
+	if (ioctl(fd, DIAG_IOCSREG, &reg) == -1)
+		return -1;
+
+	*status = reg.status_index;
+	*write = reg.write_index;
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	int data_fd, status, write;
+	char *status_page;
+	struct iovec io[2];
+	__u32 count = 0;
+
+	if (event_status(&status_page) == -1)
+		return errno;
+
+	data_fd = open(data_file, O_RDWR);
+
+	if (event_reg(data_fd, "test u32 count", &status, &write) == -1)
+		return errno;
+
+	/* Setup iovec */
+	io[0].iov_base = &write;
+	io[0].iov_len = sizeof(write);
+	io[1].iov_base = &count;
+	io[1].iov_len = sizeof(count);
+
+ask:
+	printf("Press enter to check status...\n");
+	getchar();
+
+	/* Check if anyone is listening */
+	if (status_page[status]) {
+		/* Yep, trace out our data */
+		writev(data_fd, (const struct iovec *)io, 2);
+
+		/* Increase the count */
+		count++;
+
+		printf("Something was attached, wrote data\n");
+	}
+
+	goto ask;
+
+	return 0;
+}