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c57eb47815
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>
91 lines
1.7 KiB
C
91 lines
1.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (c) 2021, Microsoft Corporation.
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*
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* Authors:
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* Beau Belgrave <beaub@linux.microsoft.com>
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*/
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#include <errno.h>
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#include <sys/ioctl.h>
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#include <sys/mman.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <linux/user_events.h>
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/* Assumes debugfs is mounted */
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const char *data_file = "/sys/kernel/debug/tracing/user_events_data";
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const char *status_file = "/sys/kernel/debug/tracing/user_events_status";
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static int event_status(char **status)
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{
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int fd = open(status_file, O_RDONLY);
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*status = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ,
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MAP_SHARED, fd, 0);
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close(fd);
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if (*status == MAP_FAILED)
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return -1;
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return 0;
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}
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static int event_reg(int fd, const char *command, int *status, int *write)
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{
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struct user_reg reg = {0};
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reg.size = sizeof(reg);
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reg.name_args = (__u64)command;
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if (ioctl(fd, DIAG_IOCSREG, ®) == -1)
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return -1;
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*status = reg.status_index;
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*write = reg.write_index;
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return 0;
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}
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int main(int argc, char **argv)
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{
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int data_fd, status, write;
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char *status_page;
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struct iovec io[2];
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__u32 count = 0;
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if (event_status(&status_page) == -1)
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return errno;
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data_fd = open(data_file, O_RDWR);
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if (event_reg(data_fd, "test u32 count", &status, &write) == -1)
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return errno;
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/* Setup iovec */
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io[0].iov_base = &write;
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io[0].iov_len = sizeof(write);
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io[1].iov_base = &count;
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io[1].iov_len = sizeof(count);
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ask:
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printf("Press enter to check status...\n");
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getchar();
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/* Check if anyone is listening */
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if (status_page[status]) {
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/* Yep, trace out our data */
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writev(data_fd, (const struct iovec *)io, 2);
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/* Increase the count */
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count++;
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printf("Something was attached, wrote data\n");
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}
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goto ask;
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return 0;
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}
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