[PATCH bpf-next 0/3] samples: bpf: Refactor XDP programs with libbpf

[PATCH bpf-next 0/3] samples: bpf: Refactor XDP programs with libbpf

[Daniel T. Lee]

To avoid confusion caused by the increasing fragmentation of the BPF
Loader program, this commit would like to convert the previous bpf_load
loader with the libbpf loader.

Thanks to libbpf's bpf_link interface, managing the tracepoint BPF
program is much easier. bpf_program__attach_tracepoint manages the
enable of tracepoint event and attach of BPF programs to it with a
single interface bpf_link, so there is no need to manage event_fd and
prog_fd separately.

And due to addition of generic bpf_program__attach() to libbpf, it is
now possible to attach BPF programs with __attach() instead of
explicitly calling __attach_<type>().

This patchset refactors xdp_monitor with using this libbpf API, and the
bpf_load is removed and migrated to libbpf. Also, attach_tracepoint()
is replaced with the generic __attach() method in xdp_redirect_cpu.
Moreover, maps in kern program have been converted to BTF-defined map.

Daniel T. Lee (3):
  samples: bpf: Refactor xdp_monitor with libbpf
  samples: bpf: Replace attach_tracepoint() to attach() in
    xdp_redirect_cpu
  samples: bpf: refactor XDP kern program maps with BTF-defined map

 samples/bpf/Makefile                |   4 +-
 samples/bpf/xdp_monitor_kern.c      |  60 ++++++------
 samples/bpf/xdp_monitor_user.c      | 144 +++++++++++++++++++++-------
 samples/bpf/xdp_redirect_cpu_user.c | 138 +++++++++++++-------------
 samples/bpf/xdp_sample_pkts_kern.c  |  14 ++-
 samples/bpf/xdp_sample_pkts_user.c  |   1 -
 6 files changed, 211 insertions(+), 150 deletions(-)

-- 
2.25.1

[PATCH bpf-next 1/3] samples: bpf: Refactor xdp_monitor with libbpf

[Daniel T. Lee]

To avoid confusion caused by the increasing fragmentation of the BPF
Loader program, this commit would like to change to the libbpf loader
instead of using the bpf_load.

Thanks to libbpf's bpf_link interface, managing the tracepoint BPF
program is much easier. bpf_program__attach_tracepoint manages the
enable of tracepoint event and attach of BPF programs to it with a
single interface bpf_link, so there is no need to manage event_fd and
prog_fd separately.

This commit refactors xdp_monitor with using this libbpf API, and the
bpf_load is removed and migrated to libbpf.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
---
 samples/bpf/Makefile           |   2 +-
 samples/bpf/xdp_monitor_user.c | 144 ++++++++++++++++++++++++---------
 2 files changed, 108 insertions(+), 38 deletions(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4f1ed0e3cf9f..0cee2aa8970f 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -99,7 +99,7 @@ per_socket_stats_example-objs := cookie_uid_helper_example.o
 xdp_redirect-objs := xdp_redirect_user.o
 xdp_redirect_map-objs := xdp_redirect_map_user.o
 xdp_redirect_cpu-objs := bpf_load.o xdp_redirect_cpu_user.o
-xdp_monitor-objs := bpf_load.o xdp_monitor_user.o
+xdp_monitor-objs := xdp_monitor_user.o
 xdp_rxq_info-objs := xdp_rxq_info_user.o
 syscall_tp-objs := syscall_tp_user.o
 cpustat-objs := cpustat_user.o
diff --git a/samples/bpf/xdp_monitor_user.c b/samples/bpf/xdp_monitor_user.c
index ef53b93db573..c627c53d6ada 100644
--- a/samples/bpf/xdp_monitor_user.c
+++ b/samples/bpf/xdp_monitor_user.c
@@ -26,12 +26,36 @@ static const char *__doc_err_only__=
 #include <net/if.h>
 #include <time.h>
 
+#include <signal.h>
 #include <bpf/bpf.h>
-#include "bpf_load.h"
+#include <bpf/libbpf.h>
 #include "bpf_util.h"
 
+enum map_type {
+	REDIRECT_ERR_CNT,
+	EXCEPTION_CNT,
+	CPUMAP_ENQUEUE_CNT,
+	CPUMAP_KTHREAD_CNT,
+	DEVMAP_XMIT_CNT,
+};
+
+static const char *const map_type_strings[] = {
+	[REDIRECT_ERR_CNT] = "redirect_err_cnt",
+	[EXCEPTION_CNT] = "exception_cnt",
+	[CPUMAP_ENQUEUE_CNT] = "cpumap_enqueue_cnt",
+	[CPUMAP_KTHREAD_CNT] = "cpumap_kthread_cnt",
+	[DEVMAP_XMIT_CNT] = "devmap_xmit_cnt",
+};
+
+#define NUM_MAP 5
+#define NUM_TP 8
+
+static int tp_cnt;
+static int map_cnt;
 static int verbose = 1;
 static bool debug = false;
+struct bpf_map *map_data[NUM_MAP] = { 0 };
+struct bpf_link *tp_links[NUM_TP] = { 0 };
 
 static const struct option long_options[] = {
 	{"help",	no_argument,		NULL, 'h' },
@@ -41,6 +65,15 @@ static const struct option long_options[] = {
 	{0, 0, NULL,  0 }
 };
 
+static void int_exit(int sig)
+{
+	/* Detach tracepoints */
+	while (tp_cnt)
+		bpf_link__destroy(tp_links[--tp_cnt]);
+
+	exit(0);
+}
+
 /* C standard specifies two constants, EXIT_SUCCESS(0) and EXIT_FAILURE(1) */
 #define EXIT_FAIL_MEM	5
 
@@ -483,23 +516,23 @@ static bool stats_collect(struct stats_record *rec)
 	 * this can happen by someone running perf-record -e
 	 */
 
-	fd = map_data[0].fd; /* map0: redirect_err_cnt */
+	fd = bpf_map__fd(map_data[REDIRECT_ERR_CNT]);
 	for (i = 0; i < REDIR_RES_MAX; i++)
 		map_collect_record_u64(fd, i, &rec->xdp_redirect[i]);
 
-	fd = map_data[1].fd; /* map1: exception_cnt */
+	fd = bpf_map__fd(map_data[EXCEPTION_CNT]);
 	for (i = 0; i < XDP_ACTION_MAX; i++) {
 		map_collect_record_u64(fd, i, &rec->xdp_exception[i]);
 	}
 
-	fd = map_data[2].fd; /* map2: cpumap_enqueue_cnt */
+	fd = bpf_map__fd(map_data[CPUMAP_ENQUEUE_CNT]);
 	for (i = 0; i < MAX_CPUS; i++)
 		map_collect_record(fd, i, &rec->xdp_cpumap_enqueue[i]);
 
-	fd = map_data[3].fd; /* map3: cpumap_kthread_cnt */
+	fd = bpf_map__fd(map_data[CPUMAP_KTHREAD_CNT]);
 	map_collect_record(fd, 0, &rec->xdp_cpumap_kthread);
 
-	fd = map_data[4].fd; /* map4: devmap_xmit_cnt */
+	fd = bpf_map__fd(map_data[DEVMAP_XMIT_CNT]);
 	map_collect_record(fd, 0, &rec->xdp_devmap_xmit);
 
 	return true;
@@ -598,8 +631,8 @@ static void stats_poll(int interval, bool err_only)
 
 	/* TODO Need more advanced stats on error types */
 	if (verbose) {
-		printf(" - Stats map0: %s\n", map_data[0].name);
-		printf(" - Stats map1: %s\n", map_data[1].name);
+		printf(" - Stats map0: %s\n", bpf_map__name(map_data[0]));
+		printf(" - Stats map1: %s\n", bpf_map__name(map_data[1]));
 		printf("\n");
 	}
 	fflush(stdout);
@@ -616,46 +649,52 @@ static void stats_poll(int interval, bool err_only)
 	free_stats_record(prev);
 }
 
-static void print_bpf_prog_info(void)
+static void print_bpf_prog_info(struct bpf_object *obj)
 {
-	int i;
+	struct bpf_program *prog;
+	struct bpf_map *map;
+	int i = 0;
 
 	/* Prog info */
-	printf("Loaded BPF prog have %d bpf program(s)\n", prog_cnt);
-	for (i = 0; i < prog_cnt; i++) {
-		printf(" - prog_fd[%d] = fd(%d)\n", i, prog_fd[i]);
+	printf("Loaded BPF prog have %d bpf program(s)\n", tp_cnt);
+	bpf_object__for_each_program(prog, obj) {
+		printf(" - prog_fd[%d] = fd(%d)\n", i++, bpf_program__fd(prog));
 	}
 
+	i = 0;
 	/* Maps info */
-	printf("Loaded BPF prog have %d map(s)\n", map_data_count);
-	for (i = 0; i < map_data_count; i++) {
-		char *name = map_data[i].name;
-		int fd     = map_data[i].fd;
+	printf("Loaded BPF prog have %d map(s)\n", map_cnt);
+	bpf_object__for_each_map(map, obj) {
+		const char *name = bpf_map__name(map);
+		int fd		 = bpf_map__fd(map);
 
-		printf(" - map_data[%d] = fd(%d) name:%s\n", i, fd, name);
+		printf(" - map_data[%d] = fd(%d) name:%s\n", i++, fd, name);
 	}
 
 	/* Event info */
-	printf("Searching for (max:%d) event file descriptor(s)\n", prog_cnt);
-	for (i = 0; i < prog_cnt; i++) {
-		if (event_fd[i] != -1)
-			printf(" - event_fd[%d] = fd(%d)\n", i, event_fd[i]);
+	printf("Searching for (max:%d) event file descriptor(s)\n", tp_cnt);
+	for (i = 0; i < tp_cnt; i++) {
+		int fd = bpf_link__fd(tp_links[i]);
+
+		if (fd != -1)
+			printf(" - event_fd[%d] = fd(%d)\n", i, fd);
 	}
 }
 
 int main(int argc, char **argv)
 {
 	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
+	struct bpf_program *prog;
+	struct bpf_object *obj;
 	int longindex = 0, opt;
 	int ret = EXIT_SUCCESS;
-	char bpf_obj_file[256];
+	enum map_type type;
+	char filename[256];
 
 	/* Default settings: */
 	bool errors_only = true;
 	int interval = 2;
 
-	snprintf(bpf_obj_file, sizeof(bpf_obj_file), "%s_kern.o", argv[0]);
-
 	/* Parse commands line args */
 	while ((opt = getopt_long(argc, argv, "hDSs:",
 				  long_options, &longindex)) != -1) {
@@ -676,33 +715,64 @@ int main(int argc, char **argv)
 		}
 	}
 
+	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
 	if (setrlimit(RLIMIT_MEMLOCK, &r)) {
 		perror("setrlimit(RLIMIT_MEMLOCK)");
 		return EXIT_FAILURE;
 	}
 
-	if (load_bpf_file(bpf_obj_file)) {
-		printf("ERROR - bpf_log_buf: %s", bpf_log_buf);
+	/* Remove tracepoint program when program is interrupted or killed */
+	signal(SIGINT, int_exit);
+	signal(SIGTERM, int_exit);
+
+	obj = bpf_object__open_file(filename, NULL);
+	if (libbpf_get_error(obj)) {
+		printf("ERROR: opening BPF object file failed\n");
+		obj = NULL;
 		return EXIT_FAILURE;
 	}
-	if (!prog_fd[0]) {
-		printf("ERROR - load_bpf_file: %s\n", strerror(errno));
+
+	/* load BPF program */
+	if (bpf_object__load(obj)) {
+		printf("ERROR: loading BPF object file failed\n");
 		return EXIT_FAILURE;
 	}
 
+	for (type = 0; type < NUM_MAP; type++) {
+		map_data[type] =
+			bpf_object__find_map_by_name(obj, map_type_strings[type]);
+
+		if (libbpf_get_error(map_data[type])) {
+			printf("ERROR: finding a map in obj file failed\n");
+			return EXIT_FAILURE;
+		}
+		map_cnt++;
+	}
+
+	bpf_object__for_each_program(prog, obj) {
+		tp_links[tp_cnt] = bpf_program__attach(prog);
+		if (libbpf_get_error(tp_links[tp_cnt])) {
+			printf("ERROR: bpf_program__attach failed\n");
+			tp_links[tp_cnt] = NULL;
+			return EXIT_FAILURE;
+		}
+		tp_cnt++;
+	}
+
 	if (debug) {
-		print_bpf_prog_info();
+		print_bpf_prog_info(obj);
 	}
 
-	/* Unload/stop tracepoint event by closing fd's */
+	/* Unload/stop tracepoint event by closing bpf_link's */
 	if (errors_only) {
-		/* The prog_fd[i] and event_fd[i] depend on the
-		 * order the functions was defined in _kern.c
+		/* The bpf_link[i] depend on the order of
+		 * the functions was defined in _kern.c
 		 */
-		close(event_fd[2]); /* tracepoint/xdp/xdp_redirect */
-		close(prog_fd[2]);  /* func: trace_xdp_redirect */
-		close(event_fd[3]); /* tracepoint/xdp/xdp_redirect_map */
-		close(prog_fd[3]);  /* func: trace_xdp_redirect_map */
+		bpf_link__destroy(tp_links[2]);	/* tracepoint/xdp/xdp_redirect */
+		tp_links[2] = NULL;
+
+		bpf_link__destroy(tp_links[3]);	/* tracepoint/xdp/xdp_redirect_map */
+		tp_links[3] = NULL;
 	}
 
 	stats_poll(interval, errors_only);
-- 
2.25.1

[PATCH bpf-next 2/3] samples: bpf: Replace attach_tracepoint() to attach() in xdp_redirect_cpu

[Daniel T. Lee]

From commit d7a18ea7e8b6 ("libbpf: Add generic bpf_program__attach()"),
for some BPF programs, it is now possible to attach BPF programs
with __attach() instead of explicitly calling __attach_<type>().

This commit refactors the __attach_tracepoint() with libbpf's generic
__attach() method. In addition, this refactors the logic of setting
the map FD to simplify the code. Also, the missing removal of
bpf_load.o in Makefile has been fixed.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
---
 samples/bpf/Makefile                |   2 +-
 samples/bpf/xdp_redirect_cpu_user.c | 138 +++++++++++++---------------
 2 files changed, 67 insertions(+), 73 deletions(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 0cee2aa8970f..ac9175705b2f 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -98,7 +98,7 @@ test_map_in_map-objs := test_map_in_map_user.o
 per_socket_stats_example-objs := cookie_uid_helper_example.o
 xdp_redirect-objs := xdp_redirect_user.o
 xdp_redirect_map-objs := xdp_redirect_map_user.o
-xdp_redirect_cpu-objs := bpf_load.o xdp_redirect_cpu_user.o
+xdp_redirect_cpu-objs := xdp_redirect_cpu_user.o
 xdp_monitor-objs := xdp_monitor_user.o
 xdp_rxq_info-objs := xdp_rxq_info_user.o
 syscall_tp-objs := syscall_tp_user.o
diff --git a/samples/bpf/xdp_redirect_cpu_user.c b/samples/bpf/xdp_redirect_cpu_user.c
index 3dd366e9474d..805b5df5e47b 100644
--- a/samples/bpf/xdp_redirect_cpu_user.c
+++ b/samples/bpf/xdp_redirect_cpu_user.c
@@ -37,18 +37,35 @@ static __u32 prog_id;
 
 static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
 static int n_cpus;
-static int cpu_map_fd;
-static int rx_cnt_map_fd;
-static int redirect_err_cnt_map_fd;
-static int cpumap_enqueue_cnt_map_fd;
-static int cpumap_kthread_cnt_map_fd;
-static int cpus_available_map_fd;
-static int cpus_count_map_fd;
-static int cpus_iterator_map_fd;
-static int exception_cnt_map_fd;
+
+enum map_type {
+	CPU_MAP,
+	RX_CNT,
+	REDIRECT_ERR_CNT,
+	CPUMAP_ENQUEUE_CNT,
+	CPUMAP_KTHREAD_CNT,
+	CPUS_AVAILABLE,
+	CPUS_COUNT,
+	CPUS_ITERATOR,
+	EXCEPTION_CNT,
+};
+
+static const char *const map_type_strings[] = {
+	[CPU_MAP] = "cpu_map",
+	[RX_CNT] = "rx_cnt",
+	[REDIRECT_ERR_CNT] = "redirect_err_cnt",
+	[CPUMAP_ENQUEUE_CNT] = "cpumap_enqueue_cnt",
+	[CPUMAP_KTHREAD_CNT] = "cpumap_kthread_cnt",
+	[CPUS_AVAILABLE] = "cpus_available",
+	[CPUS_COUNT] = "cpus_count",
+	[CPUS_ITERATOR] = "cpus_iterator",
+	[EXCEPTION_CNT] = "exception_cnt",
+};
 
 #define NUM_TP 5
+#define NUM_MAP 9
 struct bpf_link *tp_links[NUM_TP] = { 0 };
+static int map_fds[NUM_MAP];
 static int tp_cnt = 0;
 
 /* Exit return codes */
@@ -527,20 +544,20 @@ static void stats_collect(struct stats_record *rec)
 {
 	int fd, i;
 
-	fd = rx_cnt_map_fd;
+	fd = map_fds[RX_CNT];
 	map_collect_percpu(fd, 0, &rec->rx_cnt);
 
-	fd = redirect_err_cnt_map_fd;
+	fd = map_fds[REDIRECT_ERR_CNT];
 	map_collect_percpu(fd, 1, &rec->redir_err);
 
-	fd = cpumap_enqueue_cnt_map_fd;
+	fd = map_fds[CPUMAP_ENQUEUE_CNT];
 	for (i = 0; i < n_cpus; i++)
 		map_collect_percpu(fd, i, &rec->enq[i]);
 
-	fd = cpumap_kthread_cnt_map_fd;
+	fd = map_fds[CPUMAP_KTHREAD_CNT];
 	map_collect_percpu(fd, 0, &rec->kthread);
 
-	fd = exception_cnt_map_fd;
+	fd = map_fds[EXCEPTION_CNT];
 	map_collect_percpu(fd, 0, &rec->exception);
 }
 
@@ -565,7 +582,7 @@ static int create_cpu_entry(__u32 cpu, struct bpf_cpumap_val *value,
 	/* Add a CPU entry to cpumap, as this allocate a cpu entry in
 	 * the kernel for the cpu.
 	 */
-	ret = bpf_map_update_elem(cpu_map_fd, &cpu, value, 0);
+	ret = bpf_map_update_elem(map_fds[CPU_MAP], &cpu, value, 0);
 	if (ret) {
 		fprintf(stderr, "Create CPU entry failed (err:%d)\n", ret);
 		exit(EXIT_FAIL_BPF);
@@ -574,21 +591,21 @@ static int create_cpu_entry(__u32 cpu, struct bpf_cpumap_val *value,
 	/* Inform bpf_prog's that a new CPU is available to select
 	 * from via some control maps.
 	 */
-	ret = bpf_map_update_elem(cpus_available_map_fd, &avail_idx, &cpu, 0);
+	ret = bpf_map_update_elem(map_fds[CPUS_AVAILABLE], &avail_idx, &cpu, 0);
 	if (ret) {
 		fprintf(stderr, "Add to avail CPUs failed\n");
 		exit(EXIT_FAIL_BPF);
 	}
 
 	/* When not replacing/updating existing entry, bump the count */
-	ret = bpf_map_lookup_elem(cpus_count_map_fd, &key, &curr_cpus_count);
+	ret = bpf_map_lookup_elem(map_fds[CPUS_COUNT], &key, &curr_cpus_count);
 	if (ret) {
 		fprintf(stderr, "Failed reading curr cpus_count\n");
 		exit(EXIT_FAIL_BPF);
 	}
 	if (new) {
 		curr_cpus_count++;
-		ret = bpf_map_update_elem(cpus_count_map_fd, &key,
+		ret = bpf_map_update_elem(map_fds[CPUS_COUNT], &key,
 					  &curr_cpus_count, 0);
 		if (ret) {
 			fprintf(stderr, "Failed write curr cpus_count\n");
@@ -612,7 +629,7 @@ static void mark_cpus_unavailable(void)
 	int ret, i;
 
 	for (i = 0; i < n_cpus; i++) {
-		ret = bpf_map_update_elem(cpus_available_map_fd, &i,
+		ret = bpf_map_update_elem(map_fds[CPUS_AVAILABLE], &i,
 					  &invalid_cpu, 0);
 		if (ret) {
 			fprintf(stderr, "Failed marking CPU unavailable\n");
@@ -665,68 +682,40 @@ static void stats_poll(int interval, bool use_separators, char *prog_name,
 	free_stats_record(prev);
 }
 
-static struct bpf_link * attach_tp(struct bpf_object *obj,
-				   const char *tp_category,
-				   const char* tp_name)
+static int init_tracepoints(struct bpf_object *obj)
 {
+	char *tp_section = "tracepoint/";
 	struct bpf_program *prog;
-	struct bpf_link *link;
-	char sec_name[PATH_MAX];
-	int len;
+	const char *section;
 
-	len = snprintf(sec_name, PATH_MAX, "tracepoint/%s/%s",
-		       tp_category, tp_name);
-	if (len < 0)
-		exit(EXIT_FAIL);
+	bpf_object__for_each_program(prog, obj) {
+		section = bpf_program__section_name(prog);
+		if (strncmp(section, tp_section, strlen(tp_section)) != 0)
+			continue;
 
-	prog = bpf_object__find_program_by_title(obj, sec_name);
-	if (!prog) {
-		fprintf(stderr, "ERR: finding progsec: %s\n", sec_name);
-		exit(EXIT_FAIL_BPF);
+		tp_links[tp_cnt] = bpf_program__attach(prog);
+		if (libbpf_get_error(tp_links[tp_cnt])) {
+			tp_links[tp_cnt] = NULL;
+			return -EINVAL;
+		}
+		tp_cnt++;
 	}
 
-	link = bpf_program__attach_tracepoint(prog, tp_category, tp_name);
-	if (libbpf_get_error(link))
-		exit(EXIT_FAIL_BPF);
-
-	return link;
-}
-
-static void init_tracepoints(struct bpf_object *obj) {
-	tp_links[tp_cnt++] = attach_tp(obj, "xdp", "xdp_redirect_err");
-	tp_links[tp_cnt++] = attach_tp(obj, "xdp", "xdp_redirect_map_err");
-	tp_links[tp_cnt++] = attach_tp(obj, "xdp", "xdp_exception");
-	tp_links[tp_cnt++] = attach_tp(obj, "xdp", "xdp_cpumap_enqueue");
-	tp_links[tp_cnt++] = attach_tp(obj, "xdp", "xdp_cpumap_kthread");
+	return 0;
 }
 
 static int init_map_fds(struct bpf_object *obj)
 {
-	/* Maps updated by tracepoints */
-	redirect_err_cnt_map_fd =
-		bpf_object__find_map_fd_by_name(obj, "redirect_err_cnt");
-	exception_cnt_map_fd =
-		bpf_object__find_map_fd_by_name(obj, "exception_cnt");
-	cpumap_enqueue_cnt_map_fd =
-		bpf_object__find_map_fd_by_name(obj, "cpumap_enqueue_cnt");
-	cpumap_kthread_cnt_map_fd =
-		bpf_object__find_map_fd_by_name(obj, "cpumap_kthread_cnt");
-
-	/* Maps used by XDP */
-	rx_cnt_map_fd = bpf_object__find_map_fd_by_name(obj, "rx_cnt");
-	cpu_map_fd = bpf_object__find_map_fd_by_name(obj, "cpu_map");
-	cpus_available_map_fd =
-		bpf_object__find_map_fd_by_name(obj, "cpus_available");
-	cpus_count_map_fd = bpf_object__find_map_fd_by_name(obj, "cpus_count");
-	cpus_iterator_map_fd =
-		bpf_object__find_map_fd_by_name(obj, "cpus_iterator");
-
-	if (cpu_map_fd < 0 || rx_cnt_map_fd < 0 ||
-	    redirect_err_cnt_map_fd < 0 || cpumap_enqueue_cnt_map_fd < 0 ||
-	    cpumap_kthread_cnt_map_fd < 0 || cpus_available_map_fd < 0 ||
-	    cpus_count_map_fd < 0 || cpus_iterator_map_fd < 0 ||
-	    exception_cnt_map_fd < 0)
-		return -ENOENT;
+	enum map_type type;
+
+	for (type = 0; type < NUM_MAP; type++) {
+		map_fds[type] =
+			bpf_object__find_map_fd_by_name(obj,
+							map_type_strings[type]);
+
+		if (map_fds[type] < 0)
+			return -ENOENT;
+	}
 
 	return 0;
 }
@@ -831,7 +820,12 @@ int main(int argc, char **argv)
 			strerror(errno));
 		return EXIT_FAIL;
 	}
-	init_tracepoints(obj);
+
+	if (init_tracepoints(obj) < 0) {
+		fprintf(stderr, "ERR: bpf_program__attach failed\n");
+		return EXIT_FAIL;
+	}
+
 	if (init_map_fds(obj) < 0) {
 		fprintf(stderr, "bpf_object__find_map_fd_by_name failed\n");
 		return EXIT_FAIL;
-- 
2.25.1

[PATCH bpf-next 3/3] samples: bpf: refactor XDP kern program maps with BTF-defined map

[Daniel T. Lee]

Most of the samples were converted to use the new BTF-defined MAP as
they moved to libbpf, but some of the samples were missing.

Instead of using the previous BPF MAP definition, this commit refactors
xdp_monitor and xdp_sample_pkts_kern MAP definition with the new
BTF-defined MAP format.

Also, this commit removes the max_entries attribute at PERF_EVENT_ARRAY
map type. The libbpf's bpf_object__create_map() will automatically
set max_entries to the maximum configured number of CPUs on the host.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
---
 samples/bpf/xdp_monitor_kern.c     | 60 +++++++++++++++---------------
 samples/bpf/xdp_sample_pkts_kern.c | 14 +++----
 samples/bpf/xdp_sample_pkts_user.c |  1 -
 3 files changed, 36 insertions(+), 39 deletions(-)

diff --git a/samples/bpf/xdp_monitor_kern.c b/samples/bpf/xdp_monitor_kern.c
index 3d33cca2d48a..5c955b812c47 100644
--- a/samples/bpf/xdp_monitor_kern.c
+++ b/samples/bpf/xdp_monitor_kern.c
@@ -6,21 +6,21 @@
 #include <uapi/linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 
-struct bpf_map_def SEC("maps") redirect_err_cnt = {
-	.type = BPF_MAP_TYPE_PERCPU_ARRAY,
-	.key_size = sizeof(u32),
-	.value_size = sizeof(u64),
-	.max_entries = 2,
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__type(key, u32);
+	__type(value, u64);
+	__uint(max_entries, 2);
 	/* TODO: have entries for all possible errno's */
-};
+} redirect_err_cnt SEC(".maps");
 
 #define XDP_UNKNOWN	XDP_REDIRECT + 1
-struct bpf_map_def SEC("maps") exception_cnt = {
-	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
-	.key_size	= sizeof(u32),
-	.value_size	= sizeof(u64),
-	.max_entries	= XDP_UNKNOWN + 1,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__type(key, u32);
+	__type(value, u64);
+	__uint(max_entries, XDP_UNKNOWN + 1);
+} exception_cnt SEC(".maps");
 
 /* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_redirect/format
  * Code in:                kernel/include/trace/events/xdp.h
@@ -129,19 +129,19 @@ struct datarec {
 };
 #define MAX_CPUS 64
 
-struct bpf_map_def SEC("maps") cpumap_enqueue_cnt = {
-	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
-	.key_size	= sizeof(u32),
-	.value_size	= sizeof(struct datarec),
-	.max_entries	= MAX_CPUS,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__type(key, u32);
+	__type(value, struct datarec);
+	__uint(max_entries, MAX_CPUS);
+} cpumap_enqueue_cnt SEC(".maps");
 
-struct bpf_map_def SEC("maps") cpumap_kthread_cnt = {
-	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
-	.key_size	= sizeof(u32),
-	.value_size	= sizeof(struct datarec),
-	.max_entries	= 1,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__type(key, u32);
+	__type(value, struct datarec);
+	__uint(max_entries, 1);
+} cpumap_kthread_cnt SEC(".maps");
 
 /* Tracepoint: /sys/kernel/debug/tracing/events/xdp/xdp_cpumap_enqueue/format
  * Code in:         kernel/include/trace/events/xdp.h
@@ -210,12 +210,12 @@ int trace_xdp_cpumap_kthread(struct cpumap_kthread_ctx *ctx)
 	return 0;
 }
 
-struct bpf_map_def SEC("maps") devmap_xmit_cnt = {
-	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
-	.key_size	= sizeof(u32),
-	.value_size	= sizeof(struct datarec),
-	.max_entries	= 1,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__type(key, u32);
+	__type(value, struct datarec);
+	__uint(max_entries, 1);
+} devmap_xmit_cnt SEC(".maps");
 
 /* Tracepoint: /sys/kernel/debug/tracing/events/xdp/xdp_devmap_xmit/format
  * Code in:         kernel/include/trace/events/xdp.h
diff --git a/samples/bpf/xdp_sample_pkts_kern.c b/samples/bpf/xdp_sample_pkts_kern.c
index 33377289e2a8..2fc3ecc9d9aa 100644
--- a/samples/bpf/xdp_sample_pkts_kern.c
+++ b/samples/bpf/xdp_sample_pkts_kern.c
@@ -5,14 +5,12 @@
 #include <bpf/bpf_helpers.h>
 
 #define SAMPLE_SIZE 64ul
-#define MAX_CPUS 128
-
-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 = MAX_CPUS,
-};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
+	__type(key, int);
+	__type(value, u32);
+} my_map SEC(".maps");
 
 SEC("xdp_sample")
 int xdp_sample_prog(struct xdp_md *ctx)
diff --git a/samples/bpf/xdp_sample_pkts_user.c b/samples/bpf/xdp_sample_pkts_user.c
index 991ef6f0880b..4b2a300c750c 100644
--- a/samples/bpf/xdp_sample_pkts_user.c
+++ b/samples/bpf/xdp_sample_pkts_user.c
@@ -18,7 +18,6 @@
 
 #include "perf-sys.h"
 
-#define MAX_CPUS 128
 static int if_idx;
 static char *if_name;
 static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
-- 
2.25.1

Re: [PATCH bpf-next 1/3] samples: bpf: Refactor xdp_monitor with libbpf

[Andrii Nakryiko]

On Fri, Oct 9, 2020 at 9:04 AM Daniel T. Lee <danieltimlee@gmail.com> wrote:
>
> To avoid confusion caused by the increasing fragmentation of the BPF
> Loader program, this commit would like to change to the libbpf loader
> instead of using the bpf_load.
>
> Thanks to libbpf's bpf_link interface, managing the tracepoint BPF
> program is much easier. bpf_program__attach_tracepoint manages the
> enable of tracepoint event and attach of BPF programs to it with a
> single interface bpf_link, so there is no need to manage event_fd and
> prog_fd separately.
>
> This commit refactors xdp_monitor with using this libbpf API, and the
> bpf_load is removed and migrated to libbpf.
>
> Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
> ---
>  samples/bpf/Makefile           |   2 +-
>  samples/bpf/xdp_monitor_user.c | 144 ++++++++++++++++++++++++---------
>  2 files changed, 108 insertions(+), 38 deletions(-)
>

[...]

> +static int tp_cnt;
> +static int map_cnt;
>  static int verbose = 1;
>  static bool debug = false;
> +struct bpf_map *map_data[NUM_MAP] = { 0 };
> +struct bpf_link *tp_links[NUM_TP] = { 0 };

this syntax means "initialize *only the first element* to 0
(explicitly) and the rest of elements to default (which is also 0)".
So it's just misleading, use ` = {}`.

>
>  static const struct option long_options[] = {
>         {"help",        no_argument,            NULL, 'h' },
> @@ -41,6 +65,15 @@ static const struct option long_options[] = {
>         {0, 0, NULL,  0 }
>  };
>
> +static void int_exit(int sig)
> +{
> +       /* Detach tracepoints */
> +       while (tp_cnt)
> +               bpf_link__destroy(tp_links[--tp_cnt]);
> +

see below about proper cleanup

> +       exit(0);
> +}
> +
>  /* C standard specifies two constants, EXIT_SUCCESS(0) and EXIT_FAILURE(1) */
>  #define EXIT_FAIL_MEM  5
>

[...]

>
> -static void print_bpf_prog_info(void)
> +static void print_bpf_prog_info(struct bpf_object *obj)
>  {
> -       int i;
> +       struct bpf_program *prog;
> +       struct bpf_map *map;
> +       int i = 0;
>
>         /* Prog info */
> -       printf("Loaded BPF prog have %d bpf program(s)\n", prog_cnt);
> -       for (i = 0; i < prog_cnt; i++) {
> -               printf(" - prog_fd[%d] = fd(%d)\n", i, prog_fd[i]);
> +       printf("Loaded BPF prog have %d bpf program(s)\n", tp_cnt);
> +       bpf_object__for_each_program(prog, obj) {
> +               printf(" - prog_fd[%d] = fd(%d)\n", i++, bpf_program__fd(prog));
>         }
>
> +       i = 0;
>         /* Maps info */
> -       printf("Loaded BPF prog have %d map(s)\n", map_data_count);
> -       for (i = 0; i < map_data_count; i++) {
> -               char *name = map_data[i].name;
> -               int fd     = map_data[i].fd;
> +       printf("Loaded BPF prog have %d map(s)\n", map_cnt);
> +       bpf_object__for_each_map(map, obj) {
> +               const char *name = bpf_map__name(map);
> +               int fd           = bpf_map__fd(map);
>
> -               printf(" - map_data[%d] = fd(%d) name:%s\n", i, fd, name);
> +               printf(" - map_data[%d] = fd(%d) name:%s\n", i++, fd, name);

please move out increment into a separate statement, no need to
confuse readers unnecessarily

>         }
>
>         /* Event info */
> -       printf("Searching for (max:%d) event file descriptor(s)\n", prog_cnt);
> -       for (i = 0; i < prog_cnt; i++) {
> -               if (event_fd[i] != -1)
> -                       printf(" - event_fd[%d] = fd(%d)\n", i, event_fd[i]);
> +       printf("Searching for (max:%d) event file descriptor(s)\n", tp_cnt);
> +       for (i = 0; i < tp_cnt; i++) {
> +               int fd = bpf_link__fd(tp_links[i]);
> +
> +               if (fd != -1)
> +                       printf(" - event_fd[%d] = fd(%d)\n", i, fd);
>         }
>  }
>
>  int main(int argc, char **argv)
>  {

[...]

> +       obj = bpf_object__open_file(filename, NULL);
> +       if (libbpf_get_error(obj)) {
> +               printf("ERROR: opening BPF object file failed\n");
> +               obj = NULL;
>                 return EXIT_FAILURE;
>         }
> -       if (!prog_fd[0]) {
> -               printf("ERROR - load_bpf_file: %s\n", strerror(errno));
> +
> +       /* load BPF program */
> +       if (bpf_object__load(obj)) {

would be still good to call bpf_object__close(obj) here, this will
avoid warnings about memory leaks, if you run this program under ASAN

> +               printf("ERROR: loading BPF object file failed\n");
>                 return EXIT_FAILURE;
>         }
>
> +       for (type = 0; type < NUM_MAP; type++) {
> +               map_data[type] =
> +                       bpf_object__find_map_by_name(obj, map_type_strings[type]);
> +
> +               if (libbpf_get_error(map_data[type])) {
> +                       printf("ERROR: finding a map in obj file failed\n");

same about cleanup, goto into single cleanup place would be
appropriate throughout this entire function, probably.

> +                       return EXIT_FAILURE;
> +               }
> +               map_cnt++;
> +       }
> +

[...]

Re: [PATCH bpf-next 2/3] samples: bpf: Replace attach_tracepoint() to attach() in xdp_redirect_cpu

[Andrii Nakryiko]

On Fri, Oct 9, 2020 at 9:04 AM Daniel T. Lee <danieltimlee@gmail.com> wrote:
>
> From commit d7a18ea7e8b6 ("libbpf: Add generic bpf_program__attach()"),
> for some BPF programs, it is now possible to attach BPF programs
> with __attach() instead of explicitly calling __attach_<type>().
>
> This commit refactors the __attach_tracepoint() with libbpf's generic
> __attach() method. In addition, this refactors the logic of setting
> the map FD to simplify the code. Also, the missing removal of
> bpf_load.o in Makefile has been fixed.
>
> Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
> ---
>  samples/bpf/Makefile                |   2 +-
>  samples/bpf/xdp_redirect_cpu_user.c | 138 +++++++++++++---------------
>  2 files changed, 67 insertions(+), 73 deletions(-)
>

[...]

>  #define NUM_TP 5
> +#define NUM_MAP 9
>  struct bpf_link *tp_links[NUM_TP] = { 0 };

= {}

> +static int map_fds[NUM_MAP];
>  static int tp_cnt = 0;
>
>  /* Exit return codes */

[...]

> -static struct bpf_link * attach_tp(struct bpf_object *obj,
> -                                  const char *tp_category,
> -                                  const char* tp_name)
> +static int init_tracepoints(struct bpf_object *obj)
>  {
> +       char *tp_section = "tracepoint/";
>         struct bpf_program *prog;
> -       struct bpf_link *link;
> -       char sec_name[PATH_MAX];
> -       int len;
> +       const char *section;
>
> -       len = snprintf(sec_name, PATH_MAX, "tracepoint/%s/%s",
> -                      tp_category, tp_name);
> -       if (len < 0)
> -               exit(EXIT_FAIL);
> +       bpf_object__for_each_program(prog, obj) {
> +               section = bpf_program__section_name(prog);
> +               if (strncmp(section, tp_section, strlen(tp_section)) != 0)
> +                       continue;

that's a convoluted and error-prone way (you can also use "tp/bla/bla"
for tracepoint programs, for example). Use
bpf_program__is_tracepoint() check.

>
> -       prog = bpf_object__find_program_by_title(obj, sec_name);
> -       if (!prog) {
> -               fprintf(stderr, "ERR: finding progsec: %s\n", sec_name);
> -               exit(EXIT_FAIL_BPF);
> +               tp_links[tp_cnt] = bpf_program__attach(prog);
> +               if (libbpf_get_error(tp_links[tp_cnt])) {
> +                       tp_links[tp_cnt] = NULL;
> +                       return -EINVAL;
> +               }
> +               tp_cnt++;
>         }
>

[...]

Re: [PATCH bpf-next 3/3] samples: bpf: refactor XDP kern program maps with BTF-defined map

[Andrii Nakryiko]

On Fri, Oct 9, 2020 at 9:04 AM Daniel T. Lee <danieltimlee@gmail.com> wrote:
>
> Most of the samples were converted to use the new BTF-defined MAP as
> they moved to libbpf, but some of the samples were missing.
>
> Instead of using the previous BPF MAP definition, this commit refactors
> xdp_monitor and xdp_sample_pkts_kern MAP definition with the new
> BTF-defined MAP format.
>
> Also, this commit removes the max_entries attribute at PERF_EVENT_ARRAY
> map type. The libbpf's bpf_object__create_map() will automatically
> set max_entries to the maximum configured number of CPUs on the host.
>
> Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
> ---
>  samples/bpf/xdp_monitor_kern.c     | 60 +++++++++++++++---------------
>  samples/bpf/xdp_sample_pkts_kern.c | 14 +++----
>  samples/bpf/xdp_sample_pkts_user.c |  1 -
>  3 files changed, 36 insertions(+), 39 deletions(-)
>

[...]

> --- a/samples/bpf/xdp_sample_pkts_kern.c
> +++ b/samples/bpf/xdp_sample_pkts_kern.c
> @@ -5,14 +5,12 @@
>  #include <bpf/bpf_helpers.h>
>
>  #define SAMPLE_SIZE 64ul
> -#define MAX_CPUS 128
> -
> -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 = MAX_CPUS,
> -};
> +
> +struct {
> +       __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
> +       __type(key, int);
> +       __type(value, u32);


this actually will generate unnecessary libbpf warnings, because
PERF_EVENT_ARRAY doesn't support BTF types for key/value. So use
__uint(key_size, sizeof(int)) and __uint(value_size, sizeof(u32))
instead.

> +} my_map SEC(".maps");
>
>  SEC("xdp_sample")
>  int xdp_sample_prog(struct xdp_md *ctx)
> diff --git a/samples/bpf/xdp_sample_pkts_user.c b/samples/bpf/xdp_sample_pkts_user.c
> index 991ef6f0880b..4b2a300c750c 100644
> --- a/samples/bpf/xdp_sample_pkts_user.c
> +++ b/samples/bpf/xdp_sample_pkts_user.c
> @@ -18,7 +18,6 @@
>
>  #include "perf-sys.h"
>
> -#define MAX_CPUS 128
>  static int if_idx;
>  static char *if_name;
>  static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
> --
> 2.25.1
>

Re: [PATCH bpf-next 0/3] samples: bpf: Refactor XDP programs with libbpf

[Andrii Nakryiko]

On Fri, Oct 9, 2020 at 9:04 AM Daniel T. Lee <danieltimlee@gmail.com> wrote:
>
> To avoid confusion caused by the increasing fragmentation of the BPF
> Loader program, this commit would like to convert the previous bpf_load
> loader with the libbpf loader.
>
> Thanks to libbpf's bpf_link interface, managing the tracepoint BPF
> program is much easier. bpf_program__attach_tracepoint manages the
> enable of tracepoint event and attach of BPF programs to it with a
> single interface bpf_link, so there is no need to manage event_fd and
> prog_fd separately.
>
> And due to addition of generic bpf_program__attach() to libbpf, it is
> now possible to attach BPF programs with __attach() instead of
> explicitly calling __attach_<type>().
>
> This patchset refactors xdp_monitor with using this libbpf API, and the
> bpf_load is removed and migrated to libbpf. Also, attach_tracepoint()
> is replaced with the generic __attach() method in xdp_redirect_cpu.
> Moreover, maps in kern program have been converted to BTF-defined map.
>
> Daniel T. Lee (3):
>   samples: bpf: Refactor xdp_monitor with libbpf
>   samples: bpf: Replace attach_tracepoint() to attach() in
>     xdp_redirect_cpu
>   samples: bpf: refactor XDP kern program maps with BTF-defined map
>
>  samples/bpf/Makefile                |   4 +-
>  samples/bpf/xdp_monitor_kern.c      |  60 ++++++------
>  samples/bpf/xdp_monitor_user.c      | 144 +++++++++++++++++++++-------
>  samples/bpf/xdp_redirect_cpu_user.c | 138 +++++++++++++-------------
>  samples/bpf/xdp_sample_pkts_kern.c  |  14 ++-
>  samples/bpf/xdp_sample_pkts_user.c  |   1 -
>  6 files changed, 211 insertions(+), 150 deletions(-)
>
> --
> 2.25.1
>

Thanks for this clean up, Daniel! It's great! I left a few nits here
and there in the appropriate patches.

There still seem to be a bunch of users of bpf_load.c, which would be
nice to get rid of completely. But before you go do that, consider
integrating BPF skeleton into samples/bpf Makefile. That way instead
of all those look ups of maps/programs by name, you'd be writing a
straightforward skel->maps.my_map and similar short and non-failing
code. This should make the overall time spent on conversion much
smaller (and more pleasant, IMO).

You've dealt with a lot of samples/bpf reworking, so it should be too
hard for you to figure out the best way to do this, but check
selftests/bpf's Makefile, if you need some ideas. Or just ask for
help. Thanks!

Re: [PATCH bpf-next 3/3] samples: bpf: refactor XDP kern program maps with BTF-defined map

[Daniel T. Lee]

On Sat, Oct 10, 2020 at 3:25 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Fri, Oct 9, 2020 at 9:04 AM Daniel T. Lee <danieltimlee@gmail.com> wrote:
> >
> > Most of the samples were converted to use the new BTF-defined MAP as
> > they moved to libbpf, but some of the samples were missing.
> >
> > Instead of using the previous BPF MAP definition, this commit refactors
> > xdp_monitor and xdp_sample_pkts_kern MAP definition with the new
> > BTF-defined MAP format.
> >
> > Also, this commit removes the max_entries attribute at PERF_EVENT_ARRAY
> > map type. The libbpf's bpf_object__create_map() will automatically
> > set max_entries to the maximum configured number of CPUs on the host.
> >
> > Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
> > ---
> >  samples/bpf/xdp_monitor_kern.c     | 60 +++++++++++++++---------------
> >  samples/bpf/xdp_sample_pkts_kern.c | 14 +++----
> >  samples/bpf/xdp_sample_pkts_user.c |  1 -
> >  3 files changed, 36 insertions(+), 39 deletions(-)
> >
>
> [...]
>
> > --- a/samples/bpf/xdp_sample_pkts_kern.c
> > +++ b/samples/bpf/xdp_sample_pkts_kern.c
> > @@ -5,14 +5,12 @@
> >  #include <bpf/bpf_helpers.h>
> >
> >  #define SAMPLE_SIZE 64ul
> > -#define MAX_CPUS 128
> > -
> > -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 = MAX_CPUS,
> > -};
> > +
> > +struct {
> > +       __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
> > +       __type(key, int);
> > +       __type(value, u32);
>
>
> this actually will generate unnecessary libbpf warnings, because
> PERF_EVENT_ARRAY doesn't support BTF types for key/value. So use
> __uint(key_size, sizeof(int)) and __uint(value_size, sizeof(u32))
> instead.
>

Thanks for the great review!
I'll fix it right away and send the next version of patch.


> > +} my_map SEC(".maps");
> >
> >  SEC("xdp_sample")
> >  int xdp_sample_prog(struct xdp_md *ctx)
> > diff --git a/samples/bpf/xdp_sample_pkts_user.c b/samples/bpf/xdp_sample_pkts_user.c
> > index 991ef6f0880b..4b2a300c750c 100644
> > --- a/samples/bpf/xdp_sample_pkts_user.c
> > +++ b/samples/bpf/xdp_sample_pkts_user.c
> > @@ -18,7 +18,6 @@
> >
> >  #include "perf-sys.h"
> >
> > -#define MAX_CPUS 128
> >  static int if_idx;
> >  static char *if_name;
> >  static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
> > --
> > 2.25.1
> >

Re: [PATCH bpf-next 2/3] samples: bpf: Replace attach_tracepoint() to attach() in xdp_redirect_cpu

[Daniel T. Lee]

On Sat, Oct 10, 2020 at 3:23 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Fri, Oct 9, 2020 at 9:04 AM Daniel T. Lee <danieltimlee@gmail.com> wrote:
> >
> > From commit d7a18ea7e8b6 ("libbpf: Add generic bpf_program__attach()"),
> > for some BPF programs, it is now possible to attach BPF programs
> > with __attach() instead of explicitly calling __attach_<type>().
> >
> > This commit refactors the __attach_tracepoint() with libbpf's generic
> > __attach() method. In addition, this refactors the logic of setting
> > the map FD to simplify the code. Also, the missing removal of
> > bpf_load.o in Makefile has been fixed.
> >
> > Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
> > ---
> >  samples/bpf/Makefile                |   2 +-
> >  samples/bpf/xdp_redirect_cpu_user.c | 138 +++++++++++++---------------
> >  2 files changed, 67 insertions(+), 73 deletions(-)
> >
>
> [...]
>
> >  #define NUM_TP 5
> > +#define NUM_MAP 9
> >  struct bpf_link *tp_links[NUM_TP] = { 0 };
>
> = {}
>
> > +static int map_fds[NUM_MAP];
> >  static int tp_cnt = 0;
> >
> >  /* Exit return codes */
>
> [...]
>
> > -static struct bpf_link * attach_tp(struct bpf_object *obj,
> > -                                  const char *tp_category,
> > -                                  const char* tp_name)
> > +static int init_tracepoints(struct bpf_object *obj)
> >  {
> > +       char *tp_section = "tracepoint/";
> >         struct bpf_program *prog;
> > -       struct bpf_link *link;
> > -       char sec_name[PATH_MAX];
> > -       int len;
> > +       const char *section;
> >
> > -       len = snprintf(sec_name, PATH_MAX, "tracepoint/%s/%s",
> > -                      tp_category, tp_name);
> > -       if (len < 0)
> > -               exit(EXIT_FAIL);
> > +       bpf_object__for_each_program(prog, obj) {
> > +               section = bpf_program__section_name(prog);
> > +               if (strncmp(section, tp_section, strlen(tp_section)) != 0)
> > +                       continue;
>
> that's a convoluted and error-prone way (you can also use "tp/bla/bla"
> for tracepoint programs, for example). Use
> bpf_program__is_tracepoint() check.
>

Thanks for the review!
I think that's a much better way. I will send the next patch with applying
that method.

> >
> > -       prog = bpf_object__find_program_by_title(obj, sec_name);
> > -       if (!prog) {
> > -               fprintf(stderr, "ERR: finding progsec: %s\n", sec_name);
> > -               exit(EXIT_FAIL_BPF);
> > +               tp_links[tp_cnt] = bpf_program__attach(prog);
> > +               if (libbpf_get_error(tp_links[tp_cnt])) {
> > +                       tp_links[tp_cnt] = NULL;
> > +                       return -EINVAL;
> > +               }
> > +               tp_cnt++;
> >         }
> >
>
> [...]

Re: [PATCH bpf-next 1/3] samples: bpf: Refactor xdp_monitor with libbpf

[Daniel T. Lee]

On Sat, Oct 10, 2020 at 3:17 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Fri, Oct 9, 2020 at 9:04 AM Daniel T. Lee <danieltimlee@gmail.com> wrote:
> >
> > To avoid confusion caused by the increasing fragmentation of the BPF
> > Loader program, this commit would like to change to the libbpf loader
> > instead of using the bpf_load.
> >
> > Thanks to libbpf's bpf_link interface, managing the tracepoint BPF
> > program is much easier. bpf_program__attach_tracepoint manages the
> > enable of tracepoint event and attach of BPF programs to it with a
> > single interface bpf_link, so there is no need to manage event_fd and
> > prog_fd separately.
> >
> > This commit refactors xdp_monitor with using this libbpf API, and the
> > bpf_load is removed and migrated to libbpf.
> >
> > Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
> > ---
> >  samples/bpf/Makefile           |   2 +-
> >  samples/bpf/xdp_monitor_user.c | 144 ++++++++++++++++++++++++---------
> >  2 files changed, 108 insertions(+), 38 deletions(-)
> >
>
> [...]
>
> > +static int tp_cnt;
> > +static int map_cnt;
> >  static int verbose = 1;
> >  static bool debug = false;
> > +struct bpf_map *map_data[NUM_MAP] = { 0 };
> > +struct bpf_link *tp_links[NUM_TP] = { 0 };
>
> this syntax means "initialize *only the first element* to 0
> (explicitly) and the rest of elements to default (which is also 0)".
> So it's just misleading, use ` = {}`.
>

Thanks for the great review!

Come to think of it, it could be confusing as you mentioned. I will
remove the unnecessary initializer in the next patch and resend it.

> >
> >  static const struct option long_options[] = {
> >         {"help",        no_argument,            NULL, 'h' },
> > @@ -41,6 +65,15 @@ static const struct option long_options[] = {
> >         {0, 0, NULL,  0 }
> >  };
> >
> > +static void int_exit(int sig)
> > +{
> > +       /* Detach tracepoints */
> > +       while (tp_cnt)
> > +               bpf_link__destroy(tp_links[--tp_cnt]);
> > +
>
> see below about proper cleanup
>
> > +       exit(0);
> > +}
> > +
> >  /* C standard specifies two constants, EXIT_SUCCESS(0) and EXIT_FAILURE(1) */
> >  #define EXIT_FAIL_MEM  5
> >
>
> [...]
>
> >
> > -static void print_bpf_prog_info(void)
> > +static void print_bpf_prog_info(struct bpf_object *obj)
> >  {
> > -       int i;
> > +       struct bpf_program *prog;
> > +       struct bpf_map *map;
> > +       int i = 0;
> >
> >         /* Prog info */
> > -       printf("Loaded BPF prog have %d bpf program(s)\n", prog_cnt);
> > -       for (i = 0; i < prog_cnt; i++) {
> > -               printf(" - prog_fd[%d] = fd(%d)\n", i, prog_fd[i]);
> > +       printf("Loaded BPF prog have %d bpf program(s)\n", tp_cnt);
> > +       bpf_object__for_each_program(prog, obj) {
> > +               printf(" - prog_fd[%d] = fd(%d)\n", i++, bpf_program__fd(prog));
> >         }
> >
> > +       i = 0;
> >         /* Maps info */
> > -       printf("Loaded BPF prog have %d map(s)\n", map_data_count);
> > -       for (i = 0; i < map_data_count; i++) {
> > -               char *name = map_data[i].name;
> > -               int fd     = map_data[i].fd;
> > +       printf("Loaded BPF prog have %d map(s)\n", map_cnt);
> > +       bpf_object__for_each_map(map, obj) {
> > +               const char *name = bpf_map__name(map);
> > +               int fd           = bpf_map__fd(map);
> >
> > -               printf(" - map_data[%d] = fd(%d) name:%s\n", i, fd, name);
> > +               printf(" - map_data[%d] = fd(%d) name:%s\n", i++, fd, name);
>
> please move out increment into a separate statement, no need to
> confuse readers unnecessarily
>

I will fix it at the following patch.

> >         }
> >
> >         /* Event info */
> > -       printf("Searching for (max:%d) event file descriptor(s)\n", prog_cnt);
> > -       for (i = 0; i < prog_cnt; i++) {
> > -               if (event_fd[i] != -1)
> > -                       printf(" - event_fd[%d] = fd(%d)\n", i, event_fd[i]);
> > +       printf("Searching for (max:%d) event file descriptor(s)\n", tp_cnt);
> > +       for (i = 0; i < tp_cnt; i++) {
> > +               int fd = bpf_link__fd(tp_links[i]);
> > +
> > +               if (fd != -1)
> > +                       printf(" - event_fd[%d] = fd(%d)\n", i, fd);
> >         }
> >  }
> >
> >  int main(int argc, char **argv)
> >  {
>
> [...]
>
> > +       obj = bpf_object__open_file(filename, NULL);
> > +       if (libbpf_get_error(obj)) {
> > +               printf("ERROR: opening BPF object file failed\n");
> > +               obj = NULL;
> >                 return EXIT_FAILURE;
> >         }
> > -       if (!prog_fd[0]) {
> > -               printf("ERROR - load_bpf_file: %s\n", strerror(errno));
> > +
> > +       /* load BPF program */
> > +       if (bpf_object__load(obj)) {
>
> would be still good to call bpf_object__close(obj) here, this will
> avoid warnings about memory leaks, if you run this program under ASAN
>
> > +               printf("ERROR: loading BPF object file failed\n");
> >                 return EXIT_FAILURE;
> >         }
> >
> > +       for (type = 0; type < NUM_MAP; type++) {
> > +               map_data[type] =
> > +                       bpf_object__find_map_by_name(obj, map_type_strings[type]);
> > +
> > +               if (libbpf_get_error(map_data[type])) {
> > +                       printf("ERROR: finding a map in obj file failed\n");
>
> same about cleanup, goto into single cleanup place would be
> appropriate throughout this entire function, probably.
>

Jump to single cleanup will be much more intuitive.
I will update and send the next version of patch right away.

Thank you for your time and effort for the review.

Best,
Daniel

> > +                       return EXIT_FAILURE;
> > +               }
> > +               map_cnt++;
> > +       }
> > +
>
> [...]

Re: [PATCH bpf-next 0/3] samples: bpf: Refactor XDP programs with libbpf

[Daniel T. Lee]

On Sat, Oct 10, 2020 at 3:30 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Fri, Oct 9, 2020 at 9:04 AM Daniel T. Lee <danieltimlee@gmail.com> wrote:
> >
> > To avoid confusion caused by the increasing fragmentation of the BPF
> > Loader program, this commit would like to convert the previous bpf_load
> > loader with the libbpf loader.
> >
> > Thanks to libbpf's bpf_link interface, managing the tracepoint BPF
> > program is much easier. bpf_program__attach_tracepoint manages the
> > enable of tracepoint event and attach of BPF programs to it with a
> > single interface bpf_link, so there is no need to manage event_fd and
> > prog_fd separately.
> >
> > And due to addition of generic bpf_program__attach() to libbpf, it is
> > now possible to attach BPF programs with __attach() instead of
> > explicitly calling __attach_<type>().
> >
> > This patchset refactors xdp_monitor with using this libbpf API, and the
> > bpf_load is removed and migrated to libbpf. Also, attach_tracepoint()
> > is replaced with the generic __attach() method in xdp_redirect_cpu.
> > Moreover, maps in kern program have been converted to BTF-defined map.
> >
> > Daniel T. Lee (3):
> >   samples: bpf: Refactor xdp_monitor with libbpf
> >   samples: bpf: Replace attach_tracepoint() to attach() in
> >     xdp_redirect_cpu
> >   samples: bpf: refactor XDP kern program maps with BTF-defined map
> >
> >  samples/bpf/Makefile                |   4 +-
> >  samples/bpf/xdp_monitor_kern.c      |  60 ++++++------
> >  samples/bpf/xdp_monitor_user.c      | 144 +++++++++++++++++++++-------
> >  samples/bpf/xdp_redirect_cpu_user.c | 138 +++++++++++++-------------
> >  samples/bpf/xdp_sample_pkts_kern.c  |  14 ++-
> >  samples/bpf/xdp_sample_pkts_user.c  |   1 -
> >  6 files changed, 211 insertions(+), 150 deletions(-)
> >
> > --
> > 2.25.1
> >
>
> Thanks for this clean up, Daniel! It's great! I left a few nits here
> and there in the appropriate patches.
>
> There still seem to be a bunch of users of bpf_load.c, which would be
> nice to get rid of completely. But before you go do that, consider
> integrating BPF skeleton into samples/bpf Makefile. That way instead
> of all those look ups of maps/programs by name, you'd be writing a
> straightforward skel->maps.my_map and similar short and non-failing
> code. This should make the overall time spent on conversion much
> smaller (and more pleasant, IMO).
>
> You've dealt with a lot of samples/bpf reworking, so it should be too
> hard for you to figure out the best way to do this, but check
> selftests/bpf's Makefile, if you need some ideas. Or just ask for
> help. Thanks!

Thanks for the great feedback!

Thank you for letting me know about the BPF features that I can apply.
Currently, I'm not familiar with the BPF skeleton yet, but I'll take a good
look at the BPF skeleton to apply it in a more advanced form.

Thank you for your time and effort for the review.

-- 
Best,
Daniel T. Lee