Messages in this thread | | | Date | Wed, 2 Jun 2021 08:53:19 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v2] tools/perf: doc: Add permission and sysctl notice |
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Em Wed, May 26, 2021 at 11:51:29PM +0900, Masami Hiramatsu escreveu: > 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>
Ravi, can I have your Reviewed-by?
- Arnaldo
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > --- > Changes in v2: > - Add tracefs remount option for --list command. > - Mention uprobe case for kptr_restrict and vmlinux/debuginfo permission. > --- > tools/perf/Documentation/perf-probe.txt | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt > index ed3ecfa422e1..080981d38d7b 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] >
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- Arnaldo
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