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[PATCH v7 0/5] bpf: Introduce the new ability of eBPF programs to access hardware PMU counter

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  [PATCH v7 0/5] bpf: Introduce the new ability of eBPF programs to access hardware PMU counter Kaixu Xia <xiakaixu@huawei.com> - 2015-08-06 09:10 +0200
    [PATCH v7 1/5] perf: add the necessary core perf APIs when accessing events counters in eBPF programs Kaixu Xia <xiakaixu@huawei.com> - 2015-08-06 09:10 +0200
    [PATCH v7 3/5] bpf: Add new bpf map type to store the pointer to struct perf_event Kaixu Xia <xiakaixu@huawei.com> - 2015-08-06 09:10 +0200
    [PATCH v7 5/5] samples/bpf: example of get selected PMU counter value Kaixu Xia <xiakaixu@huawei.com> - 2015-08-06 09:10 +0200
      Re: [PATCH v7 5/5] samples/bpf: example of get selected PMU counter  value Alexei Starovoitov <ast@plumgrid.com> - 2015-08-12 04:00 +0200
    Re: [PATCH v7 0/5] bpf: Introduce the new ability of eBPF programs  to access hardware PMU counter David Miller <davem@davemloft.net> - 2015-08-10 08:00 +0200

#1201490 — [PATCH v7 0/5] bpf: Introduce the new ability of eBPF programs to access hardware PMU counter

This patchset is base on the net-next:
 git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git
commit 9dc20a649609c95ce7c5ac4282656ba627b67d49.

Previous patch v6 url:
https://lkml.org/lkml/2015/8/4/188

changes in V7:
 - rebase the whole patch set to net-next tree(9dc20a64);
 - split out the core perf APIs into Patch 1/5;
 - change the return value of function perf_event_attrs()
   from struct perf_event * to const struct perf_event * in
   Patch 1/5;
 - rename the function perf_event_read_internal() to perf_event_
   read_local() and rewrite it in Patch 1/5;
 - rename the function check_func_limit() to check_map_func
   _compatibility() and remove the unnecessary pass pointer to
   a pointer in Patch 4/5;

changes in V6: 
 - make the Patch 1/4 commit message more meaning and readable;
 - remove the unnecessary comment in Patch 2/4 and make it clean;
 - declare the function perf_event_release_kernel() in include/
   linux/perf_event.h to fix the build error when CONFIG_PERF_EVENTS
   isn't configured in Patch 2/4;
 - add function perf_event_attrs() to get the struct perf_event_attr
   in Patch 2/4. 
 - move the related code from kernel/trace/bpf_trace.c to kernel/
   events/core.c and add function perf_event_read_internal() to
   avoid poking inside of the event outside of perf code in Patch 3/4;
 - generial the func & map match-pair with an array in Patch 3/4;

changes in V5: 
 - move struct fd_array_map_ops* fd_ops to bpf_map;
 - move array perf event decrement refcnt function to
   map_free;
 - fix the NULL ptr of perf_event_get();
 - move bpf_perf_event_read() to kernel/bpf/bpf_trace.c;
 - get rid of the remaining struct bpf_prog;
 - move the unnecessay cast on void *;

changes in V4: 
 - make the bpf_prog_array_map more generic;
 - fix the bug of event refcnt leak;
 - use more useful errno in bpf_perf_event_read();

changes in V3: 
 - collapse V2 patches 1-3 into one;
 - drop the function map->ops->map_traverse_elem() and release
   the struct perf_event in map_free;
 - only allow to access bpf_perf_event_read() from programs;
 - update the perf_event_array_map elem via xchg();
 - pass index directly to bpf_perf_event_read() instead of
   MAP_KEY;

changes in V2:
 - put atomic_long_inc_not_zero() between fdget() and fdput();
 - limit the event type to PERF_TYPE_RAW and PERF_TYPE_HARDWARE;
 - Only read the event counter on current CPU or on current
   process;
 - add new map type BPF_MAP_TYPE_PERF_EVENT_ARRAY to store the
   pointer to the struct perf_event;
 - according to the perf_event_map_fd and key, the function
   bpf_perf_event_read() can get the Hardware PMU counter value;

Patch 5/5 is a simple example and shows how to use this new eBPF
programs ability. The PMU counter data can be found in
/sys/kernel/debug/tracing/trace(trace_pipe).(the cycles PMU
value when 'kprobe/sys_write' sampling)

  $ cat /sys/kernel/debug/tracing/trace_pipe
  $ ./tracex6
       ...
       syslog-ng-548   [000] d..1    76.905673: : CPU-0   681765271
       syslog-ng-548   [000] d..1    76.905690: : CPU-0   681787855
       syslog-ng-548   [000] d..1    76.905707: : CPU-0   681810504
       syslog-ng-548   [000] d..1    76.905725: : CPU-0   681834771
       syslog-ng-548   [000] d..1    76.905745: : CPU-0   681859519
       syslog-ng-548   [000] d..1    76.905766: : CPU-0   681890419
       syslog-ng-548   [000] d..1    76.905783: : CPU-0   681914045
       syslog-ng-548   [000] d..1    76.905800: : CPU-0   681935950
       syslog-ng-548   [000] d..1    76.905816: : CPU-0   681958299
              ls-690   [005] d..1    82.241308: : CPU-5   3138451
              sh-691   [004] d..1    82.244570: : CPU-4   7324988
           <...>-699   [007] d..1    99.961387: : CPU-7   3194027
           <...>-695   [003] d..1    99.961474: : CPU-3   288901
           <...>-695   [003] d..1    99.961541: : CPU-3   383145
           <...>-695   [003] d..1    99.961591: : CPU-3   450365
           <...>-695   [003] d..1    99.961639: : CPU-3   515751
           <...>-695   [003] d..1    99.961686: : CPU-3   579047
       ...

The detail of patches is as follow:

Patch 1/5 add the necessary core perf APIs perf_event_attrs(),
perf_event_get(),perf_event_read_local() when accessing events
counters in eBPF programs

Patch 2/5 rewrites part of the bpf_prog_array map code and make it
more generic;

Patch 3/5 introduces a new bpf map type. This map only stores the
pointer to struct perf_event;

Patch 4/5 implements function bpf_perf_event_read() that get the
selected hardware PMU conuter;

Patch 5/5 gives a simple example.

Kaixu Xia (4):
  perf: add the necessary core perf APIs when accessing events counters
    in eBPF programs
  bpf: Add new bpf map type to store the pointer to struct perf_event
  bpf: Implement function bpf_perf_event_read() that get the selected
    hardware PMU conuter
  samples/bpf: example of get selected PMU counter value

Wang Nan (1):
  bpf: Make the bpf_prog_array_map more generic

 arch/x86/net/bpf_jit_comp.c |   6 +-
 include/linux/bpf.h         |  10 +++-
 include/linux/perf_event.h  |  10 ++++
 include/uapi/linux/bpf.h    |   2 +
 kernel/bpf/arraymap.c       | 137 ++++++++++++++++++++++++++++++++++----------
 kernel/bpf/core.c           |   2 +-
 kernel/bpf/syscall.c        |   2 +-
 kernel/bpf/verifier.c       |  48 +++++++++++-----
 kernel/events/core.c        |  78 +++++++++++++++++++++++++
 kernel/trace/bpf_trace.c    |  31 ++++++++++
 samples/bpf/Makefile        |   4 ++
 samples/bpf/bpf_helpers.h   |   2 +
 samples/bpf/tracex6_kern.c  |  26 +++++++++
 samples/bpf/tracex6_user.c  |  68 ++++++++++++++++++++++
 14 files changed, 373 insertions(+), 53 deletions(-)
 create mode 100644 samples/bpf/tracex6_kern.c
 create mode 100644 samples/bpf/tracex6_user.c

-- 
1.8.3.4

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#1201499 — [PATCH v7 1/5] perf: add the necessary core perf APIs when accessing events counters in eBPF programs

This patch add three core perf APIs:
 - perf_event_attrs(): export the struct perf_event_attr from struct
   perf_event;
 - perf_event_get(): get the struct perf_event from the given fd;
 - perf_event_read_local(): read the events counters active on the
   current CPU;
These APIs are needed when accessing events counters in eBPF programs.

The API perf_event_read_local() comes from Peter and I add the
corresponding SOB. 

Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 include/linux/perf_event.h | 10 ++++++
 kernel/events/core.c       | 78 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 88 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 2027809..092a0e8 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -641,6 +641,8 @@ extern int perf_event_init_task(struct task_struct *child);
 extern void perf_event_exit_task(struct task_struct *child);
 extern void perf_event_free_task(struct task_struct *task);
 extern void perf_event_delayed_put(struct task_struct *task);
+extern struct perf_event *perf_event_get(unsigned int fd);
+extern const struct perf_event_attr *perf_event_attrs(struct perf_event *event);
 extern void perf_event_print_debug(void);
 extern void perf_pmu_disable(struct pmu *pmu);
 extern void perf_pmu_enable(struct pmu *pmu);
@@ -659,6 +661,7 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr,
 				void *context);
 extern void perf_pmu_migrate_context(struct pmu *pmu,
 				int src_cpu, int dst_cpu);
+extern u64 perf_event_read_local(struct perf_event *event);
 extern u64 perf_event_read_value(struct perf_event *event,
 				 u64 *enabled, u64 *running);
 
@@ -979,6 +982,12 @@ static inline int perf_event_init_task(struct task_struct *child)	{ return 0; }
 static inline void perf_event_exit_task(struct task_struct *child)	{ }
 static inline void perf_event_free_task(struct task_struct *task)	{ }
 static inline void perf_event_delayed_put(struct task_struct *task)	{ }
+static inline struct perf_event *perf_event_get(unsigned int fd)	{ return ERR_PTR(-EINVAL); }
+static inline const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
+{
+	return ERR_PTR(-EINVAL);
+}
+static inline u64 perf_event_read_local(struct perf_event *event)	{ return -EINVAL; }
 static inline void perf_event_print_debug(void)				{ }
 static inline int perf_event_task_disable(void)				{ return -EINVAL; }
 static inline int perf_event_task_enable(void)				{ return -EINVAL; }
@@ -1011,6 +1020,7 @@ static inline void perf_event_enable(struct perf_event *event)		{ }
 static inline void perf_event_disable(struct perf_event *event)		{ }
 static inline int __perf_event_disable(void *info)			{ return -1; }
 static inline void perf_event_task_tick(void)				{ }
+static inline int perf_event_release_kernel(struct perf_event *event)	{ return 0; }
 #endif
 
 #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_NO_HZ_FULL)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index d3dae34..e2c6a88 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3212,6 +3212,59 @@ static inline u64 perf_event_count(struct perf_event *event)
 	return __perf_event_count(event);
 }
 
+/*
+ * NMI-safe method to read a local event, that is an event that
+ * is:
+ *   - either for the current task, or for this CPU
+ *   - does not have inherit set, for inherited task events
+ *     will not be local and we cannot read them atomically
+ *   - must not have a pmu::count method
+ */
+u64 perf_event_read_local(struct perf_event *event)
+{
+	unsigned long flags;
+	u64 val;
+
+	/*
+	 * Disabling interrupts avoids all counter scheduling (context
+	 * switches, timer based rotation and IPIs).
+	 */
+	local_irq_save(flags);
+
+	/* If this is a per-task event, it must be for current */
+	WARN_ON_ONCE((event->attach_state & PERF_ATTACH_TASK) &&
+		     event->hw.target != current);
+
+	/* If this is a per-CPU event, it must be for this CPU */
+	WARN_ON_ONCE(!(event->attach_state & PERF_ATTACH_TASK) &&
+		     event->cpu != smp_processor_id());
+
+	/*
+	 * It must not be an event with inherit set, we cannot read
+	 * all child counters from atomic context.
+	 */
+	WARN_ON_ONCE(event->attr.inherit);
+
+	/*
+	 * It must not have a pmu::count method, those are not
+	 * NMI safe.
+	 */
+	WARN_ON_ONCE(event->pmu->count);
+
+	/*
+	 * If the event is currently on this CPU, its either a per-task event,
+	 * or local to this CPU. Furthermore it means its ACTIVE (otherwise
+	 * oncpu == -1).
+	 */
+	if (event->oncpu == smp_processor_id())
+		event->pmu->read(event);
+
+	val = local64_read(&event->count);
+	local_irq_restore(flags);
+
+	return val;
+}
+
 static u64 perf_event_read(struct perf_event *event)
 {
 	/*
@@ -8574,6 +8627,31 @@ void perf_event_delayed_put(struct task_struct *task)
 		WARN_ON_ONCE(task->perf_event_ctxp[ctxn]);
 }
 
+struct perf_event *perf_event_get(unsigned int fd)
+{
+	int err;
+	struct fd f;
+	struct perf_event *event;
+
+	err = perf_fget_light(fd, &f);
+	if (err)
+		return ERR_PTR(err);
+
+	event = f.file->private_data;
+	atomic_long_inc(&event->refcount);
+	fdput(f);
+
+	return event;
+}
+
+const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
+{
+	if (!event)
+		return ERR_PTR(-EINVAL);
+
+	return &event->attr;
+}
+
 /*
  * inherit a event from parent task to child task:
  */
-- 
1.8.3.4

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#1201500 — [PATCH v7 3/5] bpf: Add new bpf map type to store the pointer to struct perf_event

Introduce a new bpf map type 'BPF_MAP_TYPE_PERF_EVENT_ARRAY'.
This map only stores the pointer to struct perf_event. The
user space event FDs from perf_event_open() syscall are converted
to the pointer to struct perf_event and stored in map.

Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
---
 include/linux/bpf.h      |  1 +
 include/uapi/linux/bpf.h |  1 +
 kernel/bpf/arraymap.c    | 57 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d495211..4fc1f40 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -10,6 +10,7 @@
 #include <uapi/linux/bpf.h>
 #include <linux/workqueue.h>
 #include <linux/file.h>
+#include <linux/perf_event.h>
 
 struct bpf_map;
 
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2ce13c1..a1814e8 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -114,6 +114,7 @@ enum bpf_map_type {
 	BPF_MAP_TYPE_HASH,
 	BPF_MAP_TYPE_ARRAY,
 	BPF_MAP_TYPE_PROG_ARRAY,
+	BPF_MAP_TYPE_PERF_EVENT_ARRAY,
 };
 
 enum bpf_prog_type {
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 45df657..29ace10 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -273,3 +273,60 @@ static int __init register_prog_array_map(void)
 	return 0;
 }
 late_initcall(register_prog_array_map);
+
+static void perf_event_array_map_free(struct bpf_map *map)
+{
+	bpf_fd_array_map_clear(map);
+	fd_array_map_free(map);
+}
+
+static void *perf_event_fd_array_get_ptr(struct bpf_map *map, int fd)
+{
+	struct perf_event *event;
+	const struct perf_event_attr *attr;
+
+	event = perf_event_get(fd);
+	if (IS_ERR(event))
+		return event;
+
+	attr = perf_event_attrs(event);
+	if (IS_ERR(attr))
+		return (void *)attr;
+
+	if (attr->type != PERF_TYPE_RAW &&
+	    attr->type != PERF_TYPE_HARDWARE) {
+		perf_event_release_kernel(event);
+		return ERR_PTR(-EINVAL);
+	}
+	return event;
+}
+
+static void perf_event_fd_array_put_ptr(void *ptr)
+{
+	struct perf_event *event = ptr;
+
+	perf_event_release_kernel(event);
+}
+
+static const struct bpf_map_ops perf_event_array_ops = {
+	.map_alloc = fd_array_map_alloc,
+	.map_free = perf_event_array_map_free,
+	.map_get_next_key = array_map_get_next_key,
+	.map_lookup_elem = fd_array_map_lookup_elem,
+	.map_update_elem = fd_array_map_update_elem,
+	.map_delete_elem = fd_array_map_delete_elem,
+	.map_fd_get_ptr = perf_event_fd_array_get_ptr,
+	.map_fd_put_ptr = perf_event_fd_array_put_ptr,
+};
+
+static struct bpf_map_type_list perf_event_array_type __read_mostly = {
+	.ops = &perf_event_array_ops,
+	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
+};
+
+static int __init register_perf_event_array_map(void)
+{
+	bpf_register_map_type(&perf_event_array_type);
+	return 0;
+}
+late_initcall(register_perf_event_array_map);
-- 
1.8.3.4

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#1201501 — [PATCH v7 5/5] samples/bpf: example of get selected PMU counter value

This is a simple example and shows how to use the new ability
to get the selected Hardware PMU counter value.

Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
---
 samples/bpf/Makefile       |  4 +++
 samples/bpf/bpf_helpers.h  |  2 ++
 samples/bpf/tracex6_kern.c | 26 ++++++++++++++++++
 samples/bpf/tracex6_user.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 100 insertions(+)
 create mode 100644 samples/bpf/tracex6_kern.c
 create mode 100644 samples/bpf/tracex6_user.c

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4450fed..63e7d50 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -12,6 +12,7 @@ hostprogs-y += tracex2
 hostprogs-y += tracex3
 hostprogs-y += tracex4
 hostprogs-y += tracex5
+hostprogs-y += tracex6
 hostprogs-y += lathist
 
 test_verifier-objs := test_verifier.o libbpf.o
@@ -25,6 +26,7 @@ tracex2-objs := bpf_load.o libbpf.o tracex2_user.o
 tracex3-objs := bpf_load.o libbpf.o tracex3_user.o
 tracex4-objs := bpf_load.o libbpf.o tracex4_user.o
 tracex5-objs := bpf_load.o libbpf.o tracex5_user.o
+tracex6-objs := bpf_load.o libbpf.o tracex6_user.o
 lathist-objs := bpf_load.o libbpf.o lathist_user.o
 
 # Tell kbuild to always build the programs
@@ -37,6 +39,7 @@ always += tracex2_kern.o
 always += tracex3_kern.o
 always += tracex4_kern.o
 always += tracex5_kern.o
+always += tracex6_kern.o
 always += tcbpf1_kern.o
 always += lathist_kern.o
 
@@ -51,6 +54,7 @@ HOSTLOADLIBES_tracex2 += -lelf
 HOSTLOADLIBES_tracex3 += -lelf
 HOSTLOADLIBES_tracex4 += -lelf -lrt
 HOSTLOADLIBES_tracex5 += -lelf
+HOSTLOADLIBES_tracex6 += -lelf
 HOSTLOADLIBES_lathist += -lelf
 
 # point this to your LLVM backend with bpf support
diff --git a/samples/bpf/bpf_helpers.h b/samples/bpf/bpf_helpers.h
index c77c872..3a44d3a 100644
--- a/samples/bpf/bpf_helpers.h
+++ b/samples/bpf/bpf_helpers.h
@@ -31,6 +31,8 @@ static unsigned long long (*bpf_get_current_uid_gid)(void) =
 	(void *) BPF_FUNC_get_current_uid_gid;
 static int (*bpf_get_current_comm)(void *buf, int buf_size) =
 	(void *) BPF_FUNC_get_current_comm;
+static int (*bpf_perf_event_read)(void *map, int index) =
+	(void *) BPF_FUNC_perf_event_read;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions
diff --git a/samples/bpf/tracex6_kern.c b/samples/bpf/tracex6_kern.c
new file mode 100644
index 0000000..23d1cff
--- /dev/null
+++ b/samples/bpf/tracex6_kern.c
@@ -0,0 +1,26 @@
+#include <linux/version.h>
+#include <uapi/linux/bpf.h>
+#include "bpf_helpers.h"
+
+struct bpf_map_def SEC("maps") my_map = {
+	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
+	.key_size = sizeof(int),
+	.value_size = sizeof(u32),
+	.max_entries = 32,
+};
+
+SEC("kprobe/sys_write")
+int bpf_prog1(struct pt_regs *ctx)
+{
+	u64 count;
+	u32 key = bpf_get_smp_processor_id();
+	char fmt[] = "CPU-%d   %llu\n";
+
+	count = bpf_perf_event_read(&my_map, key);
+	bpf_trace_printk(fmt, sizeof(fmt), key, count);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+u32 _version SEC("version") = LINUX_VERSION_CODE;
diff --git a/samples/bpf/tracex6_user.c b/samples/bpf/tracex6_user.c
new file mode 100644
index 0000000..928f05e
--- /dev/null
+++ b/samples/bpf/tracex6_user.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <sys/ioctl.h>
+#include <linux/perf_event.h>
+#include <linux/bpf.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+
+#define SAMPLE_PERIOD  0x7fffffffffffffffULL
+
+static void test_bpf_perf_event(void)
+{
+	int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
+	int *pmu_fd = malloc(nr_cpus * sizeof(int));
+	unsigned long value;
+	int i;
+
+	struct perf_event_attr attr_insn_pmu = {
+		.freq = 0,
+		.sample_period = SAMPLE_PERIOD,
+		.inherit = 0,
+		.type = PERF_TYPE_HARDWARE,
+		.read_format = 0,
+		.sample_type = 0,
+		.config = 0,/* PMU: cycles */
+	};
+
+	for (i = 0; i < nr_cpus; i++) {
+		pmu_fd[i] = perf_event_open(&attr_insn_pmu, -1/*pid*/, i/*cpu*/, -1/*group_fd*/, 0);
+		if (pmu_fd[i] < 0)
+			printf("event syscall failed\n");
+
+		bpf_update_elem(map_fd[0], &i, &pmu_fd[i], BPF_ANY);
+		ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE, 0);
+	}
+
+	system("ls");
+	system("pwd");
+	system("sleep 2");
+
+	for (i = 0; i < nr_cpus; i++)
+		close(pmu_fd[i]);
+
+	close(map_fd);
+
+	free(pmu_fd);
+}
+
+int main(int argc, char **argv)
+{
+	char filename[256];
+
+	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+	if (load_bpf_file(filename)) {
+		printf("%s", bpf_log_buf);
+		return 1;
+	}
+
+	test_bpf_perf_event();
+
+	return 0;
+}
-- 
1.8.3.4

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#1205550 — Re: [PATCH v7 5/5] samples/bpf: example of get selected PMU counter value

On 8/6/15 12:02 AM, Kaixu Xia wrote:
> This is a simple example and shows how to use the new ability
> to get the selected Hardware PMU counter value.
>
> Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
> ---
>   samples/bpf/Makefile       |  4 +++
>   samples/bpf/bpf_helpers.h  |  2 ++
>   samples/bpf/tracex6_kern.c | 26 ++++++++++++++++++
>   samples/bpf/tracex6_user.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++

1.
I see a bunch of warnings building it:
   HOSTCC  samples/bpf/tracex6_user.o
../samples/bpf/tracex6_user.c: In function ‘test_bpf_perf_event’:
../samples/bpf/tracex6_user.c:49:2: warning: passing argument 1 of 
‘close’ makes integer from pointer without a cast [enabled by default]
In file included from ../samples/bpf/tracex6_user.c:2:0:
/usr/include/unistd.h:354:12: note: expected ‘int’ but argument is of 
type ‘int *’
../samples/bpf/tracex6_user.c:20:16: warning: unused variable ‘value’ 
[-Wunused-variable]
../samples/bpf/tracex6_user.c:42:8: warning: ignoring return value of 
‘system’, declared with attribute warn_unused_result [-Wunused-result]
../samples/bpf/tracex6_user.c:43:8: warning: ignoring return value of 
‘system’, declared with attribute warn_unused_result [-Wunused-result]
../samples/bpf/tracex6_user.c:44:8: warning: ignoring return value of 
‘system’, declared with attribute warn_unused_result [-Wunused-result]
   HOSTLD  samples/bpf/tracex6
   HOSTCC  samples/bpf/lathist_user.o
   HOSTLD  samples/bpf/lathist
clang  -nostdinc -isystem /usr/lib/gcc/x86_64-linux-gnu/4.7/include 
-I../arch/x86/include -Iarch/x86/include/generated/uapi 
-Iarch/x86/include/generated  -I../include -Iinclude 
-I../arch/x86/include/uapi -Iarch/x86/include/generated/uapi 
-I../include/uapi -Iinclude/generated/uapi -include 
../include/linux/kconfig.h  \
		-D__KERNEL__ -Wno-unused-value -Wno-pointer-sign \
		-O2 -emit-llvm -c ../samples/bpf/tracex6_kern.c -o -| 
../tools/bpf/llvm/bld/Debug+Asserts/bin/llc -march=bpf -filetype=obj -o 
samples/bpf/tracex6_kern.o
../samples/bpf/tracex6_kern.c:13:22: warning: declaration of 'struct 
pt_regs' will not be visible outside of this function [-Wvisibility]
int bpf_prog1(struct pt_regs *ctx)

Please fix.

2.
the example is incomplete.
Please add read_trace_pipe() otherwise it exits without printing
anything useful.

3.
please replace ls and pwd with ls > /dev/null
the spam on the screen is unnecessary.


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#1203776 — Re: [PATCH v7 0/5] bpf: Introduce the new ability of eBPF programs to access hardware PMU counter

From: Kaixu Xia <xiakaixu@huawei.com>
Date: Thu, 6 Aug 2015 07:02:31 +0000

> The detail of patches is as follow:
> 
> Patch 1/5 add the necessary core perf APIs perf_event_attrs(),
> perf_event_get(),perf_event_read_local() when accessing events
> counters in eBPF programs
> 
> Patch 2/5 rewrites part of the bpf_prog_array map code and make it
> more generic;
> 
> Patch 3/5 introduces a new bpf map type. This map only stores the
> pointer to struct perf_event;
> 
> Patch 4/5 implements function bpf_perf_event_read() that get the
> selected hardware PMU conuter;
> 
> Patch 5/5 gives a simple example.

Series applied, thanks.
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