Message ID | 20190206002949.1915237-2-andriin@fb.com |
---|---|
State | Changes Requested |
Delegated to: | BPF Maintainers |
Headers | show |
Series | tools/btf: extends libbpf APIs to work with btf w/o kernel | expand |
On Tue, Feb 05, 2019 at 04:29:48PM -0800, Andrii Nakryiko wrote: > This change splits out previous btf__new functionality of constructing > struct btf and loading it into kernel into two: > - btf__new() just creates and initializes struct btf > - btf__load() attempts to load existing struct btf into kernel > > btf__free will still close BTF fd, if it was ever loaded successfully > into kernel. > > This change allows users of libbpf to manipulate BTF using its API, > without the need to unnecessarily load it into kernel. > > One of the intended use cases is pahole using libbpf to do DWARF to BTF > conversion and deduplication using libbpf, while handling ELF sections > overwrites and other concerns on its own. > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > Acked-by: Song Liu <songliubraving@fb.com> should it be Fixes: 2d3feca8c44f ("bpf: btf: print map dump and lookup with btf info") ? Even back then btf__new() was doing the loading. So that btf support in bpftool was silently double loading btf.
On Tue, Feb 5, 2019 at 7:03 PM Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote: > > On Tue, Feb 05, 2019 at 04:29:48PM -0800, Andrii Nakryiko wrote: > > This change splits out previous btf__new functionality of constructing > > struct btf and loading it into kernel into two: > > - btf__new() just creates and initializes struct btf > > - btf__load() attempts to load existing struct btf into kernel > > > > btf__free will still close BTF fd, if it was ever loaded successfully > > into kernel. > > > > This change allows users of libbpf to manipulate BTF using its API, > > without the need to unnecessarily load it into kernel. > > > > One of the intended use cases is pahole using libbpf to do DWARF to BTF > > conversion and deduplication using libbpf, while handling ELF sections > > overwrites and other concerns on its own. > > > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > > Acked-by: Song Liu <songliubraving@fb.com> > > should it be > Fixes: 2d3feca8c44f ("bpf: btf: print map dump and lookup with btf info") > ? > Even back then btf__new() was doing the loading. > So that btf support in bpftool was silently double loading btf. > ok, will add that to commit message
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 4949f8840bda..1c2ba7182400 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -366,8 +366,6 @@ void btf__free(struct btf *btf) struct btf *btf__new(__u8 *data, __u32 size) { - __u32 log_buf_size = 0; - char *log_buf = NULL; struct btf *btf; int err; @@ -377,15 +375,6 @@ struct btf *btf__new(__u8 *data, __u32 size) btf->fd = -1; - log_buf = malloc(BPF_LOG_BUF_SIZE); - if (!log_buf) { - err = -ENOMEM; - goto done; - } - - *log_buf = 0; - log_buf_size = BPF_LOG_BUF_SIZE; - btf->data = malloc(size); if (!btf->data) { err = -ENOMEM; @@ -395,17 +384,6 @@ struct btf *btf__new(__u8 *data, __u32 size) memcpy(btf->data, data, size); btf->data_size = size; - btf->fd = bpf_load_btf(btf->data, btf->data_size, - log_buf, log_buf_size, false); - - if (btf->fd == -1) { - err = -errno; - pr_warning("Error loading BTF: %s(%d)\n", strerror(errno), errno); - if (log_buf && *log_buf) - pr_warning("%s\n", log_buf); - goto done; - } - err = btf_parse_hdr(btf); if (err) goto done; @@ -417,8 +395,6 @@ struct btf *btf__new(__u8 *data, __u32 size) err = btf_parse_type_sec(btf); done: - free(log_buf); - if (err) { btf__free(btf); return ERR_PTR(err); @@ -427,6 +403,35 @@ struct btf *btf__new(__u8 *data, __u32 size) return btf; } +int btf__load(struct btf* btf) { + __u32 log_buf_size = BPF_LOG_BUF_SIZE; + char *log_buf = NULL; + int err = 0; + + if (btf->fd >= 0) + return -EEXIST; + + log_buf = malloc(log_buf_size); + if (!log_buf) + return -ENOMEM; + + *log_buf = 0; + + btf->fd = bpf_load_btf(btf->data, btf->data_size, + log_buf, log_buf_size, false); + if (btf->fd < 0) { + err = -errno; + pr_warning("Error loading BTF: %s(%d)\n", strerror(errno), errno); + if (*log_buf) + pr_warning("%s\n", log_buf); + goto done; + } + +done: + free(log_buf); + return err; +} + int btf__fd(const struct btf *btf) { return btf->fd; diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h index 25a9d2db035d..e8410887f93a 100644 --- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h @@ -57,6 +57,7 @@ struct btf_ext_header { LIBBPF_API void btf__free(struct btf *btf); LIBBPF_API struct btf *btf__new(__u8 *data, __u32 size); +LIBBPF_API int btf__load(struct btf* btf); LIBBPF_API __s32 btf__find_by_name(const struct btf *btf, const char *type_name); LIBBPF_API __u32 btf__get_nr_types(const struct btf *btf); diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 47969aa0faf8..ff86a43a4336 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -835,7 +835,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags) obj->efile.maps_shndx = idx; else if (strcmp(name, BTF_ELF_SEC) == 0) { obj->btf = btf__new(data->d_buf, data->d_size); - if (IS_ERR(obj->btf)) { + if (IS_ERR(obj->btf) || btf__load(obj->btf)) { pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n", BTF_ELF_SEC, PTR_ERR(obj->btf)); obj->btf = NULL; diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 89c1149e32ee..f5372df143f4 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -137,6 +137,7 @@ LIBBPF_0.0.2 { btf__get_map_kv_tids; btf__get_nr_types; btf__get_strings; + btf__load; btf_ext__free; btf_ext__func_info_rec_size; btf_ext__line_info_rec_size;