lkml.org 
[lkml]   [2021]   [Dec]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v8 10/12] user_events: Add sample code for typical usage
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
>


--
Masami Hiramatsu <mhiramat@kernel.org>

\
 
 \ /
  Last update: 2021-12-23 00:18    [W:0.322 / U:0.316 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site