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

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Date:   Mon, 12 Nov 2018 13:30:59 -0800
From:   Stanislav Fomichev <sdf@...ichev.me>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
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 11/12, Jakub Kicinski wrote:
> 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:
Makes sense. I think I can actually repurpose disasm_init for that (the
function I added to wrap bfd_init, I think I can move the callsite here
without any problems).

> 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.