From: Masami Hiramatsu Date: Wed, 26 May 2021 14:51:29 +0000 (+0900) Subject: perf probe: Add permission and sysctl notice to man page X-Git-Tag: v5.15~830^2~49 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=fe4f3eb1fd5ab4bec5f105ef6e51bacac698af3b;p=platform%2Fkernel%2Flinux-starfive.git perf probe: Add permission and sysctl notice to man page Add a section to notify the permission and sysctl setting for perf probe. And fix some indentations. Reported-by: Ravi Bangoria Signed-off-by: Masami Hiramatsu Reviewed-by: Ravi Bangoria Cc: Aneesh Kumar K.V Cc: Jiri Olsa Link: http://lore.kernel.org/lkml/162204068898.388434.16842705842611255787.stgit@devnote2 Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt index ed3ecfa..080981d 100644 --- a/tools/perf/Documentation/perf-probe.txt +++ b/tools/perf/Documentation/perf-probe.txt @@ -226,7 +226,7 @@ So, "source.c:100-120" shows lines between 100th to l20th in source.c file. And LAZY MATCHING ------------- - The lazy line matching is similar to glob matching but ignoring spaces in both of pattern and target. So this accepts wildcards('*', '?') and character classes(e.g. [a-z], [!A-Z]). +The lazy line matching is similar to glob matching but ignoring spaces in both of pattern and target. So this accepts wildcards('*', '?') and character classes(e.g. [a-z], [!A-Z]). e.g. 'a=*' can matches 'a=b', 'a = b', 'a == b' and so on. @@ -235,8 +235,8 @@ This provides some sort of flexibility and robustness to probe point definitions FILTER PATTERN -------------- - The filter pattern is a glob matching pattern(s) to filter variables. - In addition, you can use "!" for specifying filter-out rule. You also can give several rules combined with "&" or "|", and fold those rules as one rule by using "(" ")". +The filter pattern is a glob matching pattern(s) to filter variables. +In addition, you can use "!" for specifying filter-out rule. You also can give several rules combined with "&" or "|", and fold those rules as one rule by using "(" ")". e.g. With --filter "foo* | bar*", perf probe -V shows variables which start with "foo" or "bar". @@ -295,6 +295,19 @@ Add a probe in a source file using special characters by backslash escape ./perf probe -x /opt/test/a.out 'foo\+bar.c:4' +PERMISSIONS AND SYSCTL +---------------------- +Since perf probe depends on ftrace (tracefs) and kallsyms (/proc/kallsyms), you have to care about the permission and some sysctl knobs. + + - Since tracefs and kallsyms requires root or privileged user to access it, the following perf probe commands also require it; --add, --del, --list (except for --cache option) + + - The system admin can remount the tracefs with 755 (`sudo mount -o remount,mode=755 /sys/kernel/tracing/`) to allow unprivileged user to run the perf probe --list command. + + - /proc/sys/kernel/kptr_restrict = 2 (restrict all users) also prevents perf probe to retrieve the important information from kallsyms. You also need to set to 1 (restrict non CAP_SYSLOG users) for the above commands. Since the user-space probe doesn't need to access kallsyms, this is only for probing the kernel function (kprobes). + + - Since the perf probe commands read the vmlinux (for kernel) and/or the debuginfo file (including user-space application), you need to ensure that you can read those files. + + SEE ALSO -------- linkperf:perf-trace[1], linkperf:perf-record[1], linkperf:perf-buildid-cache[1]