* [PATCH bpf-next 0/1] libbpf: fail early when loading programs with unspecified type @ 2020-12-01 4:41 Andrei Matei 2020-12-01 4:41 ` [PATCH bpf-next 1/1] " Andrei Matei 2020-12-02 1:39 ` [PATCH bpf-next 0/1] " Andrii Nakryiko 0 siblings, 2 replies; 4+ messages in thread From: Andrei Matei @ 2020-12-01 4:41 UTC (permalink / raw) To: bpf; +Cc: Andrei Matei This patch should help people who misunderstand the importance of using proper prefixes to their ELF sections in bpf object files. The patch assumes that programs with type BPF_PROG_TYPE_UNSPEC are always invalid, as indicated by `man 2 bpf`. Please let me know if that is not accurate. Andrei Matei (1): libbpf: fail early when loading programs with unspecified type tools/lib/bpf/libbpf.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) -- 2.27.0 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH bpf-next 1/1] libbpf: fail early when loading programs with unspecified type 2020-12-01 4:41 [PATCH bpf-next 0/1] libbpf: fail early when loading programs with unspecified type Andrei Matei @ 2020-12-01 4:41 ` Andrei Matei 2020-12-02 1:52 ` Andrii Nakryiko 2020-12-02 1:39 ` [PATCH bpf-next 0/1] " Andrii Nakryiko 1 sibling, 1 reply; 4+ messages in thread From: Andrei Matei @ 2020-12-01 4:41 UTC (permalink / raw) To: bpf; +Cc: Andrei Matei Before this patch, a program with unspecified type (BPF_PROG_TYPE_UNSPEC) would be passed to the BPF syscall, only to have the kernel reject it with an opaque invalid argument error. This patch makes libbpf reject such programs with a nicer error message - in particular libbpf now tries to diagnose bad ELF section names at both open time and load time. Signed-off-by: Andrei Matei <andreimatei1@gmail.com> --- tools/lib/bpf/libbpf.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 313034117070..abca93b4f239 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -6629,6 +6629,18 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, char *log_buf = NULL; int btf_fd, ret; + if (prog->type == BPF_PROG_TYPE_UNSPEC) { + if (!prog->sec_def) { + // We couldn't find a proper section definition at load time; that's probably why + // the program type is missing. + pr_warn("prog '%s': missing BPF prog type'; check ELF section name '%s'\n", + prog->name, prog->sec_name); + } else { + pr_warn("prog '%s': missing BPF prog type\n", prog->name); + } + return -EINVAL; + } + if (!insns || !insns_cnt) return -EINVAL; @@ -6920,9 +6932,11 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz, bpf_object__for_each_program(prog, obj) { prog->sec_def = find_sec_def(prog->sec_name); - if (!prog->sec_def) + if (!prog->sec_def) { /* couldn't guess, but user might manually specify */ + pr_debug("prog '%s': unrecognized ELF section name '%s'\n", prog->name, prog->sec_name); continue; + } if (prog->sec_def->is_sleepable) prog->prog_flags |= BPF_F_SLEEPABLE; -- 2.27.0 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH bpf-next 1/1] libbpf: fail early when loading programs with unspecified type 2020-12-01 4:41 ` [PATCH bpf-next 1/1] " Andrei Matei @ 2020-12-02 1:52 ` Andrii Nakryiko 0 siblings, 0 replies; 4+ messages in thread From: Andrii Nakryiko @ 2020-12-02 1:52 UTC (permalink / raw) To: Andrei Matei; +Cc: bpf On Mon, Nov 30, 2020 at 8:43 PM Andrei Matei <andreimatei1@gmail.com> wrote: > > Before this patch, a program with unspecified type > (BPF_PROG_TYPE_UNSPEC) would be passed to the BPF syscall, only to have > the kernel reject it with an opaque invalid argument error. This patch > makes libbpf reject such programs with a nicer error message - in > particular libbpf now tries to diagnose bad ELF section names at both > open time and load time. > > Signed-off-by: Andrei Matei <andreimatei1@gmail.com> > --- This is useful, thanks. See below for a few comments, though. > tools/lib/bpf/libbpf.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 313034117070..abca93b4f239 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -6629,6 +6629,18 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, > char *log_buf = NULL; > int btf_fd, ret; > > + if (prog->type == BPF_PROG_TYPE_UNSPEC) { > + if (!prog->sec_def) { > + // We couldn't find a proper section definition at load time; that's probably why > + // the program type is missing. no C++-style comments, please > + pr_warn("prog '%s': missing BPF prog type'; check ELF section name '%s'\n", extra ' after "prog type"? also ';' -> ',' ? > + prog->name, prog->sec_name); > + } else { > + pr_warn("prog '%s': missing BPF prog type\n", prog->name); while, technically, user can manually set program type to UNSPEC even with good section name, that's probably extreme case which we shouldn't worry about. So I'd just always emit the section name. > + } > + return -EINVAL; > + } > + > if (!insns || !insns_cnt) > return -EINVAL; > > @@ -6920,9 +6932,11 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz, > > bpf_object__for_each_program(prog, obj) { > prog->sec_def = find_sec_def(prog->sec_name); > - if (!prog->sec_def) > + if (!prog->sec_def) { > /* couldn't guess, but user might manually specify */ > + pr_debug("prog '%s': unrecognized ELF section name '%s'\n", prog->name, prog->sec_name); > continue; > + } > > if (prog->sec_def->is_sleepable) > prog->prog_flags |= BPF_F_SLEEPABLE; > -- > 2.27.0 > ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH bpf-next 0/1] libbpf: fail early when loading programs with unspecified type 2020-12-01 4:41 [PATCH bpf-next 0/1] libbpf: fail early when loading programs with unspecified type Andrei Matei 2020-12-01 4:41 ` [PATCH bpf-next 1/1] " Andrei Matei @ 2020-12-02 1:39 ` Andrii Nakryiko 1 sibling, 0 replies; 4+ messages in thread From: Andrii Nakryiko @ 2020-12-02 1:39 UTC (permalink / raw) To: Andrei Matei; +Cc: bpf On Mon, Nov 30, 2020 at 8:43 PM Andrei Matei <andreimatei1@gmail.com> wrote: > > This patch should help people who misunderstand the importance of using > proper prefixes to their ELF sections in bpf object files. The patch > assumes that programs with type BPF_PROG_TYPE_UNSPEC are always invalid, > as indicated by `man 2 bpf`. Please let me know if that is not accurate. > FYI, you don't need to send a cover letter with a single patch. > Andrei Matei (1): > libbpf: fail early when loading programs with unspecified type > > tools/lib/bpf/libbpf.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > -- > 2.27.0 > ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-12-02 1:53 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-12-01 4:41 [PATCH bpf-next 0/1] libbpf: fail early when loading programs with unspecified type Andrei Matei 2020-12-01 4:41 ` [PATCH bpf-next 1/1] " Andrei Matei 2020-12-02 1:52 ` Andrii Nakryiko 2020-12-02 1:39 ` [PATCH bpf-next 0/1] " Andrii Nakryiko
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