[PATCH net-next v4 0/2] bpf/tracing: allow user space to query prog array on the same tp

[PATCH net-next v4 0/2] bpf/tracing: allow user space to query prog array on the same tp

[Yonghong Song]

Commit e87c6bc3852b ("bpf: permit multiple bpf attachments
for a single perf event") added support to attach multiple
bpf programs to a single perf event. Given a perf event
(kprobe, uprobe, or kernel tracepoint), the perf ioctl interface
is used to query bpf programs attached to the same trace event.

There already exists a BPF_PROG_QUERY command for introspection
currently used by cgroup+bpf. We did have an implementation for
querying tracepoint+bpf through the same interface. However, it
looks cleaner to use ioctl() style of api here, since attaching
bpf prog to tracepoint/kuprobe is also done via ioctl.

Patch #1 had the core implementation and patch #2 added
a test case in tools bpf selftests suite.

Changelogs:
v3 -> v4:
  - Fix a compilation error with newer gcc like 6.3.1 while
    old gcc 4.8.5 is okay. I was using &uquery->ids to represent
    the address to the ids array to make it explicit that the
    address is passed, and this syntax is rightly rejected
    by gcc 6.3.1.
v2 -> v3:
  - Change uapi structure perf_event_query_bpf to be more
    clearer based on Peter's suggestion, and adjust
    other codes accordingly.
v1 -> v2:
  - Rebase on top of net-next.
  - Use existing bpf_prog_array_length function instead of
    implementing the same functionality in function
    bpf_prog_array_copy_info.

Yonghong Song (2):
  bpf/tracing: allow user space to query prog array on the same tp
  bpf/tracing: add a bpf test for new ioctl query interface

 include/linux/bpf.h                           |   4 +
 include/uapi/linux/perf_event.h               |  22 +++++
 kernel/bpf/core.c                             |  21 ++++
 kernel/events/core.c                          |   3 +
 kernel/trace/bpf_trace.c                      |  23 +++++
 tools/include/uapi/linux/perf_event.h         |  22 +++++
 tools/testing/selftests/bpf/Makefile          |   2 +-
 tools/testing/selftests/bpf/test_progs.c      | 134 ++++++++++++++++++++++++++
 tools/testing/selftests/bpf/test_tracepoint.c |  26 +++++
 9 files changed, 256 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/test_tracepoint.c

-- 
2.9.5

[PATCH net-next v4 1/2] bpf/tracing: allow user space to query prog array on the same tp

[Yonghong Song]

Commit e87c6bc3852b ("bpf: permit multiple bpf attachments
for a single perf event") added support to attach multiple
bpf programs to a single perf event.
Although this provides flexibility, users may want to know
what other bpf programs attached to the same tp interface.
Besides getting visibility for the underlying bpf system,
such information may also help consolidate multiple bpf programs,
understand potential performance issues due to a large array,
and debug (e.g., one bpf program which overwrites return code
may impact subsequent program results).

Commit 2541517c32be ("tracing, perf: Implement BPF programs
attached to kprobes") utilized the existing perf ioctl
interface and added the command PERF_EVENT_IOC_SET_BPF
to attach a bpf program to a tracepoint. This patch adds a new
ioctl command, given a perf event fd, to query the bpf program
array attached to the same perf tracepoint event.

The new uapi ioctl command:
  PERF_EVENT_IOC_QUERY_BPF

The new uapi/linux/perf_event.h structure:
  struct perf_event_query_bpf {
       __u32	ids_len;
       __u32	prog_cnt;
       __u32	ids[0];
  };

User space provides buffer "ids" for kernel to copy to.
When returning from the kernel, the number of available
programs in the array is set in "prog_cnt".

The usage:
  struct perf_event_query_bpf *query = malloc(...);
  query.ids_len = ids_len;
  err = ioctl(pmu_efd, PERF_EVENT_IOC_QUERY_BPF, &query);
  if (err == 0) {
    /* query.prog_cnt is the number of available progs,
     * number of progs in ids: (ids_len == 0) ? 0 : query.prog_cnt
     */
  } else if (errno == ENOSPC) {
    /* query.ids_len number of progs copied,
     * query.prog_cnt is the number of available progs
     */
  } else {
      /* other errors */
  }

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 include/linux/bpf.h             |  4 ++++
 include/uapi/linux/perf_event.h | 22 ++++++++++++++++++++++
 kernel/bpf/core.c               | 21 +++++++++++++++++++++
 kernel/events/core.c            |  3 +++
 kernel/trace/bpf_trace.c        | 23 +++++++++++++++++++++++
 5 files changed, 73 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e55e425..f812ac5 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -254,6 +254,7 @@ typedef unsigned long (*bpf_ctx_copy_t)(void *dst, const void *src,
 
 u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
 		     void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy);
+int bpf_event_query_prog_array(struct perf_event *event, void __user *info);
 
 int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
 			  union bpf_attr __user *uattr);
@@ -285,6 +286,9 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,
 
 void bpf_prog_array_delete_safe(struct bpf_prog_array __rcu *progs,
 				struct bpf_prog *old_prog);
+int bpf_prog_array_copy_info(struct bpf_prog_array __rcu *array,
+			     __u32 __user *prog_ids, u32 request_cnt,
+			     __u32 __user *prog_cnt);
 int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
 			struct bpf_prog *exclude_prog,
 			struct bpf_prog *include_prog,
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index b9a4953..7695336 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -418,6 +418,27 @@ struct perf_event_attr {
 	__u16	__reserved_2;	/* align to __u64 */
 };
 
+/*
+ * Structure used by below PERF_EVENT_IOC_QUERY_BPF command
+ * to query bpf programs attached to the same perf tracepoint
+ * as the given perf event.
+ */
+struct perf_event_query_bpf {
+	/*
+	 * The below ids array length
+	 */
+	__u32	ids_len;
+	/*
+	 * Set by the kernel to indicate the number of
+	 * available programs
+	 */
+	__u32	prog_cnt;
+	/*
+	 * User provided buffer to store program ids
+	 */
+	__u32	ids[0];
+};
+
 #define perf_flags(attr)	(*(&(attr)->read_format + 1))
 
 /*
@@ -433,6 +454,7 @@ struct perf_event_attr {
 #define PERF_EVENT_IOC_ID		_IOR('$', 7, __u64 *)
 #define PERF_EVENT_IOC_SET_BPF		_IOW('$', 8, __u32)
 #define PERF_EVENT_IOC_PAUSE_OUTPUT	_IOW('$', 9, __u32)
+#define PERF_EVENT_IOC_QUERY_BPF	_IOWR('$', 10, struct perf_event_query_bpf *)
 
 enum perf_event_ioc_flags {
 	PERF_IOC_FLAG_GROUP		= 1U << 0,
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 86b50aa..b16c6f8 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1462,6 +1462,8 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,
 	rcu_read_lock();
 	prog = rcu_dereference(progs)->progs;
 	for (; *prog; prog++) {
+		if (*prog == &dummy_bpf_prog.prog)
+			continue;
 		id = (*prog)->aux->id;
 		if (copy_to_user(prog_ids + i, &id, sizeof(id))) {
 			rcu_read_unlock();
@@ -1545,6 +1547,25 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
 	return 0;
 }
 
+int bpf_prog_array_copy_info(struct bpf_prog_array __rcu *array,
+			     __u32 __user *prog_ids, u32 request_cnt,
+			     __u32 __user *prog_cnt)
+{
+	u32 cnt = 0;
+
+	if (array)
+		cnt = bpf_prog_array_length(array);
+
+	if (copy_to_user(prog_cnt, &cnt, sizeof(cnt)))
+		return -EFAULT;
+
+	/* return early if user requested only program count or nothing to copy */
+	if (!request_cnt || !cnt)
+		return 0;
+
+	return bpf_prog_array_copy_to_user(array, prog_ids, request_cnt);
+}
+
 static void bpf_prog_free_deferred(struct work_struct *work)
 {
 	struct bpf_prog_aux *aux;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4df5b69..53c65fb 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4723,6 +4723,9 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
 		rcu_read_unlock();
 		return 0;
 	}
+
+	case PERF_EVENT_IOC_QUERY_BPF:
+		return bpf_event_query_prog_array(event, (void __user *)arg);
 	default:
 		return -ENOTTY;
 	}
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0ce99c3..b143f2a 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -820,3 +820,26 @@ void perf_event_detach_bpf_prog(struct perf_event *event)
 unlock:
 	mutex_unlock(&bpf_event_mutex);
 }
+
+int bpf_event_query_prog_array(struct perf_event *event, void __user *info)
+{
+	struct perf_event_query_bpf __user *uquery = info;
+	struct perf_event_query_bpf query = {};
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (event->attr.type != PERF_TYPE_TRACEPOINT)
+		return -EINVAL;
+	if (copy_from_user(&query, uquery, sizeof(query)))
+		return -EFAULT;
+
+	mutex_lock(&bpf_event_mutex);
+	ret = bpf_prog_array_copy_info(event->tp_event->prog_array,
+				       uquery->ids,
+				       query.ids_len,
+				       &uquery->prog_cnt);
+	mutex_unlock(&bpf_event_mutex);
+
+	return ret;
+}
-- 
2.9.5

[PATCH net-next v4 2/2] bpf/tracing: add a bpf test for new ioctl query interface

[Yonghong Song]

Added a subtest in test_progs. The tracepoint is
sched/sched_switch. Multiple bpf programs are attached to
this tracepoint and the query interface is exercised.

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 tools/include/uapi/linux/perf_event.h         |  22 +++++
 tools/testing/selftests/bpf/Makefile          |   2 +-
 tools/testing/selftests/bpf/test_progs.c      | 134 ++++++++++++++++++++++++++
 tools/testing/selftests/bpf/test_tracepoint.c |  26 +++++
 4 files changed, 183 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/test_tracepoint.c

diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index b9a4953..7695336 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -418,6 +418,27 @@ struct perf_event_attr {
 	__u16	__reserved_2;	/* align to __u64 */
 };
 
+/*
+ * Structure used by below PERF_EVENT_IOC_QUERY_BPF command
+ * to query bpf programs attached to the same perf tracepoint
+ * as the given perf event.
+ */
+struct perf_event_query_bpf {
+	/*
+	 * The below ids array length
+	 */
+	__u32	ids_len;
+	/*
+	 * Set by the kernel to indicate the number of
+	 * available programs
+	 */
+	__u32	prog_cnt;
+	/*
+	 * User provided buffer to store program ids
+	 */
+	__u32	ids[0];
+};
+
 #define perf_flags(attr)	(*(&(attr)->read_format + 1))
 
 /*
@@ -433,6 +454,7 @@ struct perf_event_attr {
 #define PERF_EVENT_IOC_ID		_IOR('$', 7, __u64 *)
 #define PERF_EVENT_IOC_SET_BPF		_IOW('$', 8, __u32)
 #define PERF_EVENT_IOC_PAUSE_OUTPUT	_IOW('$', 9, __u32)
+#define PERF_EVENT_IOC_QUERY_BPF	_IOWR('$', 10, struct perf_event_query_bpf *)
 
 enum perf_event_ioc_flags {
 	PERF_IOC_FLAG_GROUP		= 1U << 0,
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index f309ab9..b177c55 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -29,7 +29,7 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
 
 TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test_obj_id.o \
 	test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \
-	sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o
+	sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o test_tracepoint.o
 
 TEST_PROGS := test_kmod.sh test_xdp_redirect.sh test_xdp_meta.sh \
 	test_offload.py
diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index 6942753..1e0479a 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -21,8 +21,10 @@ typedef __u16 __sum16;
 #include <linux/ipv6.h>
 #include <linux/tcp.h>
 #include <linux/filter.h>
+#include <linux/perf_event.h>
 #include <linux/unistd.h>
 
+#include <sys/ioctl.h>
 #include <sys/wait.h>
 #include <sys/resource.h>
 #include <sys/types.h>
@@ -617,6 +619,137 @@ static void test_obj_name(void)
 	}
 }
 
+static void test_tp_attach_query(void)
+{
+	const int num_progs = 3;
+	int i, j, bytes, efd, err, prog_fd[num_progs], pmu_fd[num_progs];
+	__u32 duration = 0, info_len, saved_prog_ids[num_progs];
+	const char *file = "./test_tracepoint.o";
+	struct perf_event_query_bpf *query;
+	struct perf_event_attr attr = {};
+	struct bpf_object *obj[num_progs];
+	struct bpf_prog_info prog_info;
+	char buf[256];
+
+	snprintf(buf, sizeof(buf),
+		 "/sys/kernel/debug/tracing/events/sched/sched_switch/id");
+	efd = open(buf, O_RDONLY, 0);
+	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
+		return;
+	bytes = read(efd, buf, sizeof(buf));
+	close(efd);
+	if (CHECK(bytes <= 0 || bytes >= sizeof(buf),
+		  "read", "bytes %d errno %d\n", bytes, errno))
+		return;
+
+	attr.config = strtol(buf, NULL, 0);
+	attr.type = PERF_TYPE_TRACEPOINT;
+	attr.sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_CALLCHAIN;
+	attr.sample_period = 1;
+	attr.wakeup_events = 1;
+
+	query = (struct perf_event_query_bpf *)malloc(sizeof(struct perf_event_query_bpf) +
+						      sizeof(__u32) * num_progs);
+	for (i = 0; i < num_progs; i++) {
+		err = bpf_prog_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj[i],
+				    &prog_fd[i]);
+		if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
+			goto cleanup1;
+
+		bzero(&prog_info, sizeof(prog_info));
+		prog_info.jited_prog_len = 0;
+		prog_info.xlated_prog_len = 0;
+		prog_info.nr_map_ids = 0;
+		info_len = sizeof(prog_info);
+		err = bpf_obj_get_info_by_fd(prog_fd[i], &prog_info, &info_len);
+		if (CHECK(err, "bpf_obj_get_info_by_fd", "err %d errno %d\n",
+			  err, errno))
+			goto cleanup1;
+		saved_prog_ids[i] = prog_info.id;
+
+		pmu_fd[i] = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
+				    0 /* cpu 0 */, -1 /* group id */,
+				    0 /* flags */);
+		if (CHECK(pmu_fd[i] < 0, "perf_event_open", "err %d errno %d\n",
+			  pmu_fd[i], errno))
+			goto cleanup2;
+		err = ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE, 0);
+		if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n",
+			  err, errno))
+			goto cleanup3;
+
+		if (i == 0) {
+			/* check NULL prog array query */
+			query->ids_len = num_progs;
+			err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF, query);
+			if (CHECK(err || query->prog_cnt != 0,
+				  "perf_event_ioc_query_bpf",
+				  "err %d errno %d query->prog_cnt %u\n",
+				  err, errno, query->prog_cnt))
+				goto cleanup3;
+		}
+
+		err = ioctl(pmu_fd[i], PERF_EVENT_IOC_SET_BPF, prog_fd[i]);
+		if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n",
+			  err, errno))
+			goto cleanup3;
+
+		if (i == 1) {
+			/* try to get # of programs only */
+			query->ids_len = 0;
+			err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF, query);
+			if (CHECK(err || query->prog_cnt != 2,
+				  "perf_event_ioc_query_bpf",
+				  "err %d errno %d query->prog_cnt %u\n",
+				  err, errno, query->prog_cnt))
+				goto cleanup3;
+
+			/* try a few negative tests */
+			/* invalid query pointer */
+			err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF,
+				    (struct perf_event_query_bpf *)0x1);
+			if (CHECK(!err || errno != EFAULT,
+				  "perf_event_ioc_query_bpf",
+				  "err %d errno %d\n", err, errno))
+				goto cleanup3;
+
+			/* no enough space */
+			query->ids_len = 1;
+			err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF, query);
+			if (CHECK(!err || errno != ENOSPC || query->prog_cnt != 2,
+				  "perf_event_ioc_query_bpf",
+				  "err %d errno %d query->prog_cnt %u\n",
+				  err, errno, query->prog_cnt))
+				goto cleanup3;
+		}
+
+		query->ids_len = num_progs;
+		err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF, query);
+		if (CHECK(err || query->prog_cnt != (i + 1),
+			  "perf_event_ioc_query_bpf",
+			  "err %d errno %d query->prog_cnt %u\n",
+			  err, errno, query->prog_cnt))
+			goto cleanup3;
+		for (j = 0; j < i + 1; j++)
+			if (CHECK(saved_prog_ids[j] != query->ids[j],
+				  "perf_event_ioc_query_bpf",
+				  "#%d saved_prog_id %x query prog_id %x\n",
+				  j, saved_prog_ids[j], query->ids[j]))
+				goto cleanup3;
+	}
+
+	i = num_progs - 1;
+	for (; i >= 0; i--) {
+ cleanup3:
+		ioctl(pmu_fd[i], PERF_EVENT_IOC_DISABLE);
+ cleanup2:
+		close(pmu_fd[i]);
+ cleanup1:
+		bpf_object__close(obj[i]);
+	}
+	free(query);
+}
+
 int main(void)
 {
 	struct rlimit rinf = { RLIM_INFINITY, RLIM_INFINITY };
@@ -630,6 +763,7 @@ int main(void)
 	test_bpf_obj_id();
 	test_pkt_md_access();
 	test_obj_name();
+	test_tp_attach_query();
 
 	printf("Summary: %d PASSED, %d FAILED\n", pass_cnt, error_cnt);
 	return error_cnt ? EXIT_FAILURE : EXIT_SUCCESS;
diff --git a/tools/testing/selftests/bpf/test_tracepoint.c b/tools/testing/selftests/bpf/test_tracepoint.c
new file mode 100644
index 0000000..04bf084
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_tracepoint.c
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017 Facebook
+
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
+struct sched_switch_args {
+	unsigned long long pad;
+	char prev_comm[16];
+	int prev_pid;
+	int prev_prio;
+	long long prev_state;
+	char next_comm[16];
+	int next_pid;
+	int next_prio;
+};
+
+SEC("tracepoint/sched/sched_switch")
+int oncpu(struct sched_switch_args *ctx)
+{
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+__u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */
-- 
2.9.5

Re: [PATCH net-next v4 1/2] bpf/tracing: allow user space to query prog array on the same tp

[Alexei Starovoitov]

On Mon, Dec 11, 2017 at 11:39:02AM -0800, Yonghong Song wrote:
> Commit e87c6bc3852b ("bpf: permit multiple bpf attachments
> for a single perf event") added support to attach multiple
> bpf programs to a single perf event.
> Although this provides flexibility, users may want to know
> what other bpf programs attached to the same tp interface.
> Besides getting visibility for the underlying bpf system,
> such information may also help consolidate multiple bpf programs,
> understand potential performance issues due to a large array,
> and debug (e.g., one bpf program which overwrites return code
> may impact subsequent program results).
> 
> Commit 2541517c32be ("tracing, perf: Implement BPF programs
> attached to kprobes") utilized the existing perf ioctl
> interface and added the command PERF_EVENT_IOC_SET_BPF
> to attach a bpf program to a tracepoint. This patch adds a new
> ioctl command, given a perf event fd, to query the bpf program
> array attached to the same perf tracepoint event.
> 
> The new uapi ioctl command:
>   PERF_EVENT_IOC_QUERY_BPF
> 
> The new uapi/linux/perf_event.h structure:
>   struct perf_event_query_bpf {
>        __u32	ids_len;
>        __u32	prog_cnt;
>        __u32	ids[0];
>   };
> 
> User space provides buffer "ids" for kernel to copy to.
> When returning from the kernel, the number of available
> programs in the array is set in "prog_cnt".
> 
> The usage:
>   struct perf_event_query_bpf *query = malloc(...);
>   query.ids_len = ids_len;
>   err = ioctl(pmu_efd, PERF_EVENT_IOC_QUERY_BPF, &query);
>   if (err == 0) {
>     /* query.prog_cnt is the number of available progs,
>      * number of progs in ids: (ids_len == 0) ? 0 : query.prog_cnt
>      */
>   } else if (errno == ENOSPC) {
>     /* query.ids_len number of progs copied,
>      * query.prog_cnt is the number of available progs
>      */
>   } else {
>       /* other errors */
>   }
> 
> Signed-off-by: Yonghong Song <yhs@fb.com>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Acked-by: Alexei Starovoitov <ast@kernel.org>

Re: [PATCH net-next v4 0/2] bpf/tracing: allow user space to query prog array on the same tp

[Daniel Borkmann]

On 12/11/2017 08:39 PM, Yonghong Song wrote:
> Commit e87c6bc3852b ("bpf: permit multiple bpf attachments
> for a single perf event") added support to attach multiple
> bpf programs to a single perf event. Given a perf event
> (kprobe, uprobe, or kernel tracepoint), the perf ioctl interface
> is used to query bpf programs attached to the same trace event.
> 
> There already exists a BPF_PROG_QUERY command for introspection
> currently used by cgroup+bpf. We did have an implementation for
> querying tracepoint+bpf through the same interface. However, it
> looks cleaner to use ioctl() style of api here, since attaching
> bpf prog to tracepoint/kuprobe is also done via ioctl.
> 
> Patch #1 had the core implementation and patch #2 added
> a test case in tools bpf selftests suite.
> 
> Changelogs:
> v3 -> v4:
>   - Fix a compilation error with newer gcc like 6.3.1 while
>     old gcc 4.8.5 is okay. I was using &uquery->ids to represent
>     the address to the ids array to make it explicit that the
>     address is passed, and this syntax is rightly rejected
>     by gcc 6.3.1.

Series applied to bpf-next, thanks Yonghong.

Re: [PATCH net-next v4 1/2] bpf/tracing: allow user space to query prog array on the same tp

[Peter Zijlstra]

On Mon, Dec 11, 2017 at 11:39:02AM -0800, Yonghong Song wrote:
> The usage:
>   struct perf_event_query_bpf *query = malloc(...);
>   query.ids_len = ids_len;
>   err = ioctl(pmu_efd, PERF_EVENT_IOC_QUERY_BPF, &query);

You didn't spot the fixes to your changelog ;-) The above should read
something like:

    struct perf_event_query_bpf *query =
        malloc(sizeof(*query) + sizeof(u32) * ids_len);
    query->ids_len = ids_len;
    err = ioctl(pmu_efd, PERF_EVENT_IOC_QUERY_BPF, query);

Re: [PATCH net-next v4 1/2] bpf/tracing: allow user space to query prog array on the same tp

[Alexei Starovoitov]

On 12/12/17 1:03 AM, Peter Zijlstra wrote:
> On Mon, Dec 11, 2017 at 11:39:02AM -0800, Yonghong Song wrote:
>> The usage:
>>   struct perf_event_query_bpf *query = malloc(...);
>>   query.ids_len = ids_len;
>>   err = ioctl(pmu_efd, PERF_EVENT_IOC_QUERY_BPF, &query);
>
> You didn't spot the fixes to your changelog ;-) The above should read
> something like:
>
>     struct perf_event_query_bpf *query =
>         malloc(sizeof(*query) + sizeof(u32) * ids_len);
>     query->ids_len = ids_len;
>     err = ioctl(pmu_efd, PERF_EVENT_IOC_QUERY_BPF, query);

sure. I fixed up this nit in commit log of patch 1 and in test_progs.c
of patch 2.