Commit c22e150e authored Aug 07, 2019 by Igor Lubashev Committed by Arnaldo Carvalho de Melo Aug 14, 2019

perf tools: Add helpers to use capabilities if present



Add utilities to help checking capabilities of the running procss.  Make
perf link with libcap, if it is available. If no libcap-dev[el],
fallback to the geteuid() == 0 test used before.

Committer notes:

  $ perf test python
  18: 'import perf' in python                               : FAILED!
  $ perf test -v python
  Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc
  18: 'import perf' in python                               :
  --- start ---
  test child forked, pid 23288
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  ImportError: /tmp/build/perf/python/perf.so: undefined symbol: cap_get_flag
  test child finished with -1
  ---- end ----
  'import perf' in python: FAILED!
  $

This happens because differently from the perf binary generated with
this patch applied:

  $ ldd /tmp/build/perf/perf | grep libcap
  	libcap.so.2 => /lib64/libcap.so.2 (0x00007f724a4ef000)
  $

The python binding isn't linking with libcap:

  $ ldd /tmp/build/perf/python/perf.so | grep libcap
  $

So add 'cap' to the 'extra_libraries' variable in
tools/perf/util/setup.py, and rebuild:

  $ perf test python
  18: 'import perf' in python                               : Ok
  $

If we explicitely disable libcap it also continues to work:

  $ make NO_LIBCAP=1 -C tools/perf O=/tmp/build/perf install-bin
    $ ldd /tmp/build/perf/perf | grep libcap
  $ ldd /tmp/build/perf/python/perf.so | grep libcap
  $ perf test python
  18: 'import perf' in python                               : Ok
  $

Signed-off-by: Igor Lubashev <ilubashe@akamai.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
[ split from a larger patch ]
Link: http://lkml.kernel.org/r/8a1e76cf5c7c9796d0d4d240fbaa85305298aafa.1565188228.git.ilubashe@akamai.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 74d5f3d0

tools/perf/util/Build

+2 −0

Original line number	Diff line number	Diff line
		@@ -148,6 +148,8 @@ perf-$(CONFIG_ZLIB) += zlib.o
		perf-$(CONFIG_LZMA) += lzma.o
		perf-$(CONFIG_ZSTD) += zstd.o

		perf-$(CONFIG_LIBCAP) += cap.o

		perf-y += demangle-java.o
		perf-y += demangle-rust.o

tools/perf/util/cap.c

0 → 100644

+29 −0

Original line number	Diff line number	Diff line
		// SPDX-License-Identifier: GPL-2.0
		/*
		* Capability utilities
		*/

		#ifdef HAVE_LIBCAP_SUPPORT

		#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;
		}

		#endif /* HAVE_LIBCAP_SUPPORT */

tools/perf/util/cap.h

0 → 100644

+27 −0

Original line number	Diff line number	Diff line
		/* SPDX-License-Identifier: GPL-2.0 */
		#ifndef __PERF_CAP_H
		#define __PERF_CAP_H

		#include <stdbool.h>
		#include <linux/capability.h>
		#include <linux/compiler.h>

		#ifdef HAVE_LIBCAP_SUPPORT

		#include <sys/capability.h>

		bool perf_cap__capable(cap_value_t cap);

		#else

		#include <unistd.h>
		#include <sys/types.h>

		static inline bool perf_cap__capable(int cap __maybe_unused)
		{
		return geteuid() == 0;
		}

		#endif /* HAVE_LIBCAP_SUPPORT */

		#endif /* __PERF_CAP_H */

tools/perf/util/event.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -851,6 +851,7 @@ void cpu_map_data__synthesize(struct cpu_map_data data, struct perf_cpu_map m
		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;

tools/perf/util/python-ext-sources

+1 −0

Original line number	Diff line number	Diff line
		@@ -7,6 +7,7 @@

		util/python.c
		../lib/ctype.c
		util/cap.c
		util/evlist.c
		util/evsel.c
		util/cpumap.c

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