Something went wrong. Try again.
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Something went wrong. Try again.
1.4 kB · 73 lines
C
at master
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374// 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 <sys/uio.h>#include <fcntl.h>#include <stdio.h>#include <unistd.h>#include <linux/user_events.h>
const char *data_file = "/sys/kernel/tracing/user_events_data";int enabled = 0;
static int event_reg(int fd, const char *command, int *write, int *enabled){ struct user_reg reg = {0};
reg.size = sizeof(reg); reg.enable_bit = 31; reg.enable_size = sizeof(*enabled); reg.enable_addr = (__u64)enabled; reg.name_args = (__u64)command;
if (ioctl(fd, DIAG_IOCSREG, ®) == -1) return -1;
*write = reg.write_index;
return 0;}
int main(int argc, char **argv){ int data_fd, write; struct iovec io[2]; __u32 count = 0;
data_fd = open(data_file, O_RDWR);
if (event_reg(data_fd, "test u32 count", &write, &enabled) == -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 (enabled) { /* 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;}