[PATCHv5] perf tools: enable close-on-exec flag on perf file descriptor

From: Yann Droneaud
Date: Mon Jun 02 2014 - 09:59:46 EST

In commit a21b0b354d4a ('perf: Introduce a flag to enable
close-on-exec in perf_event_open()'), flag PERF_FLAG_FD_CLOEXEC
was added to perf_event_open(2) syscall to allows userspace
to atomically enable close-on-exec behavor when creating
the file descriptor.

This patch makes perf tools use the new flag if supported
by the kernel, so that the event file descriptors got
automatically closed if perf tool exec a sub-command.

Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Yann Droneaud <ydroneaud@xxxxxxxxxx>
---

Hi,

Quite the same patch from v4. I'm interested in some
feedback so that I could improve the patch if needed.

Regards.

Changes from v4 [1]:
- rebase on next-20140530 and update commit message.

Changes from v3 [2]:
- rebase on next-20140307 and resend asis.

Changes from v2 [3]:
- use safest perf attr configuration in probe function,
as used in perf_evsel__fallback().

Changes from v1 [4]:
- don't probe PERF_FLAG_FD_CLOEXEC for each call to
perf_event_open_cloexec_flag(): don't forget to set
'probed' variable once flag was probed.
- call perf_event_open_cloexec_flag() only once in
util/record.c:perf_do_probe_api().
- fixed minor coding style issue (unneeded braces)
in util/cloexec.c

Changes from v0 [5]:
- add probing for PERF_FLAG_FD_CLOEXEC flag allowing
perf to run on older kernel:
* use "missing feature" pattern in evsel to disable
PERF_FLAG_FD_CLOEXEC in perf_evsel__open() if not
supported by kernel;
* add a dedicated function to probe for
PERF_FLAG_FD_CLOEXEC support in the current kernel.
This function is to be used by other functions
calling sys_perf_event_open() directly.
- remove PERF_FLAG_FD_CLOEXEC from PowerPC selftest
as it's not related to perf tool: it should be part
of a separate patch.

[1] http://lkml.kernel.org/r/1394527147-7010-1-git-send-email-ydroneaud@xxxxxxxxxx
https://patchwork.kernel.org/patch/3809711/

[2] http://lkml.kernel.org/r/1390771203-28415-1-git-send-email-ydroneaud@xxxxxxxxxx
https://patchwork.kernel.org/patch/3540091/

[3] http://lkml.kernel.org/r/1389607770-4485-1-git-send-email-ydroneaud@xxxxxxxxxx
https://patchwork.kernel.org/patch/3474141/

[4] http://lkml.kernel.org/r/1389463628-24869-1-git-send-email-ydroneaud@xxxxxxxxxx
https://patchwork.kernel.org/patch/3469571/

[5] http://lkml.kernel.org/r/1389005485-12778-1-git-send-email-ydroneaud@xxxxxxxxxx
https://patchwork.kernel.org/patch/3437111/

tools/perf/Makefile.perf | 1 +
tools/perf/bench/mem-memcpy.c | 4 ++-
tools/perf/bench/mem-memset.c | 4 ++-
tools/perf/builtin-sched.c | 4 ++-
tools/perf/tests/bp_signal.c | 4 ++-
tools/perf/tests/bp_signal_overflow.c | 4 ++-
tools/perf/tests/rdpmc.c | 4 ++-
tools/perf/util/cloexec.c | 56 +++++++++++++++++++++++++++++++++++
tools/perf/util/cloexec.h | 6 ++++
tools/perf/util/evsel.c | 12 ++++++--
tools/perf/util/record.c | 9 ++++--
11 files changed, 96 insertions(+), 12 deletions(-)
create mode 100644 tools/perf/util/cloexec.c
create mode 100644 tools/perf/util/cloexec.h

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 02f0a4dd1a80..000d34087f77 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -373,6 +373,7 @@ LIB_OBJS += $(OUTPUT)util/stat.o
LIB_OBJS += $(OUTPUT)util/record.o
LIB_OBJS += $(OUTPUT)util/srcline.o
LIB_OBJS += $(OUTPUT)util/data.o
+LIB_OBJS += $(OUTPUT)util/cloexec.o

LIB_OBJS += $(OUTPUT)ui/setup.o
LIB_OBJS += $(OUTPUT)ui/helpline.o
diff --git a/tools/perf/bench/mem-memcpy.c b/tools/perf/bench/mem-memcpy.c
index 5ce71d3b72cf..bf5a21b848a9 100644
--- a/tools/perf/bench/mem-memcpy.c
+++ b/tools/perf/bench/mem-memcpy.c
@@ -10,6 +10,7 @@
#include "../util/util.h"
#include "../util/parse-options.h"
#include "../util/header.h"
+#include "../util/cloexec.h"
#include "bench.h"
#include "mem-memcpy-arch.h"

@@ -83,7 +84,8 @@ static struct perf_event_attr cycle_attr = {

static void init_cycle(void)
{
- cycle_fd = sys_perf_event_open(&cycle_attr, getpid(), -1, -1, 0);
+ cycle_fd = sys_perf_event_open(&cycle_attr, getpid(), -1, -1,
+ perf_event_open_cloexec_flag());

if (cycle_fd < 0 && errno == ENOSYS)
die("No CONFIG_PERF_EVENTS=y kernel support configured?\n");
diff --git a/tools/perf/bench/mem-memset.c b/tools/perf/bench/mem-memset.c
index 9af79d2b18e5..260747ea1e0e 100644
--- a/tools/perf/bench/mem-memset.c
+++ b/tools/perf/bench/mem-memset.c
@@ -10,6 +10,7 @@
#include "../util/util.h"
#include "../util/parse-options.h"
#include "../util/header.h"
+#include "../util/cloexec.h"
#include "bench.h"
#include "mem-memset-arch.h"

@@ -83,7 +84,8 @@ static struct perf_event_attr cycle_attr = {

static void init_cycle(void)
{
- cycle_fd = sys_perf_event_open(&cycle_attr, getpid(), -1, -1, 0);
+ cycle_fd = sys_perf_event_open(&cycle_attr, getpid(), -1, -1,
+ perf_event_open_cloexec_flag());

if (cycle_fd < 0 && errno == ENOSYS)
die("No CONFIG_PERF_EVENTS=y kernel support configured?\n");
diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index d7176830b9b2..bb4afc9fae54 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -10,6 +10,7 @@
#include "util/header.h"
#include "util/session.h"
#include "util/tool.h"
+#include "util/cloexec.h"

#include "util/parse-options.h"
#include "util/trace-event.h"
@@ -434,7 +435,8 @@ static int self_open_counters(void)
attr.type = PERF_TYPE_SOFTWARE;
attr.config = PERF_COUNT_SW_TASK_CLOCK;

- fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
+ fd = sys_perf_event_open(&attr, 0, -1, -1,
+ perf_event_open_cloexec_flag());

if (fd < 0)
pr_err("Error: sys_perf_event_open() syscall returned "
diff --git a/tools/perf/tests/bp_signal.c b/tools/perf/tests/bp_signal.c
index aba095489193..fdc0d3e185f9 100644
--- a/tools/perf/tests/bp_signal.c
+++ b/tools/perf/tests/bp_signal.c
@@ -25,6 +25,7 @@
#include "tests.h"
#include "debug.h"
#include "perf.h"
+#include "../util/cloexec.h"

static int fd1;
static int fd2;
@@ -78,7 +79,8 @@ static int bp_event(void *fn, int setup_signal)
pe.exclude_kernel = 1;
pe.exclude_hv = 1;

- fd = sys_perf_event_open(&pe, 0, -1, -1, 0);
+ fd = sys_perf_event_open(&pe, 0, -1, -1,
+ perf_event_open_cloexec_flag());
if (fd < 0) {
pr_debug("failed opening event %llx\n", pe.config);
return TEST_FAIL;
diff --git a/tools/perf/tests/bp_signal_overflow.c b/tools/perf/tests/bp_signal_overflow.c
index 44ac82179708..b0b17415f18c 100644
--- a/tools/perf/tests/bp_signal_overflow.c
+++ b/tools/perf/tests/bp_signal_overflow.c
@@ -24,6 +24,7 @@
#include "tests.h"
#include "debug.h"
#include "perf.h"
+#include "../util/cloexec.h"

static int overflows;

@@ -91,7 +92,8 @@ int test__bp_signal_overflow(void)
pe.exclude_kernel = 1;
pe.exclude_hv = 1;

- fd = sys_perf_event_open(&pe, 0, -1, -1, 0);
+ fd = sys_perf_event_open(&pe, 0, -1, -1,
+ perf_event_open_cloexec_flag());
if (fd < 0) {
pr_debug("failed opening event %llx\n", pe.config);
return TEST_FAIL;
diff --git a/tools/perf/tests/rdpmc.c b/tools/perf/tests/rdpmc.c
index e59143fd9e71..8432bfcffed6 100644
--- a/tools/perf/tests/rdpmc.c
+++ b/tools/perf/tests/rdpmc.c
@@ -6,6 +6,7 @@
#include "perf.h"
#include "debug.h"
#include "tests.h"
+#include "../util/cloexec.h"

#if defined(__x86_64__) || defined(__i386__)

@@ -104,7 +105,8 @@ static int __test__rdpmc(void)
sa.sa_sigaction = segfault_handler;
sigaction(SIGSEGV, &sa, NULL);

- fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
+ fd = sys_perf_event_open(&attr, 0, -1, -1,
+ perf_event_open_cloexec_flag());
if (fd < 0) {
pr_err("Error: sys_perf_event_open() syscall returned "
"with %d (%s)\n", fd, strerror(errno));
diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
new file mode 100644
index 000000000000..771ed36fcc61
--- /dev/null
+++ b/tools/perf/util/cloexec.c
@@ -0,0 +1,56 @@
+#include "util.h"
+#include "../perf.h"
+#include "cloexec.h"
+
+static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
+
+static int perf_flag_probe(void)
+{
+ /* use 'safest' configuration as used in perf_evsel__fallback() */
+ struct perf_event_attr attr = {
+ .type = PERF_COUNT_SW_CPU_CLOCK,
+ .config = PERF_COUNT_SW_CPU_CLOCK,
+ };
+ int fd;
+ int err;
+
+ /* check cloexec flag */
+ fd = sys_perf_event_open(&attr, 0, -1, -1,
+ PERF_FLAG_FD_CLOEXEC);
+ if (fd >= 0) {
+ close(fd);
+ return 1;
+ }
+
+ if (errno != EINVAL) {
+ err = errno;
+ pr_warning("sys_perf_event_open() syscall returned "
+ "%d (%d: %s)\n", fd, err, strerror(err));
+ }
+
+ /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
+ fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
+ if (fd >= 0) {
+ close(fd);
+ return 0;
+ }
+
+ err = errno;
+ die("sys_perf_event_open() syscall returned "
+ "%d (%d: %s)\n", fd, err, strerror(err));
+
+ return -1;
+}
+
+unsigned long perf_event_open_cloexec_flag(void)
+{
+ static bool probed;
+
+ if (!probed) {
+ if (perf_flag_probe() <= 0)
+ flag = 0;
+ probed = true;
+ }
+
+ return flag;
+}
diff --git a/tools/perf/util/cloexec.h b/tools/perf/util/cloexec.h
new file mode 100644
index 000000000000..94a5a7d829d5
--- /dev/null
+++ b/tools/perf/util/cloexec.h
@@ -0,0 +1,6 @@
+#ifndef __PERF_CLOEXEC_H
+#define __PERF_CLOEXEC_H
+
+unsigned long perf_event_open_cloexec_flag(void);
+
+#endif /* __PERF_CLOEXEC_H */
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 5c28d82b76c4..d32019461993 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -29,6 +29,7 @@ static struct {
bool sample_id_all;
bool exclude_guest;
bool mmap2;
+ bool cloexec;
} perf_missing_features;

#define FD(e, x, y) (*(int *)xyarray__entry(e->fd, x, y))
@@ -988,7 +989,7 @@ static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
struct thread_map *threads)
{
int cpu, thread;
- unsigned long flags = 0;
+ unsigned long flags = PERF_FLAG_FD_CLOEXEC;
int pid = -1, err;
enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;

@@ -997,11 +998,13 @@ static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
return -ENOMEM;

if (evsel->cgrp) {
- flags = PERF_FLAG_PID_CGROUP;
+ flags |= PERF_FLAG_PID_CGROUP;
pid = evsel->cgrp->fd;
}

fallback_missing_features:
+ if (perf_missing_features.cloexec)
+ flags &= ~(unsigned long)PERF_FLAG_FD_CLOEXEC;
if (perf_missing_features.mmap2)
evsel->attr.mmap2 = 0;
if (perf_missing_features.exclude_guest)
@@ -1070,7 +1073,10 @@ try_fallback:
if (err != -EINVAL || cpu > 0 || thread > 0)
goto out_close;

- if (!perf_missing_features.mmap2 && evsel->attr.mmap2) {
+ if (!perf_missing_features.cloexec && (flags & PERF_FLAG_FD_CLOEXEC)) {
+ perf_missing_features.cloexec = true;
+ goto fallback_missing_features;
+ } else if (!perf_missing_features.mmap2 && evsel->attr.mmap2) {
perf_missing_features.mmap2 = true;
goto fallback_missing_features;
} else if (!perf_missing_features.exclude_guest &&
diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
index 049e0a09ccd3..9a8d622809f6 100644
--- a/tools/perf/util/record.c
+++ b/tools/perf/util/record.c
@@ -4,6 +4,7 @@
#include "parse-events.h"
#include <api/fs/fs.h>
#include "util.h"
+#include "cloexec.h"

typedef void (*setup_probe_fn_t)(struct perf_evsel *evsel);

@@ -11,6 +12,7 @@ static int perf_do_probe_api(setup_probe_fn_t fn, int cpu, const char *str)
{
struct perf_evlist *evlist;
struct perf_evsel *evsel;
+ unsigned long flags = perf_event_open_cloexec_flag();
int err = -EAGAIN, fd;

evlist = perf_evlist__new();
@@ -22,14 +24,14 @@ static int perf_do_probe_api(setup_probe_fn_t fn, int cpu, const char *str)

evsel = perf_evlist__first(evlist);

- fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, 0);
+ fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, flags);
if (fd < 0)
goto out_delete;
close(fd);

fn(evsel);

- fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, 0);
+ fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, flags);
if (fd < 0) {
if (errno == EINVAL)
err = -EINVAL;
@@ -203,7 +205,8 @@ bool perf_evlist__can_select_event(struct perf_evlist *evlist, const char *str)
cpu = evlist->cpus->map[0];
}

- fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1, 0);
+ fd = sys_perf_event_open(&evsel->attr, -1, cpu, -1,
+ perf_event_open_cloexec_flag());
if (fd >= 0) {
close(fd);
ret = true;
--
1.9.3

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