Commit 0808b3d5 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Arnaldo Carvalho de Melo
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perf probe: Provide clearer message permission error for tracefs access 



Report permission error for the tracefs open and rewrite whole the error
message code around it.

You'll see a hint according to what you want to do with perf probe as
below.

  $ perf probe -l
  No permission to read tracefs.
  Please try 'sudo mount -o remount,mode=755 /sys/kernel/tracing/'
    Error: Failed to show event list.

  $ perf probe -d \*
  No permission to write tracefs.
  Please run this command again with sudo.
    Error: Failed to delete events.

This also fixes -ENOTSUP checking for mounting tracefs/debugfs.
Actually open returns -ENOENT in that case and we have to check it with
current mount point list. If we unmount debugfs and tracefs perf probe
shows correct message as below.

  $ perf probe -l
  Debugfs or tracefs is not mounted
  Please try 'sudo mount -t tracefs nodev /sys/kernel/tracing/'
    Error: Failed to show event list.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Link: http://lore.kernel.org/lkml/162299456839.503471.13863002017089255222.stgit@devnote2


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent bde1e7d9

tools/perf/util/probe-file.c

+65 −30
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include "symbol.h"

#include "strbuf.h"

#include <api/fs/tracing_path.h>

#include <api/fs/fs.h>

#include "probe-event.h"

#include "probe-file.h"

#include "session.h"
@@ -31,45 +32,79 @@ 
/* 4096 - 2 ('\n' + '\0') */

#define MAX_CMDLEN 4094



static void print_open_warning(int err, bool uprobe)

static bool print_common_warning(int err, bool readwrite)

{

	char sbuf[STRERR_BUFSIZE];

	if (err == -EACCES)

		pr_warning("No permission to %s tracefs.\nPlease %s\n",

			   readwrite ? "write" : "read",

			   readwrite ? "run this command again with sudo." :

				       "try 'sudo mount -o remount,mode=755 /sys/kernel/tracing/'");

	else

		return false;



	if (err == -ENOENT) {

		const char *config;

	return true;

}



		if (uprobe)

			config = "CONFIG_UPROBE_EVENTS";

		else

			config = "CONFIG_KPROBE_EVENTS";

static bool print_configure_probe_event(int kerr, int uerr)

{

	const char *config, *file;



	if (kerr == -ENOENT && uerr == -ENOENT) {

		file = "{k,u}probe_events";

		config = "CONFIG_KPROBE_EVENTS=y and CONFIG_UPROBE_EVENTS=y";

	} else if (kerr == -ENOENT) {

		file = "kprobe_events";

		config = "CONFIG_KPROBE_EVENTS=y";

	} else if (uerr == -ENOENT) {

		file = "uprobe_events";

		config = "CONFIG_UPROBE_EVENTS=y";

	} else

		return false;



		pr_warning("%cprobe_events file does not exist"

			   " - please rebuild kernel with %s.\n",

			   uprobe ? 'u' : 'k', config);

	} else if (err == -ENOTSUP)

		pr_warning("Tracefs or debugfs is not mounted.\n");

	if (!debugfs__configured() && !tracefs__configured())

		pr_warning("Debugfs or tracefs is not mounted\n"

			   "Please try 'sudo mount -t tracefs nodev /sys/kernel/tracing/'\n");

	else

		pr_warning("Failed to open %cprobe_events: %s\n",

			   uprobe ? 'u' : 'k',

		pr_warning("%s/%s does not exist.\nPlease rebuild kernel with %s.\n",

			   tracing_path_mount(), file, config);



	return true;

}



static void print_open_warning(int err, bool uprobe, bool readwrite)

{

	char sbuf[STRERR_BUFSIZE];



	if (print_common_warning(err, readwrite))

		return;



	if (print_configure_probe_event(uprobe ? 0 : err, uprobe ? err : 0))

		return;



	pr_warning("Failed to open %s/%cprobe_events: %s\n",

		   tracing_path_mount(), uprobe ? 'u' : 'k',

		   str_error_r(-err, sbuf, sizeof(sbuf)));

}



static void print_both_open_warning(int kerr, int uerr)

static void print_both_open_warning(int kerr, int uerr, bool readwrite)

{

	/* Both kprobes and uprobes are disabled, warn it. */

	if (kerr == -ENOTSUP && uerr == -ENOTSUP)

		pr_warning("Tracefs or debugfs is not mounted.\n");

	else if (kerr == -ENOENT && uerr == -ENOENT)

		pr_warning("Please rebuild kernel with CONFIG_KPROBE_EVENTS "

			   "or/and CONFIG_UPROBE_EVENTS.\n");

	else {

	char sbuf[STRERR_BUFSIZE];

		pr_warning("Failed to open kprobe events: %s.\n",



	if (kerr == uerr && print_common_warning(kerr, readwrite))

		return;



	if (print_configure_probe_event(kerr, uerr))

		return;



	if (kerr < 0)

		pr_warning("Failed to open %s/kprobe_events: %s.\n",

			   tracing_path_mount(),

			   str_error_r(-kerr, sbuf, sizeof(sbuf)));

		pr_warning("Failed to open uprobe events: %s.\n",

	if (uerr < 0)

		pr_warning("Failed to open %s/uprobe_events: %s.\n",

			   tracing_path_mount(),

			   str_error_r(-uerr, sbuf, sizeof(sbuf)));

}

}



int open_trace_file(const char *trace_file, bool readwrite)

{
@@ -109,7 +144,7 @@ int probe_file__open(int flag) 
	else

		fd = open_kprobe_events(flag & PF_FL_RW);

	if (fd < 0)

		print_open_warning(fd, flag & PF_FL_UPROBE);

		print_open_warning(fd, flag & PF_FL_UPROBE, flag & PF_FL_RW);



	return fd;

}
@@ -122,7 +157,7 @@ int probe_file__open_both(int *kfd, int *ufd, int flag) 
	*kfd = open_kprobe_events(flag & PF_FL_RW);

	*ufd = open_uprobe_events(flag & PF_FL_RW);

	if (*kfd < 0 && *ufd < 0) {

		print_both_open_warning(*kfd, *ufd);

		print_both_open_warning(*kfd, *ufd, flag & PF_FL_RW);

		return *kfd;

	}