linux-kernel - [tip:perf/core] perf tools: Document the perf sysctls

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Date:	Wed, 3 Feb 2016 02:08:24 -0800
From:	tip-bot for Ben Hutchings <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	acme@...hat.com, ben@...adent.org.uk, linux-kernel@...r.kernel.org,
	peterz@...radead.org, mingo@...nel.org, hpa@...or.com,
	tglx@...utronix.de
Subject: [tip:perf/core] perf tools: Document the perf sysctls

Commit-ID:  3379e0c3effa87d7734fc06277a7023292aadb0c
Gitweb:     http://git.kernel.org/tip/3379e0c3effa87d7734fc06277a7023292aadb0c
Author:     Ben Hutchings <ben@...adent.org.uk>
AuthorDate: Tue, 19 Jan 2016 21:35:15 +0000
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Tue, 26 Jan 2016 11:52:45 -0300

perf tools: Document the perf sysctls

perf_event_paranoid was only documented in source code and a perf error
message.  Copy the documentation from the error message to
Documentation/sysctl/kernel.txt.

perf_cpu_time_max_percent was already documented but missing from the
list at the top, so add it there.

Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: linux-doc@...r.kernel.org
Link: http://lkml.kernel.org/r/20160119213515.GG2637@decadent.org.uk
[ Remove reference to external Documentation file, provide info inline, as before ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 Documentation/sysctl/kernel.txt | 13 +++++++++++++
 tools/perf/util/evsel.c         | 15 +++++++++------
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 73c6b1e..c803e73 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -58,6 +58,8 @@ show up in /proc/sys/kernel:
 - panic_on_stackoverflow
 - panic_on_unrecovered_nmi
 - panic_on_warn
+- perf_cpu_time_max_percent
+- perf_event_paranoid
 - pid_max
 - powersave-nap               [ PPC only ]
 - printk
@@ -639,6 +641,17 @@ allowed to execute.
 
 ==============================================================
 
+perf_event_paranoid:
+
+Controls use of the performance events system by unprivileged
+users (without CAP_SYS_ADMIN).  The default value is 1.
+
+ -1: Allow use of (almost) all events by all users
+>=0: Disallow raw tracepoint access by users without CAP_IOC_LOCK
+>=1: Disallow CPU event access by users without CAP_SYS_ADMIN
+>=2: Disallow kernel profiling by users without CAP_SYS_ADMIN
+
+==============================================================
 
 pid_max:
 
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index cdbaf9b..4678086 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2362,12 +2362,15 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target,
 	case EPERM:
 	case EACCES:
 		return scnprintf(msg, size,
-		 "You may not have permission to collect %sstats.\n"
-		 "Consider tweaking /proc/sys/kernel/perf_event_paranoid:\n"
-		 " -1 - Not paranoid at all\n"
-		 "  0 - Disallow raw tracepoint access for unpriv\n"
-		 "  1 - Disallow cpu events for unpriv\n"
-		 "  2 - Disallow kernel profiling for unpriv",
+		 "You may not have permission to collect %sstats.\n\n"
+		 "Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n"
+		 "which controls use of the performance events system by\n"
+		 "unprivileged users (without CAP_SYS_ADMIN).\n\n"
+		 "The default value is 1:\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"
+		 ">= 1: Disallow CPU event access by users without CAP_SYS_ADMIN\n"
+		 ">= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN",
 				 target->system_wide ? "system-wide " : "");
 	case ENOENT:
 		return scnprintf(msg, size, "The %s event is not supported.",