On Fri, May 24, 2019 at 2:14 AM Quentin Monnet
<quentin.monnet@xxxxxxxxxxxxx> wrote:
>
> Hi Andrii,
>
> Some nits inline, nothing blocking though.
>
> 2019-05-23 13:42 UTC-0700 ~ Andrii Nakryiko <andriin@xxxxxx>
> > Utilize new libbpf's btf_dump API to emit BTF as a C definitions.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
> > ---
> > tools/bpf/bpftool/btf.c | 74 +++++++++++++++++++++++++++++++++++++++--
> > 1 file changed, 72 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
> > index a22ef6587ebe..1cdbfad42b38 100644
> > --- a/tools/bpf/bpftool/btf.c
> > +++ b/tools/bpf/bpftool/btf.c
> > @@ -340,11 +340,48 @@ static int dump_btf_raw(const struct btf *btf,
> > return 0;
> > }
> >
> > +static void btf_dump_printf(void *ctx, const char *fmt, va_list args)
>
> Nit: This function could have a printf attribute ("__printf(2, 0)").
added, though I don't think it matters as it's only used as a callback function.
>
> > +{
> > + vfprintf(stdout, fmt, args);
> > +}
> > +
> > +static int dump_btf_c(const struct btf *btf,
> > + __u32 *root_type_ids, int root_type_cnt)
> > +{
> > + struct btf_dump *d;
> > + int err = 0, i;
> > +
> > + d = btf_dump__new(btf, NULL, NULL, btf_dump_printf);
> > + if (IS_ERR(d))
> > + return PTR_ERR(d);
> > +
> > + if (root_type_cnt) {
> > + for (i = 0; i < root_type_cnt; i++) {
> > + err = btf_dump__dump_type(d, root_type_ids[i]);
> > + if (err)
> > + goto done;
> > + }
> > + } else {
> > + int cnt = btf__get_nr_types(btf);
> > +
> > + for (i = 1; i <= cnt; i++) {
> > + err = btf_dump__dump_type(d, i);
> > + if (err)
> > + goto done;
> > + }
> > + }
> > +
> > +done:
> > + btf_dump__free(d);
> > + return err;
> > +}
> > +
> > static int do_dump(int argc, char **argv)
> > {
> > struct btf *btf = NULL;
> > __u32 root_type_ids[2];
> > int root_type_cnt = 0;
> > + bool dump_c = false;
> > __u32 btf_id = -1;
> > const char *src;
> > int fd = -1;
> > @@ -431,6 +468,29 @@ static int do_dump(int argc, char **argv)
> > goto done;
> > }
> >
> > + while (argc) {
> > + if (is_prefix(*argv, "format")) {
> > + NEXT_ARG();
> > + if (argc < 1) {
> > + p_err("expecting value for 'format' option\n");
> > + goto done;
> > + }
> > + if (strcmp(*argv, "c") == 0) {
> > + dump_c = true;
> > + } else if (strcmp(*argv, "raw") == 0) {
>
> Do you think we could use is_prefix() instead of strcmp() here?
So I considered it, and then decided against it, though I can still be
convinced otherwise. Right now we have raw and c, but let's say we add
rust as an option. r will become ambiguous, but actually will be
resolved to whatever we check first: either raw or rust, which is not
great. So given that those format specifiers will tend to be short, I
decided it's ok to require to specify them fully. Does it make sense?
>
> > + dump_c = false;
> > + } else {
> > + p_err("unrecognized format specifier: '%s'",
> > + *argv);
>
> Would it be worth reminding the user about the valid specifiers in that
> message? (But then we already have it in do_help(), so maybe not.)
Added possible options to the message.
>
> > + goto done;
> > + }
> > + NEXT_ARG();
> > + } else {
> > + p_err("unrecognized option: '%s'", *argv);
> > + goto done;
> > + }
> > + }
> > +
> > if (!btf) {
> > err = btf__get_from_id(btf_id, &btf);
> > if (err) {
> > @@ -444,7 +504,16 @@ static int do_dump(int argc, char **argv)
> > }
> > }
> >
> > - dump_btf_raw(btf, root_type_ids, root_type_cnt);
> > + if (dump_c) {
> > + if (json_output) {
> > + p_err("JSON output for C-syntax dump is not supported");
> > + err = -ENOTSUP;
> > + goto done;
> > + }
> > + err = dump_btf_c(btf, root_type_ids, root_type_cnt);
> > + } else {
> > + err = dump_btf_raw(btf, root_type_ids, root_type_cnt);
> > + }
> >
> > done:
> > close(fd);
> > @@ -460,10 +529,11 @@ static int do_help(int argc, char **argv)
> > }
> >
> > fprintf(stderr,
> > - "Usage: %s btf dump BTF_SRC\n"
> > + "Usage: %s btf dump BTF_SRC [format FORMAT]\n"
> > " %s btf help\n"
> > "\n"
> > " BTF_SRC := { id BTF_ID | prog PROG | map MAP [{key | value | kv | all}] | file FILE }\n"
> > + " FORMAT := { raw | c }\n"
> > " " HELP_SPEC_MAP "\n"
> > " " HELP_SPEC_PROGRAM "\n"
> > " " HELP_SPEC_OPTIONS "\n"
> >
>
