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Date: Thu, 25 Apr 2019 15:00:46 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Quentin Monnet <quentin.monnet@...ronome.com>
Cc: Andrii Nakryiko <andriin@...com>, Kernel Team <kernel-team@...com>,
Networking <netdev@...r.kernel.org>, bpf@...r.kernel.org,
Alexei Starovoitov <ast@...com>,
Daniel Borkmann <daniel@...earbox.net>,
Yonghong Song <yhs@...com>, Song Liu <songliubraving@...com>,
Martin Lau <kafai@...com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH v3 bpf-next 1/4] bpftool: add ability to dump BTF types
On Thu, Apr 25, 2019 at 12:20 PM Quentin Monnet
<quentin.monnet@...ronome.com> wrote:
>
> 2019-04-25 09:55 UTC-0700 ~ Andrii Nakryiko <andriin@...com>
> > Add new `btf dump` sub-command to bpftool. It allows to dump
> > human-readable low-level BTF types representation of BTF types. BTF can
> > be retrieved from few different sources:
> > - from BTF object by ID;
> > - from PROG, if it has associated BTF;
> > - from MAP, if it has associated BTF data; it's possible to narrow
> > down types to either key type, value type, both, or all BTF types;
> > - from ELF file (.BTF section).
> >
> > Output format mostly follows BPF verifier log format with few notable
> > exceptions:
> > - all the type/field/param/etc names are enclosed in single quotes to
> > allow easier grepping and to stand out a little bit more;
> > - FUNC_PROTO output follows STRUCT/UNION/ENUM format of having one
> > line per each argument; this is more uniform and allows easy
> > grepping, as opposed to succinct, but inconvenient format that BPF
> > verifier log is using.
> >
> > Cc: Daniel Borkmann <daniel@...earbox.net>
> > Cc: Alexei Starovoitov <ast@...com>
> > Cc: Yonghong Song <yhs@...com>
> > Cc: Martin KaFai Lau <kafai@...com>
> > Cc: Song Liu <songliubraving@...com>
> > Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> > Acked-by: Yonghong Song <yhs@...com>
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > ---
> > tools/bpf/bpftool/btf.c | 580 +++++++++++++++++++++++++++++++++++++++
> > tools/bpf/bpftool/main.c | 3 +-
> > tools/bpf/bpftool/main.h | 1 +
> > 3 files changed, 583 insertions(+), 1 deletion(-)
> > create mode 100644 tools/bpf/bpftool/btf.c
> >
> > diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
> > new file mode 100644
> > index 000000000000..cbf04850c798
> > --- /dev/null
> > +++ b/tools/bpf/bpftool/btf.c
> > @@ -0,0 +1,580 @@
> > +// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +/* Copyright (C) 2019 Facebook */
> > +
> > +#include <errno.h>
> > +#include <fcntl.h>
> > +#include <linux/err.h>
> > +#include <stdbool.h>
> > +#include <stdio.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +#include <gelf.h>
> > +#include <bpf.h>
> > +#include <linux/btf.h>
>
> Can we have as in prog.c/map.c: standard includes sorted alphabetically,
> then linux/ includes, then bpf includes?
Sure, will do.
>
> > +
> > +#include "btf.h"
> > +#include "json_writer.h"
> > +#include "main.h"
> > +
> > +static const char * const btf_kind_str[NR_BTF_KINDS] = {
> > + [BTF_KIND_UNKN] = "UNKNOWN",
> > + [BTF_KIND_INT] = "INT",
> > + [BTF_KIND_PTR] = "PTR",
> > + [BTF_KIND_ARRAY] = "ARRAY",
> > + [BTF_KIND_STRUCT] = "STRUCT",
> > + [BTF_KIND_UNION] = "UNION",
> > + [BTF_KIND_ENUM] = "ENUM",
> > + [BTF_KIND_FWD] = "FWD",
> > + [BTF_KIND_TYPEDEF] = "TYPEDEF",
> > + [BTF_KIND_VOLATILE] = "VOLATILE",
> > + [BTF_KIND_CONST] = "CONST",
> > + [BTF_KIND_RESTRICT] = "RESTRICT",
> > + [BTF_KIND_FUNC] = "FUNC",
> > + [BTF_KIND_FUNC_PROTO] = "FUNC_PROTO",
> > + [BTF_KIND_VAR] = "VAR",
> > + [BTF_KIND_DATASEC] = "DATASEC",
> > +};
> > +
> > +static const char *btf_int_enc_str(__u8 encoding)
> > +{
> > + switch (encoding) {
> > + case 0:
> > + return "(none)";
> > + case BTF_INT_SIGNED:
> > + return "SIGNED";
> > + case BTF_INT_CHAR:
> > + return "CHAR";
> > + case BTF_INT_BOOL:
> > + return "BOOL";
> > + default:
> > + return "UNKN";
> > + }
> > +}
> > +
> > +static const char *btf_var_linkage_str(__u32 linkage)
> > +{
> > + switch (linkage) {
> > + case BTF_VAR_STATIC:
> > + return "static";
> > + case BTF_VAR_GLOBAL_ALLOCATED:
> > + return "global-alloc";
> > + default:
> > + return "(unknown)";
> > + }
> > +}
> > +
> > +static const char *btf_str(const struct btf *btf, __u32 off)
> > +{
> > + if (!off)
> > + return "(anon)";
> > + return btf__name_by_offset(btf, off) ? : "(invalid)";
> > +}
> > +
> > +static int dump_btf_type(const struct btf *btf, __u32 id,
> > + const struct btf_type *t)
> > +{
> > + int kind = BTF_INFO_KIND(t->info);
> > + int safe_kind = kind <= BTF_KIND_MAX ? kind : BTF_KIND_UNKN;
> > + json_writer_t *w = json_wtr;
>
> Can we keep reverse-Christmas tree style for declarations? Assigning the
> values can be done on its own after the declarations.
Ok.
>
> > +
> > + if (json_output) {
> > + jsonw_start_object(w);
> > + jsonw_uint_field(w, "id", id);
> > + jsonw_string_field(w, "kind", btf_kind_str[safe_kind]);
> > + jsonw_string_field(w, "name", btf_str(btf, t->name_off));
> > + } else {
> > + printf("[%u] %s '%s'", id, btf_kind_str[safe_kind],
> > + btf_str(btf, t->name_off));
> > + }
> > +
> > + switch (BTF_INFO_KIND(t->info)) {
> > + case BTF_KIND_INT: {
> > + __u32 v = *(__u32 *)(t + 1);
> > + const char *enc = btf_int_enc_str(BTF_INT_ENCODING(v));
>
> Same thing here.
Fixing.
>
> > +
> > + if (json_output) {
> > + jsonw_uint_field(w, "size", t->size);
> > + jsonw_uint_field(w, "bits_offset", BTF_INT_OFFSET(v));
> > + jsonw_uint_field(w, "nr_bits", BTF_INT_BITS(v));
> > + jsonw_string_field(w, "encoding", enc);
> > + } else {
> > + printf(" size=%u bits_offset=%u nr_bits=%u encoding=%s",
> > + t->size, BTF_INT_OFFSET(v), BTF_INT_BITS(v),
> > + enc);
> > + }
> > + break;
> > + }
> > + case BTF_KIND_PTR:
>
> [...]
>
> printf(" type_id=%u", t->type);
> > + break;
> > + case BTF_KIND_FUNC_PROTO: {
> > + const struct btf_param *p = (const void *)(t + 1);
> > + __u16 vlen = BTF_INFO_VLEN(t->info);
> > + int i;
> > +
> > + if (json_output) {
> > + jsonw_uint_field(w, "ret_type_id", t->type);
> > + jsonw_uint_field(w, "vlen", vlen);
> > + jsonw_name(w, "params");
> > + jsonw_start_array(w);
> > + } else {
> > + printf(" ret_type_id=%u vlen=%u", t->type, vlen);
> > + }
> > + for (i = 0; i < vlen; i++, p++) {
> > + const char *name = btf_str(btf, p->name_off);
> > +
> > + if (json_output) {
> > + jsonw_start_object(w);
> > + jsonw_string_field(w, "name", name);
> > + jsonw_uint_field(w, "type_id", p->type);
> > + jsonw_end_object(w);
> > + } else {
> > + printf("\n\t'%s' type_id=%u", name, p->type);
> > + }
> > + }
> > + if (json_output)
> > + jsonw_end_array(w);
> > + break;
> > + }
> > + case BTF_KIND_VAR: {
> > + const struct btf_var *v = (const void *)(t + 1);
> > + const char *linkage = btf_var_linkage_str(v->linkage);
>
> And here please.
>
> > +
> > + if (json_output) {
> > + jsonw_uint_field(w, "type_id", t->type);
> > + jsonw_string_field(w, "linkage", linkage);
> > + } else {
> > + printf(" type_id=%u, linkage=%s", t->type, linkage);
> > + }
> > + break;
> > + }
> > + case BTF_KIND_DATASEC: {
>
> [...]
>
> > +static int do_help(int argc, char **argv)
> > +{
> > + if (json_output) {
> > + jsonw_null(json_wtr);
> > + return 0;
> > + }
> > +
> > + fprintf(stderr,
> > + "Usage: %s btf dump BTF_SRC\n"
>
> Why so much space between "dump" and "BTF_SRC"?
Followed map.c's style, which has that much space (though in that case
it's aligned on longest command). But seems like prog.c doesn't follow
that. I'll make spacing tighter.
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