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Date: Tue, 8 Jun 2021 14:13:19 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org,
aneesh.kumar@...ux.ibm.com, Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH v2] perf/probe: Report permission error for tracefs access
Em Mon, Jun 07, 2021 at 12:49:28AM +0900, Masami Hiramatsu escreveu:
> 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.
Thanks, applied.
- Arnaldo
>
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
> Changes in v2:
> - Rewrite whole the error message for the tracefs access.
> ---
> tools/perf/util/probe-file.c | 95 +++++++++++++++++++++++++++++-------------
> 1 file changed, 65 insertions(+), 30 deletions(-)
>
> diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
> index 52273542e6ef..f9a6cbcd6415 100644
> --- a/tools/perf/util/probe-file.c
> +++ b/tools/perf/util/probe-file.c
> @@ -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"
> @@ -31,44 +32,78 @@
> /* 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',
> - str_error_r(-err, sbuf, sizeof(sbuf)));
> + 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",
> + char sbuf[STRERR_BUFSIZE];
> +
> + 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;
> }
>
>
--
- Arnaldo
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