diff options
author | Beau Belgrave <beaub@linux.microsoft.com> | 2022-01-18 12:43:25 -0800 |
---|---|---|
committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2022-02-10 22:38:15 -0500 |
commit | c57eb47815097d879e1fa8c81e313aec917d8f4d (patch) | |
tree | a7db6221e5e19b4cf57cea173ed0c9de565a2a60 | |
parent | 7640e77035aadcd7d50f9c7583ca25a4e1aa2874 (diff) | |
download | linux-c57eb47815097d879e1fa8c81e313aec917d8f4d.tar.bz2 |
user_events: Add sample code for typical usage
Add sample code for user_events typical usage to show how to register
and monitor status, as well as to write out data.
Link: https://lkml.kernel.org/r/20220118204326.2169-12-beaub@linux.microsoft.com
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
-rw-r--r-- | samples/user_events/Makefile | 5 | ||||
-rw-r--r-- | samples/user_events/example.c | 91 |
2 files changed, 96 insertions, 0 deletions
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, ®) == -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; +} |