samples: bpf: Replace attach_tracepoint() to attach() in xdp_redirect_cpu

>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>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201010181734.1109-3-danieltimlee@gmail.com

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 50ad7e8..aeebf5d 100644 (file)
--- 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 3dd366e..6fb8dbd 100644 (file)
--- 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
-struct bpf_link *tp_links[NUM_TP] = { 0 };
+#define NUM_MAP 9
+struct bpf_link *tp_links[NUM_TP] = {};
+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 +682,37 @@ 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)
 {
        struct bpf_program *prog;
-       struct bpf_link *link;
-       char sec_name[PATH_MAX];
-       int len;
 
-       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) {
+               if (bpf_program__is_tracepoint(prog) != true)
+                       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;
 }
@@ -795,13 +781,13 @@ int main(int argc, char **argv)
        bool stress_mode = false;
        struct bpf_program *prog;
        struct bpf_object *obj;
+       int err = EXIT_FAIL;
        char filename[256];
        int added_cpus = 0;
        int longindex = 0;
        int interval = 2;
        int add_cpu = -1;
-       int opt, err;
-       int prog_fd;
+       int opt, prog_fd;
        int *cpu, i;
        __u32 qsize;
 
@@ -824,24 +810,29 @@ int main(int argc, char **argv)
        }
 
        if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
-               return EXIT_FAIL;
+               return err;
 
        if (prog_fd < 0) {
                fprintf(stderr, "ERR: bpf_prog_load_xattr: %s\n",
                        strerror(errno));
-               return EXIT_FAIL;
+               return err;
        }
-       init_tracepoints(obj);
+
+       if (init_tracepoints(obj) < 0) {
+               fprintf(stderr, "ERR: bpf_program__attach failed\n");
+               return err;
+       }
+
        if (init_map_fds(obj) < 0) {
                fprintf(stderr, "bpf_object__find_map_fd_by_name failed\n");
-               return EXIT_FAIL;
+               return err;
        }
        mark_cpus_unavailable();
 
        cpu = malloc(n_cpus * sizeof(int));
        if (!cpu) {
                fprintf(stderr, "failed to allocate cpu array\n");
-               return EXIT_FAIL;
+               return err;
        }
        memset(cpu, 0, n_cpus * sizeof(int));
 
@@ -960,14 +951,12 @@ int main(int argc, char **argv)
        prog = bpf_object__find_program_by_title(obj, prog_name);
        if (!prog) {
                fprintf(stderr, "bpf_object__find_program_by_title failed\n");
-               err = EXIT_FAIL;
                goto out;
        }
 
        prog_fd = bpf_program__fd(prog);
        if (prog_fd < 0) {
                fprintf(stderr, "bpf_program__fd failed\n");
-               err = EXIT_FAIL;
                goto out;
        }
 
@@ -986,6 +975,8 @@ int main(int argc, char **argv)
 
        stats_poll(interval, use_separators, prog_name, mprog_name,
                   &value, stress_mode);
+
+       err = EXIT_OK;
 out:
        free(cpu);
        return err;