netdev - Re: [PATCH bpf-next] bpftool: make libbfd optional

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Date:   Mon, 12 Nov 2018 12:35:33 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Stanislav Fomichev <sdf@...ichev.me>
Cc:     Stanislav Fomichev <sdf@...gle.com>, netdev@...r.kernel.org,
        ast@...nel.org, daniel@...earbox.net, quentin.monnet@...ronome.com
Subject: Re: [PATCH bpf-next] bpftool: make libbfd optional

On Mon, 12 Nov 2018 11:58:27 -0800, Stanislav Fomichev wrote:
> On 11/12, Jakub Kicinski wrote:
> > On Mon, 12 Nov 2018 10:53:28 -0800, Stanislav Fomichev wrote:  
> > > diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
> > > index 61d82020af58..ec1bc2ae3c71 100644
> > > --- a/tools/bpf/bpftool/main.h
> > > +++ b/tools/bpf/bpftool/main.h
> > > @@ -147,8 +147,19 @@ int prog_parse_fd(int *argc, char ***argv);
> > >  int map_parse_fd(int *argc, char ***argv);
> > >  int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len);
> > >  
> > > +#ifdef HAVE_LIBBFD_SUPPORT
> > >  void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
> > >  		       const char *arch, const char *disassembler_options);
> > > +void disasm_init(void);
> > > +#else
> > > +static inline
> > > +void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
> > > +		       const char *arch, const char *disassembler_options)
> > > +{
> > > +	p_err("No libbfd support");
> > > +}  
> > 
> > I think an error per instruction is a bit much, could we make sure we
> > error out earlier?  
> 
> I can return int from disasm_print_insn as an indication to
> stop/continue. Let me know if you have better ideas, will post v2 later
> today.

Why not simply:

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 5302ee282409..44edf6705ad2 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -466,6 +466,10 @@ static int do_dump(int argc, char **argv)
        int fd;
 
        if (is_prefix(*argv, "jited")) {
+#ifndef HAVE_LIBBFD_SUPPORT
+               p_err("No libbfd support");
+               return -1;
+#endif
                member_len = &info.jited_prog_len;
                member_ptr = &info.jited_prog_insns;
        } else if (is_prefix(*argv, "xlated")) {

Perhaps wrapped into some helper in the header to avoid the yuckiness.