Allow to set user-provided log buffer on a per-program basis ([0]). This gives great deal of flexibility in terms of which programs are loaded with logging enabled and where corresponding logs go. Log buffer set with bpf_program__set_log_buf() overrides kernel_log_buf and kernel_log_size settings set at bpf_object open time through bpf_object_open_opts, if any. Adjust bpf_object_load_prog_instance() logic to not perform own log buf allocation and load retry if custom log buffer is provided by the user. [0] Closes: https://github.com/libbpf/libbpf/issues/418 Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> --- tools/lib/bpf/libbpf.c | 92 ++++++++++++++++++++++++++++++++-------- tools/lib/bpf/libbpf.h | 7 +++ tools/lib/bpf/libbpf.map | 2 + 3 files changed, 84 insertions(+), 17 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 3fd4e3d5a11f..e3e56bebd014 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -331,7 +331,11 @@ struct bpf_program { struct reloc_desc *reloc_desc; int nr_reloc; - int log_level; + + /* BPF verifier log settings */ + char *log_buf; + size_t log_size; + __u32 log_level; struct { int nr; @@ -713,6 +717,9 @@ bpf_object__init_prog(struct bpf_object *obj, struct bpf_program *prog, prog->instances.fds = NULL; prog->instances.nr = -1; + /* inherit object's log_level */ + prog->log_level = obj->log_level; + prog->sec_name = strdup(sec_name); if (!prog->sec_name) goto errout; @@ -6591,8 +6598,10 @@ static int bpf_object_load_prog_instance(struct bpf_object *obj, struct bpf_prog const char *prog_name = NULL; char *cp, errmsg[STRERR_BUFSIZE]; size_t log_buf_size = 0; - char *log_buf = NULL; + char *log_buf = NULL, *tmp; int btf_fd, ret, err; + bool own_log_buf = true; + __u32 log_level = prog->log_level; if (prog->type == BPF_PROG_TYPE_UNSPEC) { /* @@ -6627,7 +6636,7 @@ static int bpf_object_load_prog_instance(struct bpf_object *obj, struct bpf_prog load_attr.line_info_rec_size = prog->line_info_rec_size; load_attr.line_info_cnt = prog->line_info_cnt; } - load_attr.log_level = prog->log_level; + load_attr.log_level = log_level; load_attr.prog_flags = prog->prog_flags; load_attr.fd_array = obj->fd_array; @@ -6648,21 +6657,42 @@ static int bpf_object_load_prog_instance(struct bpf_object *obj, struct bpf_prog *prog_fd = -1; return 0; } -retry_load: - if (log_buf_size) { - log_buf = malloc(log_buf_size); - if (!log_buf) - return -ENOMEM; - *log_buf = 0; +retry_load: + /* if log_level is zero, we don't request logs initiallly even if + * custom log_buf is specified; if the program load fails, then we'll + * bump log_level to 1 and use either custom log_buf or we'll allocate + * our own and retry the load to get details on what failed + */ + if (log_level) { + if (prog->log_buf) { + log_buf = prog->log_buf; + log_buf_size = prog->log_size; + own_log_buf = false; + } else if (obj->log_buf) { + log_buf = obj->log_buf; + log_buf_size = obj->log_size; + own_log_buf = false; + } else { + log_buf_size = max((size_t)BPF_LOG_BUF_SIZE, log_buf_size * 2); + tmp = realloc(log_buf, log_buf_size); + if (!tmp) { + ret = -ENOMEM; + goto out; + } + log_buf = tmp; + log_buf[0] = '\0'; + own_log_buf = true; + } } load_attr.log_buf = log_buf; load_attr.log_size = log_buf_size; - ret = bpf_prog_load(prog->type, prog_name, license, insns, insns_cnt, &load_attr); + load_attr.log_level = log_level; + ret = bpf_prog_load(prog->type, prog_name, license, insns, insns_cnt, &load_attr); if (ret >= 0) { - if (log_buf && load_attr.log_level) { + if (log_level && own_log_buf) { pr_debug("prog '%s': -- BEGIN PROG LOAD LOG --\n%s-- END PROG LOAD LOG --\n", prog->name, log_buf); } @@ -6690,19 +6720,26 @@ static int bpf_object_load_prog_instance(struct bpf_object *obj, struct bpf_prog goto out; } - if (!log_buf || errno == ENOSPC) { - log_buf_size = max((size_t)BPF_LOG_BUF_SIZE, - log_buf_size << 1); - free(log_buf); + if (log_level == 0) { + log_level = 1; goto retry_load; } + /* On ENOSPC, increase log buffer size and retry, unless custom + * log_buf is specified. + * Be careful to not overflow u32, though. Kernel's log buf size limit + * isn't part of UAPI so it can always be bumped to full 4GB. So don't + * multiply by 2 unless we are sure we'll fit within 32 bits. + * Currently, we'll get -EINVAL when we reach (UINT_MAX >> 2). + */ + if (own_log_buf && errno == ENOSPC && log_buf_size <= UINT_MAX / 2) + goto retry_load; ret = -errno; cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg)); pr_warn("prog '%s': BPF program load failed: %s\n", prog->name, cp); pr_perm_msg(ret); - if (log_buf && log_buf[0] != '\0') { + if (own_log_buf && log_buf && log_buf[0] != '\0') { pr_warn("prog '%s': -- BEGIN PROG LOAD LOG --\n%s-- END PROG LOAD LOG --\n", prog->name, log_buf); } @@ -6712,7 +6749,8 @@ static int bpf_object_load_prog_instance(struct bpf_object *obj, struct bpf_prog } out: - free(log_buf); + if (own_log_buf) + free(log_buf); return ret; } @@ -8498,6 +8536,26 @@ int bpf_program__set_log_level(struct bpf_program *prog, __u32 log_level) return 0; } +const char *bpf_program__log_buf(const struct bpf_program *prog, size_t *log_size) +{ + *log_size = prog->log_size; + return prog->log_buf; +} + +int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log_size) +{ + if (log_size && !log_buf) + return -EINVAL; + if (prog->log_size > UINT_MAX) + return -EINVAL; + if (prog->obj->loaded) + return -EBUSY; + + prog->log_buf = log_buf; + prog->log_size = log_size; + return 0; +} + #define SEC_DEF(sec_pfx, ptype, atype, flags, ...) { \ .sec = sec_pfx, \ .prog_type = BPF_PROG_TYPE_##ptype, \ diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 5c984c63859f..dacde55bebff 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -591,8 +591,15 @@ bpf_program__set_expected_attach_type(struct bpf_program *prog, LIBBPF_API __u32 bpf_program__flags(const struct bpf_program *prog); LIBBPF_API int bpf_program__set_flags(struct bpf_program *prog, __u32 flags); + +/* Per-program log level and log buffer getters/setters. + * See bpf_object_open_opts comments regarding log_level and log_buf + * interactions. + */ LIBBPF_API __u32 bpf_program__log_level(const struct bpf_program *prog); LIBBPF_API int bpf_program__set_log_level(struct bpf_program *prog, __u32 log_level); +LIBBPF_API const char *bpf_program__log_buf(const struct bpf_program *prog, size_t *log_size); +LIBBPF_API int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log_size); LIBBPF_API int bpf_program__set_attach_target(struct bpf_program *prog, int attach_prog_fd, diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 08cdfe840436..4d483af7dba6 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -423,6 +423,8 @@ LIBBPF_0.6.0 { LIBBPF_0.7.0 { global: bpf_btf_load; + bpf_program__log_buf; bpf_program__log_level; + bpf_program__set_log_buf; bpf_program__set_log_level; }; -- 2.30.2
