Commit 27d7fdf0 authored by Ross Zwisler's avatar Ross Zwisler Committed by Alexei Starovoitov
Browse files

bpf: 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

Many comments and samples in the bpf code still refer to this older
debugfs path, so let's update them to avoid confusion.  There are a few
spots where the bpf code explicitly checks both tracefs and debugfs
(tools/bpf/bpftool/tracelog.c and tools/lib/api/fs/fs.c) and I've left
those alone so that the tools can continue to work with both paths.

Signed-off-by: default avatarRoss Zwisler <zwisler@google.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20230313205628.1058720-2-zwisler@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 9e36a204

include/uapi/linux/bpf.h

+4 −4
Original line number Diff line number Diff line
@@ -1647,17 +1647,17 @@ union bpf_attr { 
 * 	Description

 * 		This helper is a "printk()-like" facility for debugging. It

 * 		prints a message defined by format *fmt* (of size *fmt_size*)

 * 		to file *\/sys/kernel/debug/tracing/trace* from DebugFS, if

 * 		to file *\/sys/kernel/tracing/trace* from TraceFS, if

 * 		available. It can take up to three additional **u64**

 * 		arguments (as an eBPF helpers, the total number of arguments is

 * 		limited to five).

 *

 * 		Each time the helper is called, it appends a line to the trace.

 * 		Lines are discarded while *\/sys/kernel/debug/tracing/trace* is

 * 		open, use *\/sys/kernel/debug/tracing/trace_pipe* to avoid this.

 * 		Lines are discarded while *\/sys/kernel/tracing/trace* is

 * 		open, use *\/sys/kernel/tracing/trace_pipe* to avoid this.

 * 		The format of the trace is customizable, and the exact output

 * 		one will get depends on the options set in

 * 		*\/sys/kernel/debug/tracing/trace_options* (see also the

 * 		*\/sys/kernel/tracing/trace_options* (see also the

 * 		*README* file under the same directory). However, it usually

 * 		defaults to something like:

 *

samples/bpf/cpustat_kern.c

+2 −2
Original line number Diff line number Diff line
@@ -76,8 +76,8 @@ struct { 


/*

 * The trace events for cpu_idle and cpu_frequency are taken from:

 * /sys/kernel/debug/tracing/events/power/cpu_idle/format

 * /sys/kernel/debug/tracing/events/power/cpu_frequency/format

 * /sys/kernel/tracing/events/power/cpu_idle/format

 * /sys/kernel/tracing/events/power/cpu_frequency/format

 *

 * These two events have same format, so define one common structure.

 */

samples/bpf/hbm.c

+2 −2
Original line number Diff line number Diff line
@@ -65,7 +65,7 @@ static void Usage(void); 
static void read_trace_pipe2(void);

static void do_error(char *msg, bool errno_flag);



#define DEBUGFS "/sys/kernel/debug/tracing/"

#define TRACEFS "/sys/kernel/tracing/"



static struct bpf_program *bpf_prog;

static struct bpf_object *obj;
@@ -77,7 +77,7 @@ static void read_trace_pipe2(void) 
	FILE *outf;

	char *outFname = "hbm_out.log";



	trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);

	trace_fd = open(TRACEFS "trace_pipe", O_RDONLY, 0);

	if (trace_fd < 0) {

		printf("Error opening trace_pipe\n");

		return;

samples/bpf/ibumad_kern.c

+2 −2
Original line number Diff line number Diff line
@@ -39,8 +39,8 @@ struct { 
/* Taken from the current format defined in

 * include/trace/events/ib_umad.h

 * and

 * /sys/kernel/debug/tracing/events/ib_umad/ib_umad_read/format

 * /sys/kernel/debug/tracing/events/ib_umad/ib_umad_write/format

 * /sys/kernel/tracing/events/ib_umad/ib_umad_read/format

 * /sys/kernel/tracing/events/ib_umad/ib_umad_write/format

 */

struct ib_umad_rw_args {

	u64 pad;

samples/bpf/lwt_len_hist.sh

+1 −1
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ NS1=lwt_ns1 
VETH0=tst_lwt1a

VETH1=tst_lwt1b

BPF_PROG=lwt_len_hist.bpf.o

TRACE_ROOT=/sys/kernel/debug/tracing

TRACE_ROOT=/sys/kernel/tracing



function cleanup {

	# To reset saved histogram, remove pinned map