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>
This commit is contained in:
Igor Lubashev 2019-08-07 10:44:14 -04:00 committed by Arnaldo Carvalho de Melo
parent 74d5f3d06f
commit c22e150e3a
7 changed files with 71 additions and 0 deletions

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@ -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

29
tools/perf/util/cap.c Normal file
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@ -0,0 +1,29 @@
// 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 */

27
tools/perf/util/cap.h Normal file
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@ -0,0 +1,27 @@
/* 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 */

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@ -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;

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@ -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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@ -59,6 +59,8 @@ ext_sources = list(map(lambda x: '%s/%s' % (src_perf, x) , ext_sources))
extra_libraries = []
if '-DHAVE_LIBNUMA_SUPPORT' in cflags:
extra_libraries = [ 'numa' ]
if '-DHAVE_LIBCAP_SUPPORT' in cflags:
extra_libraries += [ 'cap' ]
perf = Extension('perf',
sources = ext_sources,

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@ -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"
@ -403,6 +405,13 @@ 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)
{