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Date: Wed, 20 Jun 2018 22:40:19 +0000
From: Song Liu <songliubraving@...com>
To: Okash Khawaja <osk@...com>
CC: Daniel Borkmann <daniel@...earbox.net>, Martin Lau <kafai@...com>,
"Alexei Starovoitov" <ast@...nel.org>, Yonghong Song <yhs@...com>,
Quentin Monnet <quentin.monnet@...ronome.com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
"David S. Miller" <davem@...emloft.net>,
Networking <netdev@...r.kernel.org>,
Kernel Team <Kernel-team@...com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 1/3] bpf: btf: export btf types and name by
offset from lib
> On Jun 20, 2018, at 1:30 PM, Okash Khawaja <osk@...com> wrote:
>
> This patch introduces btf__resolve_type() function and exports two
> existing functions from libbpf. btf__resolve_type follows modifier
> types like const and typedef until it hits a type which actually takes
> up memory, and then returns it. This function follows similar pattern
> to btf__resolve_size but instead of computing size, it just returns
> the type.
>
> These functions will be used in the followig patch which parses
> information inside array of `struct btf_type *`. btf_name_by_offset is
> used for printing variable names.
>
> Signed-off-by: Okash Khawaja <osk@...com>
> Acked-by: Martin KaFai Lau <kafai@...com>
>
> ---
> tools/lib/bpf/btf.c | 65 ++++++++++++++++++++++++++++++++++++----------------
> tools/lib/bpf/btf.h | 3 ++
> 2 files changed, 48 insertions(+), 20 deletions(-)
>
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -17,6 +17,11 @@
>
> #define BTF_MAX_NR_TYPES 65535
>
> +#define IS_MODIFIER(k) (((k) == BTF_KIND_TYPEDEF) || \
> + ((k) == BTF_KIND_VOLATILE) || \
> + ((k) == BTF_KIND_CONST) || \
> + ((k) == BTF_KIND_RESTRICT))
> +
> static struct btf_type btf_void;
>
> struct btf {
> @@ -33,14 +38,6 @@ struct btf {
> int fd;
> };
>
> -static const char *btf_name_by_offset(const struct btf *btf, uint32_t offset)
> -{
> - if (offset < btf->hdr->str_len)
> - return &btf->strings[offset];
> - else
> - return NULL;
> -}
> -
> static int btf_add_type(struct btf *btf, struct btf_type *t)
> {
> if (btf->types_size - btf->nr_types < 2) {
> @@ -190,15 +187,6 @@ static int btf_parse_type_sec(struct btf
> return 0;
> }
>
> -static const struct btf_type *btf_type_by_id(const struct btf *btf,
> - uint32_t type_id)
> -{
> - if (type_id > btf->nr_types)
> - return NULL;
> -
> - return btf->types[type_id];
> -}
nit: Why do we need to move these two functions to later of the file?
Other than this,
Acked-by: Song Liu <songliubraving@...com>
> -
> static bool btf_type_is_void(const struct btf_type *t)
> {
> return t == &btf_void || BTF_INFO_KIND(t->info) == BTF_KIND_FWD;
> @@ -234,7 +222,7 @@ int64_t btf__resolve_size(const struct b
> int64_t size = -1;
> int i;
>
> - t = btf_type_by_id(btf, type_id);
> + t = btf__type_by_id(btf, type_id);
> for (i = 0; i < MAX_RESOLVE_DEPTH && !btf_type_is_void_or_null(t);
> i++) {
> size = btf_type_size(t);
> @@ -259,7 +247,7 @@ int64_t btf__resolve_size(const struct b
> return -EINVAL;
> }
>
> - t = btf_type_by_id(btf, type_id);
> + t = btf__type_by_id(btf, type_id);
> }
>
> if (size < 0)
> @@ -271,6 +259,26 @@ int64_t btf__resolve_size(const struct b
> return nelems * size;
> }
>
> +int32_t btf__resolve_type(const struct btf *btf, uint32_t type_id)
> +{
> + const struct btf_type *t;
> + int depth = 0;
> +
> + t = btf__type_by_id(btf, type_id);
> + while (depth < MAX_RESOLVE_DEPTH &&
> + !btf_type_is_void_or_null(t) &&
> + IS_MODIFIER(BTF_INFO_KIND(t->info))) {
> + type_id = t->type;
> + t = btf__type_by_id(btf, type_id);
> + depth++;
> + }
> +
> + if (depth == MAX_RESOLVE_DEPTH || btf_type_is_void_or_null(t))
> + return -EINVAL;
> +
> + return type_id;
> +}
> +
> int32_t btf__find_by_name(const struct btf *btf, const char *type_name)
> {
> uint32_t i;
> @@ -280,7 +288,7 @@ int32_t btf__find_by_name(const struct b
>
> for (i = 1; i <= btf->nr_types; i++) {
> const struct btf_type *t = btf->types[i];
> - const char *name = btf_name_by_offset(btf, t->name_off);
> + const char *name = btf__name_by_offset(btf, t->name_off);
>
> if (name && !strcmp(type_name, name))
> return i;
> @@ -371,3 +379,20 @@ int btf__fd(const struct btf *btf)
> {
> return btf->fd;
> }
> +
> +const char *btf__name_by_offset(const struct btf *btf, uint32_t offset)
> +{
> + if (offset < btf->hdr->str_len)
> + return &btf->strings[offset];
> + else
> + return NULL;
> +}
> +
> +const struct btf_type *btf__type_by_id(const struct btf *btf,
> + uint32_t type_id)
> +{
> + if (type_id > btf->nr_types)
> + return NULL;
> +
> + return btf->types[type_id];
> +}
> --- a/tools/lib/bpf/btf.h
> +++ b/tools/lib/bpf/btf.h
> @@ -17,6 +17,9 @@ void btf__free(struct btf *btf);
> struct btf *btf__new(uint8_t *data, uint32_t size, btf_print_fn_t err_log);
> int32_t btf__find_by_name(const struct btf *btf, const char *type_name);
> int64_t btf__resolve_size(const struct btf *btf, uint32_t type_id);
> +int32_t btf__resolve_type(const struct btf *btf, uint32_t type_id);
> int btf__fd(const struct btf *btf);
> +const char *btf__name_by_offset(const struct btf *btf, uint32_t offset);
> +const struct btf_type *btf__type_by_id(const struct btf *btf, uint32_t type_id);
>
> #endif
>
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