[PATCH 0/9] use canonical ftrace path whenever possible

[PATCH 0/9] use canonical ftrace path whenever possible

[Ross Zwisler]

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

There are many places where this older debugfs path is still used in
code comments, selftests, examples and tools, so let's update them to
avoid confusion.

I've broken up the series as best I could by maintainer or directory,
and I've only sent people the patches that I think they care about to
avoid spamming everyone.

Ross Zwisler (9):
  tracing: always use canonical ftrace path
  bpf: use canonical ftrace path
  selftests/bpf: use canonical ftrace path
  perf docs: use canonical ftrace path
  tools/power: use canonical ftrace path
  selftests: use canonical ftrace path
  tools/virtio: use canonical ftrace path
  leaking_addresses: also skip canonical ftrace path
  tools/kvm_stat: use canonical ftrace path

 include/linux/kernel.h                        |  2 +-
 include/linux/tracepoint.h                    |  4 ++--
 include/uapi/linux/bpf.h                      |  8 ++++----
 kernel/trace/Kconfig                          | 20 +++++++++----------
 kernel/trace/kprobe_event_gen_test.c          |  2 +-
 kernel/trace/ring_buffer.c                    |  2 +-
 kernel/trace/synth_event_gen_test.c           |  2 +-
 kernel/trace/trace.c                          |  2 +-
 samples/bpf/cpustat_kern.c                    |  4 ++--
 samples/bpf/hbm.c                             |  4 ++--
 samples/bpf/ibumad_kern.c                     |  4 ++--
 samples/bpf/lwt_len_hist.sh                   |  2 +-
 samples/bpf/offwaketime_kern.c                |  2 +-
 samples/bpf/task_fd_query_user.c              |  4 ++--
 samples/bpf/test_lwt_bpf.sh                   |  2 +-
 samples/bpf/test_overhead_tp_kern.c           |  4 ++--
 samples/user_events/example.c                 |  4 ++--
 scripts/leaking_addresses.pl                  |  1 +
 scripts/tracing/draw_functrace.py             |  6 +++---
 scripts/tracing/ftrace-bisect.sh              |  4 ++--
 tools/include/uapi/linux/bpf.h                |  8 ++++----
 tools/kvm/kvm_stat/kvm_stat                   |  2 +-
 tools/lib/api/fs/tracing_path.c               |  4 ++--
 tools/lib/traceevent/event-parse.c            |  8 ++++----
 tools/perf/Documentation/perf-list.txt        |  2 +-
 tools/perf/Documentation/perf-script-perl.txt |  2 +-
 .../perf/Documentation/perf-script-python.txt |  4 ++--
 tools/power/pm-graph/sleepgraph.py            |  4 ++--
 .../x86/amd_pstate_tracer/amd_pstate_trace.py |  4 ++--
 .../intel_pstate_tracer.py                    | 10 +++++-----
 .../selftests/bpf/get_cgroup_id_user.c        |  2 +-
 .../bpf/prog_tests/kprobe_multi_test.c        |  2 +-
 .../bpf/prog_tests/task_fd_query_tp.c         |  2 +-
 .../bpf/prog_tests/tp_attach_query.c          |  2 +-
 .../selftests/bpf/prog_tests/trace_printk.c   |  2 +-
 .../selftests/bpf/prog_tests/trace_vprintk.c  |  2 +-
 .../selftests/bpf/progs/test_stacktrace_map.c |  2 +-
 .../selftests/bpf/progs/test_tracepoint.c     |  2 +-
 tools/testing/selftests/bpf/test_ftrace.sh    |  2 +-
 tools/testing/selftests/bpf/test_tunnel.sh    |  8 ++++----
 tools/testing/selftests/bpf/trace_helpers.c   |  4 ++--
 .../testing/selftests/user_events/dyn_test.c  |  2 +-
 .../selftests/user_events/ftrace_test.c       | 10 +++++-----
 .../testing/selftests/user_events/perf_test.c |  8 ++++----
 tools/testing/selftests/vm/protection_keys.c  |  4 ++--
 tools/tracing/latency/latency-collector.c     |  2 +-
 tools/virtio/virtio-trace/README              |  2 +-
 tools/virtio/virtio-trace/trace-agent.c       |  2 +-
 48 files changed, 96 insertions(+), 95 deletions(-)

-- 
2.39.1.456.gfc5497dd1b-goog

[PATCH 2/9] bpf: use canonical ftrace path

[Ross Zwisler]

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: Ross Zwisler <zwisler@google.com>
---
 include/uapi/linux/bpf.h            | 8 ++++----
 samples/bpf/cpustat_kern.c          | 4 ++--
 samples/bpf/hbm.c                   | 4 ++--
 samples/bpf/ibumad_kern.c           | 4 ++--
 samples/bpf/lwt_len_hist.sh         | 2 +-
 samples/bpf/offwaketime_kern.c      | 2 +-
 samples/bpf/task_fd_query_user.c    | 4 ++--
 samples/bpf/test_lwt_bpf.sh         | 2 +-
 samples/bpf/test_overhead_tp_kern.c | 4 ++--
 tools/include/uapi/linux/bpf.h      | 8 ++++----
 10 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 51b9aa640ad2..9110163dfd70 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1634,17 +1634,17 @@ 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:
  *
diff --git a/samples/bpf/cpustat_kern.c b/samples/bpf/cpustat_kern.c
index 5aefd19cdfa1..944f13fe164a 100644
--- a/samples/bpf/cpustat_kern.c
+++ b/samples/bpf/cpustat_kern.c
@@ -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.
  */
diff --git a/samples/bpf/hbm.c b/samples/bpf/hbm.c
index 516fbac28b71..ff58ec43f56a 100644
--- a/samples/bpf/hbm.c
+++ b/samples/bpf/hbm.c
@@ -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;
diff --git a/samples/bpf/ibumad_kern.c b/samples/bpf/ibumad_kern.c
index 9b193231024a..f07474c72525 100644
--- a/samples/bpf/ibumad_kern.c
+++ b/samples/bpf/ibumad_kern.c
@@ -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;
diff --git a/samples/bpf/lwt_len_hist.sh b/samples/bpf/lwt_len_hist.sh
index 0eda9754f50b..11fa0a087db6 100755
--- a/samples/bpf/lwt_len_hist.sh
+++ b/samples/bpf/lwt_len_hist.sh
@@ -5,7 +5,7 @@ NS1=lwt_ns1
 VETH0=tst_lwt1a
 VETH1=tst_lwt1b
 
-TRACE_ROOT=/sys/kernel/debug/tracing
+TRACE_ROOT=/sys/kernel/tracing
 
 function cleanup {
 	# To reset saved histogram, remove pinned map
diff --git a/samples/bpf/offwaketime_kern.c b/samples/bpf/offwaketime_kern.c
index eb4d94742e6b..23f12b47e9e5 100644
--- a/samples/bpf/offwaketime_kern.c
+++ b/samples/bpf/offwaketime_kern.c
@@ -110,7 +110,7 @@ static inline int update_counts(void *ctx, u32 pid, u64 delta)
 }
 
 #if 1
-/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
+/* taken from /sys/kernel/tracing/events/sched/sched_switch/format */
 struct sched_switch_args {
 	unsigned long long pad;
 	char prev_comm[TASK_COMM_LEN];
diff --git a/samples/bpf/task_fd_query_user.c b/samples/bpf/task_fd_query_user.c
index a33d74bd3a4b..1e61f2180470 100644
--- a/samples/bpf/task_fd_query_user.c
+++ b/samples/bpf/task_fd_query_user.c
@@ -235,7 +235,7 @@ static int test_debug_fs_uprobe(char *binary_path, long offset, bool is_return)
 	struct bpf_link *link;
 	ssize_t bytes;
 
-	snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/%s_events",
+	snprintf(buf, sizeof(buf), "/sys/kernel/tracing/%s_events",
 		 event_type);
 	kfd = open(buf, O_WRONLY | O_TRUNC, 0);
 	CHECK_PERROR_RET(kfd < 0);
@@ -252,7 +252,7 @@ static int test_debug_fs_uprobe(char *binary_path, long offset, bool is_return)
 	close(kfd);
 	kfd = -1;
 
-	snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%ss/%s/id",
+	snprintf(buf, sizeof(buf), "/sys/kernel/tracing/events/%ss/%s/id",
 		 event_type, event_alias);
 	efd = open(buf, O_RDONLY, 0);
 	CHECK_PERROR_RET(efd < 0);
diff --git a/samples/bpf/test_lwt_bpf.sh b/samples/bpf/test_lwt_bpf.sh
index 65a976058dd3..db5691e6637f 100755
--- a/samples/bpf/test_lwt_bpf.sh
+++ b/samples/bpf/test_lwt_bpf.sh
@@ -19,7 +19,7 @@ IPVETH3="192.168.111.2"
 
 IP_LOCAL="192.168.99.1"
 
-TRACE_ROOT=/sys/kernel/debug/tracing
+TRACE_ROOT=/sys/kernel/tracing
 
 function lookup_mac()
 {
diff --git a/samples/bpf/test_overhead_tp_kern.c b/samples/bpf/test_overhead_tp_kern.c
index 80edadacb692..a1d53b0d8476 100644
--- a/samples/bpf/test_overhead_tp_kern.c
+++ b/samples/bpf/test_overhead_tp_kern.c
@@ -8,7 +8,7 @@
 #include <uapi/linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 
-/* from /sys/kernel/debug/tracing/events/task/task_rename/format */
+/* from /sys/kernel/tracing/events/task/task_rename/format */
 struct task_rename {
 	__u64 pad;
 	__u32 pid;
@@ -22,7 +22,7 @@ int prog(struct task_rename *ctx)
 	return 0;
 }
 
-/* from /sys/kernel/debug/tracing/events/random/urandom_read/format */
+/* from /sys/kernel/tracing/events/random/urandom_read/format */
 struct urandom_read {
 	__u64 pad;
 	int got_bits;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 51b9aa640ad2..9110163dfd70 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1634,17 +1634,17 @@ 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:
  *
-- 
2.39.1.456.gfc5497dd1b-goog

[PATCH 3/9] selftests/bpf: use canonical ftrace path

[Ross Zwisler]

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 tests in the bpf selftest code still refer to this older debugfs
path, so let's update them to avoid confusion.

Signed-off-by: Ross Zwisler <zwisler@google.com>
---
 tools/testing/selftests/bpf/get_cgroup_id_user.c          | 2 +-
 .../testing/selftests/bpf/prog_tests/kprobe_multi_test.c  | 2 +-
 tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c | 2 +-
 tools/testing/selftests/bpf/prog_tests/tp_attach_query.c  | 2 +-
 tools/testing/selftests/bpf/prog_tests/trace_printk.c     | 2 +-
 tools/testing/selftests/bpf/prog_tests/trace_vprintk.c    | 2 +-
 tools/testing/selftests/bpf/progs/test_stacktrace_map.c   | 2 +-
 tools/testing/selftests/bpf/progs/test_tracepoint.c       | 2 +-
 tools/testing/selftests/bpf/test_ftrace.sh                | 2 +-
 tools/testing/selftests/bpf/test_tunnel.sh                | 8 ++++----
 tools/testing/selftests/bpf/trace_helpers.c               | 4 ++--
 11 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/tools/testing/selftests/bpf/get_cgroup_id_user.c b/tools/testing/selftests/bpf/get_cgroup_id_user.c
index 156743cf5870..478e080128be 100644
--- a/tools/testing/selftests/bpf/get_cgroup_id_user.c
+++ b/tools/testing/selftests/bpf/get_cgroup_id_user.c
@@ -87,7 +87,7 @@ int main(int argc, char **argv)
 	bpf_map_update_elem(pidmap_fd, &key, &pid, 0);
 
 	snprintf(buf, sizeof(buf),
-		 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
+		 "/sys/kernel/tracing/events/%s/id", probe_name);
 	efd = open(buf, O_RDONLY, 0);
 	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
 		goto close_prog;
diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
index d457a55ff408..9eaf16e9ff6e 100644
--- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
@@ -338,7 +338,7 @@ static int get_syms(char ***symsp, size_t *cntp)
 	 * Filtering out duplicates by using hashmap__add, which won't
 	 * add existing entry.
 	 */
-	f = fopen("/sys/kernel/debug/tracing/available_filter_functions", "r");
+	f = fopen("/sys/kernel/tracing/available_filter_functions", "r");
 	if (!f)
 		return -EINVAL;
 
diff --git a/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c b/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
index c717741bf8b6..6d70559fc19b 100644
--- a/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
@@ -18,7 +18,7 @@ static void test_task_fd_query_tp_core(const char *probe_name,
 		goto close_prog;
 
 	snprintf(buf, sizeof(buf),
-		 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
+		 "/sys/kernel/tracing/events/%s/id", probe_name);
 	efd = open(buf, O_RDONLY, 0);
 	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
 		goto close_prog;
diff --git a/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c b/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
index a479080533db..4308e3a828d8 100644
--- a/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
+++ b/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
@@ -17,7 +17,7 @@ void serial_test_tp_attach_query(void)
 		obj[i] = NULL;
 
 	snprintf(buf, sizeof(buf),
-		 "/sys/kernel/debug/tracing/events/sched/sched_switch/id");
+		 "/sys/kernel/tracing/events/sched/sched_switch/id");
 	efd = open(buf, O_RDONLY, 0);
 	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
 		return;
diff --git a/tools/testing/selftests/bpf/prog_tests/trace_printk.c b/tools/testing/selftests/bpf/prog_tests/trace_printk.c
index cade7f12315f..ff50a928cb98 100644
--- a/tools/testing/selftests/bpf/prog_tests/trace_printk.c
+++ b/tools/testing/selftests/bpf/prog_tests/trace_printk.c
@@ -5,7 +5,7 @@
 
 #include "trace_printk.lskel.h"
 
-#define TRACEBUF	"/sys/kernel/debug/tracing/trace_pipe"
+#define TRACEBUF	"/sys/kernel/tracing/trace_pipe"
 #define SEARCHMSG	"testing,testing"
 
 void serial_test_trace_printk(void)
diff --git a/tools/testing/selftests/bpf/prog_tests/trace_vprintk.c b/tools/testing/selftests/bpf/prog_tests/trace_vprintk.c
index 7a4e313e8558..e568d7f247ec 100644
--- a/tools/testing/selftests/bpf/prog_tests/trace_vprintk.c
+++ b/tools/testing/selftests/bpf/prog_tests/trace_vprintk.c
@@ -5,7 +5,7 @@
 
 #include "trace_vprintk.lskel.h"
 
-#define TRACEBUF	"/sys/kernel/debug/tracing/trace_pipe"
+#define TRACEBUF	"/sys/kernel/tracing/trace_pipe"
 #define SEARCHMSG	"1,2,3,4,5,6,7,8,9,10"
 
 void serial_test_trace_vprintk(void)
diff --git a/tools/testing/selftests/bpf/progs/test_stacktrace_map.c b/tools/testing/selftests/bpf/progs/test_stacktrace_map.c
index 728dbd39eff0..47568007b668 100644
--- a/tools/testing/selftests/bpf/progs/test_stacktrace_map.c
+++ b/tools/testing/selftests/bpf/progs/test_stacktrace_map.c
@@ -38,7 +38,7 @@ struct {
 	__type(value, stack_trace_t);
 } stack_amap SEC(".maps");
 
-/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
+/* taken from /sys/kernel/tracing/events/sched/sched_switch/format */
 struct sched_switch_args {
 	unsigned long long pad;
 	char prev_comm[TASK_COMM_LEN];
diff --git a/tools/testing/selftests/bpf/progs/test_tracepoint.c b/tools/testing/selftests/bpf/progs/test_tracepoint.c
index 43bd7a20cc50..4cb8bbb6a320 100644
--- a/tools/testing/selftests/bpf/progs/test_tracepoint.c
+++ b/tools/testing/selftests/bpf/progs/test_tracepoint.c
@@ -4,7 +4,7 @@
 #include <vmlinux.h>
 #include <bpf/bpf_helpers.h>
 
-/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
+/* taken from /sys/kernel/tracing/events/sched/sched_switch/format */
 struct sched_switch_args {
 	unsigned long long pad;
 	char prev_comm[TASK_COMM_LEN];
diff --git a/tools/testing/selftests/bpf/test_ftrace.sh b/tools/testing/selftests/bpf/test_ftrace.sh
index 20de7bb873bc..e3e2328a1b65 100755
--- a/tools/testing/selftests/bpf/test_ftrace.sh
+++ b/tools/testing/selftests/bpf/test_ftrace.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-TR=/sys/kernel/debug/tracing/
+TR=/sys/kernel/tracing/
 clear_trace() { # reset trace output
     echo > $TR/trace
 }
diff --git a/tools/testing/selftests/bpf/test_tunnel.sh b/tools/testing/selftests/bpf/test_tunnel.sh
index e9ebc67d73f7..6927e586a3a2 100755
--- a/tools/testing/selftests/bpf/test_tunnel.sh
+++ b/tools/testing/selftests/bpf/test_tunnel.sh
@@ -542,7 +542,7 @@ setup_xfrm_tunnel()
 test_xfrm_tunnel()
 {
 	config_device
-	> /sys/kernel/debug/tracing/trace
+	> /sys/kernel/tracing/trace
 	setup_xfrm_tunnel
 	mkdir -p ${BPF_PIN_TUNNEL_DIR}
 	bpftool prog loadall ./test_tunnel_kern.o ${BPF_PIN_TUNNEL_DIR}
@@ -551,11 +551,11 @@ test_xfrm_tunnel()
 		${BPF_PIN_TUNNEL_DIR}/xfrm_get_state
 	ip netns exec at_ns0 ping $PING_ARG 10.1.1.200
 	sleep 1
-	grep "reqid 1" /sys/kernel/debug/tracing/trace
+	grep "reqid 1" /sys/kernel/tracing/trace
 	check_err $?
-	grep "spi 0x1" /sys/kernel/debug/tracing/trace
+	grep "spi 0x1" /sys/kernel/tracing/trace
 	check_err $?
-	grep "remote ip 0xac100164" /sys/kernel/debug/tracing/trace
+	grep "remote ip 0xac100164" /sys/kernel/tracing/trace
 	check_err $?
 	cleanup
 
diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
index 9c4be2cdb21a..65895f5fb562 100644
--- a/tools/testing/selftests/bpf/trace_helpers.c
+++ b/tools/testing/selftests/bpf/trace_helpers.c
@@ -12,7 +12,7 @@
 #include <sys/mman.h>
 #include "trace_helpers.h"
 
-#define DEBUGFS "/sys/kernel/debug/tracing/"
+#define TRACEFS "/sys/kernel/tracing/"
 
 #define MAX_SYMS 300000
 static struct ksym syms[MAX_SYMS];
@@ -130,7 +130,7 @@ void read_trace_pipe(void)
 {
 	int trace_fd;
 
-	trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
+	trace_fd = open(TRACEFS "trace_pipe", O_RDONLY, 0);
 	if (trace_fd < 0)
 		return;
 
-- 
2.39.1.456.gfc5497dd1b-goog

Re: [PATCH 0/9] use canonical ftrace path whenever possible

[Michael S. Tsirkin]

On Mon, Jan 30, 2023 at 11:19:06AM -0700, Ross Zwisler wrote:
> The canonical location for the tracefs filesystem is at /sys/kernel/tracing.


Acked-by: Michael S. Tsirkin <mst@redhat.com>

> 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
> 
> There are many places where this older debugfs path is still used in
> code comments, selftests, examples and tools, so let's update them to
> avoid confusion.
> 
> I've broken up the series as best I could by maintainer or directory,
> and I've only sent people the patches that I think they care about to
> avoid spamming everyone.
> 
> Ross Zwisler (9):
>   tracing: always use canonical ftrace path
>   bpf: use canonical ftrace path
>   selftests/bpf: use canonical ftrace path
>   perf docs: use canonical ftrace path
>   tools/power: use canonical ftrace path
>   selftests: use canonical ftrace path
>   tools/virtio: use canonical ftrace path
>   leaking_addresses: also skip canonical ftrace path
>   tools/kvm_stat: use canonical ftrace path
> 
>  include/linux/kernel.h                        |  2 +-
>  include/linux/tracepoint.h                    |  4 ++--
>  include/uapi/linux/bpf.h                      |  8 ++++----
>  kernel/trace/Kconfig                          | 20 +++++++++----------
>  kernel/trace/kprobe_event_gen_test.c          |  2 +-
>  kernel/trace/ring_buffer.c                    |  2 +-
>  kernel/trace/synth_event_gen_test.c           |  2 +-
>  kernel/trace/trace.c                          |  2 +-
>  samples/bpf/cpustat_kern.c                    |  4 ++--
>  samples/bpf/hbm.c                             |  4 ++--
>  samples/bpf/ibumad_kern.c                     |  4 ++--
>  samples/bpf/lwt_len_hist.sh                   |  2 +-
>  samples/bpf/offwaketime_kern.c                |  2 +-
>  samples/bpf/task_fd_query_user.c              |  4 ++--
>  samples/bpf/test_lwt_bpf.sh                   |  2 +-
>  samples/bpf/test_overhead_tp_kern.c           |  4 ++--
>  samples/user_events/example.c                 |  4 ++--
>  scripts/leaking_addresses.pl                  |  1 +
>  scripts/tracing/draw_functrace.py             |  6 +++---
>  scripts/tracing/ftrace-bisect.sh              |  4 ++--
>  tools/include/uapi/linux/bpf.h                |  8 ++++----
>  tools/kvm/kvm_stat/kvm_stat                   |  2 +-
>  tools/lib/api/fs/tracing_path.c               |  4 ++--
>  tools/lib/traceevent/event-parse.c            |  8 ++++----
>  tools/perf/Documentation/perf-list.txt        |  2 +-
>  tools/perf/Documentation/perf-script-perl.txt |  2 +-
>  .../perf/Documentation/perf-script-python.txt |  4 ++--
>  tools/power/pm-graph/sleepgraph.py            |  4 ++--
>  .../x86/amd_pstate_tracer/amd_pstate_trace.py |  4 ++--
>  .../intel_pstate_tracer.py                    | 10 +++++-----
>  .../selftests/bpf/get_cgroup_id_user.c        |  2 +-
>  .../bpf/prog_tests/kprobe_multi_test.c        |  2 +-
>  .../bpf/prog_tests/task_fd_query_tp.c         |  2 +-
>  .../bpf/prog_tests/tp_attach_query.c          |  2 +-
>  .../selftests/bpf/prog_tests/trace_printk.c   |  2 +-
>  .../selftests/bpf/prog_tests/trace_vprintk.c  |  2 +-
>  .../selftests/bpf/progs/test_stacktrace_map.c |  2 +-
>  .../selftests/bpf/progs/test_tracepoint.c     |  2 +-
>  tools/testing/selftests/bpf/test_ftrace.sh    |  2 +-
>  tools/testing/selftests/bpf/test_tunnel.sh    |  8 ++++----
>  tools/testing/selftests/bpf/trace_helpers.c   |  4 ++--
>  .../testing/selftests/user_events/dyn_test.c  |  2 +-
>  .../selftests/user_events/ftrace_test.c       | 10 +++++-----
>  .../testing/selftests/user_events/perf_test.c |  8 ++++----
>  tools/testing/selftests/vm/protection_keys.c  |  4 ++--
>  tools/tracing/latency/latency-collector.c     |  2 +-
>  tools/virtio/virtio-trace/README              |  2 +-
>  tools/virtio/virtio-trace/trace-agent.c       |  2 +-
>  48 files changed, 96 insertions(+), 95 deletions(-)
> 
> -- 
> 2.39.1.456.gfc5497dd1b-goog

Re: [PATCH 3/9] selftests/bpf: use canonical ftrace path

[Alexei Starovoitov]

On Mon, Jan 30, 2023 at 10:19 AM Ross Zwisler <zwisler@chromium.org> wrote:
>
> 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 tests in the bpf selftest code still refer to this older debugfs
> path, so let's update them to avoid confusion.

I wish that was the case, but in reality there are still systems
out there where tracefs is only mounted in that old location.
For example in one my VMs:

$ cat /proc/mounts |grep tracefs
tracefs /sys/kernel/debug/tracing tracefs rw,relatime 0 0
$ ls /sys/kernel/tracing/
$ uname -r
6.2.0-rc5-01030-gc1a3daf7363b

So this change will break the tests. We cannot do it.

Re: [PATCH 3/9] selftests/bpf: use canonical ftrace path

[Steven Rostedt]

On Mon, 30 Jan 2023 11:52:03 -0800
Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:

> On Mon, Jan 30, 2023 at 10:19 AM Ross Zwisler <zwisler@chromium.org> wrote:
> >
> > 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 tests in the bpf selftest code still refer to this older debugfs
> > path, so let's update them to avoid confusion.  
> 
> I wish that was the case, but in reality there are still systems
> out there where tracefs is only mounted in that old location.
> For example in one my VMs:
> 
> $ cat /proc/mounts |grep tracefs
> tracefs /sys/kernel/debug/tracing tracefs rw,relatime 0 0
> $ ls /sys/kernel/tracing/
> $ uname -r
> 6.2.0-rc5-01030-gc1a3daf7363b
> 
> So this change will break the tests. We cannot do it.

Could we add a way to try to mount it?

If anything, the tests should not have the path hard coded. It should then
look to see if it is mounted and use the path that is found. Otherwise it
should try mounting it at the correct location.

Feel free to take the code from libtracefs (and modify it):

https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/tree/src/tracefs-utils.c#n89

It will make the test code much more robust.

-- Steve

Re: [PATCH 3/9] selftests/bpf: use canonical ftrace path

[Alexei Starovoitov]

On Mon, Jan 30, 2023 at 11:59 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Mon, 30 Jan 2023 11:52:03 -0800
> Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
>
> > On Mon, Jan 30, 2023 at 10:19 AM Ross Zwisler <zwisler@chromium.org> wrote:
> > >
> > > 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 tests in the bpf selftest code still refer to this older debugfs
> > > path, so let's update them to avoid confusion.
> >
> > I wish that was the case, but in reality there are still systems
> > out there where tracefs is only mounted in that old location.
> > For example in one my VMs:
> >
> > $ cat /proc/mounts |grep tracefs
> > tracefs /sys/kernel/debug/tracing tracefs rw,relatime 0 0
> > $ ls /sys/kernel/tracing/
> > $ uname -r
> > 6.2.0-rc5-01030-gc1a3daf7363b
> >
> > So this change will break the tests. We cannot do it.
>
> Could we add a way to try to mount it?
>
> If anything, the tests should not have the path hard coded. It should then
> look to see if it is mounted and use the path that is found. Otherwise it
> should try mounting it at the correct location.
>
> Feel free to take the code from libtracefs (and modify it):
>
> https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/tree/src/tracefs-utils.c#n89
>
> It will make the test code much more robust.

The point is not about tests. The point is that this change might break
some users that are working today with /sys/kernel/debug/tracing.
It also might be mounted differently.
For example from another system:
cat /proc/mounts|grep trace
tracefs /sys/kernel/tracing tracefs rw,nosuid,nodev,noexec,relatime 0 0
tracefs /sys/kernel/debug/tracing tracefs rw,relatime 0 0

So I suggest leaving the code as-is.

Re: [PATCH 3/9] selftests/bpf: use canonical ftrace path

[Steven Rostedt]

On Mon, 30 Jan 2023 12:03:52 -0800
Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> > >
> > > So this change will break the tests. We cannot do it.  
> >
> > Could we add a way to try to mount it?
> >
> > If anything, the tests should not have the path hard coded. It should then
> > look to see if it is mounted and use the path that is found. Otherwise it
> > should try mounting it at the correct location.
> >
> > Feel free to take the code from libtracefs (and modify it):
> >
> > https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/tree/src/tracefs-utils.c#n89
> >
> > It will make the test code much more robust.  
> 
> The point is not about tests. The point is that this change might break
> some users that are working today with /sys/kernel/debug/tracing.

> It also might be mounted differently.
> For example from another system:
> cat /proc/mounts|grep trace
> tracefs /sys/kernel/tracing tracefs rw,nosuid,nodev,noexec,relatime 0 0
> tracefs /sys/kernel/debug/tracing tracefs rw,relatime 0 0

Yes, and the code works when it's mounted multiple times.

> 
> So I suggest leaving the code as-is.

Why?  I want to make /sys/kernel/debug/tracing deprecated. It's a hack to
not break old code. I've had complaints about that hack, and there's even
systems that disable the auto mounting (that is, /sys/kernel/debug/tracing
would not exist in such configs) This was never expected to be a permanent
solution.

If anything, leaving hardcoded calls like that forces the user to mount
debugfs when they may not want to. The entire point of tracefs was to allow
users to have access to the trace events without having to expose debugfs
and all the crud it brings with it. This was requested several times before
it was added.

What is your technical reason for not modifying the code to look for
tracefs in /sys/kernel/tracing and if it's not there try
/sys/kernel/debug/tracing, and if both are not found, try mounting it.

That change is not hard and makes the code much more robust and does not
break anything.

-- Steve

Re: [PATCH 3/9] selftests/bpf: use canonical ftrace path

[Alexei Starovoitov]

On Mon, Jan 30, 2023 at 06:34:19PM -0500, Steven Rostedt wrote:
> On Mon, 30 Jan 2023 12:03:52 -0800
> Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> > > >
> > > > So this change will break the tests. We cannot do it.  
> > >
> > > Could we add a way to try to mount it?
> > >
> > > If anything, the tests should not have the path hard coded. It should then
> > > look to see if it is mounted and use the path that is found. Otherwise it
> > > should try mounting it at the correct location.
> > >
> > > Feel free to take the code from libtracefs (and modify it):
> > >
> > > https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/tree/src/tracefs-utils.c#n89
> > >
> > > It will make the test code much more robust.  
> > 
> > The point is not about tests. The point is that this change might break
> > some users that are working today with /sys/kernel/debug/tracing.
> 
> > It also might be mounted differently.
> > For example from another system:
> > cat /proc/mounts|grep trace
> > tracefs /sys/kernel/tracing tracefs rw,nosuid,nodev,noexec,relatime 0 0
> > tracefs /sys/kernel/debug/tracing tracefs rw,relatime 0 0
> 
> Yes, and the code works when it's mounted multiple times.
> 
> > 
> > So I suggest leaving the code as-is.
> 
> Why?  I want to make /sys/kernel/debug/tracing deprecated. It's a hack to
> not break old code. I've had complaints about that hack, and there's even
> systems that disable the auto mounting (that is, /sys/kernel/debug/tracing
> would not exist in such configs) This was never expected to be a permanent
> solution.

I don't think /sys/kernel/debug/tracing can ever be deprecated.
There are plenty of user space applications (not bpf related at all) that
expect it to be in that location.

Quick search shows:

android profiler:
https://android.googlesource.com/platform/external/perfetto/+/refs/heads/master/src/tools/dump_ftrace_stats/main.cc#60

java profiler:
https://github.com/jvm-profiling-tools/async-profiler/blob/master/src/perfEvents_linux.cpp#L85

> If anything, leaving hardcoded calls like that forces the user to mount
> debugfs when they may not want to. The entire point of tracefs was to allow
> users to have access to the trace events without having to expose debugfs
> and all the crud it brings with it. This was requested several times before
> it was added.

All makes sense.

> What is your technical reason for not modifying the code to look for
> tracefs in /sys/kernel/tracing and if it's not there try
> /sys/kernel/debug/tracing, and if both are not found, try mounting it.

libbpf already has code to probe both locations.
The point that full deprecation of /sys/kernel/debug/tracing is not possible,
hence no point doing the diff:
48 files changed, 96 insertions(+), 95 deletions(-)
It doesn't move the needle. Just a code churn.

Re: [PATCH 3/9] selftests/bpf: use canonical ftrace path

[Steven Rostedt]

On Mon, 30 Jan 2023 16:53:15 -0800
Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:

> I don't think /sys/kernel/debug/tracing can ever be deprecated.
> There are plenty of user space applications (not bpf related at all) that
> expect it to be in that location.
> 
> Quick search shows:
> 
> android profiler:
> https://android.googlesource.com/platform/external/perfetto/+/refs/heads/master/src/tools/dump_ftrace_stats/main.cc#60
> 
> java profiler:
> https://github.com/jvm-profiling-tools/async-profiler/blob/master/src/perfEvents_linux.cpp#L85

These can easily be changed. We have deprecated stuff in the past, by
making sure all the affected code is updated properly.

One way is to start adding printks when used. Then update to WARN() to get
people to complain. Yes, the burden is on us (me and others) to go out and
fix the issues. But it is possible to do, as I've done it before.

> 
> > If anything, leaving hardcoded calls like that forces the user to mount
> > debugfs when they may not want to. The entire point of tracefs was to allow
> > users to have access to the trace events without having to expose debugfs
> > and all the crud it brings with it. This was requested several times before
> > it was added.  
> 
> All makes sense.
> 
> > What is your technical reason for not modifying the code to look for
> > tracefs in /sys/kernel/tracing and if it's not there try
> > /sys/kernel/debug/tracing, and if both are not found, try mounting it.  
> 
> libbpf already has code to probe both locations.
> The point that full deprecation of /sys/kernel/debug/tracing is not possible,
> hence no point doing the diff:
> 48 files changed, 96 insertions(+), 95 deletions(-)
> It doesn't move the needle. Just a code churn.

As code in the Linux kernel is used as examples for future work, it should
not be using an interface that is obsolete. That's enough rational for code
churn. This "we can never deprecated so we won't even try" BS is not an
answer.

-- Steve

Re: [PATCH 3/9] selftests/bpf: use canonical ftrace path

[Alexei Starovoitov]

On Tue, Jan 31, 2023 at 11:50 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> As code in the Linux kernel is used as examples for future work, it should
> not be using an interface that is obsolete. That's enough rational for code
> churn.

Fair enough. Please resubmit these two patches towards bpf-next
with [PATCH bpf-next] subj, so that BPF CI can chew on it.

Re: [PATCH 3/9] selftests/bpf: use canonical ftrace path

[Ross Zwisler]

On Tue, Jan 31, 2023 at 4:26 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
> Fair enough. Please resubmit these two patches towards bpf-next
> with [PATCH bpf-next] subj, so that BPF CI can chew on it.

Will do, thanks.