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tools/virtio: use canonical ftrace path 

The canonical location for the tracefs filesystem is at /sys/kernel/tracing.

But, from Documentation/trace/ftrace.rst:

  Before 4.1, all ftrace tracing control files were within the debugfs
  file system, which is typically located at /sys/kernel/debug/tracing.
  For backward compatibility, when mounting the debugfs file system,
  the tracefs file system will be automatically mounted at:

  /sys/kernel/debug/tracing

A few spots in tools/virtio still refer to this older debugfs
path, so let's update them to avoid confusion.

Signed-off-by: Ross Zwisler <zwisler@google.com>
Message-Id: <20230215223350.2658616-6-zwisler@google.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
This commit is contained in:
Ross Zwisler 2023-02-15 15:33:49 -07:00 committed by Michael S. Tsirkin
parent beee7fdb5b
commit 07496eeab5
2 changed files with 9 additions and 5 deletions
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2
tools/virtio/virtio-trace/README
View File

@ -95,7 +95,7 @@ Run
1) Enable ftrace in the guest
<Example>
# echo 1 > /sys/kernel/debug/tracing/events/sched/enable
# echo 1 > /sys/kernel/tracing/events/sched/enable
2) Run trace agent in the guest
This agent must be operated as root.

12
tools/virtio/virtio-trace/trace-agent.c
View File

@ -18,8 +18,9 @@
#define PIPE_DEF_BUFS 16
#define PIPE_MIN_SIZE (PAGE_SIZE*PIPE_DEF_BUFS)
#define PIPE_MAX_SIZE (1024*1024)
#define READ_PATH_FMT \
"/sys/kernel/debug/tracing/per_cpu/cpu%d/trace_pipe_raw"
#define TRACEFS "/sys/kernel/tracing"
#define DEBUGFS "/sys/kernel/debug/tracing"
#define READ_PATH_FMT "%s/per_cpu/cpu%d/trace_pipe_raw"
#define WRITE_PATH_FMT "/dev/virtio-ports/trace-path-cpu%d"
#define CTL_PATH "/dev/virtio-ports/agent-ctl-path"
@ -120,9 +121,12 @@ static const char *make_path(int cpu_num, bool this_is_write_path)
if (this_is_write_path)
/* write(output) path */
ret = snprintf(buf, PATH_MAX, WRITE_PATH_FMT, cpu_num);
else
else {
/* read(input) path */
ret = snprintf(buf, PATH_MAX, READ_PATH_FMT, cpu_num);
ret = snprintf(buf, PATH_MAX, READ_PATH_FMT, TRACEFS, cpu_num);
if (ret > 0 && access(buf, F_OK) != 0)
ret = snprintf(buf, PATH_MAX, READ_PATH_FMT, DEBUGFS, cpu_num);
}
if (ret <= 0) {
pr_err("Failed to generate %s path(CPU#%d):%d\n",