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tracing/user_events: Use write ABI in example

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The ABI has changed to use a remote write approach. Update the example
to show the expected use of this new ABI. Also remove debugfs
path and use tracefs to ensure example works in more environments.

Link: https://lkml.kernel.org/r/20230328235219.203-9-beaub@linux.microsoft.com

Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Beau Belgrave 2023-03-28 16:52:15 -07:00 committed by Steven Rostedt (Google)
parent 60b1af8de8
commit 9211ddaa78
1 changed files with 8 additions and 37 deletions
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45
samples/user_events/example.c
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@ -9,51 +9,28 @@
#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 <asm/bitsperlong.h>
#include <endian.h>
#include <linux/user_events.h>
#if __BITS_PER_LONG == 64
#define endian_swap(x) htole64(x)
#else
#define endian_swap(x) htole32(x)
#endif
/* Assumes debugfs is mounted */
const char *data_file = "/sys/kernel/tracing/user_events_data";
const char *status_file = "/sys/kernel/tracing/user_events_status";
int enabled = 0;
static int event_status(long **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, long *index, long *mask,
int *write)
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, &reg) == -1)
return -1;
*index = reg.status_bit / __BITS_PER_LONG;
*mask = endian_swap(1L << (reg.status_bit % __BITS_PER_LONG));
*write = reg.write_index;
return 0;
@ -62,17 +39,12 @@ static int event_reg(int fd, const char *command, long *index, long *mask,
int main(int argc, char **argv)
{
int data_fd, write;
long index, mask;
long *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", &index, &mask, &write) == -1)
if (event_reg(data_fd, "test u32 count", &write, &enabled) == -1)
return errno;
/* Setup iovec */
@ -80,13 +52,12 @@ int main(int argc, char **argv)
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[index] & mask) {
if (enabled) {
/* Yep, trace out our data */
writev(data_fd, (const struct iovec *)io, 2);