Messages in this thread | | | Date | Wed, 26 May 2021 22:16:47 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH] tools/perf: doc: Add permission and sysctl notice |
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On Wed, 26 May 2021 15:20:58 +0530 Ravi Bangoria <ravi.bangoria@linux.ibm.com> wrote:
> > > On 5/26/21 2:31 PM, Masami Hiramatsu wrote: > > Add a section to notify the permission and sysctl setting > > for perf probe. And fix some indentations. > > Yes, it makes sense to have this detail in man page. > > Few minor points below ... > > > > > +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. > > 1) Last two points are applicable to kprobes only, not uprobes. Would > it make sense to clarify that?
Ah, right. And the last one may be also related to uprobes.
> 2) For 3rd point, simple perf probe on function entry will work without > vmlinux/debuginfo (by using kallsyms). Should we mention that?
Hmm, that depends on the options. If we use -k option, it will get the symbols from the given vmlinux.
> > In any case, > > Acked-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Thanks! I'll update it for uprobe.
> > Ravi
-- Masami Hiramatsu <mhiramat@kernel.org>
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