libbpf: Improve logging around BPF program loading

Add missing "prog '%s': " prefixes in few places and use consistently
markers for beginning and end of program load logs. Here's an example of
log output:

libbpf: prog 'handler': BPF program load failed: Permission denied
libbpf: -- BEGIN PROG LOAD LOG ---
arg#0 reference type('UNKNOWN ') size cannot be determined: -22
; out1 = in1;
0: (18) r1 = 0xffffc9000cdcc000
2: (61) r1 = *(u32 *)(r1 +0)

...

81: (63) *(u32 *)(r4 +0) = r5
 R1_w=map_value(id=0,off=16,ks=4,vs=20,imm=0) R4=map_value(id=0,off=400,ks=4,vs=16,imm=0)
invalid access to map value, value_size=16 off=400 size=4
R4 min value is outside of the allowed memory range
processed 63 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
 -- END PROG LOAD LOG --
libbpf: failed to load program 'handler'
libbpf: failed to load object 'test_skeleton'

The entire verifier log, including BEGIN and END markers are now always
youtput during a single print callback call. This should make it much
easier to post-process or parse it, if necessary. It's not an explicit
API guarantee, but it can be reasonably expected to stay like that.

Also __bpf_object__open is renamed to bpf_object_open() as it's always
an adventure to find the exact function that implements bpf_object's
open phase, so drop the double underscored and use internal libbpf
naming convention.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211209193840.1248570-6-andrii@kernel.org

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 38999e9..f07ff39 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -6662,8 +6662,10 @@ retry_load:
        ret = bpf_prog_load(prog->type, prog_name, license, insns, insns_cnt, &load_attr);
 
        if (ret >= 0) {
-               if (log_buf && load_attr.log_level)
-                       pr_debug("verifier log:\n%s", log_buf);
+               if (log_buf && load_attr.log_level) {
+                       pr_debug("prog '%s': -- BEGIN PROG LOAD LOG --\n%s-- END PROG LOAD LOG --\n",
+                                prog->name, log_buf);
+               }
 
                if (obj->has_rodata && kernel_supports(obj, FEAT_PROG_BIND_MAP)) {
                        struct bpf_map *map;
@@ -6676,8 +6678,8 @@ retry_load:
 
                                if (bpf_prog_bind_map(ret, bpf_map__fd(map), NULL)) {
                                        cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
-                                       pr_warn("prog '%s': failed to bind .rodata map: %s\n",
-                                               prog->name, cp);
+                                       pr_warn("prog '%s': failed to bind map '%s': %s\n",
+                                               prog->name, map->real_name, cp);
                                        /* Don't fail hard if can't bind rodata. */
                                }
                        }
@@ -6691,23 +6693,22 @@ retry_load:
        if (!log_buf || errno == ENOSPC) {
                log_buf_size = max((size_t)BPF_LOG_BUF_SIZE,
                                   log_buf_size << 1);
-
                free(log_buf);
                goto retry_load;
        }
        ret = errno ? -errno : -LIBBPF_ERRNO__LOAD;
        cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
-       pr_warn("load bpf program failed: %s\n", cp);
+       pr_warn("prog '%s': BPF program load failed: %s\n", prog->name, cp);
        pr_perm_msg(ret);
 
        if (log_buf && log_buf[0] != '\0') {
                ret = -LIBBPF_ERRNO__VERIFY;
-               pr_warn("-- BEGIN DUMP LOG ---\n");
-               pr_warn("\n%s\n", log_buf);
-               pr_warn("-- END LOG --\n");
-       } else if (insns_cnt >= BPF_MAXINSNS) {
-               pr_warn("Program too large (%d insns), at most %d insns\n",
-                       insns_cnt, BPF_MAXINSNS);
+               pr_warn("prog '%s': -- BEGIN PROG LOAD LOG --\n%s-- END PROG LOAD LOG --\n",
+                       prog->name, log_buf);
+       }
+       if (insns_cnt >= BPF_MAXINSNS) {
+               pr_warn("prog '%s': program too large (%d insns), at most %d insns\n",
+                       prog->name, insns_cnt, BPF_MAXINSNS);
                ret = -LIBBPF_ERRNO__PROG2BIG;
        } else if (prog->type != BPF_PROG_TYPE_KPROBE) {
                /* Wrong program type? */
@@ -6931,9 +6932,8 @@ static int bpf_object_init_progs(struct bpf_object *obj, const struct bpf_object
        return 0;
 }
 
-static struct bpf_object *
-__bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
-                  const struct bpf_object_open_opts *opts)
+static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf, size_t obj_buf_sz,
+                                         const struct bpf_object_open_opts *opts)
 {
        const char *obj_name, *kconfig, *btf_tmp_path;
        struct bpf_object *obj;
@@ -7033,7 +7033,7 @@ __bpf_object__open_xattr(struct bpf_object_open_attr *attr, int flags)
                return NULL;
 
        pr_debug("loading %s\n", attr->file);
-       return __bpf_object__open(attr->file, NULL, 0, &opts);
+       return bpf_object_open(attr->file, NULL, 0, &opts);
 }
 
 struct bpf_object *bpf_object__open_xattr(struct bpf_object_open_attr *attr)
@@ -7059,7 +7059,7 @@ bpf_object__open_file(const char *path, const struct bpf_object_open_opts *opts)
 
        pr_debug("loading %s\n", path);
 
-       return libbpf_ptr(__bpf_object__open(path, NULL, 0, opts));
+       return libbpf_ptr(bpf_object_open(path, NULL, 0, opts));
 }
 
 struct bpf_object *
@@ -7069,7 +7069,7 @@ bpf_object__open_mem(const void *obj_buf, size_t obj_buf_sz,
        if (!obj_buf || obj_buf_sz == 0)
                return libbpf_err_ptr(-EINVAL);
 
-       return libbpf_ptr(__bpf_object__open(NULL, obj_buf, obj_buf_sz, opts));
+       return libbpf_ptr(bpf_object_open(NULL, obj_buf, obj_buf_sz, opts));
 }
 
 struct bpf_object *
@@ -7086,7 +7086,7 @@ bpf_object__open_buffer(const void *obj_buf, size_t obj_buf_sz,
        if (!obj_buf || obj_buf_sz == 0)
                return errno = EINVAL, NULL;
 
-       return libbpf_ptr(__bpf_object__open(NULL, obj_buf, obj_buf_sz, &opts));
+       return libbpf_ptr(bpf_object_open(NULL, obj_buf, obj_buf_sz, &opts));
 }
 
 static int bpf_object_unload(struct bpf_object *obj)

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
index 94e03df..8daca0a 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
@@ -217,14 +217,16 @@ static bool found;
 static int libbpf_debug_print(enum libbpf_print_level level,
                              const char *format, va_list args)
 {
-       char *log_buf;
+       const char *log_buf;
 
        if (level != LIBBPF_WARN ||
-           strcmp(format, "libbpf: \n%s\n")) {
+           !strstr(format, "-- BEGIN PROG LOAD LOG --")) {
                vprintf(format, args);
                return 0;
        }
 
+       /* skip prog_name */
+       va_arg(args, char *);
        log_buf = va_arg(args, char *);
        if (!log_buf)
                goto out;