linux-kernel - [PATCH] tools/perf: fix documentation for sysctls perf_event_paranoid and perf_event_mlock

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Date:   Sun, 20 Aug 2017 14:39:20 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     Peter Zijlstra <peterz@...radead.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: [PATCH] tools/perf: fix documentation for sysctls
 perf_event_paranoid and perf_event_mlock_kb

Fix misprint CAP_IOC_LOCK -> CAP_IPC_LOCK. This capability have nothing
to do with raw tracepoints. This part is about bypassing mlock limits.

Sysctl kernel.perf_event_paranoid = -1 allows raw and ftrace function
tracepoints without CAP_SYS_ADMIN.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
 Documentation/sysctl/kernel.txt |   13 ++++++++++++-
 tools/perf/util/evsel.c         |    4 +++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index bac23c198360..ce61d1fe08ca 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -61,6 +61,7 @@ show up in /proc/sys/kernel:
 - perf_cpu_time_max_percent
 - perf_event_paranoid
 - perf_event_max_stack
+- perf_event_mlock_kb
 - perf_event_max_contexts_per_stack
 - pid_max
 - powersave-nap               [ PPC only ]
@@ -654,7 +655,9 @@ Controls use of the performance events system by unprivileged
 users (without CAP_SYS_ADMIN).  The default value is 2.
 
  -1: Allow use of (almost) all events by all users
->=0: Disallow raw tracepoint access by users without CAP_IOC_LOCK
+     Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
+>=0: Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN
+     Disallow raw tracepoint access by users without CAP_SYS_ADMIN
 >=1: Disallow CPU event access by users without CAP_SYS_ADMIN
 >=2: Disallow kernel profiling by users without CAP_SYS_ADMIN
 
@@ -673,6 +676,14 @@ The default value is 127.
 
 ==============================================================
 
+perf_event_mlock_kb:
+
+Control size of per-cpu ring buffer not counted agains mlock limit.
+
+The default value is 512 + 1 page
+
+==============================================================
+
 perf_event_max_contexts_per_stack:
 
 Controls maximum number of stack frame context entries for
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 413f74df08de..5ed7056d1fd0 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2535,7 +2535,9 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target,
 		 "unprivileged users (without CAP_SYS_ADMIN).\n\n"
 		 "The current value is %d:\n\n"
 		 "  -1: Allow use of (almost) all events by all users\n"
-		 ">= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK\n"
+		 "      Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK\n"
+		 ">= 0: Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN\n"
+		 "      Disallow raw tracepoint access by users without CAP_SYS_ADMIN\n"
 		 ">= 1: Disallow CPU event access by users without CAP_SYS_ADMIN\n"
 		 ">= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN\n\n"
 		 "To make this setting permanent, edit /etc/sysctl.conf too, e.g.:\n\n"