Subject: Re: [PATCH 1/3] perf: Add capability-related utilities

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Wed, 17 Jul 2019 20:48:43 -0300

Em Wed, Jul 17, 2019 at 08:46:52PM -0300, Arnaldo Carvalho de Melo escreveu:
> I'll do it if there is any difficulty, just not right now as I'm busy
> and want to get a pull req out of the door.

Also please find the first patch fixed up wrt a conflict with the
pythong binding, please use it instead as that is what applies to my
current perf/core branch.

It has the ack from Alexey and one I think Jiri would provide, judging
from his positive tone to the patches :)

- Arnaldo

commit 8048a0884a3f98bae2434d141711d72382b784b0
Author: Igor Lubashev <[email-masked]>
Date:   Wed Jul 17 20:39:03 2019 -0300

    perf tools: Add capability-related utilities
    
    Add utilities to help checking capabilities of the running process.
    Make perf link with libcap.
    
    Signed-off-by: Igor Lubashev <[email-masked]>
    Acked-by: Alexey Budankov <[email-masked]>
    Acked-by: Jiri Olsa <[email-masked]>
    CC: Alexander Shishkin <[email-masked]>
    Cc: James Morris <[email-masked]>
    Cc: Mathieu Poirier <[email-masked]>
    Cc: Namhyung Kim <[email-masked]>
    Cc: Peter Zijlstra <[email-masked]>
    Cc: Suzuki K Poulose <[email-masked]>
    Link: https://lkml.kernel.org/r/[email-masked]
    Signed-off-by: Arnaldo Carvalho de Melo <[email-masked]>

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 89ac5a1f1550..b9cf084f32d7 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -259,7 +259,7 @@ CXXFLAGS += -Wno-strict-aliasing
 # adding assembler files missing the .GNU-stack linker note.
 LDFLAGS += -Wl,-z,noexecstack
 
-EXTLIBS = -lpthread -lrt -lm -ldl
+EXTLIBS = -lpthread -lrt -lm -ldl -lcap
 
 ifeq ($(FEATURES_DUMP),)
 include $(srctree)/tools/build/Makefile.feature
diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index 14f812bb07a7..61ed1a3005d4 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -1,6 +1,7 @@
 perf-y += annotate.o
 perf-y += block-range.o
 perf-y += build-id.o
+perf-y += cap.o
 perf-y += config.o
 perf-y += ctype.o
 perf-y += db-export.o
diff --git a/tools/perf/util/cap.c b/tools/perf/util/cap.c
new file mode 100644
index 000000000000..c42ea32663cf
--- /dev/null
+++ b/tools/perf/util/cap.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Capability utilities
+ */
+#include "cap.h"
+#include <stdbool.h>
+#include <sys/capability.h>
+
+bool perf_cap__capable(cap_value_t cap)
+{
+	cap_flag_value_t val;
+	cap_t caps = cap_get_proc();
+
+	if (!caps)
+		return false;
+
+	if (cap_get_flag(caps, cap, CAP_EFFECTIVE, &val) != 0)
+		val = CAP_CLEAR;
+
+	if (cap_free(caps) != 0)
+		return false;
+
+	return val == CAP_SET;
+}
diff --git a/tools/perf/util/cap.h b/tools/perf/util/cap.h
new file mode 100644
index 000000000000..5521de78b228
--- /dev/null
+++ b/tools/perf/util/cap.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_CAP_H
+#define __PERF_CAP_H
+
+#include <stdbool.h>
+#include <sys/capability.h>
+
+bool perf_cap__capable(cap_value_t cap);
+
+#endif /* __PERF_CAP_H */
diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 1f1da6082806..b4128f72f2e8 100644
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h
@@ -851,6 +851,7 @@ void  cpu_map_data__synthesize(struct cpu_map_data *data, struct cpu_map *map,
 void event_attr_init(struct perf_event_attr *attr);
 
 int perf_event_paranoid(void);
+bool perf_event_paranoid_check(int max_level);
 
 extern int sysctl_perf_event_max_stack;
 extern int sysctl_perf_event_max_contexts_per_stack;
diff --git a/tools/perf/util/python-ext-sources b/tools/perf/util/python-ext-sources
index ceb8afdf9a89..afba10684b65 100644
--- a/tools/perf/util/python-ext-sources
+++ b/tools/perf/util/python-ext-sources
@@ -9,6 +9,7 @@ util/python.c
 ../lib/ctype.c
 util/evlist.c
 util/evsel.c
+util/cap.c
 util/cpumap.c
 util/memswap.c
 util/mmap.c
diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index a61535cf1bca..4f0da8a03697 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -16,10 +16,12 @@
 #include <string.h>
 #include <errno.h>
 #include <limits.h>
+#include <linux/capability.h>
 #include <linux/kernel.h>
 #include <linux/log2.h>
 #include <linux/time64.h>
 #include <unistd.h>
+#include "cap.h"
 #include "strlist.h"
 #include "string2.h"
 
@@ -443,6 +445,13 @@ int perf_event_paranoid(void)
 
 	return value;
 }
+
+bool perf_event_paranoid_check(int max_level)
+{
+	return perf_cap__capable(CAP_SYS_ADMIN) ||
+			perf_event_paranoid() <= max_level;
+}
+
 static int
 fetch_ubuntu_kernel_version(unsigned int *puint)
 {

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