Messages in this thread Patch in this message | | | From | Masami Hiramatsu <> | Subject | [PATCH] tools/perf: doc: Add permission and sysctl notice | Date | Wed, 26 May 2021 18:01:18 +0900 |
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Add a section to notify the permission and sysctl setting for perf probe. And fix some indentations.
Reported-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> --- tools/perf/Documentation/perf-probe.txt | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt index ed3ecfa422e1..38f60ac58a8e 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 +295,17 @@ 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) + + - /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 perf probe commands read the vmlinux and/or the debuginfo file, 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]
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