Merge branch 'bpf-event-output-offload'

Jakub Kicinski says:

====================
This series centres on NFP offload of bpf_event_output().  The
first patch allows perf event arrays to be used by offloaded
programs.  Next patch makes the nfp driver keep track of such
arrays to be able to filter FW events referring to maps.
Perf event arrays are not device bound.  Having driver
reimplement and manage the perf array seems brittle and unnecessary.

Patch 4 moves slightly the verifier step which replaces map fds
with map pointers.  This is useful for nfp JIT since we can then
easily replace host pointers with NFP table ids (patch 6).  This
allows us to lift the limitation on map helpers having to be used
with the same map pointer on all paths.  Second use of replacing
fds with real host map pointers is that we can use the host map
pointer as a key for FW events in perf event array offload.

Patch 5 adds perf event output offload support for the NFP.

There are some differences between bpf_event_output() offloaded
and non-offloaded version.  The FW messages which carry events
may get dropped and reordered relatively easily.  The return codes
from the helper are also not guaranteed to match the host.  Users
are warned about some of those discrepancies with a one time
warning message to kernel logs.

bpftool gains an ability to dump perf ring events in a very simple
format.  This was very useful for testing and simple debug, maybe
it will be useful to others?

Last patch is a trivial comment fix.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

8 files changed, 512 insertions, 84 deletions

diff --git a/tools/bpf/bpftool/Documentation/bpftool-map.rst b/tools/bpf/bpftool/Documentation/bpftool-map.rst
index 5f512b14bff9..a6258bc8ec4f 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-map.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-map.rst
@@ -22,17 +22,19 @@ MAP COMMANDS
 =============
 
 |	**bpftool** **map { show | list }**   [*MAP*]
-|	**bpftool** **map dump**    *MAP*
-|	**bpftool** **map update**  *MAP*  **key** [**hex**] *BYTES*   **value** [**hex**] *VALUE* [*UPDATE_FLAGS*]
-|	**bpftool** **map lookup**  *MAP*  **key** [**hex**] *BYTES*
-|	**bpftool** **map getnext** *MAP* [**key** [**hex**] *BYTES*]
-|	**bpftool** **map delete**  *MAP*  **key** [**hex**] *BYTES*
-|	**bpftool** **map pin**     *MAP*  *FILE*
+|	**bpftool** **map dump**       *MAP*
+|	**bpftool** **map update**     *MAP*  **key** *DATA*   **value** *VALUE* [*UPDATE_FLAGS*]
+|	**bpftool** **map lookup**     *MAP*  **key** *DATA*
+|	**bpftool** **map getnext**    *MAP* [**key** *DATA*]
+|	**bpftool** **map delete**     *MAP*  **key** *DATA*
+|	**bpftool** **map pin**        *MAP*  *FILE*
+|	**bpftool** **map event_pipe** *MAP* [**cpu** *N* **index** *M*]
 |	**bpftool** **map help**
 |
 |	*MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
+|	*DATA* := { [**hex**] *BYTES* }
 |	*PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* }
-|	*VALUE* := { *BYTES* | *MAP* | *PROG* }
+|	*VALUE* := { *DATA* | *MAP* | *PROG* }
 |	*UPDATE_FLAGS* := { **any** | **exist** | **noexist** }
 
 DESCRIPTION
@@ -48,7 +50,7 @@ DESCRIPTION
 	**bpftool map dump**    *MAP*
 		  Dump all entries in a given *MAP*.
 
-	**bpftool map update**  *MAP*  **key** [**hex**] *BYTES*   **value** [**hex**] *VALUE* [*UPDATE_FLAGS*]
+	**bpftool map update**  *MAP*  **key** *DATA*   **value** *VALUE* [*UPDATE_FLAGS*]
 		  Update map entry for a given *KEY*.
 
 		  *UPDATE_FLAGS* can be one of: **any** update existing entry
@@ -61,13 +63,13 @@ DESCRIPTION
 		  the bytes are parsed as decimal values, unless a "0x" prefix
 		  (for hexadecimal) or a "0" prefix (for octal) is provided.
 
-	**bpftool map lookup**  *MAP*  **key** [**hex**] *BYTES*
+	**bpftool map lookup**  *MAP*  **key** *DATA*
 		  Lookup **key** in the map.
 
-	**bpftool map getnext** *MAP* [**key** [**hex**] *BYTES*]
+	**bpftool map getnext** *MAP* [**key** *DATA*]
 		  Get next key.  If *key* is not specified, get first key.
 
-	**bpftool map delete**  *MAP*  **key** [**hex**] *BYTES*
+	**bpftool map delete**  *MAP*  **key** *DATA*
 		  Remove entry from the map.
 
 	**bpftool map pin**     *MAP*  *FILE*
@@ -75,6 +77,22 @@ DESCRIPTION
 
 		  Note: *FILE* must be located in *bpffs* mount.
 
+	**bpftool** **map event_pipe** *MAP* [**cpu** *N* **index** *M*]
+		  Read events from a BPF_MAP_TYPE_PERF_EVENT_ARRAY map.
+
+		  Install perf rings into a perf event array map and dump
+		  output of any bpf_perf_event_output() call in the kernel.
+		  By default read the number of CPUs on the system and
+		  install perf ring for each CPU in the corresponding index
+		  in the array.
+
+		  If **cpu** and **index** are specified, install perf ring
+		  for given **cpu** at **index** in the array (single ring).
+
+		  Note that installing a perf ring into an array will silently
+		  replace any existing ring.  Any other application will stop
+		  receiving events if it installed its rings earlier.
+
 	**bpftool map help**
 		  Print short help message.
 
diff --git a/tools/bpf/bpftool/Documentation/bpftool.rst b/tools/bpf/bpftool/Documentation/bpftool.rst
index 20689a321ffe..564cb0d9692b 100644
--- a/tools/bpf/bpftool/Documentation/bpftool.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool.rst
@@ -23,7 +23,7 @@ SYNOPSIS
 
 	*MAP-COMMANDS* :=
 	{ **show** | **list** | **dump** | **update** | **lookup** | **getnext** | **delete**
-	| **pin** | **help** }
+	| **pin** | **event_pipe** | **help** }
 
 	*PROG-COMMANDS* := { **show** | **list** | **dump jited** | **dump xlated** | **pin**
 	| **load** | **help** }
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 4e69782c4a79..892dbf095bff 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -39,7 +39,12 @@ CC = gcc
 
 CFLAGS += -O2
 CFLAGS += -W -Wall -Wextra -Wno-unused-parameter -Wshadow -Wno-missing-field-initializers
-CFLAGS += -DPACKAGE='"bpftool"' -D__EXPORTED_HEADERS__ -I$(srctree)/tools/include/uapi -I$(srctree)/tools/include -I$(srctree)/tools/lib/bpf -I$(srctree)/kernel/bpf/
+CFLAGS += -DPACKAGE='"bpftool"' -D__EXPORTED_HEADERS__ \
+	-I$(srctree)/kernel/bpf/ \
+	-I$(srctree)/tools/include \
+	-I$(srctree)/tools/include/uapi \
+	-I$(srctree)/tools/lib/bpf \
+	-I$(srctree)/tools/perf
 CFLAGS += -DBPFTOOL_VERSION='"$(BPFTOOL_VERSION)"'
 LIBS = -lelf -lbfd -lopcodes $(LIBBPF)
 
diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
index 852d84a98acd..b301c9b315f1 100644
--- a/tools/bpf/bpftool/bash-completion/bpftool
+++ b/tools/bpf/bpftool/bash-completion/bpftool
@@ -1,6 +1,6 @@
 # bpftool(8) bash completion                               -*- shell-script -*-
 #
-# Copyright (C) 2017 Netronome Systems, Inc.
+# Copyright (C) 2017-2018 Netronome Systems, Inc.
 #
 # This software is dual licensed under the GNU General License
 # Version 2, June 1991 as shown in the file COPYING in the top-level
@@ -79,6 +79,14 @@ _bpftool_get_map_ids()
         command sed -n 's/.*"id": \(.*\),$/\1/p' )" -- "$cur" ) )
 }
 
+_bpftool_get_perf_map_ids()
+{
+    COMPREPLY+=( $( compgen -W "$( bpftool -jp map  2>&1 | \
+        command grep -C2 perf_event_array | \
+        command sed -n 's/.*"id": \(.*\),$/\1/p' )" -- "$cur" ) )
+}
+
+
 _bpftool_get_prog_ids()
 {
     COMPREPLY+=( $( compgen -W "$( bpftool -jp prog 2>&1 | \
@@ -359,10 +367,34 @@ _bpftool()
                     fi
                     return 0
                     ;;
+                event_pipe)
+                    case $prev in
+                        $command)
+                            COMPREPLY=( $( compgen -W "$MAP_TYPE" -- "$cur" ) )
+                            return 0
+                            ;;
+                        id)
+                            _bpftool_get_perf_map_ids
+                            return 0
+                            ;;
+                        cpu)
+                            return 0
+                            ;;
+                        index)
+                            return 0
+                            ;;
+                        *)
+                            _bpftool_once_attr 'cpu'
+                            _bpftool_once_attr 'index'
+                            return 0
+                            ;;
+                    esac
+                    ;;
                 *)
                     [[ $prev == $object ]] && \
                         COMPREPLY=( $( compgen -W 'delete dump getnext help \
-                            lookup pin show list update' -- "$cur" ) )
+                            lookup pin event_pipe show list update' -- \
+                            "$cur" ) )
                     ;;
             esac
             ;;
diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
index 465995281dcd..32f9e397a6c0 100644
--- a/tools/bpf/bpftool/common.c
+++ b/tools/bpf/bpftool/common.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2017 Netronome Systems, Inc.
+ * Copyright (C) 2017-2018 Netronome Systems, Inc.
  *
  * This software is dual licensed under the GNU General License Version 2,
  * June 1991 as shown in the file COPYING in the top-level directory of this
@@ -33,6 +33,7 @@
 
 /* Author: Jakub Kicinski <kubakici@wp.pl> */
 
+#include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <fts.h>
@@ -330,6 +331,16 @@ char *get_fdinfo(int fd, const char *key)
 	return NULL;
 }
 
+void print_data_json(uint8_t *data, size_t len)
+{
+	unsigned int i;
+
+	jsonw_start_array(json_wtr);
+	for (i = 0; i < len; i++)
+		jsonw_printf(json_wtr, "%d", data[i]);
+	jsonw_end_array(json_wtr);
+}
+
 void print_hex_data_json(uint8_t *data, size_t len)
 {
 	unsigned int i;
@@ -420,6 +431,70 @@ void delete_pinned_obj_table(struct pinned_obj_table *tab)
 	}
 }
 
+unsigned int get_page_size(void)
+{
+	static int result;
+
+	if (!result)
+		result = getpagesize();
+	return result;
+}
+
+unsigned int get_possible_cpus(void)
+{
+	static unsigned int result;
+	char buf[128];
+	long int n;
+	char *ptr;
+	int fd;
+
+	if (result)
+		return result;
+
+	fd = open("/sys/devices/system/cpu/possible", O_RDONLY);
+	if (fd < 0) {
+		p_err("can't open sysfs possible cpus");
+		exit(-1);
+	}
+
+	n = read(fd, buf, sizeof(buf));
+	if (n < 2) {
+		p_err("can't read sysfs possible cpus");
+		exit(-1);
+	}
+	close(fd);
+
+	if (n == sizeof(buf)) {
+		p_err("read sysfs possible cpus overflow");
+		exit(-1);
+	}
+
+	ptr = buf;
+	n = 0;
+	while (*ptr && *ptr != '\n') {
+		unsigned int a, b;
+
+		if (sscanf(ptr, "%u-%u", &a, &b) == 2) {
+			n += b - a + 1;
+
+			ptr = strchr(ptr, '-') + 1;
+		} else if (sscanf(ptr, "%u", &a) == 1) {
+			n++;
+		} else {
+			assert(0);
+		}
+
+		while (isdigit(*ptr))
+			ptr++;
+		if (*ptr == ',')
+			ptr++;
+	}
+
+	result = n;
+
+	return result;
+}
+
 static char *
 ifindex_to_name_ns(__u32 ifindex, __u32 ns_dev, __u32 ns_ino, char *buf)
 {
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index b8e9584d6246..6173cd997e7a 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2017 Netronome Systems, Inc.
+ * Copyright (C) 2017-2018 Netronome Systems, Inc.
  *
  * This software is dual licensed under the GNU General License Version 2,
  * June 1991 as shown in the file COPYING in the top-level directory of this
@@ -117,14 +117,19 @@ int do_pin_fd(int fd, const char *name);
 
 int do_prog(int argc, char **arg);
 int do_map(int argc, char **arg);
+int do_event_pipe(int argc, char **argv);
 int do_cgroup(int argc, char **arg);
 
 int prog_parse_fd(int *argc, char ***argv);
+int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len);
 
 void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
 		       const char *arch);
+void print_data_json(uint8_t *data, size_t len);
 void print_hex_data_json(uint8_t *data, size_t len);
 
+unsigned int get_page_size(void);
+unsigned int get_possible_cpus(void);
 const char *ifindex_to_bfd_name_ns(__u32 ifindex, __u64 ns_dev, __u64 ns_ino);
 
 #endif
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index a6cdb640a0d7..af6766e956ba 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2017 Netronome Systems, Inc.
+ * Copyright (C) 2017-2018 Netronome Systems, Inc.
  *
  * This software is dual licensed under the GNU General License Version 2,
  * June 1991 as shown in the file COPYING in the top-level directory of this
@@ -34,7 +34,6 @@
 /* Author: Jakub Kicinski <kubakici@wp.pl> */
 
 #include <assert.h>
-#include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <stdbool.h>
@@ -69,61 +68,6 @@ static const char * const map_type_name[] = {
 	[BPF_MAP_TYPE_CPUMAP]		= "cpumap",
 };
 
-static unsigned int get_possible_cpus(void)
-{
-	static unsigned int result;
-	char buf[128];
-	long int n;
-	char *ptr;
-	int fd;
-
-	if (result)
-		return result;
-
-	fd = open("/sys/devices/system/cpu/possible", O_RDONLY);
-	if (fd < 0) {
-		p_err("can't open sysfs possible cpus");
-		exit(-1);
-	}
-
-	n = read(fd, buf, sizeof(buf));
-	if (n < 2) {
-		p_err("can't read sysfs possible cpus");
-		exit(-1);
-	}
-	close(fd);
-
-	if (n == sizeof(buf)) {
-		p_err("read sysfs possible cpus overflow");
-		exit(-1);
-	}
-
-	ptr = buf;
-	n = 0;
-	while (*ptr && *ptr != '\n') {
-		unsigned int a, b;
-
-		if (sscanf(ptr, "%u-%u", &a, &b) == 2) {
-			n += b - a + 1;
-
-			ptr = strchr(ptr, '-') + 1;
-		} else if (sscanf(ptr, "%u", &a) == 1) {
-			n++;
-		} else {
-			assert(0);
-		}
-
-		while (isdigit(*ptr))
-			ptr++;
-		if (*ptr == ',')
-			ptr++;
-	}
-
-	result = n;
-
-	return result;
-}
-
 static bool map_is_per_cpu(__u32 type)
 {
 	return type == BPF_MAP_TYPE_PERCPU_HASH ||
@@ -186,8 +130,7 @@ static int map_parse_fd(int *argc, char ***argv)
 	return -1;
 }
 
-static int
-map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len)
+int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len)
 {
 	int err;
 	int fd;
@@ -873,23 +816,25 @@ static int do_help(int argc, char **argv)
 
 	fprintf(stderr,
 		"Usage: %s %s { show | list }   [MAP]\n"
-		"       %s %s dump    MAP\n"
-		"       %s %s update  MAP  key [hex] BYTES value [hex] VALUE [UPDATE_FLAGS]\n"
-		"       %s %s lookup  MAP  key [hex] BYTES\n"
-		"       %s %s getnext MAP [key [hex] BYTES]\n"
-		"       %s %s delete  MAP  key [hex] BYTES\n"
-		"       %s %s pin     MAP  FILE\n"
+		"       %s %s dump       MAP\n"
+		"       %s %s update     MAP  key DATA value VALUE [UPDATE_FLAGS]\n"
+		"       %s %s lookup     MAP  key DATA\n"
+		"       %s %s getnext    MAP [key DATA]\n"
+		"       %s %s delete     MAP  key DATA\n"
+		"       %s %s pin        MAP  FILE\n"
+		"       %s %s event_pipe MAP [cpu N index M]\n"
 		"       %s %s help\n"
 		"\n"
 		"       MAP := { id MAP_ID | pinned FILE }\n"
+		"       DATA := { [hex] BYTES }\n"
 		"       " HELP_SPEC_PROGRAM "\n"
-		"       VALUE := { BYTES | MAP | PROG }\n"
+		"       VALUE := { DATA | MAP | PROG }\n"
 		"       UPDATE_FLAGS := { any | exist | noexist }\n"
 		"       " HELP_SPEC_OPTIONS "\n"
 		"",
 		bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2],
 		bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2],
-		bin_name, argv[-2], bin_name, argv[-2]);
+		bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2]);
 
 	return 0;
 }
@@ -904,6 +849,7 @@ static const struct cmd cmds[] = {
 	{ "getnext",	do_getnext },
 	{ "delete",	do_delete },
 	{ "pin",	do_pin },
+	{ "event_pipe",	do_event_pipe },
 	{ 0 }
 };
 
diff --git a/tools/bpf/bpftool/map_perf_ring.c b/tools/bpf/bpftool/map_perf_ring.c
new file mode 100644
index 000000000000..c5a2ced8552d
--- /dev/null
+++ b/tools/bpf/bpftool/map_perf_ring.c
@@ -0,0 +1,347 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (C) 2018 Netronome Systems, Inc. */
+/* This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include <errno.h>
+#include <fcntl.h>
+#include <libbpf.h>
+#include <poll.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+#include <linux/bpf.h>
+#include <linux/perf_event.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+
+#include <bpf.h>
+#include <perf-sys.h>
+
+#include "main.h"
+
+#define MMAP_PAGE_CNT	16
+
+static bool stop;
+
+struct event_ring_info {
+	int fd;
+	int key;
+	unsigned int cpu;
+	void *mem;
+};
+
+struct perf_event_sample {
+	struct perf_event_header header;
+	__u32 size;
+	unsigned char data[];
+};
+
+static void int_exit(int signo)
+{
+	fprintf(stderr, "Stopping...\n");
+	stop = true;
+}
+
+static void
+print_bpf_output(struct event_ring_info *ring, struct perf_event_sample *e)
+{
+	struct {
+		struct perf_event_header header;
+		__u64 id;
+		__u64 lost;
+	} *lost = (void *)e;
+	struct timespec ts;
+
+	if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
+		perror("Can't read clock for timestamp");
+		return;
+	}
+
+	if (json_output) {
+		jsonw_start_object(json_wtr);
+		jsonw_name(json_wtr, "timestamp");
+		jsonw_uint(json_wtr, ts.tv_sec * 1000000000ull + ts.tv_nsec);
+		jsonw_name(json_wtr, "type");
+		jsonw_uint(json_wtr, e->header.type);
+		jsonw_name(json_wtr, "cpu");
+		jsonw_uint(json_wtr, ring->cpu);
+		jsonw_name(json_wtr, "index");
+		jsonw_uint(json_wtr, ring->key);
+		if (e->header.type == PERF_RECORD_SAMPLE) {
+			jsonw_name(json_wtr, "data");
+			print_data_json(e->data, e->size);
+		} else if (e->header.type == PERF_RECORD_LOST) {
+			jsonw_name(json_wtr, "lost");
+			jsonw_start_object(json_wtr);
+			jsonw_name(json_wtr, "id");
+			jsonw_uint(json_wtr, lost->id);
+			jsonw_name(json_wtr, "count");
+			jsonw_uint(json_wtr, lost->lost);
+			jsonw_end_object(json_wtr);
+		}
+		jsonw_end_object(json_wtr);
+	} else {
+		if (e->header.type == PERF_RECORD_SAMPLE) {
+			printf("== @%ld.%ld CPU: %d index: %d =====\n",
+			       (long)ts.tv_sec, ts.tv_nsec,
+			       ring->cpu, ring->key);
+			fprint_hex(stdout, e->data, e->size, " ");
+			printf("\n");
+		} else if (e->header.type == PERF_RECORD_LOST) {
+			printf("lost %lld events\n", lost->lost);
+		} else {
+			printf("unknown event type=%d size=%d\n",
+			       e->header.type, e->header.size);
+		}
+	}
+}
+
+static void
+perf_event_read(struct event_ring_info *ring, void **buf, size_t *buf_len)
+{
+	volatile struct perf_event_mmap_page *header = ring->mem;
+	__u64 buffer_size = MMAP_PAGE_CNT * get_page_size();
+	__u64 data_tail = header->data_tail;
+	__u64 data_head = header->data_head;
+	void *base, *begin, *end;
+
+	asm volatile("" ::: "memory"); /* in real code it should be smp_rmb() */
+	if (data_head == data_tail)
+		return;
+
+	base = ((char *)header) + get_page_size();
+
+	begin = base + data_tail % buffer_size;
+	end = base + data_head % buffer_size;
+
+	while (begin != end) {
+		struct perf_event_sample *e;
+
+		e = begin;
+		if (begin + e->header.size > base + buffer_size) {
+			long len = base + buffer_size - begin;
+
+			if (*buf_len < e->header.size) {
+				free(*buf);
+				*buf = malloc(e->header.size);
+				if (!*buf) {
+					fprintf(stderr,
+						"can't allocate memory");
+					stop = true;
+					return;
+				}
+				*buf_len = e->header.size;
+			}
+
+			memcpy(*buf, begin, len);
+			memcpy(*buf + len, base, e->header.size - len);
+			e = (void *)*buf;
+			begin = base + e->header.size - len;
+		} else if (begin + e->header.size == base + buffer_size) {
+			begin = base;
+		} else {
+			begin += e->header.size;
+		}
+
+		print_bpf_output(ring, e);
+	}
+
+	__sync_synchronize(); /* smp_mb() */
+	header->data_tail = data_head;
+}
+
+static int perf_mmap_size(void)
+{
+	return get_page_size() * (MMAP_PAGE_CNT + 1);
+}
+
+static void *perf_event_mmap(int fd)
+{
+	int mmap_size = perf_mmap_size();
+	void *base;
+
+	base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (base == MAP_FAILED) {
+		p_err("event mmap failed: %s\n", strerror(errno));
+		return NULL;
+	}
+
+	return base;
+}
+
+static void perf_event_unmap(void *mem)
+{
+	if (munmap(mem, perf_mmap_size()))
+		fprintf(stderr, "Can't unmap ring memory!\n");
+}
+
+static int bpf_perf_event_open(int map_fd, int key, int cpu)
+{
+	struct perf_event_attr attr = {
+		.sample_type = PERF_SAMPLE_RAW,
+		.type = PERF_TYPE_SOFTWARE,
+		.config = PERF_COUNT_SW_BPF_OUTPUT,
+	};
+	int pmu_fd;
+
+	pmu_fd = sys_perf_event_open(&attr, -1, cpu, -1, 0);
+	if (pmu_fd < 0) {
+		p_err("failed to open perf event %d for CPU %d", key, cpu);
+		return -1;
+	}
+
+	if (bpf_map_update_elem(map_fd, &key, &pmu_fd, BPF_ANY)) {
+		p_err("failed to update map for event %d for CPU %d", key, cpu);
+		goto err_close;
+	}
+	if (ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0)) {
+		p_err("failed to enable event %d for CPU %d", key, cpu);
+		goto err_close;
+	}
+
+	return pmu_fd;
+
+err_close:
+	close(pmu_fd);
+	return -1;
+}
+
+int do_event_pipe(int argc, char **argv)
+{
+	int i, nfds, map_fd, index = -1, cpu = -1;
+	struct bpf_map_info map_info = {};
+	struct event_ring_info *rings;
+	size_t tmp_buf_sz = 0;
+	void *tmp_buf = NULL;
+	struct pollfd *pfds;
+	__u32 map_info_len;
+	bool do_all = true;
+
+	map_info_len = sizeof(map_info);
+	map_fd = map_parse_fd_and_info(&argc, &argv, &map_info, &map_info_len);
+	if (map_fd < 0)
+		return -1;
+
+	if (map_info.type != BPF_MAP_TYPE_PERF_EVENT_ARRAY) {
+		p_err("map is not a perf event array");
+		goto err_close_map;
+	}
+
+	while (argc) {
+		if (argc < 2)
+			BAD_ARG();
+
+		if (is_prefix(*argv, "cpu")) {
+			char *endptr;
+
+			NEXT_ARG();
+			cpu = strtoul(*argv, &endptr, 0);
+			if (*endptr) {
+				p_err("can't parse %s as CPU ID", **argv);
+				goto err_close_map;
+			}
+
+			NEXT_ARG();
+		} else if (is_prefix(*argv, "index")) {
+			char *endptr;
+
+			NEXT_ARG();
+			index = strtoul(*argv, &endptr, 0);
+			if (*endptr) {
+				p_err("can't parse %s as index", **argv);
+				goto err_close_map;
+			}
+
+			NEXT_ARG();
+		} else {
+			BAD_ARG();
+		}
+
+		do_all = false;
+	}
+
+	if (!do_all) {
+		if (index == -1 || cpu == -1) {
+			p_err("cpu and index must be specified together");
+			goto err_close_map;
+		}
+
+		nfds = 1;
+	} else {
+		nfds = min(get_possible_cpus(), map_info.max_entries);
+		cpu = 0;
+		index = 0;
+	}
+
+	rings = calloc(nfds, sizeof(rings[0]));
+	if (!rings)
+		goto err_close_map;
+
+	pfds = calloc(nfds, sizeof(pfds[0]));
+	if (!pfds)
+		goto err_free_rings;
+
+	for (i = 0; i < nfds; i++) {
+		rings[i].cpu = cpu + i;
+		rings[i].key = index + i;
+
+		rings[i].fd = bpf_perf_event_open(map_fd, rings[i].key,
+						  rings[i].cpu);
+		if (rings[i].fd < 0)
+			goto err_close_fds_prev;
+
+		rings[i].mem = perf_event_mmap(rings[i].fd);
+		if (!rings[i].mem)
+			goto err_close_fds_current;
+
+		pfds[i].fd = rings[i].fd;
+		pfds[i].events = POLLIN;
+	}
+
+	signal(SIGINT, int_exit);
+	signal(SIGHUP, int_exit);
+	signal(SIGTERM, int_exit);
+
+	if (json_output)
+		jsonw_start_array(json_wtr);
+
+	while (!stop) {
+		poll(pfds, nfds, 200);
+		for (i = 0; i < nfds; i++)
+			perf_event_read(&rings[i], &tmp_buf, &tmp_buf_sz);
+	}
+	free(tmp_buf);
+
+	if (json_output)
+		jsonw_end_array(json_wtr);
+
+	for (i = 0; i < nfds; i++) {
+		perf_event_unmap(rings[i].mem);
+		close(rings[i].fd);
+	}
+	free(pfds);
+	free(rings);
+	close(map_fd);
+
+	return 0;
+
+err_close_fds_prev:
+	while (i--) {
+		perf_event_unmap(rings[i].mem);
+err_close_fds_current:
+		close(rings[i].fd);
+	}
+	free(pfds);
+err_free_rings:
+	free(rings);
+err_close_map:
+	close(map_fd);
+	return -1;
+}