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Date: Mon, 7 Oct 2019 14:50:50 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Stanislav Fomichev <sdf@...ichev.me>
Cc: Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
Networking <netdev@...r.kernel.org>,
Alexei Starovoitov <ast@...com>,
Daniel Borkmann <daniel@...earbox.net>,
Stanislav Fomichev <sdf@...gle.com>,
Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next] bpftool: fix bpftool build by switching to bpf_object__open_file()
On Mon, Oct 7, 2019 at 2:46 PM Stanislav Fomichev <sdf@...ichev.me> wrote:
>
> On 10/07, Andrii Nakryiko wrote:
> > As part of libbpf in 5e61f2707029 ("libbpf: stop enforcing kern_version,
> > populate it for users") non-LIBBPF_API __bpf_object__open_xattr() API
> > was removed from libbpf.h header. This broke bpftool, which relied on
> > that function. This patch fixes the build by switching to newly added
> > bpf_object__open_file() which provides the same capabilities, but is
> > official and future-proof API.
> >
> > Fixes: 5e61f2707029 ("libbpf: stop enforcing kern_version, populate it for users")
> > Reported-by: Stanislav Fomichev <sdf@...gle.com>
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > ---
> > tools/bpf/bpftool/main.c | 4 ++--
> > tools/bpf/bpftool/main.h | 2 +-
> > tools/bpf/bpftool/prog.c | 22 ++++++++++++----------
> > 3 files changed, 15 insertions(+), 13 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
> > index 93d008687020..4764581ff9ea 100644
> > --- a/tools/bpf/bpftool/main.c
> > +++ b/tools/bpf/bpftool/main.c
> > @@ -27,7 +27,7 @@ bool json_output;
> > bool show_pinned;
> > bool block_mount;
> > bool verifier_logs;
> > -int bpf_flags;
> > +bool relaxed_maps;
> > struct pinned_obj_table prog_table;
> > struct pinned_obj_table map_table;
> >
> > @@ -396,7 +396,7 @@ int main(int argc, char **argv)
> > show_pinned = true;
> > break;
> > case 'm':
> > - bpf_flags = MAPS_RELAX_COMPAT;
> > + relaxed_maps = true;
> > break;
> > case 'n':
> > block_mount = true;
> > diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
> > index af9ad56c303a..2899095f8254 100644
> > --- a/tools/bpf/bpftool/main.h
> > +++ b/tools/bpf/bpftool/main.h
> > @@ -94,7 +94,7 @@ extern bool json_output;
> > extern bool show_pinned;
> > extern bool block_mount;
> > extern bool verifier_logs;
> > -extern int bpf_flags;
> > +extern bool relaxed_maps;
> > extern struct pinned_obj_table prog_table;
> > extern struct pinned_obj_table map_table;
> >
> > diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> > index 43fdbbfe41bb..8191cd595963 100644
> > --- a/tools/bpf/bpftool/prog.c
> > +++ b/tools/bpf/bpftool/prog.c
> > @@ -1092,9 +1092,7 @@ static int do_run(int argc, char **argv)
> > static int load_with_options(int argc, char **argv, bool first_prog_only)
> > {
> > struct bpf_object_load_attr load_attr = { 0 };
> > - struct bpf_object_open_attr open_attr = {
> > - .prog_type = BPF_PROG_TYPE_UNSPEC,
> > - };
> > + enum bpf_prog_type prog_type = BPF_PROG_TYPE_UNSPEC;
> > enum bpf_attach_type expected_attach_type;
> > struct map_replace *map_replace = NULL;
> > struct bpf_program *prog = NULL, *pos;
> > @@ -1105,11 +1103,16 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> > const char *pinfile;
> > unsigned int i, j;
> > __u32 ifindex = 0;
> > + const char *file;
> > int idx, err;
> >
> > + LIBBPF_OPTS(bpf_object_open_opts, open_opts,
> > + .relaxed_maps = relaxed_maps,
> > + );
> > +
> > if (!REQ_ARGS(2))
> > return -1;
> > - open_attr.file = GET_ARG();
> > + file = GET_ARG();
> > pinfile = GET_ARG();
> >
> > while (argc) {
> > @@ -1118,7 +1121,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >
> > NEXT_ARG();
> >
> > - if (open_attr.prog_type != BPF_PROG_TYPE_UNSPEC) {
> > + if (prog_type != BPF_PROG_TYPE_UNSPEC) {
> > p_err("program type already specified");
> > goto err_free_reuse_maps;
> > }
> > @@ -1135,8 +1138,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> > strcat(type, *argv);
> > strcat(type, "/");
> >
> > - err = libbpf_prog_type_by_name(type,
> > - &open_attr.prog_type,
> > + err = libbpf_prog_type_by_name(type, &prog_type,
> > &expected_attach_type);
> > free(type);
> > if (err < 0)
> > @@ -1224,16 +1226,16 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >
> > set_max_rlimit();
> >
> > - obj = __bpf_object__open_xattr(&open_attr, bpf_flags);
> > + obj = bpf_object__open_file(file, &open_opts);
> > if (IS_ERR_OR_NULL(obj)) {
> > p_err("failed to open object file");
> > goto err_free_reuse_maps;
> > }
> >
> > bpf_object__for_each_program(pos, obj) {
> > - enum bpf_prog_type prog_type = open_attr.prog_type;
> > + enum bpf_prog_type prog_type = prog_type;
> Are you sure it works that way?
Oh, I did this pretty mechanically, didn't notice I'm shadowing. In
either case I'd like to avoid shadowing, so I'll rename one of them,
good catch!
>
> $ cat tmp.c
> #include <stdio.h>
>
> int main()
> {
> int x = 1;
> printf("outer x=%d\n", x);
>
> {
> int x = x;
> printf("inner x=%d\n", x);
> }
>
> return 0;
> }
>
> $ gcc tmp.c && ./a.out
> outer x=1
> inner x=0
>
> Other than that:
> Reviewed-by: Stanislav Fomichev <sdf@...gle.com>
>
> >
> > - if (open_attr.prog_type == BPF_PROG_TYPE_UNSPEC) {
> > + if (prog_type == BPF_PROG_TYPE_UNSPEC) {
> > const char *sec_name = bpf_program__title(pos, false);
> >
> > err = libbpf_prog_type_by_name(sec_name, &prog_type,
> > --
> > 2.17.1
> >
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